JP3646245B2 - Processing method for fly ash containing heavy metals - Google Patents
Processing method for fly ash containing heavy metals Download PDFInfo
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- JP3646245B2 JP3646245B2 JP32400198A JP32400198A JP3646245B2 JP 3646245 B2 JP3646245 B2 JP 3646245B2 JP 32400198 A JP32400198 A JP 32400198A JP 32400198 A JP32400198 A JP 32400198A JP 3646245 B2 JP3646245 B2 JP 3646245B2
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- Prior art keywords
- heavy metal
- fly ash
- salt
- filtered water
- water
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- 229910001385 heavy metal Inorganic materials 0.000 title claims description 108
- 239000010881 fly ash Substances 0.000 title claims description 74
- 238000003672 processing method Methods 0.000 title claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 88
- 238000000034 method Methods 0.000 claims description 60
- 150000003839 salts Chemical class 0.000 claims description 47
- 238000000926 separation method Methods 0.000 claims description 44
- 238000000975 co-precipitation Methods 0.000 claims description 38
- 150000002505 iron Chemical class 0.000 claims description 34
- 239000007788 liquid Substances 0.000 claims description 33
- 239000000706 filtrate Substances 0.000 claims description 30
- 239000011133 lead Substances 0.000 claims description 29
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 claims description 27
- 229910052802 copper Inorganic materials 0.000 claims description 25
- 239000010949 copper Substances 0.000 claims description 25
- 229910052725 zinc Inorganic materials 0.000 claims description 25
- 239000011701 zinc Substances 0.000 claims description 25
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 24
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 24
- 238000005406 washing Methods 0.000 claims description 21
- 238000006243 chemical reaction Methods 0.000 claims description 20
- 238000001179 sorption measurement Methods 0.000 claims description 19
- 238000010828 elution Methods 0.000 claims description 17
- 239000000047 product Substances 0.000 claims description 17
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 16
- 229910052801 chlorine Inorganic materials 0.000 claims description 16
- 239000000460 chlorine Substances 0.000 claims description 16
- 239000002253 acid Substances 0.000 claims description 14
- 239000002002 slurry Substances 0.000 claims description 14
- 239000012298 atmosphere Substances 0.000 claims description 13
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 12
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 12
- 239000011707 mineral Substances 0.000 claims description 12
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 11
- 238000011027 product recovery Methods 0.000 claims description 11
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- 229910052742 iron Inorganic materials 0.000 claims description 6
- 239000008213 purified water Substances 0.000 claims description 6
- 230000003647 oxidation Effects 0.000 claims description 4
- 238000007254 oxidation reaction Methods 0.000 claims description 4
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- 238000004140 cleaning Methods 0.000 claims description 2
- 238000004062 sedimentation Methods 0.000 claims 4
- 229910052751 metal Inorganic materials 0.000 claims 2
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- 239000002351 wastewater Substances 0.000 description 18
- 230000000694 effects Effects 0.000 description 13
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 9
- 235000010755 mineral Nutrition 0.000 description 9
- 239000011669 selenium Substances 0.000 description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 8
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 238000003723 Smelting Methods 0.000 description 7
- 229910052793 cadmium Inorganic materials 0.000 description 7
- 229910052711 selenium Inorganic materials 0.000 description 7
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 6
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 6
- 239000002994 raw material Substances 0.000 description 6
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 5
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 5
