JP7356860B2 - Method for suppressing hexavalent selenium elution from cement kiln bleed dust - Google Patents
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- 239000000428 dust Substances 0.000 title claims description 67
- 229910052711 selenium Inorganic materials 0.000 title claims description 60
- 239000011669 selenium Substances 0.000 title claims description 60
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 title claims description 57
- 239000004568 cement Substances 0.000 title claims description 47
- 238000000034 method Methods 0.000 title claims description 36
- 238000010828 elution Methods 0.000 title claims description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 53
- 238000005406 washing Methods 0.000 claims description 42
- 239000002253 acid Substances 0.000 claims description 34
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 26
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 7
- 229910017604 nitric acid Inorganic materials 0.000 claims description 7
- 239000007788 liquid Substances 0.000 claims description 2
- 239000007787 solid Substances 0.000 claims 1
- 230000000694 effects Effects 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 8
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 7
- 239000000460 chlorine Substances 0.000 description 7
- 229910052801 chlorine Inorganic materials 0.000 description 7
- 239000002351 wastewater Substances 0.000 description 7
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 6
- 239000003513 alkali Substances 0.000 description 6
- 229910052717 sulfur Inorganic materials 0.000 description 6
- 239000011593 sulfur Substances 0.000 description 6
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 5
- 235000011941 Tilia x europaea Nutrition 0.000 description 5
- 239000012153 distilled water Substances 0.000 description 5
- 239000004571 lime Substances 0.000 description 5
- -1 rare earth compound Chemical class 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- 150000007513 acids Chemical class 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 3
- 229910001385 heavy metal Inorganic materials 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 238000012790 confirmation Methods 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 150000007522 mineralic acids Chemical class 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- LIKWJCOGLYRYIU-UHFFFAOYSA-N [Se](O)(O)(=O)=O.[Se] Chemical compound [Se](O)(O)(=O)=O.[Se] LIKWJCOGLYRYIU-UHFFFAOYSA-N 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 238000005273 aeration Methods 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 159000000009 barium salts Chemical class 0.000 description 1
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 1
- 239000004327 boric acid Substances 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 239000000292 calcium oxide Substances 0.000 description 1
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
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- 230000001419 dependent effect Effects 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000010842 industrial wastewater Substances 0.000 description 1
- 239000003456 ion exchange resin Substances 0.000 description 1
- 229920003303 ion-exchange polymer Polymers 0.000 description 1
- 150000002506 iron compounds Chemical class 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 230000033116 oxidation-reduction process Effects 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000011002 quantification Methods 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 229940065287 selenium compound Drugs 0.000 description 1
- 150000003343 selenium compounds Chemical class 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000007655 standard test method Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
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Description
本発明は、セメントキルン抽気ダストからの六価セレン溶出抑制方法に関する。 The present invention relates to a method for suppressing hexavalent selenium elution from cement kiln bleed dust.
セメントクリンカー原料中の塩素、アルカリ、硫黄の量が多くなると、これらがセメントキルン内の比較的温度の低い部分で凝縮してコーティングを形成するため、製造上のトラブルの原因となる。これを避けるために、セメントキルンの窯尻部分から排ガスの一部を抽気して、セメントキルン内を循環する塩素、アルカリ、硫黄の量を低減することが行われる。抽気においては、塩素、アルカリ、硫黄の含有量が多い抽気ダストが必然的に同伴するため、これを減容するために水洗処理が行われている。 When the amount of chlorine, alkali, and sulfur in cement clinker raw materials increases, they condense and form a coating in the relatively low-temperature parts of the cement kiln, causing manufacturing problems. In order to avoid this, a portion of the exhaust gas is extracted from the bottom of the cement kiln to reduce the amount of chlorine, alkali, and sulfur circulating within the cement kiln. During extraction, extraction dust containing a large amount of chlorine, alkali, and sulfur is inevitably accompanied, so washing with water is performed to reduce the volume of this dust.
