JP4549579B2 - Waste treatment method with high chlorine and lead content - Google Patents
Waste treatment method with high chlorine and lead content Download PDFInfo
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Description
【０００１】
【発明の属する技術分野】
本発明は、ゴミ焼却設備や下水汚泥焼却設備などから排出される煤塵、あるいはセメントキルンや産業廃棄物処理施設の高温処理工程から排出される各種の煤塵に含まれる塩素分および鉛分などを効果的に除去する処理方法に関する。本発明の処理方法は、塩素や鉛の含有量が多い塩素バイパスダストの処理方法として特に好適である。
【０００２】
【従来技術】
ゴミ焼却設備や下水汚泥焼却設備などから排出される煤塵や溶融スラグ飛灰、あるいはセメントキルンや産業廃棄物処理施設の高温処理工程から排出される各種の煤塵には塩素や銅、鉛、亜鉛等の重金属類が含まれており、これらの廃棄物をそのまま埋立処理すると鉛などの重金属類が溶出して環境汚染を引き起こす問題がある。このためこれらの金属類をできるだけ分離除去することが求められている。
【０００３】
また、ゴミ焼却設備や下水汚泥焼却設備などから排出される煤塵などの廃棄物をセメント原料として用いる技術が実用化されているが、廃棄物に含まれている塩素分や重金属(特に鉛)はセメントの品質を確保する上で問題となるので、塩素分や重金属をできる限り低減することが求められる。また、セメント焼成設備において、廃棄物に含まれる塩素分はキルンの高温部で揮発して燃焼ガスと共にサスペンションプレヒータに導かれ、凝縮されて再びキルンに戻る経路を繰り返すので塩素分が次第に濃縮され、比較的温度の低い流路壁面などに付着して閉塞を招くなどの問題があるので、キルンの操業上からもできるだけ除去する必要がある。
【０００４】
そこで、セメント焼成工程の燃焼ガスから塩素分を抜き出す塩素バイパス技術が実用化されている。この一例は、キルンから高温ガスの一部を抽気してサイクロンに送り、ここで粗粉ダストをガス分から回収してキルンの燃焼系に戻し、一方、ガス分は冷却して微粉ダストを除去した後に燃焼系に送り、回収した微粉ダストは脱塩処理および脱重金属処理を行い、更にその排水を脱カルシウム処理および塩分回収処理する方法である。この抽気型塩素バイパス技術は、キルン排ガスの僅か約２％程度を抽気するだけで約８０％の塩素分を燃焼系から除去することができる処理方法である。
【０００５】
【発明が解決しようとする課題】
本発明は、上記塩素バイパス技術に適用できる脱塩・脱鉛処理方法を提供するものであって、塩素含有量および鉛含有量が高い廃棄物から更に効率良く、塩素分および鉛分を分離除去する処理方法に関する。なお、本発明の処理方法は上記塩素バイパスで回収したダストに限らず、高塩素・高鉛含有の廃棄物について広く適用することができる。
【０００６】
【課題を解決する手段】
本発明によれば、（１）廃棄物を水洗して塩素分および鉛分を溶出させて固液分離する工程(水洗工程)、濾別した固形分にアルカリ溶液を加えて鉛分を溶出させると共にカルシウムを水酸化物に転じて濾別する工程(アルカリ溶出工程)、この濾液を水洗工程で分離した濾液に加え、硫化剤を添加して鉛を沈澱分離する工程(脱鉛工程)、この脱鉛した濾液に炭酸源を加えてカルシウムを沈澱分離する工程(脱カルシウム工程)、さらに、この濾液を加熱し塩化物を析出させて分離回収する工程(塩分回収工程)を有することを特徴とする廃棄物の処理方法が提供される。
【０００７】
この処理方法によれば、水洗工程で溶出した鉛分を硫化鉛として沈澱させるので、これを濾別することより、容易に鉛分を分離除去することができる。また、水洗工程で溶出せずに固形分に残る鉛分はアルカリ溶出によって溶出され、この濾液を水洗工程の濾液に加えて脱鉛処理するので、廃棄物に含まれる鉛の大部分を除去することができる。さらに、アルカリ溶出の際に、カルシウムは水酸化物に転じて固形分に残るので鉛と分離することができ、鉛含有量の少ない水酸化カルシウムを回収することができる。
【０００８】