- 239000003513 alkali Substances 0.000 description 5
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- 229910052791 calcium Inorganic materials 0.000 description 5
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- 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 description 4
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 description 4
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 4
- 239000004568 cement Substances 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 239000011734 sodium Substances 0.000 description 4
- 229910052708 sodium Inorganic materials 0.000 description 4
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- 238000004056 waste incineration Methods 0.000 description 4
- 230000002378 acidificating effect Effects 0.000 description 3
- 229910052787 antimony Inorganic materials 0.000 description 3
- -1 chlorine and calcium Chemical class 0.000 description 3
- 150000001805 chlorine compounds Chemical class 0.000 description 3
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- 230000008018 melting Effects 0.000 description 3
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- 229910052753 mercury Inorganic materials 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 235000011121 sodium hydroxide Nutrition 0.000 description 3
- 238000000967 suction filtration Methods 0.000 description 3
- IRPGOXJVTQTAAN-UHFFFAOYSA-N 2,2,3,3,3-pentafluoropropanal Chemical compound FC(F)(F)C(F)(F)C=O IRPGOXJVTQTAAN-UHFFFAOYSA-N 0.000 description 2
- KLZUFWVZNOTSEM-UHFFFAOYSA-K Aluminum fluoride Inorganic materials F[Al](F)F KLZUFWVZNOTSEM-UHFFFAOYSA-K 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- 239000011790 ferrous sulphate Substances 0.000 description 2
- 235000003891 ferrous sulphate Nutrition 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 2
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Substances [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- JJLJMEJHUUYSSY-UHFFFAOYSA-L Copper hydroxide Chemical compound [OH-].[OH-].[Cu+2] JJLJMEJHUUYSSY-UHFFFAOYSA-L 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- 101100291369 Mus musculus Mip gene Proteins 0.000 description 1
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- 150000007513 acids Chemical class 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- 239000002956 ash Substances 0.000 description 1
- 238000011001 backwashing Methods 0.000 description 1
- 239000001110 calcium chloride Substances 0.000 description 1
- 229910001628 calcium chloride Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000002738 chelating agent Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
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- 238000011033 desalting Methods 0.000 description 1
- 239000003657 drainage water Substances 0.000 description 1
- 229940024464 emollients and protectives zinc product Drugs 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 229960002089 ferrous chloride Drugs 0.000 description 1
- 229910001448 ferrous ion Inorganic materials 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000036571 hydration Effects 0.000 description 1
- 238000006703 hydration reaction Methods 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 description 1
- 229910021506 iron(II) hydroxide Inorganic materials 0.000 description 1
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 1
- 229910052745 lead Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 150000004692 metal hydroxides Chemical class 0.000 description 1
- 239000010813 municipal solid waste Substances 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
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- 230000001105 regulatory effect Effects 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 239000010802 sludge Substances 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- HYHCSLBZRBJJCH-UHFFFAOYSA-M sodium hydrosulfide Chemical compound [Na+].[SH-] HYHCSLBZRBJJCH-UHFFFAOYSA-M 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
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- Removal Of Specific Substances (AREA)
- Water Treatment By Sorption (AREA)
- Processing Of Solid Wastes (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、都市ゴミ焼却施設や産業廃棄物焼却場等における焼却炉や溶融炉あるいは汚泥を処理するセメントキルン等から発生する重金属含有飛灰の処理方法に関する。