しかし、このような抽気ダストには、有害物質、特にセレンが含まれており、水洗処理の排水に溶出したセレンを除去する必要がある。通常は、凝集沈殿法や酸化還元法などの一般的な重金属処理法が適用されているが、六価セレン（セレン酸）は反応性が低く処理が難しい。そのため、排水に溶出した六価セレン量が変動すると、処理後の排水中のセレン濃度も変動することになる。したがって、処理後の排水中のセレン濃度を安定して一定の濃度以下とするためには薬剤の所要量を増加させる必要があり、処理コストが増大するという問題を抱えている。 However, such bleed dust contains harmful substances, particularly selenium, and it is necessary to remove the selenium eluted into the waste water from the washing process. Normally, common heavy metal treatment methods such as coagulation-precipitation method and redox method are applied, but hexavalent selenium (selenic acid) has low reactivity and is difficult to treat. Therefore, if the amount of hexavalent selenium eluted into wastewater changes, the selenium concentration in the treated wastewater will also change. Therefore, in order to stably keep the selenium concentration in the treated wastewater below a certain level, it is necessary to increase the amount of chemicals required, resulting in the problem of increased treatment costs.
抽気ダストの水洗処理において、セレンを安定に処理する技術としては、水洗処理時に所定の酸化還元電位になるよう鉄化合物を添加する方法が知られている（特許文献１）。また、処理水をイオン交換樹脂に供給してセレンを回収除去する方法（特許文献２）、希土類化合物を含む吸着剤と接触させる方法（特許文献３）、硫化物とバリウム塩を添加してセレンを不溶化する方法（特許文献４）、水洗処理の排水に曝気処理を行う方法（特許文献５）が知られている。その他、水洗前の処理技術として、特許文献６には抽気ダストを予めマイクロ波等で加熱して、セレンを不溶化する方法が開示されている。 As a technique for stably treating selenium in water washing of bleed dust, a method is known in which an iron compound is added so that a predetermined oxidation-reduction potential is achieved during the water washing (Patent Document 1). In addition, a method of supplying treated water to an ion exchange resin to collect and remove selenium (Patent Document 2), a method of contacting it with an adsorbent containing a rare earth compound (Patent Document 3), and a method of adding sulfide and barium salt to selenium A method of insolubilizing the water (Patent Document 4) and a method of performing aeration treatment on wastewater from washing treatment (Patent Document 5) are known. In addition, as a treatment technique before washing with water, Patent Document 6 discloses a method in which bleed dust is heated in advance using microwaves or the like to insolubilize selenium.
しかしながら、これらの技術はほとんどが水洗処理で発生した排水の処理技術であり、抽気ダストの水洗処理時の六価セレンの溶出を低減するものではない。したがって、抽気ダストのロットによって六価セレンの溶出量が予期せず変動すると、処理コストが増加するという問題を解決できない。さらに、特許文献６の方法では、水洗処理前のセレンを不溶化できたとしても、加熱処理設備を新設する必要があり、安価な処理に繋がるものではない。
このように、特殊な設備を設けることなく、抽気ダストの水洗処理における六価セレン溶出量を低減し、それによって排水中のセレン濃度の変動を抑制する方法は、これまでに見出されていなかった。
However, most of these techniques are techniques for treating wastewater generated during washing, and do not reduce the elution of hexavalent selenium during washing of extracted air dust. Therefore, if the amount of hexavalent selenium eluted varies unexpectedly depending on the lot of bleed dust, the problem of increased processing costs cannot be solved. Furthermore, in the method of Patent Document 6, even if selenium before water washing can be insolubilized, it is necessary to newly install heat treatment equipment, and this does not lead to an inexpensive treatment.
In this way, no method has been found to date to reduce the amount of hexavalent selenium eluted during the washing process of extracted air dust without installing special equipment, thereby suppressing fluctuations in the selenium concentration in wastewater. Ta.
そこで、本発明の課題は、セメントキルン抽気ダストの水洗処理における六価セレンの溶出を効率的に抑制する方法を提供することにある。 Therefore, an object of the present invention is to provide a method for efficiently suppressing the elution of hexavalent selenium during water washing of cement kiln bleed dust.
本発明者らは、上記の課題を解決すべく鋭意検討した結果、セメントキルン抽気ダストの水洗処理で溶出する六価セレンの量は、抽気ダスト自身のセレン含有量やキルンの運転条件にあまり依存せず、水洗処理開始時の液相環境に強く影響を受けることを見出した。そして、予め酸を添加した洗浄水を用いて抽気ダストの水洗処理を行うことにより、六価セレン溶出量を低減できることを見出し、本発明を成すに至った。 As a result of intensive studies to solve the above problems, the present inventors found that the amount of hexavalent selenium eluted during water washing of cement kiln bleed dust is not very dependent on the selenium content of the bleed dust itself and the kiln operating conditions. It was found that the liquid phase environment at the start of the water washing treatment is strongly affected. The inventors have also discovered that the amount of hexavalent selenium eluted can be reduced by washing the bleed dust with washing water to which acid has been added in advance, and have accomplished the present invention.