また本発明によれば、（２）廃棄物を水洗して塩素分および鉛分を溶出させて固液分離する工程(水洗工程)、この濾液に硫化剤を添加して鉛を沈澱分離する工程(脱鉛工程)を有し、脱鉛工程で分離した濾液の一部を水洗工程に戻して再使用することによって液中の塩素濃度と鉛の溶出率を高める一方、水洗工程に循環しない濾液に炭酸源を加えてカルシウムを沈澱分離する工程(脱カルシウム工程)、さらに、この濾液を加熱し塩化物を析出させて分離回収する工程(塩分回収工程)を有する廃棄物の処理方法であって、
廃棄物の水洗工程の後に、濾別した固形分にアルカリ溶液を加えて鉛分を溶出させると共にカルシウムを水酸化物に転じて濾別するアルカリ溶出工程を有し、水洗工程で分離した濾液とアルカリ溶出工程で分離した濾液を混合し、これに硫化剤を添加して鉛を沈澱分離する脱鉛工程の後に、脱鉛工程で分離した濾液の一部を水洗工程に戻して再使用する廃棄物の処理方法が提供される。
【０００９】
この処理方法によれば、脱鉛処理した溶液を水洗工程に戻して再使用するので鉛の溶出率を高めることができる。因みに、洗浄水を脱鉛処理せず循環使用すると、洗浄２〜３回目頃から鉛の溶出率が急激に低下するが、本発明の処理方法によれば鉛の溶出率は実質的に低下せず、高い溶出率を維持することができる。また、上記処理方法によれば、脱鉛処理した溶液の一部を水洗工程に循環して再利用するので、処理系全体の水量を低減することができる。
【００１０】
さらに本発明は上記処理方法において、（４）塩分回収工程において、溶液を５０℃以上に加熱して析出した塩化ナトリウムを濾別する工程(高温晶析工程)、さらに、この濾液を３０℃以下に冷却して析出した塩化カリウムを濾別する工程(低温晶析工程)を有する処理方法、（５）低温晶析工程で分離した濾液を高温晶析工程に戻して晶析を繰り返す一方、晶析工程で生じた蒸発水を水洗工程に導いて水洗に用いる処理方法、（６）アルカリ溶出工程で回収した水酸化カルシウム、脱カルシウム工程で回収した炭酸カルシウムをセメント原料として用いる処理方法、（７）廃棄物が塩素バイパスダストである処理方法を含む。
【００１１】
上記処理方法において、低温晶析工程で分離した濾液を高温晶析工程に戻して晶析を繰り返し、さらに晶析工程で生じた蒸発水を水洗工程に導いて水洗に用いることにより、処理系の水を実質的に外部に排水せずに循環して使用することができる。また、晶析工程から回収した塩化ナトリウムや塩化カリウムを製品として再利用することができる。さらに、本発明の上記処理方法は塩素バイパスダストの処理方法として好適である。
【００１２】
【発明の実施の形態】
以下、本発明を実施例に基づいて具体的に説明する。
本発明の処理方法を図１に示す。図示するように、本発明の処理方法は、廃棄物を水洗して塩素分と鉛分を溶出させて固液分離する工程(水洗工程)、濾別した固形分にアルカリ溶液を加えて鉛分を溶出させると共にカルシウムを水酸化物に転じて濾別する工程(アルカリ溶出工程)、この濾液を水洗工程で分離した濾液に加え、硫化剤を添加して鉛を沈澱させ、濾別する工程(脱鉛工程)、脱鉛した濾液に炭酸源を加えてカルシウムを沈澱分離する工程(脱カルシウム工程)、この濾液を加熱し塩化物を析出させて分離する工程(塩分回収工程)を有する。さらに脱鉛工程で分離した濾液の一部を水洗工程に戻して再使用する循環系を有する。
【００１３】
本発明の処理方法で処理する廃棄物は塩素バイパスダストやその他の塩素分および鉛分の含有量が高い廃棄物を含む。本発明の処理方法はこれらの処理に適する。塩素バイパスダストの主な成分は、酸化物換算重量％で、カルシウム約２３％、カリウム約３０％、硫黄約１０％であり、含有金属は鉛が約３３５００mg/kg、塩素が約２２％含まれており、金属類では鉛の含有割合が高く、また一般の都市ゴミ焼却灰などよりも塩素含有量が高い。
【００１４】
〔水洗工程〕
上記廃棄物(ダスト等)を水洗して塩素および鉛を溶出させる。なお、塩素バイパスダスト等はカルシウムの含有量も多いので、硫酸溶出を行うと多量の石膏を生じ、鉛の溶出が抑制されるので、硫酸溶出よりも水溶出が好ましい。水洗はダスト等の廃棄物を水洗槽に入れ、水中で所定時間攪拌すれば良い。水洗により廃棄物に含まれる塩素分および鉛分の多くが液中に溶出する。カルシウム分は溶出せずに固形分として残る。この水洗懸濁液を濾別して固形分と液分に分離する。なお、ダストの３倍以上の水量で水洗するのが好ましい。洗浄水量がこれより少ないとケーキに付着する水分中の塩素濃度が高くなり、脱塩率が低下する。
【００１５】
〔アルカリ溶出工程〕