【０００２】
【従来の技術】
一般事業所や一般家庭から排出されるゴミ（「都市ゴミ」または「一般廃棄 物」と称されている）は都市ゴミ焼却施設や産業廃棄物焼却工場等に集められ焼却処分されている。その際に焼却炉から発生する焼却灰や飛灰は薬剤処理、または、溶融炉、セメントキルン処理等の中間処理を施し最終処分場に堆積されている。
【０００３】
しかしながら、上記溶融炉やセメントキルン等での中間処理では、蒸気圧の高い鉛、亜鉛およびカドミウム等の重金属は炉内で揮発して排ガスに入り、この排ガスに入った重金属は排ガス処理設備のなかで凝縮して再び飛灰となってしまうという問題があった。
この再度の飛灰中には、塩素、ナトリウム、カルシウム等の塩類と共に鉛、 銅、亜鉛、カドミウム等の重金属が多量に含まれれており、これらの回収を含めた安定した処理方法が求められていた。
【０００４】
このような飛灰について、特開平７−１０９５３３号公報には、飛灰を槽内の水に懸濁し、この懸濁液を酸またはアルカリの添加によりアルカリ域の適当値にｐＨ調整することによって飛灰中の重金属を水酸化物として沈殿させ、その沈殿を回収する方法について開示している。また本出願人も、先に、湿式処理方式によって対処する方法を出願している（特開平８−１１７７２７号公報および特開平８−１４１５３９号公報）。
特開平８−１１７７２４号公報には、飛灰を水でスラリー化し、ｐＨ調整して浸出し、固液分離する第１工程と、該第１工程からの殿物をリパルプし、硫酸により浸出溶解した後、固液分離して鉛産物を得る第２工程と、前記第１工程と前記第２工程からの酸性濾液に中和剤またさらに水硫化ソーダを加えて亜鉛、銅を含む産物を濾別し、濾過水を排水液とする第３工程とからなる方法が開示されており、特開平８−１４１５３９号公報には、飛灰を水と中和剤で中和して固液分離する第１工程と、該第１工程からの殿物をリパルプし、硫酸により浸出溶解して後。固液分離して鉛産物を得る第２工程と、該第２工程からの濾液に中和剤を加えて亜鉛、銅を含む産物を濾別する第３工程と、該第３工程の濾過水を該第１工程の中和液として繰り返し、該第１工程からの濾液について硫化剤を添加して排液処理する方法が開示されている。
【０００５】
このような湿式処理方法により、飛灰に含まれている重金属を安定な形で分離し、重金属資源として有効に回収すると共に、飛灰を湿式処理した後の排水を、国の排水基準すなわち水質汚濁防止法第３条第１項の規制に沿って無害化できるようになった。
【０００６】
【発明が解決しようとする課題】
しかしながら、特開平７−１０９５３３号公報においては回収した重金属殿物中に塩化カルシウム等の塩類が多量に入り込み、製錬工程では塩素の持ち込みを嫌うことから重金属のリサイクルという面での問題が残った。さらに、近年、地域によっては環境公害に対する懸念からさらに規制を強化し、上記の国の排水基準値を上回る厳しい基準値で上乗せ規制を課すところがでている。
例えば、地方条例（Ｉ市の上乗せ基準値）によれば、カドミウム０．０１ｍｇ／ｌ（国の排水基準値０．１ｍｇ／ｌ，以下同様）、フッ素１０ｍｇ／ｌ（１５ｍｇ／ｌ）、水銀０．０００５ｍｇ／ｌ（０．００５ｍｇ／ｌ）、ＣＯＤ１０ｍｇ／ｌ（１２０ｍｇ／ｌ）を上限とするように厳しく規制されるような状況にある。
【０００７】
また、飛灰を湿式処理した排水は、２０〜５０ｇ／ｌにも及ぶ多量の塩素が含まれ、溶存する重金属類は塩化物錯イオンを形成し易く、その除去が非常に困難な特異的な排水になっており、従来の技術では上記の地域の上乗せ規制に対応できない場合が生じているのが現状である。
また前記排水にセレンが混入した場合も従来法では排水基準値以下に除去するのは非常に困難で、多くの工数やコストをかけていた。
【０００８】
本発明は、このような状況に鑑み、飛灰中の有用重金属を塩素、カルシウム等の塩類と分離し、製錬工程において再利用可能な形で分離回収でき、且つ飛灰処理の多量に塩素を含有する排水についてセレンが混入しても他の重金属と同時に除去でき、厳しい地域排水規制に対応できる飛灰処理方法の提供を目的とする。
【０００９】
【課題を解決するための手段】
上記の目的を達成するため、本発明は、第１に、亜鉛、銅、鉛の少なくとも一種と塩素とを含む飛灰の処理方法であって、前記飛灰に鉱酸を加えてスラリー化し、ｐＨを５以下に調整して塩類、特に塩化物を溶出させる塩類溶出工程と、該塩類溶出工程のスラリーに中和剤を添加してｐＨを８〜１２に調整し、重金属含有殿物と塩類含有濾液とに固液分離する重金属分離工程と、該重金属分離工程で得られた塩類含有濾液に第１鉄塩を添加しｐＨを８以上に調整して固液分離し、共沈重金属を含む鉄塩殿物と濾過水を得る鉄塩共沈工程とからなることを特徴とする重金属含有飛灰の処理方法；第２に、前記鉄塩共沈工程の反応温度が３０℃以上であることを特徴とする前記第１に記載の重金属含有飛灰に処理方法；第３に、前記鉄塩共沈工程の反応温度が３０℃以上であり、且つ、反応は酸化が抑制された雰囲気下で行うことを特徴とする前記第１に記載の重金属含有飛灰の処理方法；第４に、前記鉄塩共沈工程で得られた濾過水に、アルミニウム塩を添加しｐＨを６〜８に調整して固液分離し、共沈重金属を含むアルミニウム塩殿物と濾過水を得るアルミ塩共沈工程を有することを特徴とする前記第１〜第３のいずれかに記載の重金属含有飛灰の処理方法；第５に、前記鉄塩共沈工程で得られた濾過水に、アルミニウム塩を添加しｐＨを６〜８に調整して固液分離し、共沈重金属を含むアルミニウム塩殿物と濾過水を得るアルミ塩共沈工程と、得られた濾過水に、吸着剤によるＣＯＤ成分の吸着処理を施して清浄水を得るＣＯＤ吸着工程を有することを特徴とする前記第１〜第３のいずれかに記載の重金属含有飛灰の処理方法；第６に、前記鉄塩共沈工程で得られた濾過水に、吸着剤によるＣＯＤ成分の吸着処理を施して清浄水を得るＣＯＤ吸着工程を有することを特徴とする前記第１〜第３のいずれかに記載の重金属含有飛灰の処理方法；第７に、前記重金属分離工程で得られた重金属含有殿物を、湯または水で洗浄し、洗浄殿物と洗浄濾過水を得、得られた洗浄濾過水を前記塩類溶出工程における飛灰のスラリー化用水とする洗浄工程を有することを特徴とする前記第１〜第６のいずれかに記載の重金属含有飛灰の処理方法；第８に、亜鉛、銅、鉛の少なくとも一種と塩素とを含む飛灰の処理方法であって、前記飛灰に水および鉱酸を加えてスラリー化し、ｐＨを５以下に調整して塩類、特に塩化物を溶出させる塩類溶出工程と、該塩類溶出工程のスラリーに中和剤を添加してｐＨを８〜１２に調整し、重金属含有殿物と塩類含有濾液とに固液分離する重金属分離工程と、該重金属分離工程で得られた前記重金属含有殿物に鉱酸を加えてリパルプすると共に、ｐＨを４以下に調整して固液分離し、鉛を主成分とする鉛産物を得る鉛産物回収工程と、該鉛産物回収工程で得られた濾液に中和剤を添加し、ｐＨを８以上に調整して固液分離し、銅と亜鉛を主成分とする銅・亜鉛産物を得る銅・亜鉛産物回収工程と、前記重金属分離工程で得られた塩類含有濾液に第１鉄塩を添加しｐＨを８以上に調整して固液分離し、共沈重金属を含む鉄塩殿物と濾過水を得る鉄塩共沈工程とからなることを特徴とする重金属含有飛灰の処理方法；第９に、前記鉄塩共沈工程の反応温度が、３０℃以上であることを特徴とする前記第８に記載の重金属含有飛灰の処理方法；第１０に、前記鉄塩共沈工程の反応温度が、３０℃以上であ り、且つ、反応は酸化が抑制された雰囲気下で行われることを特徴とする前記第８に記載の重金属含有飛灰の処理方法；第１１に、前記鉄塩共沈工程で得られた濾過水に、アルミニウム塩を添加しｐＨを６〜８に調整して固液分離し、共沈重金属を含むアルミニウム塩残渣と濾過水を得るアルミ塩共沈工程を有することを特徴とする前記第８〜第１０のいずれかに記載の重金属含有飛灰の処理方法；第１２に、前記鉄塩共沈工程で得られた濾過水に、アルミニウム塩を添加しｐＨを６〜８に調整して固液分離し、共沈重金属を含むアルミニウム塩殿物と濾過水を得るアルミ塩共沈工程と、得られた濾過水に吸着剤によるＣＯＤ成分の吸着処理を施して清浄水を得るＣＯＤ吸着工程を有することを特徴とする前記第８〜第１０のいずれかに記載の重金属含有飛灰の処理方法；第１３に、前記鉄塩共沈工程で得られた濾過水に吸着剤によるＣＯＤ成分の吸着処理を施して清浄水を得るＣＯＤ吸着工程を有することを特徴とする前記第８〜第１０のいずれかに記載の重金属含有飛灰の処理方法；第１４に、前記重金属分離工程で得られた重金属含有殿物を湯または水で洗浄し、洗浄殿物と洗浄濾過水を得る洗浄工程を有し、該洗浄濾過水を、前記銅・亜鉛産物回収工程からの濾過水と共に前記塩類溶出工程の飛灰のスラリー化用水とすることを特徴とする前記第８〜１３のいずれかに記載の重金属含有飛灰の処理方法を提供する。
【００１０】
【発明の実施の態様】
本発明を、産業廃棄物を対象とする焼却炉からの飛灰の処理方法の場合を例に図１の処理工程図によって説明する。先ず、飛灰を水と混合させてスラリー化させ、このスラリーを攪拌しながら、塩酸または硫酸等の鉱酸を添加してｐＨを５以下、好ましくは、ｐＨ４以下に調整し、塩素、ナトリウム、カルシウム等の塩類、特に塩化物を液側に移行させる（塩類溶出工程）。なお、前記スラリーのｐＨは、飛灰の組成によって異なるため、鉱酸の添加量は飛灰に応じて調整する。したがって、前記スラリーのｐＨがすでに最適ｐＨにある場合には鉱酸を加える必要はない。
【００１１】
次いで、水酸化ナトリウムまたは炭酸ナトリウム等のアルカリ中和剤を添加してｐＨを８〜１２の間に調整した後、固液分離することによって重金属を含有する殿物と、塩素、ナトリウム、カルシウム等塩類を含有する濾液とに固液分離する（重金属分離工程）。以上のように、塩類溶出工程で飛灰中の塩類を酸性側において十分に溶出させた後、重金属分離工程でこの酸性の溶出液を中和することにより、重金属含有殿物中の塩素等の塩類の含有率を著しく減少させることが可能となる。この塩素含有率の低い重金属含有殿物は、そのまま製錬工程の原料とすることもできる。