すなわち、本発明は、予め酸を添加した洗浄水を用いてセメントキルン抽気ダストの水洗処理を行う、セメントキルン抽気ダストからの六価セレン溶出抑制方法である。 That is, the present invention is a method for suppressing the elution of hexavalent selenium from cement kiln bleed dust, in which the cement kiln bleed dust is washed with washing water to which acid has been added in advance.
前記の酸の添加量は、抽気ダスト１００ｇに対して、一価の酸換算で０．１ｍｏｌ以上０．８ｍｏｌ未満であることが好ましい。 The amount of the acid added is preferably 0.1 mol or more and less than 0.8 mol in terms of monovalent acid per 100 g of extracted air dust.
前記セメントキルン抽気ダストと洗浄水の比率は、水／セメントキルン抽気ダストの質量比で１以上１００未満であることが好ましい。 The ratio of the cement kiln bleed air dust to the cleaning water is preferably 1 or more and less than 100 in terms of water/cement kiln bleed dust mass ratio.
前記の酸は、塩酸または硝酸であることが好ましい。 Preferably, the acid is hydrochloric acid or nitric acid.
本発明の六価セレン溶出抑制方法によれば、セメントキルン抽気ダストに手を加えず、水洗処理に用いる洗浄水に予め酸を添加するという簡便な操作のみで、水洗処理における六価セレン溶出量を効果的に低減できる。これにより、セメントキルン抽気ダストの水洗処理におけるコストの削減に繋げることができる。 According to the method for suppressing hexavalent selenium elution of the present invention, the amount of hexavalent selenium eluted in the washing process can be reduced by simply adding an acid in advance to the washing water used for the washing process without touching the cement kiln bleed dust. can be effectively reduced. This can lead to cost reduction in the water washing process for cement kiln bleed dust.
本発明の好適な実施形態を以下に説明する。なお、本発明は以下の実施形態に限定されるものではない。
本発明のセメントキルン抽気ダストからの六価セレン溶出抑制方法は、予め酸を添加した洗浄水を用いてセメントキルン抽気ダストの水洗処理を行うことを特徴とする。
Preferred embodiments of the invention will be described below. Note that the present invention is not limited to the following embodiments.
The method of suppressing the elution of hexavalent selenium from cement kiln bleed dust according to the present invention is characterized in that the cement kiln bleed dust is washed with washing water to which acid has been added in advance.
セメントキルン抽気ダストとは、セメントキルンで発生する排ガスの一部を窯尻部分から抽気して、セメントキルン内を循環する塩素、アルカリ、硫黄の量を低減する工程で、抽気した排ガスを冷却する際に発生する、抽気ガスに同伴してセメントキルン内から取り出されたダスト（粉状物）のことである。 Cement kiln bleed dust is a process in which a portion of the exhaust gas generated in a cement kiln is extracted from the bottom of the kiln to reduce the amount of chlorine, alkali, and sulfur circulating in the cement kiln, and the extracted exhaust gas is cooled. This refers to the dust (powder) that is taken out from inside the cement kiln along with the bleed gas that is generated during this process.
セメントキルンから抽気した排ガス中には、塩素、アルカリ、硫黄のほかに、セレン、鉛等の重金属類もガス状になって含まれ、また、遊離石灰の含有量が高い仮焼原料が微粒子として含まれる。そのため、セメントキルン抽気ダスト中には、揮発成分である塩素、アルカリ、硫黄、重金属類と、仮焼原料由来の遊離石灰やその他成分が共存する。 In addition to chlorine, alkali, and sulfur, the exhaust gas extracted from the cement kiln also contains heavy metals such as selenium and lead in gaseous form, and calcined raw materials with a high content of free lime are contained in the form of fine particles. included. Therefore, volatile components such as chlorine, alkali, sulfur, and heavy metals coexist in cement kiln extracted air dust, as well as free lime derived from calcined raw materials and other components.
