JP3591587B2 - Processing method of fly ash containing dioxin - Google Patents
Processing method of fly ash containing dioxin Download PDFInfo
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- JP3591587B2 JP3591587B2 JP2001086083A JP2001086083A JP3591587B2 JP 3591587 B2 JP3591587 B2 JP 3591587B2 JP 2001086083 A JP2001086083 A JP 2001086083A JP 2001086083 A JP2001086083 A JP 2001086083A JP 3591587 B2 JP3591587 B2 JP 3591587B2
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- Prior art keywords
- dioxin
- weight
- fly ash
- decomposition catalyst
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- HGUFODBRKLSHSI-UHFFFAOYSA-N 2,3,7,8-tetrachloro-dibenzo-p-dioxin Chemical compound O1C2=CC(Cl)=C(Cl)C=C2OC2=C1C=C(Cl)C(Cl)=C2 HGUFODBRKLSHSI-UHFFFAOYSA-N 0.000 title claims description 192
- 239000010881 fly ash Substances 0.000 title claims description 72
- 238000003672 processing method Methods 0.000 title 1
- 239000003054 catalyst Substances 0.000 claims description 111
- 238000000354 decomposition reaction Methods 0.000 claims description 110
- 239000007789 gas Substances 0.000 claims description 82
- 239000000843 powder Substances 0.000 claims description 66
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 52
- 150000002506 iron compounds Chemical class 0.000 claims description 52
- 238000000034 method Methods 0.000 claims description 45
- 239000002253 acid Substances 0.000 claims description 39
- -1 amine compound Chemical class 0.000 claims description 38
- 239000000428 dust Substances 0.000 claims description 38
- 239000002245 particle Substances 0.000 claims description 36
- 230000000694 effects Effects 0.000 claims description 34
- 239000003795 chemical substances by application Substances 0.000 claims description 32
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 28
- MVPPADPHJFYWMZ-UHFFFAOYSA-N chlorobenzene Chemical compound ClC1=CC=CC=C1 MVPPADPHJFYWMZ-UHFFFAOYSA-N 0.000 claims description 28
- 238000010438 heat treatment Methods 0.000 claims description 28
- 230000003472 neutralizing effect Effects 0.000 claims description 28
- 238000002485 combustion reaction Methods 0.000 claims description 22
- 239000002131 composite material Substances 0.000 claims description 15
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 14
- 239000012298 atmosphere Substances 0.000 claims description 14
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 14
- 229910052760 oxygen Inorganic materials 0.000 claims description 14
- 239000001301 oxygen Substances 0.000 claims description 14
- 229910052698 phosphorus Inorganic materials 0.000 claims description 14
- 239000011574 phosphorus Substances 0.000 claims description 14
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 13
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 13
- 239000011734 sodium Substances 0.000 claims description 13
- 229910052708 sodium Inorganic materials 0.000 claims description 13
- 229910052717 sulfur Inorganic materials 0.000 claims description 13
- 239000011593 sulfur Substances 0.000 claims description 13
- 239000011261 inert gas Substances 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 239000002912 waste gas Substances 0.000 claims 3
- AEIXRCIKZIZYPM-UHFFFAOYSA-M hydroxy(oxo)iron Chemical compound [O][Fe]O AEIXRCIKZIZYPM-UHFFFAOYSA-M 0.000 description 12
- 229910052598 goethite Inorganic materials 0.000 description 11
- 150000002896 organic halogen compounds Chemical class 0.000 description 10
- 239000002243 precursor Substances 0.000 description 10
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 9
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- 150000002013 dioxins Chemical class 0.000 description 8
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- 239000002956 ash Substances 0.000 description 5
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- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 4
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- 239000011019 hematite Substances 0.000 description 4
- LIKBJVNGSGBSGK-UHFFFAOYSA-N iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Fe+3].[Fe+3] LIKBJVNGSGBSGK-UHFFFAOYSA-N 0.000 description 4
- MPDDTAJMJCESGV-CTUHWIOQSA-M (3r,5r)-7-[2-(4-fluorophenyl)-5-[methyl-[(1r)-1-phenylethyl]carbamoyl]-4-propan-2-ylpyrazol-3-yl]-3,5-dihydroxyheptanoate Chemical compound C1([C@@H](C)N(C)C(=O)C2=NN(C(CC[C@@H](O)C[C@@H](O)CC([O-])=O)=C2C(C)C)C=2C=CC(F)=CC=2)=CC=CC=C1 MPDDTAJMJCESGV-CTUHWIOQSA-M 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- 230000002378 acidificating effect Effects 0.000 description 3
- 239000003513 alkali Substances 0.000 description 3
- 150000001412 amines Chemical class 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 238000004817 gas chromatography Methods 0.000 description 3
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 3
- 230000008569 process Effects 0.000 description 3
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- HZAXFHJVJLSVMW-UHFFFAOYSA-N 2-Aminoethan-1-ol Chemical compound NCCO HZAXFHJVJLSVMW-UHFFFAOYSA-N 0.000 description 2
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- PAYRUJLWNCNPSJ-UHFFFAOYSA-N Aniline Chemical compound NC1=CC=CC=C1 PAYRUJLWNCNPSJ-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
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- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 2
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 150000001491 aromatic compounds Chemical class 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
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- TXCDCPKCNAJMEE-UHFFFAOYSA-N dibenzofuran Chemical compound C1=CC=C2C3=CC=CC=C3OC2=C1 TXCDCPKCNAJMEE-UHFFFAOYSA-N 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
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- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000010813 municipal solid waste Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- ACVYVLVWPXVTIT-UHFFFAOYSA-N phosphinic acid Chemical compound O[PH2]=O ACVYVLVWPXVTIT-UHFFFAOYSA-N 0.000 description 2