水洗工程で濾別した固形分に苛性ソーダ等のアルカリ溶液を加えｐＨ１２.５以上に調整して、固形分に含まれる鉛を溶出させる。アルカリ溶液の添加量は溶液のｐＨが上記範囲になる量であれば良い。塩化カルシウムなどの形でダスト中に含まれるカルシウム分はアルカリ溶出によって水酸化カルシウムに転じる。一方、水洗工程で溶出せずに固形分に残留した鉛分はこのアルカリ溶出によって液中に溶出する。この鉛分は液中に溶存するので、濾別して水酸化カルシウムを回収する。この水酸化カルシウムの鉛含有量は極めて少ないので、セメント原料に適する。なお、アルカリ溶出工程において用いる苛性ソーダは液量を抑制するために１mol/l以上の濃度が好ましい。また、苛性ソーダ１リットルに対してダストの量は３００ｇ以下が適当である。ダストの量がこれより多いと鉛の溶出量が低下する。
【００１６】
〔脱鉛工程〕
水洗工程で濾別した濾液と、アルカリ溶出工程で濾別した濾液とを加え、硫化剤を添加して液中の鉛を硫化鉛に転じて沈澱させる。硫化剤としては水硫化ソーダ(NaSH)などを用いることができる。硫化鉛の沈澱を濾別して回収し、液分を次工程に送る。固液分離する際にシックナーなどを経由し、この上澄液を分離して水洗工程に戻し、再使用することができる。回収した硫化鉛は製錬原料などに利用することができる。なお、硫化剤の添加量は液中の鉛を全て硫化鉛にするのに必要な量よりも若干少ない量が適当である。液中に硫化剤が残ると、硫化鉛を分離した後の濾液を水洗工程に循環したときに、残留した硫化剤によって鉛の溶出が抑制されるので好ましくない。一方、硫化剤が不足して液中に鉛が残留しても、後の脱カルシウム工程やキレート工程で鉛が除去されるので支障はない。
【００１７】
本発明の処理方法の好ましい態様の一つとして、脱鉛工程で分離した濾液の一部を水洗工程に戻して再使用することによって液中の塩素濃度と鉛の溶出率を高める。なお、水洗工程(水溶出)において洗浄水を循環して使用することにより、液中の溶出金属濃度を高めることが一般に知られているが、塩素バイパスダストなどの処理において、洗浄水を脱鉛処理せず循環使用すると、洗浄２〜３回目頃から水洗液中の鉛濃度が数１００ppm程度で飽和し、鉛の溶出率が急激に低下する。これを脱鉛処理して液中の鉛濃度を低下した濾液を循環使用することによって鉛の溶出率を高く維持することができる。また、脱鉛処理した濾液の一部を水洗工程に循環して再利用することにより、処理系全体の水量を低減することができる。
【００１８】
〔脱カルシウム工程〕
水洗工程に循環しない濾液に炭酸源を加えて液中のカルシウムを沈澱させて分離する。炭酸源としては炭酸ナトリウムなどの炭酸塩、あるいはキルン排ガスなどの炭酸ガスを含むガスなどを用いることができる。廃棄物に含まれるカルシウムの大部分は、アルカリ溶出工程において水酸化カルシウムとして回収されるが、液中に残留するものは炭酸イオンと反応して炭酸カルシウムの沈澱を生じるので、これを濾別して分離回収する。この炭酸カルシウムはセメント原料に利用することができる。なお、炭酸塩は過剰に添加しても支障ないが、キルン排ガスなどを吹き込む場合には、溶液のｐＨが７以下に低下しないように制御する。溶液が酸性になると炭酸カルシウムおよび炭酸鉛が再溶解するので、これらを液中から除去するためには好ましくない。なお、脱カルシウム処理の後に溶液をキレート槽に導き、液中に残留する鉛をキレートに吸着させて除去する工程を経ても良い。
【００１９】
〔塩分回収工程〕
脱カルシウム工程で濾別した濾液を加熱し塩化物を析出させて分離回収する。この塩分回収工程を二段階に行うことにより、塩化ナトリウムと塩化カリウムを分離して回収することができる。すなわち、溶液を５０℃以上に加熱して塩化ナトリウムを析出させ、これを濾別して回収する（高温晶析工程）。さらに、この濾液を３０℃以下に冷却して塩化カリウムを析出させ、これを濾別して回収する(低温晶析工程)。また、この低温晶析工程で分離した濾液を高温晶析工程に戻して晶析を繰り返す一方、高温晶析工程で生じた蒸発水を水洗工程に導いて水洗に用いることにより、系外に放出する排水量を大幅に低減することができ、好ましくは処理系の水を実質的に外部に排水せずに循環して使用することができる。晶析工程から回収した塩化ナトリウムはソーダ原料となり、塩化カリウムは肥料などに利用することができる。
【００２０】
【実施例】
〔実施例１〕