【００１２】
そして、前記重金属分離工程からの塩類含有濾液に塩化第１鉄等の第１鉄塩を添加し、ｐＨを８以上に調整し、液中に残留する微量の重金属を鉄塩と共に共沈させた後、これを固液分離することにより、鉄塩共沈殿物と清浄な濾過水を得ることができる（鉄共沈工程）。
【００１３】
すなわち、第１鉄塩を添加してｐＨ調整することにより、高い溶存塩素に拘らず、第１鉄イオンが総て水酸化第１鉄を生成し、この晶出初期の活性な水酸化第１鉄がその沈殿過程で液中の残存重金属例えばＨｇやＳｅの他Ｃｕ，Ｐｂ，Ｚ ｎ，Ｃｄ，Ｃｒ，Ａｓ，Ｓｂ，Ｂｉ，Ｎｉ等を取り込んで共沈させるものと考えられ、重金属を極低レベルまで低減できる等除去効率を飛躍的に高めることができる。例えば、従来の技術では活性炭等吸着剤による吸着処理を必要としていた水銀についても、本方法の鉄塩共沈処理で十分に処理可能となった。
【００１４】
前記鉄塩共沈工程の反応温度は室温以上、好ましくは３０℃以上、さらに好ましくは４５℃以上で行う。また、この反応は大気雰囲気においても可能である が、好ましくは空気を遮断した槽中で行う、さらに好ましくは窒素ガス雰囲気等の非酸化性雰囲気下で行う等、酸化が抑制された雰囲気下で行うことにより顕著に効率を高めることができる。反応温度を３０℃以上とし、且つ、反応を酸化性が抑制された雰囲気下で行うことにより、重金属の析出効率が相乗的に高まるのみならず、反応液からの濾過効率も向上する。
【００１５】
前記塩類含有濾液にフッ素を含有する場合は、鉄塩共沈工程からの濾過水に塩化アルミニウム等のアルミニウム塩を添加してｐＨを６〜８程度に調整することにより残留するフッ素をフッ化アルミニウムとして除去することができ、同時に生成する水酸化アルミニウムにより微量に残存する重金属をも共沈させることができ、この溶液を固液分離することにより、アルミニウム塩共沈殿物と共に清浄な濾過水を得ることができる（アルミ塩共沈工程）。
【００１６】
また、前記アルミ塩共沈工程からの濾過水が、なお問題となる程度にＣＯＤを含む場合は、さらに、活性炭あるいはキレート剤等の吸着剤による吸着処理に供することにより、ＣＯＤを低減させることができる。この活性炭での吸着処理 は、勿論カラムを使用してもよいが、前工程のアルミニウム塩と共に、顆粒状あるいは粉状で加えて固液分離してもよい。勿論液中のＣＯＤは除去され、また水酸化アルミニウムの濾過性を極度に改善することができる。
【００１７】
なお、前記鉄塩共沈工程からの濾過水が問題になる程度のフッ素を含まず、且つ問題になる程度のＣＯＤを含む場合は、アルミ塩共沈工程を省略し、前記濾過水をそのまま吸着工程に供することができる。
【００１８】
さらに、前記重金属分離工程からの中和殿物即ち重金属含有殿物をリパルプあるいはフィルタープレス中での通水洗浄（正洗、逆洗）により、塩素、ナトリウム、カルシウム等塩類をさらに中和殿物より分離することができ、洗浄濾過水は飛灰のスラリー化用水として前記塩類溶出工程に循環させる（洗浄工程）。
【００１９】
前記重金属分離工程からの重金属含有殿物はそのまま製錬工程の原料となりうるが、さらに分別しておくと製錬工程の処理の軽減となる。すなわち前記重金属含有殿物を洗浄工程において、水で洗浄し、含有塩類を回収した後の洗浄殿物を処理対象としてもよい。対象殿物に水を加えてリパルプし、塩酸または硫酸等の鉱酸を添加してｐＨを４以下好ましくはｐＨ３以下に調整し、亜鉛、銅、カドミウムを主成分とする重金属を溶解させ、固液分離により、鉱酸に難溶の鉛を主成分とする重金属を鉛産物として回収する（鉛産物回収工程）。
【００２０】
前記鉛産物回収工程からの濾液には、アルカリ中和剤を添加してｐＨを８以上好ましくはｐＨ１１程度に調整することにより、亜鉛、銅、カドミウムを主成分とする重金属の水酸化物を生成させ、固液分離することにより、銅・亜鉛産物と濾過水を得ることができる。この濾過水は、前記洗浄工程からの洗浄濾過水と合わせて、塩類溶出工程における飛灰のスラリー化用水として繰り返すことによ り、重金属の回収性と共に飛灰処理の経済性を高めることができる。
【００２１】
以上のように、本発明においては、飛灰に含まれている重金属を、鉛を主体とする鉛産物と、水酸化物態の銅、亜鉛およびカドミウムを主体とする銅・亜鉛産物として分別回収して製練原料として利用でき、また、鉄塩殿物あるいはアルミニウム塩殿物を回収して、溶鉱炉、セメントキルンの原料としてリサイクルで き、さらに、排水としては、重金属や有害元素が十分に除去され、国の排水規制は勿論、地域の上乗せ規制をも満足できる清浄な濾過水を得ることができるものである。
【００２２】
【実施例１】
先ず、１０リットルビーカーに純水８リットルを入れて攪拌しながら、原料としてＡ処理工場の飛灰８００ｇを入れてスラリーとし、１０分間攪拌しながら、鉱酸として３６％塩酸を添加してｐＨを４に調整・維持し、３０分間溶解処理を行い（塩類溶出工程）、次いで、アルカリ中和剤として２００ｇ／リットルの苛性ソーダ溶液を添加してｐＨを１１に調整し３０分間維持した後、濾過操作により重金属を主とする重金属含有殿物と塩類を主とする塩類含有濾液とに分離した（重金属分離工程）。次いで得られた重金属含有殿物を５リットルビーカーに移し、純水を２．０リットル入れてスラリーとし３０分間攪拌維持した後、洗浄殿物と洗浄濾液を得た（洗浄工程）。
表１に原料飛灰の組成および洗浄工程で得られた洗浄殿物の品位を、また、表２に前記脱塩工程からの塩類含有濾液の組成を示した。
【００２３】
【表１】
【表２】
引き続き得られた洗浄殿物を１０リットルビーカーに移し、純水５リットルでリパルプし、９５％Ｈ2ＳＯ4を添加し、ｐＨを3に調整して鉛以外の重金属を溶 出せしめ、鉛を主とした鉛産物を得た（鉛産物回収工程）。得られた鉛産物の品位を表１に示した。
さらに分別された濾液に２００ｇ／ｌの苛性ソーダ溶液を添加してｐＨを１１に調整し、銅・亜鉛を主成分とする水酸化物の産物と中和後、濾過水とに濾別した（銅・亜鉛産物回収工程）。得られた銅・亜鉛産物の品位を表１に示した。
【００２５】
【実施例２】
〔試験１〕
表２に示す塩類含有濾液３００ミリリットルを５００ミリリットルのビーカーにとり、第一鉄塩として硫酸第一鉄を鉄量として３５０ｍｇ／リットルを添加 し、各設定温度と雰囲気のもとにｐＨを９に調整・維持して３０分間反応させた後、吸引濾過（Ｃ濾紙使用）により、鉄殿物と濾液とに分離した（鉄塩共沈工 程）。
表３に得られた濾液のＳｅとＳｂの品位を示した。
【００２６】
【表３】
【００２７】
ＳｅとＳｂについて鉄塩共沈工程における反応温度と反応雰囲気を調査したものであるが、約３０℃付近から顕著な除去効果が見られる。また、反応温度４５℃での比較であるが、窒素雰囲気とすることによりさらに顕著な除去効果が得られた。
【００２８】
〔試験２〕
次に表２に示す塩類含有濾液を４リットルを５リットルビーカーにとり、第一鉄塩として硫酸第一鉄を鉄量として５００ｍｇ／リットルを添加し、６０℃に加温のもとでｐＨを９に調整・維持して３０分間反応させた後、吸引濾過（Ｃ濾紙使用）により鉄塩殿物と濾過水とに分離した（鉄塩共沈工程）。
得られた濾過水の品位を表４に示した。
【００２９】
【表４】
【００３０】
〔試験３〕
試験２で処理された濾過水（処理後）２．５リットル（Ｆ：１６ｍｇ／リットル含有）を３リットルビーカーにとり、アルミニウム塩として塩化アルミニウムをアルミニウム量で５０ｍｇ／リットルを添加し、４５℃に加温のもとで、ｐＨを７に調整・維持して３０分間反応させた後、吸引濾過（Ｃ濾紙使用）により、殿物と濾液とに分離した（アルミ塩共沈工程）。
得られた濾液のフッ素濃度は４．２ｍｇ／リットルであり、前記Ｉ市の上乗せ基準値の１０ｍｇ／リットルを大きく下回った。
【００３１】
〔試験４〕
試験３で得られた濾液を排水処理用ヤシがら系活性炭を充填したミニカラムに対してＳＶ比が５の条件で通液処理を施し、最終排水を得た（ＣＯＤ吸着工 程）。
最終排水中のＣＯＤは＜１ｍｇ／リットルの値を示し、前記Ｉ市の上乗せ基準値の１０ｍｇ／リットルを十分に下回った。
【００３２】
【発明の効果】
請求項１の発明によれば、飛灰中の塩類を酸により十分に溶解した後、中和することによって重金属含有殿物中から塩素を著しく除くことが可能となり製錬工程の原料となりえる。且つセレンが混入した飛灰処理の排水についても、セレンの他、銅、鉛等の重金属を同時に極低レベルまで低減でき、国の排水規制を上回る厳しい地域排水規制に対応できる濾過排水を得ることができるという効果を奏する。
請求項２および３の発明によれば、さらに重金属を低減した濾過排水が安定して得られるという効果を奏する。請求項４〜６の発明によれば、さらに飛灰の組成に対応した追加的な排水浄化処理を行え、濾過排水に万全を期すことができるという効果を奏する。請求項７の発明によれば、上記の効果に加えて、重金属の回収性および飛灰処理の経済性を高めることができるという効果を奏する。
【００３３】
請求項８の発明によれば、飛灰における塩類と重金属の十分な分離を可能と し、厳しい地域排水規制に対応できる濾過排水を得ると共に、銅、亜鉛、鉛等の有用重金属を製練原料として塩素の少ない安定した形で得られるという効果を奏する。
請求項９および１０の発明によれば、さらに重金属を低減した濾過排水が安定して得られるという効果を奏する。請求項１１〜１３の発明によれば、飛灰の組成に対応した追加的な排水浄化処理を行い濾過排水に万全を期すことができるという効果を奏する。請求項１４の発明によれば、上記の効果に加えて、重金属の回収性および飛灰処理の経済性を高めるという効果を奏する。
【図面の簡単な説明】