- 239000012716 precipitator Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
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- 239000004576 sand Substances 0.000 description 2
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- 239000011949 solid catalyst Substances 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- ISIJQEHRDSCQIU-UHFFFAOYSA-N tert-butyl 2,7-diazaspiro[4.5]decane-7-carboxylate Chemical compound C1N(C(=O)OC(C)(C)C)CCCC11CNCC1 ISIJQEHRDSCQIU-UHFFFAOYSA-N 0.000 description 2
- 239000004408 titanium dioxide Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 238000004056 waste incineration Methods 0.000 description 2
- VILCJCGEZXAXTO-UHFFFAOYSA-N 2,2,2-tetramine Chemical compound NCCNCCNCCN VILCJCGEZXAXTO-UHFFFAOYSA-N 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- RPNUMPOLZDHAAY-UHFFFAOYSA-N Diethylenetriamine Chemical compound NCCNCCN RPNUMPOLZDHAAY-UHFFFAOYSA-N 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
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- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
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- 229910001854 alkali hydroxide Inorganic materials 0.000 description 1
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- 229910052782 aluminium Inorganic materials 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
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- 125000004432 carbon atom Chemical group C* 0.000 description 1
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- 125000001309 chloro group Chemical group Cl* 0.000 description 1
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- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Catalysts (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、ごみ焼却炉等の各種焼却炉から排出される飛灰中に含まれるダイオキシンを効率的に分解する処理方法を提供するものである。
【０００２】
【従来の技術】
都市ごみや産業廃棄物を焼却するごみ焼却炉から発生する排ガスや飛灰、主灰中には、微量ではあるが人体に対して極めて強い毒性を持つ芳香族ハロゲン化合物であるダイオキシンが含まれている。ダイオキシンは、ジベンゾ−ｐ−ジオキシン、ジベンゾフランなどの水素を塩素で置換した化合物の総称をいう。
【０００３】
このダイオキシンは、難分解性である上に発癌性物質であるために、大気中への排出、あるいは地下水、土壌などの汚染による環境問題は深刻になっている。特に、ごみ焼却炉から排出される飛灰はダイオキシンの含有量が高いため、その分解・無害化が必要とされている。しかし、ダイオキシンの除去方法については、様々な提案がなされているが、経済的で、効率的な分解、無害化技術は未だ十分に確立されていない。
【０００４】
従来、このようなダイオキシン含有飛灰の分解、無害化についての技術としては、様々な報告がされている。例えば、酸化鉄等の触媒の存在下２００〜５５０℃で加熱することにより少なくとも炭素原子５個以上を有するポリハロゲン化芳香族化合物を分解する方法（特公平６−３８８６３号公報）、１００℃以上３００℃未満の条件下でガス状のアミン化合物と接触させてダイオキシン又はダイオキシン含有物質を分解する方法（特開平１０−２７２４４０号公報）、処理灰類と脱塩素剤とを混合して加熱処理する方法（特開平１１−１９６１６公報）、酸化鉄等及び／又は二酸化チタンをベースとする固体触媒を用いて酸素存在下で有機ハロゲン化合物を分解させる方法（特開平１１−１８８２３５号公報、特開平１１−１８８２３６号公報）、固体状廃棄物に亜リン酸類及び／又は次亜リン酸類とアルミニウム化合物及び／又はチタン化合物とを添加して加熱処理する方法（特開平１１−２９０８２４号公報）等が知られている。
【０００５】
また、特定の触媒活性を有する鉄化合物触媒及び該鉄化合物触媒を焼却炉の燃焼室に噴霧添加して、ダイオキシン発生を抑制する方法（特開平１１−２６７５０７号公報）が知られている。
【０００６】
【発明が解決しようとする課題】
現在、ごみ焼却炉から排出される飛灰に含まれるダイオキシンを分解・無害化する処理方法は現在最も要求されているところであるが、前出各公報記載の方法は未だ十分なものとは言い難いものである。
【０００７】
前出特公平６−３８８６３号公報記載の方法は、焼却炉で発生したフライアッシュ、または、固体中のポリハロゲン化化合物を非通り抜け系、閉鎖系の装置で、酸素欠乏雰囲気、または、不活性ガス雰囲気においてフライアッシュや金属、酸化鉄を含む金属酸化物、炭酸塩、ケイ酸塩等を触媒として用いて、ポリハロゲン化シクロアルキル化合物、ポリハロゲン化芳香族化合物を分解するものであるが、処理する雰囲気を閉鎖系、または、不活性ガス雰囲気に特定していることから、装置の大型化、高気密化、高額化と設備維持コストが高く工業的に満足できるものとは言い難い。
【０００８】
特開平１０−２７２４４０号公報に記載の方法は、ダイオキシン又はダイオキシン含有物質と、ガス状のアミン化合物とを１００℃以上３００℃未満の条件下で接触させて、ダイオキシンの塩素イオンとアミン化合物中のアミノ基（窒素原子）とが反応することにより、ダイオキシンを分解するものであるが、ダイオキシンの分解率が悪く、ダイオキシンを十分に分解できるとは言い難いものである。
【０００９】
前出特開平１１−１９６１６号公報に記載の方法は、焼却灰、飛灰などとアルカリ物質からなる脱塩剤とを混合した後、加熱処理するものであるが、被処理物を加熱して発生した塩素系ガスとアルカリ物質とを接触させる必要があることから、塩素系ガスを発生させるために被処理物を高温で加熱する必要があり、有機ハロゲン化合物を直接、分解・無害化するものではなく、ダイオキシンの無害化については十分とは言い難いものである。
【００１０】
前出特開平１１−１８８２３５号公報及び特開平１１−１８８２３６号公報に記載の方法は、酸化鉄等及び／又は二酸化チタンをベースとする固体触媒を用いて、ガス中の有機ハロゲン化合物を酸素存在下で分解させる方法であって、ガス中の有機ハロゲン化合物を対象としており、固体中に含有している有機ハロゲン化合物を分解するためには、十分とは言い難いものである。
【００１１】
前出特開平１１−２９０８２４号公報に記載の方法は、亜リン酸類及び次亜リン酸類を含有する処理剤を用いるものであるが、ダイオキシンの分解率が悪く、ダイオキシンを十分に分解できるとは言い難いものである。
【００１２】
さらに、前出特公平６−３８８６３号公報、特開平１１−１９６１６公報及び特開平１１−２９０８２４号公報の記載の方法では、効率的なダイオキシンの分解を行うためには、触媒や処理剤とダイオキンシン類を含む飛灰と均一に混合する必要があり、そのためには専用の混合装置を付加しなければならず、装置の大型化、高気密化、高額化と設備維持コストが高くなる。
【００１３】
また、前出特開平１１−２６７５０７号公報に記載している触媒を用いて、飛灰中に含有するダイオキシンの含有量を低減することはできるが、未だ十分とは言い難いものである。
【００１４】
そこで、本発明は、ごみ焼却炉等の各種焼却炉から排出される飛灰中に含まれるダイオキシンを、経済的に、効率よく分解除去することができ、かつ、酸素存在下でも実施可能なダイオキシンの分解方法を提供することを技術的課題とする。
【００１５】
【課題を解決するための手段】
前記技術的課題は以下の通りの本発明により達成できる。
【００１６】
即ち、本発明は、リン含有量が０．０２重量％以下であって、硫黄含有量が０．３重量％以下であって、ナトリウム含有量が０．３重量％以下である平均粒径が０．０１〜２．０μｍの鉄化合物粉末とアミン化合物との複合触媒であり、該鉄化合物粉末を空気中にて３００℃で、６０分間熱処理して得られた酸化鉄粉末と上記アミン化合物との複合物５０ｍｇをパルス式触媒反応装置を用いて不活性ガス雰囲気中にて５．０×１０−７ｍｏｌのモノクロロベンゼンと３００℃の温度においてＳＶ＝１５００００ｈ−１の条件で瞬時に接触させた場合に、上記モノクロロベンゼンの５０％以上を分解できる活性を有するダイオキシン分解触媒を用いるダイオキシンを含有する飛灰の処理方法において、ごみ焼却炉の燃焼室以降から集じん器までの排ガス中に、単位時間当りに燃焼させる乾燥ごみに対して、前記ダイオキシン分解触媒０．０２〜０．５重量％を添加した後、集じん器にて捕集された飛灰を、酸素含有気体流通下で１５０〜４５０℃にて加熱処理することを特徴とするダイオキシンを含有する飛灰の処理方法である。
【００１７】
また、本発明は、リン含有量が０．０２重量％以下であって、硫黄含有量が０．３重量％以下であって、ナトリウム含有量が０．３重量％以下である平均粒径が０．０１〜２．０μｍの鉄化合物粉末とアミン化合物との複合触媒であり、該鉄化合物粉末を空気中にて３００℃で、６０分間熱処理して得られた酸化鉄粉末と上記アミン化合物との複合物５０ｍｇをパルス式触媒反応装置を用いて不活性ガス雰囲気中にて５．０×１０−７ｍｏｌのモノクロロベンゼンと３００℃の温度においてＳＶ＝１５００００ｈ−１の条件で瞬時に接触させた場合に、上記モノクロロベンゼンの５０％以上を分解できる活性を有するダイオキシン分解触媒を用いるダイオキシンを含有する飛灰の処理方法において、ごみ焼却炉の燃焼室以降から集じん器までの排ガス中に、前記ダイオキシン分解触媒と酸性ガス中和剤とを、単位時間当りに燃焼させる乾燥ごみに対してダイオキシン分解触媒と酸性ガス中和剤の合計量で０．２５〜２．５重量％を添加した後、集じん器にて捕集された飛灰を、酸素含有気体流通下で１５０〜４５０℃にて加熱処理することを特徴とするダイオキシンを含有する飛灰の処理方法である。
【００１８】
また、本発明は、リン含有量が０．０２重量％以下であって、硫黄含有量が０．３重量％以下であって、ナトリウム含有量が０．３重量％以下である平均粒径が０．０１〜２．０μｍの鉄化合物粉末とアミン化合物との複合触媒であり、該鉄化合物粉末を空気中にて３００℃で、６０分間熱処理して得られた酸化鉄粉末と上記アミン化合物との複合物５０ｍｇをパルス式触媒反応装置を用いて不活性ガス雰囲気中にて５．０×１０−７ｍｏｌのモノクロロベンゼンと３００℃の温度においてＳＶ＝１５００００ｈ−１の条件で瞬時に接触させた場合に、上記モノクロロベンゼンの５０％以上を分解できる活性を有するダイオキシン分解触媒を用いるダイオキシンを含有する飛灰の処理方法において、ごみ焼却炉の燃焼室以降から集じん器までの排ガス中に、前記ダイオキシン分解触媒、酸性ガス中和剤及び活性炭とを、単位時間当りに燃焼させる乾燥ごみに対してダイオキシン分解触媒、酸性ガス中和剤及び活性炭の合計量で０．３０〜３．０重量％を添加した後、集じん器にて捕集された飛灰を、酸素含有気体流通下で１５０〜４５０℃にて加熱処理することを特徴とするダイオキシンを含有する飛灰の処理方法である。
【００１９】
本発明の構成を詳しく説明すれば、次の通りである。
【００２０】
本発明におけるダイオキシン分解触媒は、鉄化合物粉末とアミン化合物の複合触媒である。
【００２１】
ダイオキシン分解触媒における鉄化合物粉末の平均粒径は、０．０１〜２．０μｍ、好ましくは、０．０２〜２．０μｍ、より好ましくは０．０２〜１．０μｍである。
【００２２】
鉄化合物粉末の平均粒径が２．０μｍを超える場合には、有機ハロゲン化合物との接触効率が低下して充分なダイオキシン分解活性を発現しない。０．０１μｍ未満の場合には、粒子間での凝集力が大きくなり凝集体の粉砕に大きなエネルギーを必要とするため実施が困難となる。また、工業的に量産が困難である。
【００２３】
本発明における鉄化合物粉末のＢＥＴ比表面積は、０．２〜２００ｍ２／ｇ、好ましくは１．０〜２００ｍ２／ｇ、より好ましくは２．０〜１５０ｍ２／ｇである。