塩素バイパスダスト（CaO：23％、SO3：10％、Na2O：2.0％、K2O：25％、Cl：20％、Pb：3.3％）１kgに、液温３０℃の水４kgを加え、０.５時間攪拌して洗浄した後に、この懸濁液を固液分離し、固形分を回収した。この固形分０.６kg(乾燥重量)に苛性ソーダ(２mol/l濃度)６リットルを加えてｐＨ１３.５に調整し、沈澱を生成させた後に固液分離し、水酸化カルシウム０.３kg(乾燥重量)を回収した。さらに、この濾液と水洗工程で濾別した濾液とを混合し、この溶液９リットルに水硫化ソーダ６ｇを加えて沈澱を生成させた後に固液分離し、硫化鉛２６ｇを回収した。
次に、この濾液(pH12)の一部を水洗工程に戻して洗浄水として使用する一方、残余の濾液２リットルに炭酸ナトリウム５５ｇを添加して沈澱を生成させ、固液分離して炭酸カルシウム５０ｇを回収した。さらに、この濾液を真空下で７０℃に加熱して液分を蒸発させ、析出した塩化ナトリウム４ｇを回収した。さらにこの濾液を２５℃に冷却して析出した塩化カリウム６５ｇを回収した。また、塩化ナトリウムの蒸発析出で発生した蒸気は凝縮して最初の水洗工程に戻し、繰り返し使用した。
【００２１】
〔実施例２〕
塩素バイパスダスト（CaO：23％、SO3：10％、Na2O：2.0％、K2O：25％、Cl：20％、Pb：3.3％）１kgに、硫化鉛を濾別した濾液（Ca:2％、Cl:6％）５リットルを添加し、０.５時間攪拌して洗浄した後、この懸濁液を固液分離して固形分を回収した。この固形分０.４kg(乾燥重量)に苛性ソーダ(２mol/l濃度)１.５リットルを加えてｐＨ１３.５に調整し、沈澱を生成させた後に固液分離し、水酸化カルシウム０.３kg(乾燥重量)を回収した。さらに、この濾液と水洗工程で濾別した濾液とを混合し、この溶液９リットルに水硫化ソーダ６ｇを加えて沈澱を生成させた後に固液分離し、硫化鉛２６ｇを回収した。
次に、この濾液(pH12)の一部を水洗工程に戻して洗浄水として使用する一方、残余の濾液２リットルに炭酸ナトリウム１７０ｇを添加して沈澱を生成させ、固液分離して炭酸カルシウム１５５ｇを回収した。さらに、この濾液を真空下で６０℃に加熱して液分を蒸発させ、析出した塩化ナトリウム６ｇを回収した。さらにこの濾液を２５℃に冷却して析出した塩化カリウム７５ｇを回収した。また、塩化ナトリウムの蒸発析出で発生した蒸気は凝縮して最初の水洗工程に戻し、繰り返し使用した。
【００２２】
【発明の効果】
本発明の処理方法によれば、水洗工程およびアルカリ溶出によって廃棄物に含まれる鉛分を溶出させるので、大部分の鉛が溶出し、これを硫化鉛として沈澱させるので、容易に鉛分の殆どを分離除去することができ、また、鉛含有量の少ない水酸化カルシウムを回収することができる。また、脱鉛処理した溶液を水洗工程に戻して再使用することによって鉛の溶出率を高めることができる。さらに、低温晶析工程で分離した濾液を高温晶析工程に戻して晶析を繰り返し、晶析工程で生じた蒸発水を水洗工程に導いて水洗に用いることにより、処理系の水を実質的に外部に排水せずに循環して使用することができる。また、晶析工程から回収した塩化ナトリウムや塩化カリウムを製品として再利用することができる。
【図面の簡単な説明】
【図１】 本発明の処理方法を示すフロー図[0001]
BACKGROUND OF THE INVENTION
The present invention is effective for the dust, chlorine, and lead contained in various dusts discharged from waste incineration equipment, sewage sludge incineration equipment, etc., or high temperature treatment processes of cement kilns and industrial waste treatment facilities. The present invention relates to a processing method that removes automatically. The treatment method of the present invention is particularly suitable as a treatment method for chlorine bypass dust having a high chlorine or lead content.