【図１】本発明の重金属含有飛灰の処理方法を示す工程図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating heavy metal-containing fly ash generated from an incinerator, a melting furnace, a cement kiln for treating sludge, or the like in a municipal waste incineration facility or an industrial waste incineration plant.
[0002]
[Prior art]
Garbage discharged from general offices and households (referred to as “urban waste” or “general waste”) is collected and incinerated at municipal waste incineration facilities and industrial waste incineration plants. Incineration ash and fly ash generated from the incinerator at that time are subjected to chemical treatment or intermediate treatment such as melting furnace and cement kiln treatment, and are deposited in the final disposal site.
[0003]
However, in the intermediate treatment in the above melting furnace, cement kiln, etc., heavy metals such as lead, zinc and cadmium with high vapor pressure volatilize in the furnace and enter the exhaust gas, and the heavy metal contained in the exhaust gas is in the exhaust gas treatment equipment. There was a problem that it would condense and become fly ash again.
This second fly ash contains a large amount of heavy metals such as lead, copper, zinc and cadmium together with salts such as chlorine, sodium and calcium, and a stable treatment method including recovery of these is required. It was.
[0004]
JP-A-7-109533 discloses such fly ash by suspending fly ash in water in a tank and adjusting the pH of the suspension to an appropriate value in the alkali range by adding acid or alkali. It discloses a method for precipitating heavy metals in fly ash as hydroxides and recovering the precipitates. The present applicant has also filed a method for coping with the wet processing method (Japanese Patent Laid-Open Nos. 8-117727 and 8-141539).
In JP-A-8-117724, fly ash is slurried with water, adjusted to pH and leached, and solid-liquid separation is performed. The pulp from the first step is repulped and leached and dissolved with sulfuric acid. After that, a second step for obtaining a lead product by solid-liquid separation, and a neutralizer or further sodium hydrosulfide are added to the acidic filtrate from the first step and the second step to filter the product containing zinc and copper. Separately, a method comprising a third step in which filtered water is used as drainage is disclosed, and Japanese Patent Application Laid-Open No. 8-141539 discloses solid-liquid separation by neutralizing fly ash with water and a neutralizing agent. After the first step and the pulp from the first step are repulped and leached and dissolved with sulfuric acid. A second step of obtaining a lead product by solid-liquid separation, a third step of adding a neutralizing agent to the filtrate from the second step to separate a product containing zinc and copper, and filtered water of the third step Is repeatedly used as a neutralization liquid in the first step, and a draining treatment is performed by adding a sulfiding agent to the filtrate from the first step.
[0005]
By such a wet treatment method, heavy metals contained in fly ash are stably separated and effectively recovered as heavy metal resources, and waste water after wet treatment of fly ash is treated with national wastewater standards, that is, water quality. It has become possible to detoxify in accordance with the regulations of Article 3, Paragraph 1 of the Pollution Control Law.
[0006]
[Problems to be solved by the invention]
However, in JP-A-7-109533, a large amount of salt such as calcium chloride enters the recovered heavy metal deposit, and the problem in terms of recycling heavy metal remains because it dislikes the introduction of chlorine in the smelting process. . Furthermore, in recent years, regulations have been further tightened due to concerns about environmental pollution in some regions, and regulations are imposed with strict standards exceeding the national wastewater standards.
For example, according to the local ordinance (I city additional standard value), cadmium 0.01 mg / l (national wastewater standard value 0.1 mg / l, the same applies hereinafter), fluorine 10 mg / l (15 mg / l), mercury 0 .0005 mg / l (0.005 mg / l) and COD of 10 mg / l (120 mg / l) are severely regulated.