セメントキルン抽気ダストの水洗処理とは、セメントキルン内から取り出された抽気ダストと洗浄水とを一定量で混合してスラリーとし、抽気ダスト中の塩素を含むアルカリ金属塩等が充分に溶出する時間ほど攪拌した後に、不溶の抽気ダスト分と洗浄水とを分離する処理である。例えば、セメントキルン抽気ダストの水洗処理設備や、水槽と攪拌設備からなる施設で行うことができる。 Washing of cement kiln bleed dust is a process in which the bleed dust taken out from inside the cement kiln is mixed with a certain amount of washing water to form a slurry, and the time is sufficient for the chlorine-containing alkali metal salts, etc. in the bleed dust to be eluted. After stirring for some time, the insoluble bleed dust and wash water are separated. For example, it can be carried out in a water washing treatment facility for cement kiln bleed dust, or in a facility consisting of a water tank and stirring equipment.
本発明では、セメントキルン抽気ダストを水洗処理する際に、予め酸を添加した洗浄水と抽気ダストとを接触させることが肝要であり、これにより、洗浄水への六価セレンの溶出量を効果的に低減でき、水洗処理における六価セレン溶出量を低減することができる。本発明における酸とは、水中で解離しやすい塩酸、硫酸、硝酸、リン酸、ホウ酸、フッ化水素酸等の無機酸のことであり、これらのうちの１種または混合物が使用できる。なお、抽気ダストと洗浄水を混合した後で酸を添加しても、十分な六価セレンの溶出抑制効果は得られないため好ましくない。 In the present invention, when washing the cement kiln extracted air dust with water, it is important to bring the extracted air dust into contact with the washing water to which acid has been added in advance, thereby effectively controlling the amount of hexavalent selenium eluted into the washing water. It is possible to reduce the amount of hexavalent selenium eluted during water washing. The acid in the present invention refers to inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, and hydrofluoric acid that are easily dissociated in water, and one or a mixture of these can be used. Note that even if an acid is added after mixing the bleed dust and the cleaning water, it is not preferable because a sufficient effect of suppressing elution of hexavalent selenium cannot be obtained.
洗浄水に予め酸を添加することで、六価セレンの溶出を抑制できる理由は明らかではないが、本発明者は以下のように推測している。
（１）抽気ダストに存在する可溶性のセレンとして、ＳｅＯ２（四価）、ＳｅＯ３（六価）、ＳｅＣｌ４（四価）、Ｎａ２ＳｅＯ３（四価）、Ｎａ２ＳｅＯ４（六価）、Ｋ２ＳｅＯ３（四価）、Ｋ２ＳｅＯ４（六価）、ＣａＳｅＯ３（四価）、ＣａＳｅＯ４（六価）が考えられ、これらは水と接触すると速やかに溶解して電離する。
（２）本発明者は、この際、抽気ダストに共存する遊離石灰の影響を受けて、六価セレンの溶出率が増加することを見出している。これは、上記セレン化合物が電離した際、遊離石灰の影響によりセレンイオン近傍のｐＨが高い状態となり、瞬時に六価セレンが安定となるためと推察した。
（３）ここで、洗浄水に事前に酸を添加しておくと、上記の状態が生じ難くなることで、六価セレンの溶出抑制効果が得られると推察される。つまり、ｐＨの低い洗浄水と抽気ダストとを接触させることが重要であり、時間を経過した後で酸を添加しても顕著な効果は得られない。
Although the reason why the elution of hexavalent selenium can be suppressed by adding acid to the washing water in advance is not clear, the present inventor speculates as follows.
(1) Soluble selenium present in the bleed dust includes SeO 2 (tetravalent), SeO 3 (hexavalent), SeCl 4 (tetravalent), Na 2 SeO 3 (tetravalent), and Na 2 SeO 4 (hexavalent). ), K 2 SeO 3 (tetravalent), K 2 SeO 4 (hexavalent), CaSeO 3 (tetravalent), and CaSeO 4 (hexavalent), which quickly dissolve and ionize when they come into contact with water. .
(2) The present inventor has discovered that the elution rate of hexavalent selenium increases under the influence of free lime coexisting in the bleed dust. This is presumed to be because when the selenium compound is ionized, the pH near the selenium ions becomes high due to the influence of free lime, and hexavalent selenium instantly becomes stable.