[0002]
[Prior art]
Chlorine, copper, lead, zinc, etc. may be used for soot and molten slag fly ash discharged from garbage incinerators and sewage sludge incinerators, or various types of soot discharged from high-temperature processing in cement kilns and industrial waste treatment facilities. Heavy metals are contained, and if these wastes are landfilled as they are, heavy metals such as lead are eluted to cause environmental pollution. For this reason, it is required to separate and remove these metals as much as possible.
[0003]
In addition, technology that uses waste such as dust discharged from garbage incinerators and sewage sludge incinerators as cement raw materials has been put into practical use, but chlorine and heavy metals (especially lead) contained in waste Since it becomes a problem in ensuring the quality of cement, it is required to reduce chlorine and heavy metals as much as possible. Also, in the cement firing equipment, the chlorine content contained in the waste is volatilized in the high temperature part of the kiln and is led to the suspension preheater together with the combustion gas, and is condensed and repeated again to return to the kiln, so the chlorine content is gradually concentrated. Since there is a problem such as adhering to the wall surface of the channel having a relatively low temperature and causing clogging, it is necessary to remove it as much as possible from the kiln operation.
[0004]
Therefore, a chlorine bypass technique for extracting chlorine from the combustion gas in the cement firing process has been put into practical use. In this example, a portion of the hot gas is extracted from the kiln and sent to the cyclone where the coarse dust is recovered from the gas and returned to the kiln combustion system, while the gas is cooled to remove the fine dust. The fine dust collected and sent to the combustion system later is subjected to a desalting treatment and a heavy metal treatment, and the waste water is further subjected to a decalcification treatment and a salt recovery treatment. This extraction-type chlorine bypass technique is a treatment method that can remove about 80% of chlorine from the combustion system by extracting only about 2% of the kiln exhaust gas.
[0005]
[Problems to be solved by the invention]
The present invention provides a desalting / deleading treatment method applicable to the above chlorine bypass technology, and more efficiently separating and removing chlorine and lead from wastes having high chlorine and lead content. It relates to the processing method. The treatment method of the present invention is not limited to dust recovered by the chlorine bypass, and can be widely applied to waste containing high chlorine and high lead.
[0006]
[Means for solving the problems]
According to the present invention, (1) a step of washing waste with water to elute chlorine and lead to separate solid and liquid (water washing step), an alkaline solution is added to the filtered solid to elute lead. In addition, the step of converting calcium to hydroxide and filtering (alkali elution step), adding the filtrate to the filtrate separated in the water washing step, adding a sulfurizing agent to precipitate and separating the lead (deleading step), A step of adding a carbonic acid source to the deleaded filtrate to precipitate and separate calcium (decalcification step), and further, a step of heating the filtrate to precipitate chloride and separating and recovering (salt recovery step) A waste disposal method is provided.
[0007]
According to this treatment method, since the lead content eluted in the water washing step is precipitated as lead sulfide, the lead content can be easily separated and removed by filtering this. In addition, the lead that remains in the solid content without being eluted in the water washing step is eluted by alkali elution, and this filtrate is added to the filtrate in the water washing step for deleading treatment, so that most of the lead contained in the waste is removed. be able to. Furthermore, during alkali elution, calcium turns into a hydroxide and remains in a solid content, so that it can be separated from lead and calcium hydroxide having a low lead content can be recovered.
[0008]
In addition, according to the present invention, (2) a step of washing waste with water to elute chlorine and lead and separating it into solid and liquid (water washing step), a step of adding a sulfurizing agent to the filtrate and precipitating and separating lead (Deleading process) A part of the filtrate separated in the deleading process is returned to the washing process and reused to increase the chlorine concentration and lead elution rate in the liquid, but the filtrate does not circulate in the washing process A method of treating waste by adding a carbonic acid source to precipitate and separate calcium (decalcification step), and further heating and heating the filtrate to precipitate chloride and separating and recovering (salt content recovery step). ,
After the waste water washing step, an alkali solution is added to the filtered solid content to elute the lead content, and the alkali separated step is performed by converting calcium into a hydroxide and filtering, and the filtrate separated in the water washing step After mixing the filtrate separated in the alkali elution process, adding a sulfiding agent to the lead and precipitating and separating the lead, a part of the filtrate separated in the delead process is returned to the water washing process and reused. An article processing method is provided.
[0009]
According to this treatment method, the lead-free solution can be returned to the water washing step and reused, so that the lead elution rate can be increased. By the way, if the wash water is recycled without being de-leaded, the elution rate of lead is drastically reduced from the second to third washing, but according to the treatment method of the present invention, the elution rate of lead is substantially reduced. Therefore, a high elution rate can be maintained. Moreover, according to the said processing method, since a part of solution which carried out the deleading process is circulated and reused in a water washing process, the amount of water of the whole processing system can be reduced.