[0007]
In addition, wastewater obtained by wet-treating fly ash contains a large amount of chlorine ranging from 20 to 50 g / l, and dissolved heavy metals easily form chloride complex ions, which are very difficult to remove. The current situation is that there is a case where the conventional technology cannot cope with the above-mentioned additional regulations.
Further, even when selenium is mixed into the waste water, it is very difficult to remove the waste water below the waste water standard value by the conventional method, and many man-hours and costs are required.
[0008]
In view of such a situation, the present invention can separate useful heavy metals in fly ash from salts such as chlorine and calcium, and can be separated and recovered in a form that can be reused in the smelting process, and a large amount of fly ash can be treated with chlorine. The purpose of the present invention is to provide a fly ash treatment method that can be removed at the same time as other heavy metals even if selenium is mixed in wastewater containing selenium, and can meet strict regional drainage regulations.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, first, the present invention is a method for treating fly ash containing at least one of zinc, copper, lead and chlorine, and slurrying the fly ash by adding a mineral acid, A salt elution step for eluting salts, particularly chlorides, by adjusting the pH to 5 or less, and a neutralizer is added to the slurry of the salt elution step to adjust the pH to 8-12, and heavy metal-containing residue and salts A heavy metal separation step for solid-liquid separation into a contained filtrate, and a ferrous salt added to the salt-containing filtrate obtained in the heavy metal separation step to adjust the pH to 8 or higher for solid-liquid separation, including a coprecipitated heavy metal A method for treating heavy metal-containing fly ash comprising an iron salt deposit and an iron salt coprecipitation step for obtaining filtered water; secondly, the reaction temperature of the iron salt coprecipitation step is 30 ° C. or higher. A method for treating the heavy metal-containing fly ash according to the first aspect, wherein the iron salt coprecipitation step is characterized in that: The method for treating heavy metal-containing fly ash according to the first aspect, wherein the reaction temperature is 30 ° C. or higher and the reaction is performed in an atmosphere in which oxidation is suppressed; fourth, the iron salt coprecipitation It has an aluminum salt coprecipitation step of adding aluminum salt to the filtered water obtained in the process, adjusting the pH to 6-8 and performing solid-liquid separation to obtain an aluminum salt deposit containing coprecipitated heavy metals and filtered water. The method for treating heavy metal-containing fly ash according to any one of 1 to 3 above, characterized in that: Fifth, an aluminum salt is added to the filtered water obtained in the iron salt coprecipitation step to adjust the pH to 6 The aluminum salt co-precipitation step for obtaining a solid solution and a co-precipitated heavy metal and filtered water by adjusting to ~ 8, and subjecting the obtained filtered water to COD component adsorption treatment with an adsorbent It has the COD adsorption | suction process of obtaining clean water, The said 1st-3rd characterized by the above-mentioned A method for treating heavy metal-containing fly ash according to any one of the above; sixth, a COD adsorption step of obtaining purified water by subjecting the filtered water obtained in the iron salt coprecipitation step to adsorption of a COD component with an adsorbent The method for treating heavy metal-containing fly ash according to any one of the first to third aspects, characterized by comprising: seventh, washing the heavy metal-containing residue obtained in the heavy metal separation step with hot water or water In any one of the first to sixth aspects, the method includes a washing step of obtaining a washing residue and washing filtrate, and using the obtained washing filtrate as water for slurrying fly ash in the salt elution step. A method for treating heavy metal-containing fly ash as described above; eighth, a method for treating fly ash containing at least one of zinc, copper, lead and chlorine, and adding water and mineral acid to the fly ash to make a slurry; Salts that adjust pH to 5 or less and elute salts, especially chlorides An elution step, a heavy metal separation step of adjusting the pH to 8 to 12 by adding a neutralizing agent to the slurry of the salt elution step, and solid-liquid separation into a heavy metal-containing residue and a salt-containing filtrate, and the heavy metal separation step A lead product recovery step of adding a mineral acid to the heavy metal-containing product obtained in step 1 and repulping, adjusting the pH to 4 or less, and solid-liquid separation to obtain a lead product containing lead as a main component, and the lead A copper / zinc product recovery step in which a neutralizer is added to the filtrate obtained in the product recovery step, the pH is adjusted to 8 or more, and solid-liquid separation is performed to obtain a copper / zinc product mainly composed of copper and zinc; The ferrous salt is obtained by adding ferrous salt to the salt-containing filtrate obtained in the heavy metal separation step, adjusting the pH to 8 or higher, and performing solid-liquid separation to obtain a salt solution containing coprecipitated heavy metal and filtered water. A method for treating heavy metal-containing fly ash characterized by comprising: a precipitation step; The method for treating heavy metal-containing fly ash according to the eighth aspect, wherein the temperature is 30 ° C. or higher; tenth, the reaction temperature of the iron salt coprecipitation step is 30 ° C. or higher; and The method for treating heavy metal-containing fly ash according to the eighth aspect, wherein the reaction is performed in an atmosphere in which oxidation is suppressed; eleventh, to the filtered water obtained in the iron salt coprecipitation step, The above-mentioned eighth to tenth steps characterized by comprising aluminum salt coprecipitation steps of adding aluminum salt to adjust pH to 6-8 and performing solid-liquid separation to obtain aluminum salt residue containing coprecipitated heavy metal and filtered water. A method for treating heavy metal-containing fly ash according to any one of the above; twelfth, an aluminum salt is added to the filtered water obtained in the iron salt coprecipitation step and the pH is adjusted to 6-8, followed by solid-liquid separation. , An aluminum salt coprecipitation step for obtaining coagulated heavy metal containing aluminum salt and filtered water, The method for treating heavy metal-containing fly ash according to any one of the eighth to tenth aspects, further comprising a COD adsorption step of obtaining purified water by subjecting the filtered water to adsorption of a COD component with an adsorbent; Thirteenth, any of the eighth to tenth aspects, further comprising a COD adsorption step of obtaining purified water by subjecting the filtered water obtained in the iron salt coprecipitation step to adsorption treatment of a COD component with an adsorbent. A method for treating heavy metal-containing fly ash according to claim 14; and a washing step of washing the heavy metal-containing residue obtained in the heavy metal separation step with hot water or water to obtain the washed residue and washing filtered water. The heavy metal-containing material according to any one of the eighth to thirteenth aspects, wherein the washed filtered water is used as water for slurrying fly ash in the salt elution step together with filtered water from the copper / zinc product recovery step. A method for treating fly ash is provided.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will be described with reference to the process diagram of FIG. 1 by taking as an example a method for treating fly ash from an incinerator intended for industrial waste. First, fly ash is mixed with water to make a slurry, and while stirring this slurry, a mineral acid such as hydrochloric acid or sulfuric acid is added to adjust the pH to 5 or less, preferably pH 4 or less, chlorine, sodium, Salts such as calcium, especially chlorides are transferred to the liquid side (salt elution step). In addition, since the pH of the slurry varies depending on the fly ash composition, the amount of mineral acid added is adjusted according to the fly ash. Therefore, it is not necessary to add mineral acid when the pH of the slurry is already at the optimum pH.