【００２４】
本発明における鉄化合物粉末は、ゲータイト、アカゲナイト、レピドクロサイト等の含水酸化鉄粉末、ヘマタイト、マグヘマイト、マグネタイト等の酸化鉄粉末の１種又は２種以上からなる。好ましくはゲータイト、ヘマタイトである。
【００２５】
本発明における鉄化合物粉末の粒子形状は、球状、粒状、八面体状、六面体状、多面体状等の粒状粒子及び針状、紡錘状、米粒状等の針状粒子のいずれであってもよく、好ましくは紡錘状又は針状である。
【００２６】
本発明における鉄化合物粉末は、リン含有量が０．０２重量％以下、好ましくは０．０１重量％以下、より好ましくは０．００５重量％以下である。０．０２重量％を超える場合には、このリンが触媒毒として働くため、ダイオキシン及びダイオキシン前駆体の分解活性が低下する。
【００２７】
本発明における鉄化合物粉末は、硫黄含有量が０．３重量％以下、好ましくは０．１重量％以下、より好ましくは０．０７重量％以下である。０．３重量％を超える場合には、この硫黄が触媒毒として働くため、ダイオキシン及びダイオキシン前駆体の分解活性が低下する。
【００２８】
本発明における鉄化合物粉末は、ナトリウム含有量が０．３重量％以下、好ましくは０．２重量％以下、より好ましくは０．１５重量％以下である。０．３重量％を超える場合には、このナトリウムが触媒毒として働くため、ダイオキシン及びダイオキシン前駆体の分解活性が低下する。
【００２９】
本発明における鉄化合物粉末は、リン含有量、硫黄化合物含有量及びナトリウム含有量の合計含有量が０．５重量％以下が好ましく、より好ましくは０．３重量％以下、更により好ましくは０．２重量％以下である。０．５重量％を超える場合には、ダイオキシン及びダイオキシン前駆体の分解活性が低下する。
【００３０】
本発明における鉄化合物粉末は、空気中にて３００℃、６０分間熱処理して得られた酸化鉄粉末５０ｍｇを、パルス式触媒反応装置を用いて、５．０×１０−７ｍｏｌのモノクロロベンゼンと、３００℃の温度の不活性ガス雰囲気中にて、ＳＶ＝１５００００ｈ−１の条件で瞬時に接触させた場合に、該モノクロロベンゼンの２０％以上を分解できる活性を有する。
【００３１】
鉄化合物粉末によるモノクロロベンゼンの分解活性が２０％未満の場合には、本発明の効果が得られない。好ましくは、２５％以上、より好ましくは、３０％以上である。
【００３２】
ダイオキシン分解触媒におけるアミン化合物は、ジエチレントリアミン、トリエチレンテトラミン等のアルキルアミン、トリエタノールアミン、ジエタノールアミン等のアルカノールアミン、アニリン等の環式アミンなどの１種又は２種以上を用いることができる。
【００３３】
本発明におけるアミン化合物は、沸点が１５０℃以上のものが好ましい。アミン化合物の沸点が１５０℃未満であると、ダイオキシン及びダイオキシン前駆体との処理時に揮発しやすく、鉄化合物と複合化した効果が得られない。
【００３４】
本発明におけるダイオキシン分解触媒の粒子形状及び粒子径は、鉄化合物粉末の粒子形状及び粒子径とほぼ同程度である。
【００３５】
本発明におけるダイオキシン分解触媒のＢＥＴ比表面積値は、０．２〜２００ｍ２／ｇ、好ましくは１．０〜２００ｍ２／ｇ、より好ましくは、２．０〜１５０ｍ２／ｇである。
【００３６】
本発明におけるダイオキシン分解触媒における鉄化合物粉末とアミン化合物との混合割合は、鉄化合物粉末に対するアミン化合物の重量比が０．０１〜１０重量％が好ましく、より好ましくは０．０５〜５．０重量％である。０．０１重量％未満ではアミン化合物によるダイオキシン分解の促進効果が小さく、１０重量％を超える場合では鉄化合物粉末のダイオキシンの分解活性を低下させる。
【００３７】
本発明におけるダイオキシン分解触媒は、前記鉄化合物粉末を空気中にて３００℃、６０分間熱処理して得られた酸化鉄粉末と前記アミン化合物とを前記所定の割合で混合した複合物５０ｍｇを、パルス式触媒反応装置を用いて、５．０×１０−７ｍｏｌのモノクロロベンゼンと、３００℃の温度の不活性ガス雰囲気中にて、ＳＶ＝１５００００ｈ−１の条件で瞬時に接触させた場合に、該モノクロロベンゼンの５０％以上を分解できる活性を有する。好ましくは５５％以上のモノクロロベンゼンを分解する活性を有する。
【００３８】
本発明におけるダイオキシン分解触媒の上記測定法による分解活性が５０％未満の場合には、効果的にダイオキシンを分解することができない。
【００３９】
ここでモノクロロベンゼンは、有機ハロゲン化合物の代表的なものであり、またダイオキシンの前駆体と言われており、モノクロロベンゼンを分解する活性を有することは、ダイオキシンを分解する、あるいは生成を抑制する活性を有することの指標となる。尚、モノクロロベンゼンの分解率は下記数１で示した値である。
【００４０】
【数１】
モノクロロベンゼン分解率［％］＝［１−（反応後モノクロロベンゼン検出量／反応前モノクロロベンゼン注入量）］×１００
【００４１】
次に、本発明におけるダイオキシン分解触媒の製造法について述べる。
【００４２】
先ず、本発明における鉄化合物の製造方法について述べる。
【００４３】
本発明における鉄化合物のうち、ゲータイト粉末の製造法としては、例えば、第一鉄塩と、水酸化アルカリ、炭酸アルカリ又はアンモニアから選ばれる１種又は２種以上とを用いて反応して得られる鉄の水酸化物や炭酸鉄等の第一鉄含有沈殿物を含む懸濁液中に空気等の酸素含有ガスを通気してゲータイト粒子を生成させて得ることができる。
【００４４】
本発明における鉄化合物のうち、ヘマタイト粉末は、例えば、前記ゲータイト粉末を空気中２００〜８００℃の温度範囲で加熱脱水、加熱処理を行って得ることができ、マグネタイト粉末は、例えば、前記ヘマタイト粉末を還元性雰囲気下、３００〜６００℃で加熱還元して得られる。マグヘマイト粉末は、例えば、前記マグネタイト粉末を空気中２００〜６００℃で加熱酸化して得ることができる。
【００４５】
本発明における鉄化合物の製造にあたっては、触媒毒となるリン、硫黄及びナトリウムの含有量が所定量以下となるようにすることが必要である。具体的には、第一鉄塩溶液としては、触媒毒となるリン、硫黄等の含有量が少ないものが好ましい。また、通常、加熱焼成時の焼結防止処理に用いられるヘキサメタリン酸ナトリウムを使用せず、第一鉄原料に由来する硫酸イオンやアルカリに由来するナトリウムイオンについては充分な水洗等の精製処理を行うことによりリン、硫黄及びナトリウムの含有量の低減を図ることが好ましい。
【００４６】
鉄化合物粉末とアミン化合物の複合化処理は、鉄化合物粉末とアミン化合物とをサンドミル、ヘンシェルミキサー及びナウターミキサー等の混合機、ファインミル、ピンミル等の粉砕機を用いて乾式混合する。
【００４７】
前記乾式混合において、必要により、粒子の濡れ性を改善するために、アミン化合物に水又はアルコール（例えば、エタノール、イソプロピルアルコール）等の溶媒を加えてもよい。溶媒を用いた場合は加熱又は減圧下で溶媒を蒸発するのが望ましい。
【００４８】
サンドミルを用いた場合の混合条件は、線圧５〜５０ｋｇ／ｃｍで１５〜９０分混合することが好ましい。ヘンシェルミキサーを用いた場合には、１０〜１００℃の温度範囲で、回転数５００〜３０００ｒｐｍにて５〜３０分混合することが好ましい。ナウターミキサーを用いた場合には、自転回転数２５〜２００ｒｐｍ、公転回転数１〜５ｒｐｍで１５〜６０分混合することが好ましい。ファインミル、ピンミルを用いた場合には、鉄化合物粉末にアミン化合物を添加しながら回転数１，０００〜１０，０００ｒｐｍで粉砕混合することが好ましい。
【００４９】
本発明に係る有機ハロゲン化合物分解触媒は、上記複合化処理によって、鉄化合物粉末の粒子表面の一部にアミン化合物が担持された形態となることが好ましい。
【００５０】
次に、本発明に係るダイオキシン分解触媒を用いたダイオキシンを含有する飛灰の処理方法ついて述べる。
【００５１】
本発明における焼却炉の対象は、機械化バッチ炉、准連続炉等の間欠運転型及び連続運転型のごみ焼却施設である。
【００５２】
本発明に係る飛灰の処理方法は、気流搬送式で焼却炉の燃焼室以降から集じん器までの排ガス中にダイオキシン分解触媒を噴霧添加した後、集じん器にて捕集された飛灰を酸素含有気体流通下で加熱処理する。焼却炉の燃焼室以降から集じん器までの排ガスの温度範囲は１５０〜５００℃であることが好ましい。
【００５３】
本発明においてはダイオキシン分解触媒を焼却炉の燃焼室以降から集じん器までの排ガス中に噴霧添加することによって、新たな処理工程を経ることなく、集じん器で捕集された飛灰中にダイオキシン分解触媒が均一に混合した状態とすることができる。ダイオキシン分解触媒を焼却炉の燃焼室に添加した場合、燃焼室内でのダイオキシンの発生は抑制できるが、燃焼室以降から集じん器までの冷却過程でのダイオキシン及びダイオキシン前駆体を十分に分解できず、また、飛灰の加熱処理でもダイオキシンを十分に分解することができない。一方、飛灰とダイオキシン分解触媒とを直接混合した場合には、飛灰とダイオキシン分解触媒を均一に混合させることが困難となり、飛灰中のダイオキシンを十分に低減できるものとは言い難いものである。
【００５４】
前記気流搬送方法としては空気輸送、窒素輸送等をすることができる。
【００５５】
前記気流搬送におけるダイオキシン分解触媒の形態は、粒子粉末、スラリーのいずれであってもよい。好ましくは粒子粉末である。
【００５６】
本発明におけるダイオキシン分解触媒の添加量は、集じん器で捕集された飛灰中に最適量のダイオキシン分解触媒を含有させることができればよく、単位時間当たりに燃焼させる乾燥ごみに対して０．０２〜０．５重量％、好ましくは０．０５〜０．５重量％、より好ましくは０．１〜０．５重量％を排ガス中に噴霧添加する。前記ダイオキシン分解触媒の添加量によって飛灰中には０．２〜２０重量％のダイオキシン分解触媒を含有させることができる。
【００５７】
添加量が０．０２重量％未満の場合には、ダイオキシン分解の本発明の効果が充分得られない。０．５重量％を越える場合には、効果が飽和するので必要以上に添加する意味がない。
【００５８】
本発明におけるダイオキシン分解触媒の添加には、酸性ガス中和剤を同時に添加するのが望ましい。酸性ガス中和剤は、燃焼室以降から集じん器までの冷却過程やその後の加熱処理において、ダイオキシン分解触媒によって分解されたダイオキシン及びダイオキシン前駆体の構成元素である塩素を固定化する作用があり、ダイオキシンの分解を促進することができる。
【００５９】
本発明における酸性ガス中和剤としては、一般的に乾式の酸性ガス除去用に使用されている粉末状ものでよく、消石灰、生石灰、炭酸カルシウム、酸化マグネシウム、炭酸マグネシウム及びドロマイト等のアルカリ土類金属化合物や炭酸リチウム、炭酸ナトリウム、炭酸水素ナトリウム及び炭酸水素カリウム等のアルカリ金属化合物であり、好ましくは、カルシウム化合物であり、より好ましくは消石灰である。尚、酸性ガス中和剤としては上記のうち一種又は二種以上を混合して用いてもよい。
【００６０】
本発明における酸性ガス中和剤は、平均粒径Ｄ５０（乾式粒度分布計による総体積の５０％の粒径）２０μｍ以下、より好ましくは１５μｍ以下、ＢＥＴ比表面積値０．５ｍ２／ｇ以上、より好ましくは１ｍ２／ｇ以上であることが好ましい。
【００６１】
ダイオキシン分解触媒と酸性ガス中和剤との添加割合は、ダイオキシン分解触媒／酸性ガス中和剤の重量比で２／１〜１／１００が好ましく、より好ましくは２／１〜１／２０である。ダイオキシン分解触媒／酸性ガス中和剤の重量比が前記範囲外では十分な酸性ガス中和剤の添加効果が得られない。
【００６２】
また、ダイオキシン分解触媒と酸性ガス中和剤の添加量は、乾燥ごみに対して分解触媒と酸性ガス中和剤の合計で０．２５〜２．５重量％が望ましい。より好ましくは０．３０〜２．０重量％である。０．２５重量％未満の場合には、十分な酸性ガス中和剤の添加効果が得られない。２．５重量％を越える場合には添加量が多量となって後段の集じん器に過負荷を与えたり、また、集じん器出口のばいじん量が増えてしまうため好ましくない。
【００６３】
ダイオキシン分解触媒と酸性ガス中和剤の添加は、それぞれ単独で添加してもよいが、ダイオキシン分解触媒と酸性ガス中和剤とをあらかじめ混合することで、ダイオキシン及びダイオキシン前駆体を更に効果的に分解することができる。
【００６４】
また、本発明におけるダイオキシン分解触媒の添加時に、酸性ガス中和剤ともに活性炭を添加することによって、ダイオキシンの排出を効果的に抑制することができる。活性炭には、ガス状のダイオキシンを吸着する作用があり、燃焼室以降から集じん器までの冷却過程に噴霧添加することによって、排ガス中のガス状ダイオキシンを効率的に飛灰中へ移行させることができるため、結果的に飛灰中だけでなく、排ガス中のダイオキシン含めたダイオキシン総排出量を可及的に減少させることになる。
【００６５】
本発明における活性炭は、一般的にダイオキシン除去用に使用されている粉末状ものでよく、平均粒径Ｄ５０（乾式粒度分布計による総体積の５０％の粒径）５０μｍ以下、より好ましくは、３０μｍ以下、ＢＥＴ比表面積値６００ｍ２／ｇ以上、より好ましくは８００ｍ２／ｇ以上である。
【００６６】
活性炭の平均粒径及びＢＥＴ比表面積値が上記範囲以外の場合には、燃焼室以降から集じん器までの移動が十分に行われず、また、ダイオキシンの吸着性能が劣るため、十分な活性炭の添加効果が得られない。
【００６７】
ダイオキシン分解触媒、酸性ガス中和剤及び活性炭の添加割合は、ダイオキシン分解触媒／酸性ガス中和剤の重量比で２／１〜１／１００であって、且つ、ダイオキシン分解触媒／活性炭の重量比で１０／１〜１／２５が好ましく、より好ましくはダイオキシン分解触媒／酸性ガス中和剤の重量比で２／１〜１／２０であって、且つ、ダイオキシン分解触媒／活性炭の重量比で１０／１〜１／５である。ダイオキシン分解触媒／酸性ガス中和剤の重量比が２／１〜１／１００の範囲外の場合及びダイオキシン分解触媒／活性炭の重量比が１０／１〜１／２５の範囲外の場合には、十分な酸性ガス中和剤及び活性炭の添加効果が得られない。