[0010]
Furthermore, the present invention provides the above treatment method, wherein (4) in the salt recovery step, the solution is heated to 50 ° C. or higher and the precipitated sodium chloride is separated by filtration (high temperature crystallization step). (5) A process having a step (low-temperature crystallization step) of separating the precipitated potassium chloride by cooling to (5) The filtrate separated in the low-temperature crystallization step is returned to the high-temperature crystallization step and the crystallization is repeated. A treatment method in which the evaporated water generated in the analysis step is guided to the water washing step and used in the water washing step, (6) a treatment method using calcium hydroxide collected in the alkali elution step and calcium carbonate collected in the decalcification step as a cement raw material, (7 ) Including treatment methods where the waste is chlorine bypass dust.
[0011]
In the above treatment method, the filtrate separated in the low-temperature crystallization step is returned to the high-temperature crystallization step and crystallization is repeated, and the evaporated water generated in the crystallization step is further introduced into the water-washing step and used for water-washing. Water can be circulated and used without substantially draining to the outside. Further, sodium chloride and potassium chloride recovered from the crystallization step can be reused as a product. Furthermore, the above treatment method of the present invention is suitable as a treatment method for chlorine bypass dust.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described based on examples.
The processing method of the present invention is shown in FIG. As shown in the figure, in the treatment method of the present invention, the waste is washed with water to elute the chlorine and lead components to separate into solid and liquid (water washing step), and an alkaline solution is added to the filtered solid to add lead. The step of filtering calcium by turning it into a hydroxide (alkaline elution step), adding this filtrate to the filtrate separated in the water washing step, adding a sulfiding agent to precipitate lead, and filtering ( A deleading step), a step of adding a carbonic acid source to the deleaded filtrate to precipitate and separate calcium (decalcification step), and a step of heating the filtrate to precipitate chlorides (salt recovery step). Furthermore, it has a circulation system in which a part of the filtrate separated in the deleading process is returned to the water washing process and reused.
[0013]
Waste to be treated by the treatment method of the present invention includes chlorine bypass dust and other wastes having a high content of chlorine and lead. The treatment method of the present invention is suitable for these treatments. The main components of chlorine bypass dust are about 23% calcium, about 30% calcium, about 10% sulfur, and about 33500mg / kg lead and about 22% chlorine. Metals have a high lead content and a higher chlorine content than ordinary municipal waste incineration ash.
[0014]
[Washing process]
The wastes (dust etc.) are washed with water to elute chlorine and lead. Since chlorine bypass dust and the like have a high calcium content, elution with sulfuric acid produces a large amount of gypsum and suppresses elution of lead, so water elution is preferable to sulfuric acid elution. For washing, waste such as dust is put in a washing tank and stirred in water for a predetermined time. Most of the chlorine and lead contained in the waste are eluted in the liquid by washing with water. The calcium content does not elute and remains as a solid content. This water-washed suspension is separated by filtration to separate into a solid content and a liquid content. In addition, it is preferable to wash with water 3 times or more of dust. If the amount of washing water is less than this, the chlorine concentration in the water adhering to the cake increases, and the desalination rate decreases.
[0015]
[Alkali elution process]
An alkaline solution such as caustic soda is added to the solid content filtered off in the water washing step to adjust the pH to 12.5 or higher, and lead contained in the solid content is eluted. The addition amount of the alkaline solution may be an amount that makes the pH of the solution within the above range. The calcium content contained in the dust in the form of calcium chloride is converted to calcium hydroxide by alkali elution. On the other hand, the lead remaining in the solid content without being eluted in the water washing step is eluted in the liquid by this alkali elution. Since this lead content is dissolved in the liquid, the calcium hydroxide is recovered by filtration. This calcium hydroxide has a very low lead content and is suitable as a cement raw material. The caustic soda used in the alkali elution step preferably has a concentration of 1 mol / l or more in order to suppress the amount of liquid. The amount of dust is suitably 300 g or less per 1 liter of caustic soda. If the amount of dust is larger than this, the amount of lead elution will decrease.
[0016]
[Deleading process]
The filtrate filtered off in the water washing step and the filtrate filtered off in the alkali elution step are added, and a sulfurizing agent is added to convert the lead in the solution into lead sulfide for precipitation. As the sulfiding agent, sodium hydrosulfide (NaSH) or the like can be used. The lead sulfide precipitate is collected by filtration and the liquid is sent to the next step. When the solid-liquid separation is performed, the supernatant is separated through a thickener or the like, returned to the water washing step, and can be reused. The recovered lead sulfide can be used as a raw material for smelting. It is to be noted that the addition amount of the sulfiding agent is appropriate to be slightly smaller than the amount necessary for converting all the lead in the liquid to lead sulfide. If the sulfiding agent remains in the liquid, it is not preferable since the elution of lead is suppressed by the remaining sulfiding agent when the filtrate after separation of lead sulfide is circulated in the water washing step. On the other hand, even if lead is left in the liquid due to a shortage of the sulfurizing agent, there is no problem because lead is removed in a subsequent decalcification process or chelation process.