(3) Here, it is presumed that if an acid is added to the washing water in advance, the above-mentioned condition becomes less likely to occur, and thus an effect of suppressing the elution of hexavalent selenium can be obtained. In other words, it is important to bring the cleaning water with a low pH into contact with the bleed dust, and adding acid after a certain period of time will not produce any significant effect.
本発明のセメントキルン抽気ダストからの六価セレン溶出抑制方法は、さらに、前記の酸の添加量が、抽気ダスト１００ｇに対して、一価の酸換算で０．１ｍｏｌ以上０．８ｍｏｌ未満であることを特徴とする。これにより、少ない酸添加量で効率的に六価セレンの溶出抑制効果を得ることができる。０．８ｍｏｌ以上になると、六価セレンの溶出抑制効果は頭打ちとなり、費用対効果の面で好ましくない。好ましい酸の添加量は０．１ｍｏｌ以上０．５ｍｏｌであり、更に好ましくは０．１５ｍｏｌ以上０．４ｍｏｌ未満である。
なお、洗浄水のｐＨは２未満が好ましく、これを維持するため、セメントキルン抽気ダストと洗浄水の比率は、水／セメントキルン抽気ダストの質量比で１以上１００未満が好ましい。より好ましい水／セメントキルン抽気ダストの質量比は２以上５０未満であり、更に好ましくは５以上２０未満である。
In the method for suppressing hexavalent selenium elution from cement kiln bleed dust of the present invention, the amount of the acid added is 0.1 mol or more and less than 0.8 mol in terms of monovalent acid per 100 g of bleed dust. It is characterized by Thereby, the effect of suppressing elution of hexavalent selenium can be efficiently obtained with a small amount of acid added. If it exceeds 0.8 mol, the effect of suppressing the elution of hexavalent selenium reaches a ceiling, which is not preferable in terms of cost effectiveness. The amount of acid added is preferably 0.1 mol or more and 0.5 mol, more preferably 0.15 mol or more and less than 0.4 mol.
Note that the pH of the washing water is preferably less than 2, and in order to maintain this pH, the ratio of cement kiln bleed air dust to washing water is preferably 1 or more and less than 100 in mass ratio of water/cement kiln bleed air dust. The mass ratio of water/cement kiln bleed air dust is more preferably 2 or more and less than 50, and even more preferably 5 or more and less than 20.
本発明のセメントキルン抽気ダストからの六価セレン溶出抑制方法は、さらに、前記の酸が、塩酸または硝酸であることを特徴とする。これにより、少ない添加量で極めて優れた六価セレン溶出抑制効果を有することができる。
これらの酸は、酸解離定数（常用対数ｐＫａ）が塩酸で－３．７、硝酸で－１．８と負の値であり、無機酸の中でも強い酸であるため、前述した通り、洗浄水と接触した直後のセレンイオン近傍のｐＨを効率的に下げる作用があると考えられる。
The method for suppressing hexavalent selenium elution from cement kiln bleed dust of the present invention is further characterized in that the acid is hydrochloric acid or nitric acid. Thereby, it is possible to have an extremely excellent hexavalent selenium elution suppressing effect with a small amount added.
These acids have negative acid dissociation constants (common logarithm pKa) of -3.7 for hydrochloric acid and -1.8 for nitric acid, and are strong acids among inorganic acids. This is thought to have the effect of efficiently lowering the pH in the vicinity of selenium ions immediately after contact with selenium ions.
本発明において、セメントキルン抽気ダストの水洗処理方法は特に制限されず、セメントキルン抽気ダストと洗浄水とを混合し、その後、固液分離すればよい。水洗処理の条件としては、例えば、５～５０℃で１～１２０分間撹拌する方法が挙げられるが、撹拌は必須ではなく、静置してもよい。 In the present invention, the method for washing the cement kiln extracted air dust with water is not particularly limited, and it is sufficient to mix the cement kiln extracted air dust and washing water, and then perform solid-liquid separation. Conditions for the water washing treatment include, for example, a method of stirring at 5 to 50°C for 1 to 120 minutes, but stirring is not essential and it may be allowed to stand still.
以下に、本発明について実施例及び比較例を挙げて詳細に説明する。なお、本発明はこれらによって限定されるものではない。 EXAMPLES The present invention will be described in detail below with reference to Examples and Comparative Examples. Note that the present invention is not limited to these.