【００６８】
ダイオキシン分解触媒、酸性ガス中和剤及び活性炭の混合物の添加量は、乾燥ごみに対してダイオキシン分解触媒、酸性ガス中和剤及び活性炭の合計で０．３０〜３．０重量％が望ましい。より好ましくは０．３０〜２．５重量％である。０．３重量％未満の場合には、十分な酸性ガス中和剤の添加効果が得られず、また、活性炭によるダイオキシンの吸着効果が得られない。３．０重量％を越える場合には添加量が多量となって後段の集じん器に過負荷を与えたり、また、集じん器出口のばいじん量が増えてしまうため好ましくない。
【００６９】
ダイオキシン分解触媒、酸性ガス中和剤及び活性炭の添加は、それぞれ単独で添加してもよいが、ダイオキシン分解触媒、酸性ガス中和剤及び活性炭とを予め混合した混合物を添加することで効果的にダイオキシン総排出量を低減させることができる。
【００７０】
ダイオキシン分解触媒、酸性ガス中和剤及び活性炭を混合したダイオキシン分解複合触媒を添加する場合の乾燥ごみに対する複合触媒の添加量は、上記単独で添加するときの乾燥ごみに対する添加量と同様である。前記ダイオキシン分解触媒、酸性ガス中和剤及び活性炭の添加量によって飛灰中には０．２〜２０重量％のダイオキシン分解触媒を含有させることができる。
【００７１】
飛灰の加熱処理における処理装置は、特に限定されるものではなく、捕集された飛灰中にダイオキシン分解触媒が均一に混合した状態であるため、単に飛灰を加熱処理できる装置でもよい。より効率よくダイオキシンを分解するためには、連続式又はバッチ式のロータリーキルン、多段式炉やバッチ連続式のプッシャー炉等を用いることができるが、連続式又はバッチ式のロータリーキルン、多段式炉が好ましい。
【００７２】
飛灰の加熱処理は、空気やごみ焼却炉から排出される排ガス等の酸素含有気体の流通下で行う。
【００７３】
飛灰の加熱処理における処理温度は、反応時間に応じて変化させればよく、１５０〜４５０℃が好ましく、より好ましくは２００〜４００℃、更に好ましくは２００〜３８０℃である。１５０℃未満ではダイオキシン分解触媒の分解活性が低く、また、４５０℃を越える場合は、ダイオキシンの分解は可能であるが、加熱に要するエネルギーに見合ったダイオキシンの分解効果は得られない。また、飛灰の加熱時間は１〜６０分が好ましい。
【００７４】
本発明に係る飛灰の処理方法によって、ダイオキシン分解触媒を添加しない場合の集じん器にて捕集された飛灰に含まれるダイオキシン濃度に対して９０％以上、より好ましくは９５％以上のダイオキシンを削減することができる。
【００７５】
【発明の実施の形態】
本発明の代表的な実施の形態は以下の通りである。
【００７６】
本発明における鉄化合物粉末の平均粒径は電子顕微鏡写真から測定した数値の平均値で示した。また、比表面積はＢＥＴ法により測定した。
【００７７】
本発明における鉄化合物粉末に含有されるリン、ナトリウムの含有量は、誘導結合プラズマ原子発光分光光度計 ＳＰＳ‐４０００（セイコー電子工業（株）製〉で測定した値で示した。
【００７８】
本発明における鉄化合物粉末に含有される硫黄の含有量は、炭素−硫黄分析計ＥＭＩＡ−２２００型（（株）堀場製作所製）によって測定した値で示した。
【００７９】
鉄化合物粉末を空気中にて、３００℃で６０分間熱処理して得られる酸化鉄粒子粉末と該アミン化合物との複合物５０ｍｇをパルス式触媒反応装置を用いて不活性ガス雰囲気中にて５．０×１０−７ｍｏｌのモノクロロベンゼンと３００℃の温度においてＳＶ＝１５００００ｈ−１の条件で瞬時に接触させた場合に分解する該モノクロロベンゼン量を測定することでダイオキシン分解触媒の触媒特性を示した。
【００８０】
前記パルス式触媒反応装置としては、リアクター部とガスクロマトグラフィー質量分析計部からなり、ガスクロマトグラフィー質量分析計部は、ガスクロマトグラフィー質量分析計 ＧＣ／ＭＳＱＰ−５０５０（（株）島津製作所製）である。
【００８１】
なお、本評価法は、Ｋｏｂｅｓらの文献（Ｒ．Ｊ．Ｋｏｂｅｓ，ｅｔ ａｌ Ｊ．Ａｍ．Ｃｈｅｍ．Ｓｏｃ．，７７，５８６０（１９５５））や、日本化学会編「実験化学講座１１ 反応と速度」（丸善、東京（１９９３））を参考にして行った。
【００８２】
＜鉄化合物粉末＞
鉄化合物粉末として、ゲータイト粉末（平均粒径０．２５μｍ、リン含有量０．００２重量％、硫黄含有量０．０５重量％、ナトリウム含有量０．０８重量％、ＢＥＴ比表面積８５ｍ２／ｇ）を用いた。
【００８３】
前記ゲータイト粉末は、所定の評価法による３００℃におけるモノクロロベンゼンの分解率は３３％であった。
【００８４】
＜ダイオキシン分解触媒の製造＞
前記ゲータイト粉末１．５ｋｇとトリエタノールアミン７５ｇ（該ゲータイト粉末に対して５．０ｗｔ％）を一緒にヘンシェルミキサー（公称容量１０ｌ）中で５０℃にて乾式混合（１４４０ｒｐｍ、５ｍｉｎ）を行い、トリエタノールアミンを担持したゲータイト粉末を得た。
【００８５】
前記トリエタノールアミン担持ゲータイト粉末は、所定の評価法による３００℃におけるモノクロロベンゼンの分解率は８８％であった。
【００８６】
＜ダイオキシンの分解試験＞
本試験に用いた間欠運転型ごみ焼却施設の模式図を図１に示す。同図において、１はごみホッパ、２は焼却炉、３は燃焼室、４は助燃バーナ口、５はガス冷却室、６は空気予熱器、７はダイオキシン分解触媒等供給用ブロワ、８はダイオキシン分解触媒等供給タンク、９は電気集じん器、１０は誘引送風機、１１は煙突、１２は押込送風機、１３は煙道、１４〜１７はダイオキシン分解触媒等供給口である。
【００８７】
燃焼室３には焼却炉の炉床等から、ごみの完全燃焼に必要な理論空気量の１．５〜３．５倍程度の燃焼空気を供給する。該燃焼空気は、押込送風機１２によって空気を吸入し、空気予熱器６によって加温された空気を用いる。また燃焼室３には助燃バーナ口４が設けられている。ダイオキシン分解触媒、酸性ガス中和剤（消石灰等）及び活性炭は、供給口１４〜１７等から気流搬送で供給する。
【００８８】
上記の間欠運転型ごみ焼却施設（１日１６時間運転でごみ焼却能力が１日３０トン）において、乾燥ごみに対して０．２５重量％の前記ダイオキシン分解触媒を空気輸送により供給口１６（排ガス温度２６２℃）から焼却炉の立ち上げ時から定常運転時及び立ち下げ時までの１６時間噴霧添加した。また、乾燥ごみに対して０．５０重量％の宇部マテリアルズ（株）製ＪＩＳ特号消石灰粉末（平均粒径Ｄ５０５．７μｍ、ＢＥＴ比表面積１３．７ｍ２／ｇ）を空気輸送により供給口１７から同様に焼却炉の立ち上げ時から定常運転時及び立ち下げ時までの１６時間噴霧添加した（ダイオキシン分解触媒と消石灰との合計で、乾燥ごみに対して０．７５重量％となる）。
【００８９】
ダイオキシン含有量は、電気集じん器９の出口で採取した排ガスと電気集じん器下の飛灰について測定した。ダイオキシンの測定分析は、「廃棄物処理におけるダイオキシン類標準測定分析マニュアル」（平成９年２月 厚生省生活衛生局水道環境部環境整備係制定）に従って行った。
【００９０】
電気集じん器出口の排ガス中のダイオキシン濃度は１．１ｎｇＴＥＱ／Ｎｍ３であり、電気集じん器によって捕集した飛灰中のダイオキシン濃度は４．０ｎｇＴＥＱ／ｇであった。
【００９１】
電気集じん器によって捕集した飛灰４００ｇを内容量１１リットルのバッチ式ロータリーキルンに移し、３００℃、空気（３リットル／分）流通下で１０分間加熱処理を行った。
【００９２】
飛灰中のダイオキシン濃度は０．１８ｇ−ＴＥＱ／ｇであった。後述する消石灰のみを添加した場合のダイオキシン濃度（ＳＴＤ）に対する低減率は９９．１％であった。
【００９３】
なお、ブランク試験として、ダイオキシン抑制用鉄化合物触媒を添加せず、消石灰のみを添加した場合の焼却炉の運転を同様にして行い、その電気集じん器出口の排ガス中と飛灰中のダイオキシン濃度を測定した。
【００９４】
電気集じん器出口の排ガス中のダイオキシン濃度は１６ｎｇＴＥＱ／Ｎｍ３であり、電気集じん器で捕集した飛灰中のダイオキシン濃度（ＳＴＤ）は２０ｎｇＴＥＱ／ｇであった。
【００９５】
【作用】
本発明において重要な点は、本発明に係る飛灰の処理方法によって、飛灰中のダイオキシンを効果的に、しかも、経済的に分解できるという点である。
【００９６】
飛灰中のダイオキシンを効果的に分解できる理由として、本発明者は、ごみ焼却施設の燃焼室以降から集じん器までの排ガス中に高い触媒特性を有するダイオキシン分解触媒を添加することで、集じん器によって捕集されるまでの間に飛灰中のダイオキシンが効果的に分解されたこと、また、排ガス中にダイオキシン分解触媒を噴霧することによって特殊な混合装置を用いることなく飛灰中にダイオキシン分解触媒を均一混合させることができ、飛灰の加熱処理におけるダイオキシン分解触媒による効率的なダイオキシンの分解反応ができることによると考えている。
【００９７】
ダイオキシン分解触媒の触媒活性については、鉄化合物自体のダイオキシンの分解能が優れていること、鉄化合物の表面に担持されたアミン化合物によって有機ハロゲン化合物の吸着反応が促進されたこと及び鉄化合物とアミン化合物が接触していることによって、吸着された有機ハロゲン化合物の鉄化合物による分解反応が促進されているものと考えている。また、アミン化合物はダイオキシンを吸着するとともに、ダイオキシンの脱塩素反応も生じているものと考えている。
【００９８】
ダイオキシン分解触媒とともに酸性ガス中和剤を添加した場合に、よりダイオキシンの発生を抑制できる理由としては、酸性ガス中和剤がダイオキシン又はダイオキシン前駆体の構成元素である塩素を固定化するために、結果的にダイオキシンの発生を効率的に抑制することができるものと考えている。
【００９９】
また、活性炭を添加した場合には、活性炭が排ガス中のガス状のダイオキシンを効率的に吸着して飛灰に移行させ、その後の加熱処理で可及的に飛灰中のダイオキシンを減少できるため、結果的にダイオキシン総排出量を低減することができると考えている。
【０１００】
【実施例】
次に、本発明の実施例及び比較例を挙げる。
【０１０１】
鉄化合物粉末１〜５：
鉄化合物粉末として表１に示す鉄化合物１〜５を用意した。
【０１０２】
【表１】
複合触媒１〜７
鉄化合物粉末の種類及びアミン化合物の種類を種々変更した以外は、前記発明の実施の形態と同様にして複合触媒を得た。
【０１０４】
得られた複合触媒の諸特性を表２に示す。なお、シリカゲルとアミン化合物とを複合化させた場合には触媒特性が１０％と触媒活性が低いものであった。
【０１０５】
【表２】
＜ダイオキシンの分解試験＞
実施例１〜７、比較例１〜４
ダイオキシン分解触媒の種類、酸性ガス中和剤、活性炭、それぞれの添加量、添加場所、飛灰の加熱処理の温度、保持時間を種々変化させた以外は前記発明の実施の形態と同様にして飛灰中のダイオキシンの分解試験を行った。尚、酸性ガス中和剤としては、宇部マテリアルズ（株）製ＪＩＳ特号消石灰粉末（平均粒径Ｄ５０５．７μｍ、ＢＥＴ比表面積１３．７ｍ２／ｇ）を、活性炭としては、三菱化学（株）製ＰＸＳ（商品名）（平均粒径Ｄ５０１５μｍ、ＢＥＴ比表面積１０５０ｍ２／ｇ）を用いた。表３中の添加位置の欄に示したＡはダイオキシン分解触媒と酸性ガス中和剤とをあらかじめ混合して添加したことを示す。また、Ｂはダイオキシン分解触媒、酸性ガス中和剤及び活性炭をあらかじめ混合して添加することを示す。
【０１０７】
このときの諸条件を表３に、飛灰の加熱処理の結果を表４に示す。なお、ダイオキシン濃度の低減率は、消石灰のみを添加したブランク試験の飛灰中のダイオキシン濃度（ＳＴＤ）に対する値であり、数値が高いほどダイオキシンをよく分解していることを示す。なお、表３中の飛灰中のダイオキシン濃度はダイオキシン分解触媒などの添加剤を除いたばいじん重量に換算した値である。
【０１０８】
【表３】
【表４】
この結果から、本発明に係るダイオキシンを含有する飛灰の処理方法により、加熱処理前の飛灰中のダイオキシンを低減でき、更に、加熱処理を行うことによって効果的にダイオキシンを分解できることが認められた。
【０１１１】
【発明の効果】
本発明は、ごみ焼却炉の燃焼室以降から集じん器までの排ガス中に、特定の触媒特性を有するダイオキシン分解触媒を添加した後、集じん器にて捕集された飛灰を加熱処理することで、飛灰中のダイオキシンを経済的に、効率よく分解除去することができ、かつ、酸素存在下でもダイオキシンを分解させることができる。
【図面の簡単な説明】
【図１】本発明におけるごみ焼却施設の模式図である。
【符号の説明】
１：ごみホッパ
２：焼却炉
３：燃焼室
４：助燃バーナ口
５：ガス冷却室
６：空気予熱器
７：ダイオキシン分解触媒等供給用ブロワ
８：ダイオキシン分解触媒等供給タンク
９：集じん器
１０：誘引送風機
１１：煙突
１２：押込送風機
１３：煙道
１４〜１７：ダイオキシン分解触媒等添加供給口[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a treatment method for efficiently decomposing dioxin contained in fly ash discharged from various incinerators such as a refuse incinerator.
[0002]
[Prior art]