[0017]
As one of the preferable embodiments of the treatment method of the present invention, a part of the filtrate separated in the deleading step is returned to the water washing step and reused to increase the chlorine concentration and lead elution rate in the solution. In addition, it is generally known to increase the concentration of the eluted metal in the liquid by circulating and using the wash water in the water washing step (water elution). If it is circulated without treatment, the lead concentration in the washing water will be saturated at about several hundred ppm from the second to third washing, and the elution rate of lead will be drastically reduced. The lead elution rate can be maintained high by circulating the filtrate in which the lead concentration in the solution is reduced by deleading this. In addition, by recycling a part of the deleaded filtrate to the water washing step and reusing it, the amount of water in the entire treatment system can be reduced.
[0018]
[Decalcification process]
A carbonic acid source is added to the filtrate which is not circulated in the washing step to precipitate calcium in the liquid and separate it. As the carbonic acid source, carbonates such as sodium carbonate, or gas containing carbon dioxide such as kiln exhaust gas can be used. Most of the calcium contained in the waste is recovered as calcium hydroxide in the alkaline elution process, but what remains in the liquid reacts with carbonate ions to cause precipitation of calcium carbonate, which is separated by filtration. to recover. This calcium carbonate can be used as a raw material for cement. It should be noted that the carbonate may be added excessively, but when kiln exhaust gas or the like is blown in, the pH of the solution is controlled so as not to drop to 7 or less. When the solution becomes acidic, calcium carbonate and lead carbonate are redissolved, which is not preferable for removing them from the solution. In addition, you may pass through the process which guides a solution to a chelate tank after a decalcification process, and adsorb | sucks the lead which remains in a liquid to chelate, and removes.
[0019]
[Salt recovery process]
The filtrate separated by filtration in the decalcification step is heated to precipitate chloride, which is separated and recovered. By performing this salt recovery process in two stages, sodium chloride and potassium chloride can be separated and recovered. That is, the solution is heated to 50 ° C. or more to precipitate sodium chloride, which is separated by filtration and recovered (high temperature crystallization step). Further, the filtrate is cooled to 30 ° C. or lower to precipitate potassium chloride, which is collected by filtration (low-temperature crystallization step). The filtrate separated in the low-temperature crystallization process is returned to the high-temperature crystallization process, and crystallization is repeated. On the other hand, the evaporated water generated in the high-temperature crystallization process is introduced into the water washing process and used for water washing. The amount of waste water to be discharged can be greatly reduced, and preferably the water of the treatment system can be circulated and used without substantially draining it to the outside. Sodium chloride recovered from the crystallization process becomes a soda raw material, and potassium chloride can be used as a fertilizer.
[0020]
【Example】
[Example 1]
Chlorine bypass dust (CaO: 23%, SO 3 : 10%, Na 2 O: 2.0%, K 2 O: 25%, Cl: 20%, Pb: 3.3%) 1 kg, 4 kg of water with a liquid temperature of 30 ° C In addition, after stirring and washing for 0.5 hour, this suspension was subjected to solid-liquid separation to recover the solid content. To this solid content of 0.6 kg (dry weight), 6 liters of caustic soda (concentration of 2 mol / l) was added to adjust the pH to 13.5, and after forming a precipitate, solid-liquid separation was performed to obtain 0.3 kg of calcium hydroxide (dry weight). ) Was recovered. Further, this filtrate and the filtrate filtered in the water washing step were mixed, and 6 g of sodium hydrosulfide was added to 9 liters of this solution to form a precipitate, followed by solid-liquid separation to recover 26 g of lead sulfide.
Next, a part of this filtrate (pH 12) is returned to the water washing step and used as washing water, while 55 g of sodium carbonate is added to the remaining 2 liters of filtrate to form a precipitate, followed by solid-liquid separation and 50 g of calcium carbonate. Was recovered. Further, this filtrate was heated to 70 ° C. under vacuum to evaporate the liquid, and 4 g of precipitated sodium chloride was recovered. Further, the filtrate was cooled to 25 ° C., and 65 g of precipitated potassium chloride was recovered. Moreover, the vapor | steam generate | occur | produced by the evaporation precipitation of sodium chloride condensed, returned to the first water washing process, and was used repeatedly.