〔１．抽気ダストの採取〕
セメントキルン設備から抽気ダストを採取した。採取したのはロータリーキルン入口フッド部近傍から排ガスを抽気した際に同伴したセメントキルン抽気ダストである。採取した抽気ダストについて、セレン含有量をＪＩＳ Ｒ ５２０２「セメントの化学分析方法」に準拠して測定した結果、１１９ｍｇ／ｋｇであった。また、遊離石灰量をセメント協会標準試験方法のＪＣＡＳ Ｉ－０１：１９９７「遊離酸化カルシウムの定量方法」に準拠して測定した結果、３２．８質量％であった。
[1. Collection of bleed air dust]
Bleed dust was collected from cement kiln equipment. What was collected was cement kiln bleed dust that was entrained when exhaust gas was extracted from the vicinity of the rotary kiln inlet hood. The selenium content of the collected bleed dust was measured in accordance with JIS R 5202 "Cement chemical analysis method" and was found to be 119 mg/kg. In addition, the amount of free lime was measured in accordance with JCAS I-01:1997 "Method for quantification of free calcium oxide" of the Cement Association Standard Test Methods, and it was found to be 32.8% by mass.
〔２．六価セレン溶出量の測定〕
（比較例１：酸無添加）
上記の抽気ダスト１４０ｇと蒸留水１４００ｇを２Ｌビーカーで３０分混合し、５Ｃろ紙でろ過したろ液をＪＩＳ Ｋ ０１０２「工場排水試験方法」に準拠して測定した。この際、四価セレンは共沈法により回収して定量し、全セレン量から四価セレン量を減ずることで六価セレン溶出量を算出した。
[2. Measurement of hexavalent selenium elution amount]
(Comparative Example 1: No acid added)
140 g of the above bleed dust and 1400 g of distilled water were mixed in a 2 L beaker for 30 minutes, and the filtrate was filtered through 5C filter paper and measured in accordance with JIS K 0102 "Industrial Wastewater Test Method". At this time, tetravalent selenium was recovered and quantified by a coprecipitation method, and the amount of hexavalent selenium eluted was calculated by subtracting the amount of tetravalent selenium from the total amount of selenium.
（実施例１及び２：塩酸の添加効果の確認）
予め塩酸を添加した蒸留水１４００ｇを調製し、比較例１と同様の方法で抽気ダスト１４０ｇと混合及びろ過を行い六価セレン溶出量を測定した。塩酸の添加量は、抽気ダスト１００ｇあたり０．１８ｍｏｌ（実施例１）または０．３６ｍｏｌ（実施例２）とした。
(Examples 1 and 2: Confirmation of the effect of adding hydrochloric acid)
1400 g of distilled water to which hydrochloric acid had been added in advance was prepared, mixed with 140 g of bleed dust and filtered in the same manner as in Comparative Example 1, and the amount of hexavalent selenium eluted was measured. The amount of hydrochloric acid added was 0.18 mol (Example 1) or 0.36 mol (Example 2) per 100 g of extracted air dust.
（実施例３及び４：酸の種類の影響確認）
塩酸に代えて予め硫酸（実施例３）または硝酸（実施例４）を添加した蒸留水１４００ｇを調製し、比較例１と同様の方法で抽気ダスト１４０ｇと混合及びろ過を行い六価セレン溶出量を測定した。酸の添加量は、抽気ダスト１００ｇあたり、一価の酸換算で０．３６ｍｏｌとした。
(Examples 3 and 4: Confirmation of influence of acid type)
Prepare 1400 g of distilled water to which sulfuric acid (Example 3) or nitric acid (Example 4) has been added in advance instead of hydrochloric acid, and mix and filter with 140 g of bleed dust in the same manner as in Comparative Example 1 to determine the amount of hexavalent selenium eluted. was measured. The amount of acid added was 0.36 mol in terms of monovalent acid per 100 g of extracted dust.
（比較例２：酸を後添加した場合の効果）
抽気ダスト１４０ｇと蒸留水１４００ｇを２Ｌビーカーで３０分混合する際、混合開始から２０分後に塩酸を添加した以外は比較例１と同様の方法で六価セレン溶出量を測定した。塩酸の添加量は、抽気ダスト１００ｇあたり０．３６ｍｏｌとした。
(Comparative Example 2: Effect of post-adding acid)
When 140 g of bleed dust and 1400 g of distilled water were mixed in a 2 L beaker for 30 minutes, the amount of hexavalent selenium eluted was measured in the same manner as in Comparative Example 1, except that hydrochloric acid was added 20 minutes after the start of mixing. The amount of hydrochloric acid added was 0.36 mol per 100 g of extracted dust.