Exhaust gas, fly ash, and main ash generated from refuse incinerators that incinerate municipal waste and industrial waste contain dioxin, a small amount of aromatic halogen compounds that are extremely toxic to the human body. I have. Dioxin is a general term for compounds in which hydrogen is replaced with chlorine, such as dibenzo-p-dioxin and dibenzofuran.
[0003]
Since dioxin is hardly decomposable and is a carcinogen, environmental problems due to emission into the air or pollution of groundwater, soil, etc. have become serious. In particular, fly ash discharged from refuse incinerators is required to be decomposed and made harmless because of its high dioxin content. However, although various proposals have been made on dioxin removal methods, economical and efficient decomposition and detoxification techniques have not yet been sufficiently established.
[0004]
Conventionally, various reports have been made on techniques for decomposing and detoxifying such dioxin-containing fly ash. For example, a method of decomposing a polyhalogenated aromatic compound having at least 5 carbon atoms by heating at 200 to 550 ° C. in the presence of a catalyst such as iron oxide (Japanese Patent Publication No. 6-38863), 100 ° C. or higher A method of decomposing dioxin or a dioxin-containing substance by contacting it with a gaseous amine compound under a condition of less than 300 ° C. (Japanese Patent Laid-Open No. Hei 10-272440), mixing treated ash with a dechlorinating agent, and performing heat treatment. (JP-A-11-19616), a method of decomposing an organic halogen compound in the presence of oxygen using a solid catalyst based on iron oxide or the like and / or titanium dioxide (JP-A-11-188235, JP-A-11-188235) 188236), phosphorous acid and / or hypophosphorous acid and aluminum compound and / or titanium compound are added to solid waste. And a method of heat treatment is added (JP-A-11-290824) is known.
[0005]
Further, an iron compound catalyst having a specific catalytic activity and a method for suppressing the generation of dioxin by spray addition of the iron compound catalyst to a combustion chamber of an incinerator (Japanese Patent Application Laid-Open No. 11-267507) are known.
[0006]
[Problems to be solved by the invention]
At present, treatment methods for decomposing and detoxifying dioxins contained in fly ash discharged from refuse incinerators are the most required at present, but the methods described in the above publications are still not satisfactory. Things.
[0007]
The method described in Japanese Patent Publication No. Hei 6-38863 discloses a method in which a fly ash generated in an incinerator or a polyhalogenated compound in a solid is not passed through or closed, and an oxygen-deficient atmosphere or an inert gas is used. In a gas atmosphere, fly ash and metals, metal oxides containing iron oxide, carbonates, silicates, and the like are used as catalysts to decompose polyhalogenated cycloalkyl compounds and polyhalogenated aromatic compounds. Since the atmosphere to be treated is specified as a closed system or an inert gas atmosphere, it is difficult to say that the apparatus is large in size, high in airtightness, expensive and equipment maintenance cost is high, and is industrially satisfactory.
[0008]
The method described in JP-A-10-272440 discloses that a dioxin or a dioxin-containing substance is brought into contact with a gaseous amine compound under a condition of 100 ° C. or more and less than 300 ° C. to obtain chlorine ions of dioxin and the amine compound in the amine compound. Dioxin is decomposed by reacting with an amino group (nitrogen atom). However, the decomposition rate of dioxin is poor, and it cannot be said that dioxin can be sufficiently decomposed.
[0009]
The method described in Japanese Patent Application Laid-Open No. H11-19616 discloses a method in which incineration ash, fly ash, and the like are mixed with a desalinating agent composed of an alkaline substance, and then a heat treatment is performed. Since it is necessary to contact the generated chlorine-based gas with an alkali substance, it is necessary to heat the object to be treated at a high temperature in order to generate the chlorine-based gas, which directly decomposes and detoxifies the organic halogen compound. Rather, detoxification of dioxins is not enough.
[0010]
The methods described in JP-A-11-188235 and JP-A-11-188236 mentioned above use a solid catalyst based on iron oxide or the like and / or titanium dioxide to convert an organic halogen compound in a gas into a gas containing oxygen. It is a method of decomposing under a condition, and is intended for an organic halogen compound in a gas, and it is hardly sufficient to decompose an organic halogen compound contained in a solid.
[0011]
The method described in Japanese Patent Application Laid-Open No. H11-290824 uses a treating agent containing phosphorous acid and hypophosphorous acid. However, the decomposition rate of dioxin is low, and dioxin can be sufficiently decomposed. It is hard to say.
[0012]
Further, according to the methods described in Japanese Patent Publication No. 6-38863, JP-A-11-19616 and JP-A-11-290824, in order to efficiently decompose dioxin, a catalyst or a treating agent and It is necessary to uniformly mix with fly ash containing kinsins, and for that purpose, a dedicated mixing device must be added, which increases the size, airtightness, cost, and equipment maintenance cost of the device.
[0013]
Further, the content of dioxin contained in fly ash can be reduced by using the catalyst described in the above-mentioned Japanese Patent Application Laid-Open No. 11-267507, but it is still not enough.
[0014]
Thus, the present invention provides a dioxin that can be economically and efficiently decomposed and removed from fly ash discharged from various incinerators such as refuse incinerators, and can be implemented even in the presence of oxygen. It is an object of the present invention to provide a method for disassembling the above.
[0015]
[Means for Solving the Problems]
The technical problem can be achieved by the present invention as described below.