[0021]
[Example 2]
A filtrate obtained by filtering lead sulfide into 1 kg of chlorine bypass dust (CaO: 23%, SO 3 : 10%, Na 2 O: 2.0%, K 2 O: 25%, Cl: 20%, Pb: 3.3%) ( 5 liters of Ca: 2%, Cl: 6%) was added and the mixture was stirred and washed for 0.5 hour, and then this suspension was subjected to solid-liquid separation to recover a solid content. To this solid content of 0.4 kg (dry weight), 1.5 liters of caustic soda (2 mol / l concentration) was added to adjust the pH to 13.5, precipitate was formed, solid-liquid separation was performed, and calcium hydroxide 0.3 kg ( (Dry weight) was recovered. Further, this filtrate and the filtrate filtered in the water washing step were mixed, and 6 g of sodium hydrosulfide was added to 9 liters of this solution to form a precipitate, followed by solid-liquid separation to recover 26 g of lead sulfide.
Next, a part of this filtrate (pH 12) is returned to the washing step and used as washing water, while 170 g of sodium carbonate is added to the remaining 2 liters of filtrate to form a precipitate, and solid-liquid separation is performed to obtain 155 g of calcium carbonate. Was recovered. Furthermore, this filtrate was heated to 60 ° C. under vacuum to evaporate the liquid, and 6 g of precipitated sodium chloride was recovered. Further, this filtrate was cooled to 25 ° C., and 75 g of precipitated potassium chloride was recovered. Moreover, the vapor | steam generate | occur | produced by the evaporation precipitation of sodium chloride condensed, returned to the first water washing process, and was used repeatedly.
[0022]
【The invention's effect】
According to the treatment method of the present invention, since the lead contained in the waste is eluted by the water washing step and the alkali elution, most of the lead is eluted and precipitated as lead sulfide. Can be separated and removed, and calcium hydroxide with a low lead content can be recovered. Moreover, the elution rate of lead can be increased by returning the deleaded solution to the water washing step and reusing it. Furthermore, the filtrate separated in the low-temperature crystallization process is returned to the high-temperature crystallization process, and crystallization is repeated. It can be circulated and used without draining to the outside. Further, sodium chloride and potassium chloride recovered from the crystallization step can be reused as a product.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a processing method of the present invention.
Claims (6)
廃棄物の水洗工程の後に、濾別した固形分にアルカリ溶液を加えて鉛分を溶出させると共にカルシウムを水酸化物に転じて濾別するアルカリ溶出工程を有し、水洗工程で分離した濾液とアルカリ溶出工程で分離した濾液を混合し、これに硫化剤を添加して鉛を沈澱分離する脱鉛工程の後に、脱鉛工程で分離した濾液の一部を水洗工程に戻して再使用する廃棄物の処理方法。 The waste is washed with water to elute chlorine and lead and is separated into solid and liquid (water washing), and the filtrate is added with a sulfiding agent to precipitate and separate lead (deleading). Part of the filtrate separated in the lead process is returned to the water washing process and reused to increase the chlorine concentration and lead elution rate in the liquid, while adding a carbon dioxide source to the filtrate that does not circulate in the water washing process to precipitate calcium. A waste treatment method further comprising a step (decalcification step) of heating the filtrate to separate and recover the chloride by precipitation (salt recovery step) ,
After the waste water washing step, an alkali solution is added to the filtered solid content to elute the lead content, and the alkali separated step is performed by converting calcium into a hydroxide and filtering, and the filtrate separated in the water washing step After mixing the filtrate separated in the alkali elution process, adding a sulfiding agent to the lead and precipitating and separating the lead, a part of the filtrate separated in the delead process is returned to the water washing process and reused. How to handle things.
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| WO1998056464A1 (en) * | 1997-06-11 | 1998-12-17 | B Et C Services, S.A.R.L. | Method for treating residues resulting from the purification of garbage and/or industrial waste incineration fumes |
| JPH11100243A (en) * | 1997-07-14 | 1999-04-13 | Taiheiyo Cement Corp | Conversion treatment of waste into cement raw material |
| JPH11209121A (en) * | 1998-01-26 | 1999-08-03 | Hitachi Ltd | Concentrating and crystallizing device of mineral component |
| JP2000034142A (en) * | 1998-07-17 | 2000-02-02 | Tsukishima Kikai Co Ltd | Treatment of cement dust and apparatus therefor |
| JP2000119761A (en) * | 1998-10-16 | 2000-04-25 | Unitika Ltd | Recycling method of fly ash |
| JP2001017939A (en) * | 1999-07-07 | 2001-01-23 | Sumitomo Osaka Cement Co Ltd | Treatment of cement kiln waste gas dust |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9499420B2 (en) | 2012-11-06 | 2016-11-22 | Thatcher Company, Inc. | Formulations and methods for removing heavy metals from waste solutions containing chelating agents |
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| JP2003001218A (en) | 2003-01-07 |
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