上記比較例及び実施例の六価セレン溶出量を表１に示す。表より、予め蒸留水に各種の酸を添加することで、六価セレン溶出量を顕著に低減できることがわかる。酸の種類に着目すると、実施例２～４の比較から、塩酸及び硝酸の添加効果が大きいといえる。また、実施例１と２の比較からわかるように、酸の添加量を２倍にしても六価セレン低減率は２倍にならず、費用対効果を考慮して添加量を定める必要があるといえる。さらに、比較例２は、実施例２と同じ塩酸添加量であっても、六価セレンの溶出抑制効果は非常に小さく、洗浄水に予め酸を添加しておくことが重要であると理解できる。 Table 1 shows the amounts of hexavalent selenium eluted in the Comparative Examples and Examples. The table shows that the amount of hexavalent selenium eluted can be significantly reduced by adding various acids to distilled water in advance. Focusing on the type of acid, from a comparison of Examples 2 to 4, it can be said that the effect of adding hydrochloric acid and nitric acid is large. Furthermore, as can be seen from the comparison between Examples 1 and 2, even if the amount of acid added is doubled, the hexavalent selenium reduction rate does not double, and it is necessary to determine the amount added in consideration of cost effectiveness. It can be said. Furthermore, in Comparative Example 2, even if the amount of hydrochloric acid added is the same as in Example 2, the effect of suppressing the elution of hexavalent selenium is very small, and it can be understood that it is important to add acid to the washing water in advance. .
以上のとおり、本発明の六価セレン溶出抑制方法によれば、セメントキルン抽気ダストに手を加えず、水洗処理に用いる洗浄水に予め酸を添加するという簡便な操作のみで、水洗処理における六価セレンの溶出を効果的に抑制できる。これにより、セメントキルン抽気ダストの水洗処理におけるコストの削減に繋げることができる。
As described above, according to the method for suppressing the elution of hexavalent selenium of the present invention, the hexavalent selenium elution control method of the present invention does not require any modification to the cement kiln bleed air dust, and only requires the simple operation of adding acid in advance to the wash water used for the water washing process. The elution of valent selenium can be effectively suppressed. This can lead to cost reduction in the water washing process for cement kiln bleed dust.
Claims (3)
セメントキルン抽気ダスト１００ｇに対して、一価の酸換算で０．１ｍｏｌ以上０．８ｍｏｌ未満の添加量となるよう予め酸を添加した洗浄水を用いてセメントキルン抽気ダストの水洗処理を行う、セメントキルン抽気ダストからの六価セレン溶出抑制方法。 In the water washing process of cement kiln extracted air dust, which mixes cement kiln extracted air dust and washing water in a certain amount and then separates it into solid and liquid,
Cement kiln bleed air dust is washed with water using washing water to which acid has been added in advance so that the amount added is 0.1 mol or more and less than 0.8 mol in terms of monovalent acid per 100 g of cement kiln bleed air dust. Method for suppressing hexavalent selenium elution from kiln bleed air dust.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2003236504A (en) | 2002-02-19 | 2003-08-26 | Taiheiyo Cement Corp | Treatment method of waste containing selenium and chlorine component |
| JP2009255070A (en) | 2008-03-28 | 2009-11-05 | Ube Ind Ltd | Method of treating dust |
| JP2010075849A (en) | 2008-09-26 | 2010-04-08 | Denka Consult & Eng Co Ltd | Treatment method for chlorine-containing fine powder waste |
| JP2012187537A (en) | 2011-03-11 | 2012-10-04 | Ube Industries Ltd | Dust treatment device |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2003236504A (en) | 2002-02-19 | 2003-08-26 | Taiheiyo Cement Corp | Treatment method of waste containing selenium and chlorine component |
| JP2009255070A (en) | 2008-03-28 | 2009-11-05 | Ube Ind Ltd | Method of treating dust |
| JP2010075849A (en) | 2008-09-26 | 2010-04-08 | Denka Consult & Eng Co Ltd | Treatment method for chlorine-containing fine powder waste |
| JP2012187537A (en) | 2011-03-11 | 2012-10-04 | Ube Industries Ltd | Dust treatment device |
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