[0016]
That is, according to the present invention, the average particle diameter of the phosphorus content is 0.02% by weight or less, the sulfur content is 0.3% by weight or less, and the sodium content is 0.3% by weight or less. A composite catalyst of an iron compound powder and an amine compound having a particle size of 0.01 to 2.0 μm, and an iron oxide powder obtained by heat treating the iron compound powder in air at 300 ° C. for 60 minutes and the amine compound 50 mg of the compound of the formula was -7 SV = 150,000 h at mol temperature of monochlorobenzene and 300 ° C -1 In the method of treating fly ash containing dioxin using a dioxin decomposition catalyst having an activity capable of decomposing 50% or more of the above monochlorobenzene when contacted instantaneously under the conditions of After adding 0.02 to 0.5% by weight of the dioxin decomposition catalyst to the dry refuse to be burned per unit time in the exhaust gas to the collector, the fly ash collected by the dust collector is This is a method for treating fly ash containing dioxin, which comprises performing heat treatment at 150 to 450 ° C. in an oxygen-containing gas flow.
[0017]
In the present invention, the average particle diameter of the phosphorus content is 0.02% by weight or less, the sulfur content is 0.3% by weight or less, and the sodium content is 0.3% by weight or less. A composite catalyst of an iron compound powder and an amine compound having a particle size of 0.01 to 2.0 μm, and an iron oxide powder obtained by heat treating the iron compound powder in air at 300 ° C. for 60 minutes and the amine compound 50 mg of the compound of the formula was -7 SV = 150,000 h at mol temperature of monochlorobenzene and 300 ° C -1 In the method of treating fly ash containing dioxin using a dioxin decomposition catalyst having an activity capable of decomposing 50% or more of the above monochlorobenzene when contacted instantaneously under the conditions of The dioxin decomposing catalyst and the acid gas neutralizing agent are burned in the exhaust gas to the reactor in a unit amount of 0.25 to 2. A method for treating fly ash containing dioxin, comprising heating the fly ash collected by a dust collector at 150 to 450 ° C. under an oxygen-containing gas flow after adding 5% by weight. It is.
[0018]
In the present invention, the average particle diameter of the phosphorus content is 0.02% by weight or less, the sulfur content is 0.3% by weight or less, and the sodium content is 0.3% by weight or less. A composite catalyst of an iron compound powder and an amine compound having a particle size of 0.01 to 2.0 μm, and an iron oxide powder obtained by heat treating the iron compound powder in air at 300 ° C. for 60 minutes and the amine compound 50 mg of the compound of the formula was -7 SV = 150,000 h at mol temperature of monochlorobenzene and 300 ° C -1 In the method of treating fly ash containing dioxin using a dioxin decomposition catalyst having an activity capable of decomposing 50% or more of the above monochlorobenzene when contacted instantaneously under the conditions of The dioxin decomposition catalyst, the acid gas neutralizing agent and the activated carbon are mixed in the exhaust gas to the vessel with a total amount of the dioxin decomposition catalyst, the acid gas neutralizing agent and the activated carbon of 0 to dry refuse to be burned per unit time. After adding 30 to 3.0% by weight, fly ash collected by a dust collector is subjected to a heat treatment at 150 to 450 ° C. under a flow of an oxygen-containing gas. Ash treatment method.
[0019]
The configuration of the present invention will be described in detail as follows.
[0020]
The dioxin decomposition catalyst in the present invention is a composite catalyst of an iron compound powder and an amine compound.
[0021]
The average particle size of the iron compound powder in the dioxin decomposition catalyst is 0.01 to 2.0 μm, preferably 0.02 to 2.0 μm, more preferably 0.02 to 1.0 μm.
[0022]
When the average particle size of the iron compound powder exceeds 2.0 μm, the contact efficiency with the organic halogen compound is reduced, and sufficient dioxin decomposition activity is not exhibited. When the particle size is less than 0.01 μm, the cohesion between the particles becomes large and a large amount of energy is required for pulverizing the aggregates, so that it is difficult to carry out. In addition, mass production is difficult industrially.
[0023]
The BET specific surface area of the iron compound powder in the present invention is 0.2 to 200 m 2 / G, preferably 1.0 to 200 m 2 / G, more preferably 2.0 to 150 m 2 / G.
[0024]
The iron compound powder in the present invention comprises one or more iron oxide powders such as goethite, akagenite, lepidocrocite and the like, and iron oxide powders such as hematite, maghemite and magnetite. Goethite and hematite are preferred.
[0025]
The particle shape of the iron compound powder in the present invention may be any of spherical, granular, octahedral, hexahedral, polyhedral, and other granular particles and needles, spindles, and rice grains. Preferably it is spindle-shaped or needle-shaped.
[0026]
The iron compound powder in the present invention has a phosphorus content of 0.02% by weight or less, preferably 0.01% by weight or less, more preferably 0.005% by weight or less. When the content exceeds 0.02% by weight, the phosphorus acts as a catalyst poison, so that the decomposition activity of dioxin and dioxin precursor is reduced.
[0027]
The iron compound powder in the present invention has a sulfur content of 0.3% by weight or less, preferably 0.1% by weight or less, more preferably 0.07% by weight or less. If the content exceeds 0.3% by weight, the sulfur acts as a catalyst poison, so that the decomposition activity of dioxin and the dioxin precursor decreases.
[0028]
The iron compound powder in the present invention has a sodium content of 0.3% by weight or less, preferably 0.2% by weight or less, more preferably 0.15% by weight or less. If it exceeds 0.3% by weight, the sodium acts as a catalyst poison, so that the decomposition activity of dioxin and dioxin precursor is reduced.
[0029]
The iron compound powder in the present invention preferably has a total content of phosphorus content, sulfur compound content and sodium content of 0.5% by weight or less, more preferably 0.3% by weight or less, still more preferably 0.1% by weight or less. Not more than 2% by weight. If it exceeds 0.5% by weight, the decomposition activity of dioxin and dioxin precursor is reduced.
[0030]
The iron compound powder in the present invention was prepared by heat-treating 50 mg of iron oxide powder obtained by heat treatment at 300 ° C. for 60 minutes in the air using a pulse-type catalytic reactor to obtain 5.0 × 10 5 -7 mol of monochlorobenzene and an inert gas atmosphere at a temperature of 300 ° C., SV = 150,000 h -1 Has the activity of decomposing 20% or more of the monochlorobenzene when it is brought into contact instantaneously under the following conditions.
[0031]
When the activity of decomposing monochlorobenzene by the iron compound powder is less than 20%, the effect of the present invention cannot be obtained. Preferably, it is at least 25%, more preferably at least 30%.
[0032]
As the amine compound in the dioxin decomposition catalyst, one or more kinds of alkylamines such as diethylenetriamine and triethylenetetramine, alkanolamines such as triethanolamine and diethanolamine, and cyclic amines such as aniline can be used.
[0033]
The amine compound in the present invention preferably has a boiling point of 150 ° C. or higher. When the boiling point of the amine compound is less than 150 ° C., the amine compound is easily volatilized during the treatment with the dioxin and the dioxin precursor, and the effect of complexing with the iron compound cannot be obtained.
[0034]
The particle shape and particle size of the dioxin decomposition catalyst in the present invention are almost the same as the particle shape and particle size of the iron compound powder.
[0035]
The BET specific surface area of the dioxin decomposition catalyst in the present invention is 0.2 to 200 m 2 / G, preferably 1.0 to 200 m 2 / G, more preferably 2.0 to 150 m 2 / G.
[0036]
The mixing ratio of the iron compound powder and the amine compound in the dioxin decomposition catalyst in the present invention is preferably such that the weight ratio of the amine compound to the iron compound powder is 0.01 to 10% by weight, more preferably 0.05 to 5.0% by weight. %. If it is less than 0.01% by weight, the effect of promoting the decomposition of dioxin by the amine compound is small, and if it exceeds 10% by weight, the dioxin decomposition activity of the iron compound powder is reduced.
[0037]
The dioxin decomposition catalyst according to the present invention is obtained by subjecting the iron compound powder to heat treatment in air at 300 ° C. for 60 minutes and mixing the amine compound with the amine compound at a predetermined ratio of 50 mg. 5.0 × 10 -7 mol of monochlorobenzene and an inert gas atmosphere at a temperature of 300 ° C., SV = 150,000 h -1 Has the activity of decomposing 50% or more of the monochlorobenzene when contacted instantaneously under the following conditions. It preferably has an activity of decomposing 55% or more of monochlorobenzene.
[0038]
If the decomposition activity of the dioxin decomposition catalyst according to the present invention is less than 50%, dioxin cannot be decomposed effectively.
[0039]
Here, monochlorobenzene is a representative of organic halogen compounds, and is also referred to as a precursor of dioxin. Having an activity of decomposing monochlorobenzene means an activity of decomposing dioxin or suppressing the production thereof. Is an index of having The decomposition rate of monochlorobenzene is a value shown by the following equation (1).
[0040]
(Equation 1)
Monochlorobenzene decomposition rate [%] = [1- (monochlorobenzene detection amount after reaction / monochlorobenzene injection amount before reaction)] × 100
[0041]
Next, a method for producing the dioxin decomposition catalyst in the present invention will be described.
[0042]
First, a method for producing an iron compound according to the present invention will be described.
[0043]
Among the iron compounds in the present invention, the method for producing goethite powder is, for example, obtained by reacting with a ferrous salt and one or more selected from alkali hydroxide, alkali carbonate or ammonia. Goethite particles can be obtained by passing an oxygen-containing gas such as air through a suspension containing a ferrous precipitate such as iron hydroxide or iron carbonate.
[0044]
Among the iron compounds in the present invention, the hematite powder can be obtained, for example, by subjecting the goethite powder to heat dehydration and heat treatment in the temperature range of 200 to 800 ° C in the air, and the magnetite powder is, for example, the hematite powder. Is heated and reduced at 300 to 600 ° C. in a reducing atmosphere. The maghemite powder can be obtained, for example, by heating and oxidizing the magnetite powder in air at 200 to 600 ° C.
[0045]
In the production of the iron compound in the present invention, it is necessary that the contents of phosphorus, sulfur and sodium, which are poisons of the catalyst, be less than a predetermined amount. Specifically, the ferrous salt solution preferably has a low content of phosphorus, sulfur and the like, which are poisons of the catalyst. Further, normally, without using sodium hexametaphosphate used for sintering prevention treatment at the time of heating and sintering, purification treatment such as sufficient washing with water is performed for sulfate ions derived from ferrous raw materials and sodium ions derived from alkali. It is therefore preferable to reduce the contents of phosphorus, sulfur and sodium.
[0046]
In the compounding treatment of the iron compound powder and the amine compound, the iron compound powder and the amine compound are dry-mixed using a mixer such as a sand mill, a Henschel mixer or a Nauter mixer, or a pulverizer such as a fine mill or a pin mill.
[0047]
In the dry mixing, if necessary, a solvent such as water or an alcohol (for example, ethanol or isopropyl alcohol) may be added to the amine compound in order to improve the wettability of the particles. When a solvent is used, it is desirable to evaporate the solvent under heating or reduced pressure.