[0011]
Next, an alkali neutralizing agent such as sodium hydroxide or sodium carbonate is added to adjust the pH to between 8 and 12, and then a solid containing a heavy metal and chlorine, sodium, calcium, etc. by solid-liquid separation. Solid-liquid separation into a filtrate containing salts (heavy metal separation step). As described above, after the salts in the fly ash are sufficiently eluted on the acidic side in the salt elution step, the acidic eluate is neutralized in the heavy metal separation step, so that It becomes possible to significantly reduce the salt content. This heavy metal-containing residue having a low chlorine content can be used as a raw material for the smelting process as it is.
[0012]
Then, a ferrous salt such as ferrous chloride was added to the salt-containing filtrate from the heavy metal separation step, the pH was adjusted to 8 or more, and a trace amount of heavy metal remaining in the liquid was coprecipitated with the iron salt. Thereafter, this is subjected to solid-liquid separation, whereby an iron salt coprecipitate and clean filtered water can be obtained (iron coprecipitation step).
[0013]
That is, by adjusting the pH by adding a ferrous salt, all ferrous ions produce ferrous hydroxide regardless of high dissolved chlorine, and this active first active hydration hydroxide is crystallized. It is thought that iron takes in and coprecipitates residual heavy metals such as Cu, Pb, Zn, Cd, Cr, As, Sb, Bi, Ni, etc. in addition to Hg and Se during the precipitation process. The removal efficiency, such as being able to reduce to a low level, can be dramatically increased. For example, mercury that has been required to be adsorbed by an adsorbent such as activated carbon in the prior art can be sufficiently treated by the iron salt coprecipitation treatment of this method.
[0014]
The reaction temperature of the iron salt coprecipitation step is room temperature or higher, preferably 30 ° C. or higher, more preferably 45 ° C. or higher. Although this reaction can be performed in an air atmosphere, it is preferably performed in a tank where air is shut off, and more preferably in a non-oxidizing atmosphere such as a nitrogen gas atmosphere. This can significantly increase efficiency. By carrying out the reaction in an atmosphere in which the reaction temperature is 30 ° C. or higher and the oxidizability is suppressed, the deposition efficiency of heavy metals is not only synergistically increased, but also the filtration efficiency from the reaction solution is improved.
[0015]
When the salt-containing filtrate contains fluorine, aluminum fluoride such as aluminum chloride is added to the filtered water from the iron salt coprecipitation step to adjust the pH to about 6 to 8, and the remaining fluorine is aluminum fluoride. At the same time, trace amounts of heavy metal remaining can be coprecipitated with the aluminum hydroxide produced at the same time, and this solution is solid-liquid separated to obtain clean filtered water together with the aluminum salt coprecipitate. (Aluminum salt coprecipitation process).
[0016]
Further, when the filtered water from the aluminum salt coprecipitation step still contains COD to the extent that it causes a problem, the COD can be reduced by subjecting it to an adsorption treatment with an adsorbent such as activated carbon or a chelating agent. it can. Of course, a column may be used for this adsorption treatment with activated carbon, but it may be added in the form of granules or powder together with the aluminum salt of the previous step and separated into solid and liquid. Of course, COD in the liquid is removed, and the filterability of aluminum hydroxide can be extremely improved.
[0017]
If the filtered water from the iron salt coprecipitation step does not contain a significant amount of fluorine and contains a problematic amount of COD, the aluminum salt coprecipitation step is omitted and the filtered water is adsorbed as it is. It can be used for the process.
[0018]
Further, the neutralized precipitate from the heavy metal separation step, that is, the heavy metal-containing precipitate, is washed with water in a repulp or filter press (normal washing, backwashing) to further neutralize salts such as chlorine, sodium and calcium. The washed filtered water can be circulated in the salt elution process as water for slurrying fly ash (washing process).
[0019]
The heavy metal-containing residue from the heavy metal separation step can be used as a raw material for the smelting step as it is, but if further separated, the processing of the smelting step is reduced. That is, in the cleaning process, the heavy metal-containing residue may be treated with water and the washed residue after the contained salts are recovered may be treated. Water is added to the object and repulped, and a mineral acid such as hydrochloric acid or sulfuric acid is added to adjust the pH to 4 or less, preferably 3 or less, to dissolve heavy metals mainly composed of zinc, copper and cadmium, By liquid separation, heavy metals mainly composed of lead that is hardly soluble in mineral acids are recovered as lead products (lead product recovery step).
[0020]
In the filtrate from the lead product recovery step, an alkali neutralizer is added to adjust the pH to 8 or more, preferably about pH 11, thereby producing heavy metal hydroxides mainly composed of zinc, copper and cadmium. And solid-liquid separation can obtain a copper / zinc product and filtered water. This filtered water, together with the washed filtered water from the washing step, is repeated as the fly ash slurry water in the salt elution step, thereby improving the recovery of heavy metals and the economics of fly ash treatment. .
[0021]
As described above, in the present invention, heavy metals contained in fly ash are separated and recovered as lead products mainly composed of lead and copper / zinc products mainly composed of hydroxide copper, zinc and cadmium. It can be used as a raw material for smelting, and iron salt or aluminum salt can be recovered and recycled as raw materials for blast furnaces and cement kilns. In addition, heavy metals and harmful elements are sufficiently removed as waste water. Thus, it is possible to obtain clean filtered water that satisfies not only the national drainage regulations but also the local regulations.
[0022]
[Example 1]
First, 8 liters of pure water is put into a 10 liter beaker and stirred, and 800 g of fly ash from the A processing plant is added as a raw material to make a slurry. While stirring for 10 minutes, 36% hydrochloric acid is added as mineral acid to adjust the pH. Adjusted to and maintained at 4, dissolved for 30 minutes (salt elution step), then added with 200 g / liter of caustic soda solution as an alkali neutralizer, adjusted to pH 11 and maintained for 30 minutes, followed by filtration operation Thus, a heavy metal-containing residue mainly composed of heavy metals and a salt-containing filtrate mainly composed of salts were separated (heavy metal separation step). Next, the obtained heavy metal-containing residue was transferred to a 5 liter beaker, and 2.0 liters of pure water was added to form a slurry and maintained for 30 minutes, and then a washing residue and a washing filtrate were obtained (washing step).
Table 1 shows the composition of the raw fly ash and the quality of the washed residue obtained in the washing step, and Table 2 shows the composition of the salt-containing filtrate from the desalting step.
[0023]
[Table 1]
[Table 2]
Subsequently, the resulting washed product is transferred to a 10 liter beaker, repulped with 5 liters of pure water, added with 95% H 2 SO 4 , adjusted to pH 3 to dissolve heavy metals other than lead, and lead is removed. The main lead products were obtained (lead product recovery process). Table 1 shows the quality of the lead products obtained.
Further, 200 g / l of caustic soda solution was added to the separated filtrate to adjust the pH to 11, neutralized with a hydroxide product mainly composed of copper / zinc, and then filtered into filtered water (copper).・ Zinc product recovery process). The quality of the obtained copper / zinc product is shown in Table 1.
[0025]
[Example 2]
[Test 1]
Take 300 ml of the salt-containing filtrate shown in Table 2 in a 500 ml beaker, add ferrous sulfate as the ferrous salt and 350 mg / liter of iron, and adjust the pH to 9 under each set temperature and atmosphere. -After maintaining for 30 minutes, the mixture was separated into iron and filtrate by suction filtration (using C filter paper) (iron salt coprecipitation process).
Table 3 shows the grade of Se and Sb of the filtrate obtained.
[0026]
[Table 3]
[0027]
Regarding Se and Sb, the reaction temperature and reaction atmosphere in the iron salt coprecipitation step were investigated, and a remarkable removal effect was observed from around 30 ° C. Moreover, as compared with the reaction temperature of 45 ° C., a more remarkable removal effect was obtained by using a nitrogen atmosphere.
[0028]
[Test 2]
Next, 4 liters of the salt-containing filtrate shown in Table 2 was placed in a 5 liter beaker, and 500 mg / liter of ferrous sulfate as the ferrous salt was added in an amount of iron, and the pH was adjusted to 9 at 60 ° C. under heating. The mixture was allowed to react for 30 minutes and then separated into iron salt and filtered water by suction filtration (using C filter paper) (iron salt coprecipitation step).
The quality of the obtained filtered water is shown in Table 4.
[0029]
[Table 4]
[0030]
[Test 3]
Take 2.5 liters of filtered water (after treatment) treated in Test 2 (F: containing 16 mg / liter) into a 3 liter beaker, add aluminum chloride as an aluminum salt in an amount of 50 mg / liter, and heat to 45 ° C. After adjusting and maintaining the pH at 7 under temperature and reacting for 30 minutes, the mixture was separated into a residue and a filtrate by suction filtration (using C filter paper) (aluminum salt coprecipitation step).
The fluorine concentration of the obtained filtrate was 4.2 mg / liter, which was significantly lower than the above-mentioned reference value of 10 mg / liter.
[0031]
[Test 4]
The filtrate obtained in Test 3 was subjected to liquid passing treatment on a mini-column filled with palm activated carbon for wastewater treatment under the condition of SV ratio of 5 to obtain final wastewater (COD adsorption process).
The COD in the final wastewater showed a value of <1 mg / liter, which was well below the above-mentioned reference value of 10 mg / liter.
[0032]
【The invention's effect】
According to the first aspect of the present invention, the salt in the fly ash is sufficiently dissolved with an acid and then neutralized, so that chlorine can be remarkably removed from the heavy metal-containing residue, which can be a raw material for the smelting process. In addition to selenium, heavy metals such as copper and lead can be simultaneously reduced to extremely low levels, and filtered effluent that can meet strict regional effluent regulations exceeding the national effluent regulations. There is an effect that can be.
According to invention of Claim 2 and 3, there exists an effect that the filtration waste_water | drain which further reduced heavy metal is obtained stably. According to invention of Claims 4-6, the additional waste water purification process corresponding to the composition of fly ash can be performed, and there exists an effect that a drainage can be ensured completely. According to invention of Claim 7, in addition to said effect, there exists an effect that the recoverability of heavy metal and the economical efficiency of a fly ash process can be improved.
[0033]
According to the invention of
According to the ninth and tenth aspects of the present invention, there is an effect that the filtered waste water further reducing heavy metals can be obtained stably. According to invention of Claims 11-13, there exists an effect that the additional waste water purification process corresponding to the composition of fly ash can be performed, and a filtering drainage can be ensured. According to the invention of claim 14, in addition to the above effects, there is an effect of improving the recoverability of heavy metals and the economics of fly ash treatment.
[Brief description of the drawings]
FIG. 1 is a process diagram showing a method for treating heavy metal-containing fly ash according to the present invention.
Claims (14)
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| JP32400198A JP3646245B2 (en) | 1998-11-13 | 1998-11-13 | Processing method for fly ash containing heavy metals |
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| CN108525639A (en) * | 2018-04-27 | 2018-09-14 | 福州大学 | The preparation method and applications of chlorine sorbing material in a kind of waste incineration |
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| JP4629851B2 (en) * | 2000-10-30 | 2011-02-09 | 太平洋セメント株式会社 | Wastewater treatment method |
| JP4219138B2 (en) * | 2002-09-06 | 2009-02-04 | 株式会社クボタ | Method and apparatus for adding heavy metal insolubilizer |
| JP4431767B2 (en) * | 2003-10-27 | 2010-03-17 | Ｄｏｗａメタルマイン株式会社 | Wet ash processing method |
| JP2005288413A (en) * | 2004-04-05 | 2005-10-20 | Mitsubishi Materials Corp | Method for treating flying-ash leachate |
| CN100431688C (en) * | 2006-12-13 | 2008-11-12 | 大连理工大学 | Modified fly ash absorbent and method for processing nitrophenol polymerization inhibitor production waste water |
| JP2013014789A (en) * | 2011-06-30 | 2013-01-24 | Mitsubishi Materials Corp | Method for treating flue cinder |
| JP6486877B2 (en) * | 2016-09-21 | 2019-03-20 | 株式会社ダイワエクセル | Waste water treatment device and waste water treatment method using the waste water treatment device |
| CN112570419B (en) * | 2020-11-20 | 2023-04-18 | 四川科龙达环保股份有限公司 | Aluminum ash recycling method, harmless aluminum ash and application of harmless aluminum ash |
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| CN108525639A (en) * | 2018-04-27 | 2018-09-14 | 福州大学 | The preparation method and applications of chlorine sorbing material in a kind of waste incineration |
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