[0048]
As for the mixing conditions when a sand mill is used, it is preferable to mix at a linear pressure of 5 to 50 kg / cm for 15 to 90 minutes. When using a Henschel mixer, it is preferable to mix at a temperature of 10 to 100 ° C. and a rotation speed of 500 to 3000 rpm for 5 to 30 minutes. When a Nauter mixer is used, mixing is preferably performed at a rotation speed of 25 to 200 rpm and a revolution speed of 1 to 5 rpm for 15 to 60 minutes. When a fine mill or a pin mill is used, it is preferable to pulverize and mix at a rotation speed of 1,000 to 10,000 rpm while adding an amine compound to the iron compound powder.
[0049]
The organohalogen compound decomposition catalyst according to the present invention preferably has a form in which an amine compound is supported on a part of the particle surface of the iron compound powder by the complexing treatment.
[0050]
Next, a method of treating fly ash containing dioxin using the dioxin decomposition catalyst according to the present invention will be described.
[0051]
The objects of the incinerator in the present invention are intermittent operation type and continuous operation type incineration facilities such as mechanized batch furnaces and quasi-continuous furnaces.
[0052]
The method for treating fly ash according to the present invention is a method in which a dioxin decomposition catalyst is spray-added to exhaust gas from a combustion chamber of an incinerator to a dust collector by a pneumatic conveying method, and then the fly ash collected by the dust collector. Is heated under a flow of an oxygen-containing gas. The temperature range of the exhaust gas from the combustion chamber of the incinerator to the dust collector is preferably 150 to 500C.
[0053]
In the present invention, the dioxin decomposition catalyst is spray-added to the exhaust gas from the combustion chamber of the incinerator to the dust collector, so that the fly ash collected by the dust collector is added without passing through a new treatment step. The dioxin decomposition catalyst can be in a uniformly mixed state. When a dioxin decomposition catalyst is added to the combustion chamber of an incinerator, the generation of dioxin in the combustion chamber can be suppressed, but dioxin and the dioxin precursor cannot be sufficiently decomposed in the cooling process from the combustion chamber to the dust collector. Also, dioxin cannot be sufficiently decomposed by heat treatment of fly ash. On the other hand, when the fly ash and the dioxin decomposition catalyst are directly mixed, it becomes difficult to uniformly mix the fly ash and the dioxin decomposition catalyst, and it is difficult to say that the dioxin in the fly ash can be sufficiently reduced. is there.
[0054]
Pneumatic transport, nitrogen transport, and the like can be used as the airflow transport method.
[0055]
The form of the dioxin decomposition catalyst in the airflow conveyance may be any of particle powder and slurry. Preferably, it is a particle powder.
[0056]
The amount of the dioxin decomposition catalyst to be added in the present invention may be any amount as long as an optimum amount of the dioxin decomposition catalyst can be contained in fly ash collected by the dust collector. 02-0.5% by weight, preferably 0.05-0.5% by weight, more preferably 0.1-0.5% by weight is spray-added into the exhaust gas. Fly ash can contain 0.2 to 20% by weight of a dioxin decomposition catalyst depending on the amount of the dioxin decomposition catalyst added.
[0057]
If the addition amount is less than 0.02% by weight, the effect of the present invention on decomposition of dioxin cannot be sufficiently obtained. If the amount exceeds 0.5% by weight, the effect is saturated, and there is no point in adding more than necessary.
[0058]
In the addition of the dioxin decomposition catalyst in the present invention, it is desirable to add an acid gas neutralizer at the same time. The acid gas neutralizer acts to fix dioxin decomposed by the dioxin decomposition catalyst and chlorine, which is a constituent element of the dioxin precursor, in the cooling process from the combustion chamber to the dust collector and in the subsequent heat treatment. , Can promote the decomposition of dioxin.
[0059]
As the acid gas neutralizing agent in the present invention, powdery substances generally used for dry acid gas removal may be used, and alkaline earths such as slaked lime, quicklime, calcium carbonate, magnesium oxide, magnesium carbonate and dolomite may be used. It is a metal compound or an alkali metal compound such as lithium carbonate, sodium carbonate, sodium hydrogencarbonate and potassium hydrogencarbonate, preferably a calcium compound, and more preferably slaked lime. The acid gas neutralizer may be used alone or in combination of two or more.
[0060]
The acidic gas neutralizer in the present invention has an average particle diameter D 50 (Particle size of 50% of total volume by dry particle size distribution meter) 20 μm or less, more preferably 15 μm or less, BET specific surface area value 0.5 m 2 / G or more, more preferably 1 m 2 / G or more.
[0061]
The addition ratio of the dioxin decomposition catalyst and the acid gas neutralizing agent is preferably 2/1 to 1/100, more preferably 2/1 to 1/20, by weight ratio of dioxin decomposition catalyst / acid gas neutralizing agent. . If the weight ratio of the dioxin decomposition catalyst / acid gas neutralizer is out of the above range, a sufficient effect of adding the acid gas neutralizer cannot be obtained.
[0062]
Further, the addition amount of the dioxin decomposition catalyst and the acid gas neutralizing agent is desirably 0.25 to 2.5% by weight in total of the decomposition catalyst and the acid gas neutralizing agent based on the dry waste. More preferably, it is 0.30 to 2.0% by weight. If the amount is less than 0.25% by weight, a sufficient effect of adding the acid gas neutralizer cannot be obtained. If the amount exceeds 2.5% by weight, the amount of addition is large, and an overload is applied to the dust collector at the subsequent stage, and the amount of dust at the outlet of the dust collector is undesirably increased.
[0063]
The addition of the dioxin decomposition catalyst and the acid gas neutralizing agent may be added alone, but by mixing the dioxin decomposition catalyst and the acid gas neutralizing agent in advance, the dioxin and the dioxin precursor can be more effectively reduced. Can be disassembled.
[0064]
Further, at the time of adding the dioxin decomposition catalyst in the present invention, the emission of dioxin can be effectively suppressed by adding activated carbon together with the acid gas neutralizing agent. Activated carbon has the effect of adsorbing gaseous dioxin, and the gaseous dioxin in the exhaust gas is efficiently transferred to fly ash by spray addition in the cooling process from the combustion chamber to the dust collector. As a result, the total emission of dioxins including dioxin in exhaust gas as well as in fly ash is reduced as much as possible.
[0065]
The activated carbon in the present invention may be a powdery substance generally used for dioxin removal, and may have an average particle diameter D. 50 (Particle size of 50% of total volume by dry particle size distribution meter) 50 μm or less, more preferably 30 μm or less, BET specific surface area value 600 m 2 / G or more, more preferably 800 m 2 / G or more.
[0066]
If the average particle size and the BET specific surface area value of the activated carbon are out of the above ranges, the transfer from the combustion chamber to the dust collector is not performed sufficiently, and the dioxin adsorption performance is poor. No effect.
[0067]
The addition ratio of the dioxin decomposition catalyst, the acid gas neutralizing agent and the activated carbon is 2/1 to 1/100 in weight ratio of dioxin decomposition catalyst / acid gas neutralizing agent, and the weight ratio of dioxin decomposition catalyst / activated carbon. And the weight ratio of the dioxin decomposition catalyst / acidic gas neutralizing agent is 2/1 to 1/20, and the weight ratio of the dioxin decomposition catalyst / activated carbon is 10/10. / 1 to 1/5. When the weight ratio of dioxin decomposition catalyst / acid gas neutralizer is out of the range of 2/1 to 1/100 and when the weight ratio of dioxin decomposition catalyst / activated carbon is out of the range of 10/1 to 1/25, The effect of adding a sufficient acid gas neutralizer and activated carbon cannot be obtained.
[0068]
The addition amount of the mixture of the dioxin decomposition catalyst, the acid gas neutralizing agent and the activated carbon is desirably 0.30 to 3.0% by weight in total of the dioxin decomposition catalyst, the acid gas neutralizing agent and the activated carbon based on the dry waste. More preferably, it is 0.30 to 2.5% by weight. If the amount is less than 0.3% by weight, a sufficient effect of adding an acid gas neutralizer cannot be obtained, and an effect of adsorbing dioxin by activated carbon cannot be obtained. If the content exceeds 3.0% by weight, the amount of addition is large, and an overload is applied to the dust collector in the subsequent stage, and the amount of dust at the outlet of the dust collector is undesirably increased.
[0069]
The addition of the dioxin decomposition catalyst, the acid gas neutralizing agent and the activated carbon may be added independently, but it is effective to add a mixture obtained by previously mixing the dioxin decomposition catalyst, the acid gas neutralizing agent and the activated carbon. Dioxin total emission can be reduced.
[0070]
The amount of the composite catalyst added to the dry waste when the dioxin decomposition catalyst, the acidic gas neutralizer, and the activated carbon mixed with the dioxin decomposition composite catalyst are added is the same as the amount added to the dry waste when added alone. Fly ash may contain 0.2 to 20% by weight of a dioxin decomposition catalyst depending on the amounts of the dioxin decomposition catalyst, the acid gas neutralizer and the activated carbon.
[0071]
The processing apparatus in the heat treatment of the fly ash is not particularly limited. Since the dioxin decomposition catalyst is uniformly mixed in the collected fly ash, an apparatus that can simply heat-treat the fly ash may be used. In order to decompose dioxin more efficiently, a continuous or batch type rotary kiln, a multi-stage furnace or a batch continuous pusher furnace can be used, but a continuous or batch type rotary kiln or a multi-stage furnace is preferable. .
[0072]
The heat treatment of the fly ash is performed under the flow of air or an oxygen-containing gas such as exhaust gas discharged from a refuse incinerator.
[0073]
The processing temperature in the heat treatment of fly ash may be changed according to the reaction time, and is preferably from 150 to 450 ° C, more preferably from 200 to 400 ° C, and still more preferably from 200 to 380 ° C. If the temperature is lower than 150 ° C., the decomposition activity of the dioxin decomposition catalyst is low. If the temperature is higher than 450 ° C., the dioxin can be decomposed, but the dioxin decomposition effect corresponding to the energy required for heating cannot be obtained. The heating time of the fly ash is preferably 1 to 60 minutes.
[0074]
By the method for treating fly ash according to the present invention, 90% or more, more preferably 95% or more of the dioxin concentration relative to the dioxin concentration in the fly ash collected by the dust collector when the dioxin decomposition catalyst is not added. Can be reduced.
[0075]
BEST MODE FOR CARRYING OUT THE INVENTION
A typical embodiment of the present invention is as follows.
[0076]
The average particle size of the iron compound powder in the present invention was represented by an average value of numerical values measured from an electron micrograph. The specific surface area was measured by the BET method.
[0077]
The contents of phosphorus and sodium contained in the iron compound powder according to the present invention are shown by values measured by an inductively coupled plasma atomic emission spectrophotometer SPS-4000 (manufactured by Seiko Electronic Industry Co., Ltd.).
[0078]
The content of sulfur contained in the iron compound powder in the present invention was indicated by a value measured by a carbon-sulfur analyzer EMIA-2200 (manufactured by Horiba, Ltd.).
[0079]
4. A 50 mg compound of the iron oxide particle powder and the amine compound obtained by heat-treating the iron compound powder in air at 300 ° C. for 60 minutes in an inert gas atmosphere using a pulse type catalytic reactor. 0x10 -7 SV = 150,000 h at mol temperature of monochlorobenzene and 300 ° C -1 The catalytic properties of the dioxin decomposition catalyst were shown by measuring the amount of monochlorobenzene which decomposes when contacted instantaneously under the following conditions.
[0080]
The pulse type catalytic reaction device includes a reactor section and a gas chromatography mass spectrometer section, and the gas chromatography mass spectrometer section is a gas chromatography mass spectrometer GC / MSQP-5050 (manufactured by Shimadzu Corporation). It is.
[0081]
This evaluation method is described in Kobes et al.'S literature (RJ. Kobes, et al J. Am. Chem. Soc., 77, 5860 (1955)), and the Chemical Chemistry Society of Japan, "Experimental Chemistry Lecture 11, Reaction and Rate". (Maruzen, Tokyo (1993)).
[0082]
<Iron compound powder>
As iron compound powder, goethite powder (average particle size 0.25 μm, phosphorus content 0.002% by weight, sulfur content 0.05% by weight, sodium content 0.08% by weight, BET specific surface area 85m) 2 / G) was used.
[0083]
The goethite powder had a decomposition rate of monochlorobenzene of 33% at 300 ° C. according to a predetermined evaluation method.
[0084]
<Production of dioxin decomposition catalyst>
1.5 kg of the goethite powder and 75 g of triethanolamine (5.0 wt% based on the goethite powder) were dry-mixed (1440 rpm, 5 min) at 50 ° C. in a Henschel mixer (nominal volume: 10 liters), and A goethite powder supporting ethanolamine was obtained.
[0085]
The triethanolamine-supported goethite powder had a monochlorobenzene decomposition rate of 88% at 300 ° C. by a predetermined evaluation method.
[0086]
<Decomposition test of dioxin>
The schematic diagram of the intermittent operation type waste incineration facility used in this test is shown in FIG. In the figure, 1 is a refuse hopper, 2 is an incinerator, 3 is a combustion chamber, 4 is an auxiliary burner port, 5 is a gas cooling chamber, 6 is an air preheater, 7 is a blower for supplying a dioxin decomposition catalyst and the like, and 8 is dioxin. Decomposition catalyst supply tank, 9 is an electric dust collector, 10 is an induction blower, 11 is a chimney, 12 is a push-in blower, 13 is a flue, and 14 to 17 are dioxin decomposition catalyst and other supply ports.
[0087]
The combustion chamber 3 is supplied from the hearth of an incinerator with combustion air about 1.5 to 3.5 times the theoretical air amount required for complete combustion of the refuse. As the combustion air, air is sucked in by a forced air blower 12 and air heated by an air preheater 6 is used. The combustion chamber 3 is provided with an auxiliary burner port 4. The dioxin decomposition catalyst, the acid gas neutralizing agent (eg, slaked lime) and the activated carbon are supplied by airflow from the supply ports 14 to 17 and the like.
[0088]
In the above-mentioned intermittently operating incineration facility (operating for 16 hours a day and having an incineration capacity of 30 tons / day), the dioxin decomposition catalyst in an amount of 0.25% by weight based on the dry waste is supplied to the supply port 16 (exhaust gas) by air transport. (Temperature: 262 ° C.), and spray addition was performed for 16 hours from the start-up of the incinerator to the steady operation and the shutdown. Also, 0.50% by weight of dry garbage, JIS special name slaked lime powder manufactured by Ube Materials Co., Ltd. (average particle diameter D 50 5.7 μm, BET specific surface area 13.7 m 2 / G) by pneumatic transport from the supply port 17 in the same manner as above, from the start-up of the incinerator to the steady operation and the start-up of the incinerator for 16 hours (total of the dioxin decomposition catalyst and slaked lime, 0.75% by weight).
[0089]
The dioxin content was measured for the exhaust gas collected at the outlet of the electrostatic precipitator 9 and fly ash below the electric precipitator. The measurement and analysis of dioxin was performed in accordance with the "Standard Manual for Measurement and Analysis of Dioxins in Waste Disposal" (established in February 1997 by the Ministry of Health and Welfare Bureau, Ministry of Health and Welfare, Water Supply Environment Department, Environment Improvement Section).
[0090]
The dioxin concentration in the exhaust gas at the outlet of the electric dust collector is 1.1 ng TEQ / Nm 3 The dioxin concentration in fly ash collected by the electric dust collector was 4.0 ng TEQ / g.
[0091]
400 g of fly ash collected by an electric dust collector was transferred to a batch-type rotary kiln having an internal volume of 11 liters, and subjected to a heat treatment at 300 ° C. for 10 minutes under a flow of air (3 liters / minute).
[0092]
The dioxin concentration in the fly ash was 0.18 g-TEQ / g. The reduction rate with respect to the dioxin concentration (STD) when only slaked lime described later was added was 99.1%.
[0093]
As a blank test, the operation of the incinerator in the case where slaked lime alone was added without adding the iron compound catalyst for dioxin suppression was performed in the same manner, and the dioxin concentration in the exhaust gas and fly ash at the outlet of the electric precipitator. Was measured.
[0094]
The dioxin concentration in the exhaust gas at the outlet of the electric dust collector is 16 ng TEQ / Nm 3 The dioxin concentration (STD) in fly ash collected by the electric dust collector was 20 ng TEQ / g.
[0095]
[Action]
An important point in the present invention is that dioxin in fly ash can be effectively and economically decomposed by the method for treating fly ash according to the present invention.
[0096]
As a reason why dioxin in fly ash can be effectively decomposed, the present inventor added a dioxin decomposition catalyst having high catalytic properties to exhaust gas from the combustion chamber of a refuse incineration plant to a dust collector, thereby improving the collection efficiency. The dioxin in the fly ash was effectively decomposed before being collected by the dust generator, and by spraying the dioxin decomposition catalyst in the exhaust gas, the dioxin was dispersed in the fly ash without using a special mixing device. It is considered that the dioxin decomposition catalyst can be uniformly mixed, and the dioxin decomposition catalyst can be efficiently reacted by the dioxin decomposition catalyst in the heat treatment of fly ash.
[0097]
Regarding the catalytic activity of the dioxin decomposition catalyst, the ability of the iron compound itself to excel in dioxin resolution, that the amine compound carried on the surface of the iron compound promoted the adsorption reaction of organic halogen compounds, and that the iron compound and the amine compound It is considered that the decomposition reaction of the adsorbed organic halogen compound by the iron compound is promoted by the contact of the compound. It is considered that the amine compound adsorbs dioxin and also causes a dechlorination reaction of dioxin.
[0098]
When an acid gas neutralizing agent is added together with a dioxin decomposition catalyst, the reason why the generation of dioxin can be further suppressed is that the acid gas neutralizing agent fixes dioxin or chlorine which is a constituent element of the dioxin precursor, As a result, it is thought that the generation of dioxin can be efficiently suppressed.
[0099]
In addition, when activated carbon is added, activated carbon efficiently adsorbs gaseous dioxin in exhaust gas and transfers it to fly ash, and the subsequent heat treatment can reduce dioxin in fly ash as much as possible. As a result, we believe that total dioxin emissions can be reduced.
[0100]
【Example】
Next, examples and comparative examples of the present invention will be described.
[0101]
Iron compound powders 1 to 5:
Iron compounds 1 to 5 shown in Table 1 were prepared as iron compound powders.
[0102]
[Table 1]
Composite catalyst 1-7
A composite catalyst was obtained in the same manner as in the embodiment of the invention except that the type of the iron compound powder and the type of the amine compound were variously changed.
[0104]
Table 2 shows properties of the obtained composite catalyst. When the silica gel and the amine compound were combined, the catalytic activity was as low as 10%.
[0105]
[Table 2]
<Decomposition test of dioxin>
Examples 1 to 7, Comparative Examples 1 to 4
Except for changing the type of dioxin decomposition catalyst, acid gas neutralizing agent, activated carbon, the amount of each added, the place of addition, the temperature of the heat treatment of fly ash, and the holding time, flying was carried out in the same manner as in the embodiment of the present invention. A decomposition test of dioxin in the ash was performed. As the acid gas neutralizer, slaked lime powder manufactured by Ube Materials Co., Ltd. 50 5.7 μm, BET specific surface area 13.7 m 2 / G) as activated carbon, PXS (trade name) manufactured by Mitsubishi Chemical Corporation (average particle diameter D 50 15μm, BET specific surface area 1050m 2 / G) was used. A shown in the column of addition position in Table 3 indicates that the dioxin decomposition catalyst and the acid gas neutralizing agent were previously mixed and added. B indicates that a dioxin decomposition catalyst, an acid gas neutralizing agent and activated carbon are previously mixed and added.
[0107]
Table 3 shows the conditions at this time, and Table 4 shows the results of the heat treatment of fly ash. The reduction rate of the dioxin concentration is a value with respect to the dioxin concentration (STD) in the fly ash in the blank test to which only slaked lime was added, and the higher the value, the better the dioxin is decomposed. Note that the dioxin concentration in fly ash in Table 3 is a value converted into a soot and dust excluding additives such as a dioxin decomposition catalyst.
[0108]
[Table 3]
[Table 4]
From these results, it is recognized that the dioxin-containing fly ash treatment method according to the present invention can reduce the dioxin in the fly ash before the heat treatment, and can further effectively decompose the dioxin by performing the heat treatment. Was.
[0111]
【The invention's effect】
In the present invention, after adding a dioxin decomposition catalyst having a specific catalytic property to exhaust gas from a combustion chamber of a refuse incinerator to a dust collector, the fly ash collected by the dust collector is heat-treated. Thus, dioxin in fly ash can be economically and efficiently decomposed and removed, and dioxin can be decomposed even in the presence of oxygen.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a waste incineration facility according to the present invention.
[Explanation of symbols]
1: Garbage hopper
2: Incinerator
3: Combustion chamber
4: Burner burner opening
5: Gas cooling chamber
6: Air preheater
7: Blower for supplying dioxin decomposition catalyst etc.
8: Dioxin decomposition catalyst supply tank
9: Dust collector
10: Induction blower
11: chimney
12: Push blower
13: Flue
14-17: Supply port for addition of dioxin decomposition catalyst
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