JP5201455B2 - Phosphorus recovery material, its manufacturing method and phosphorus recovery method - Google Patents
Phosphorus recovery material, its manufacturing method and phosphorus recovery method Download PDFInfo
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- JP5201455B2 JP5201455B2 JP2008143896A JP2008143896A JP5201455B2 JP 5201455 B2 JP5201455 B2 JP 5201455B2 JP 2008143896 A JP2008143896 A JP 2008143896A JP 2008143896 A JP2008143896 A JP 2008143896A JP 5201455 B2 JP5201455 B2 JP 5201455B2
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- calcium silicate
- silicate hydrate
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- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 title claims description 201
- 239000011574 phosphorus Substances 0.000 title claims description 200
- 229910052698 phosphorus Inorganic materials 0.000 title claims description 200
- 238000011084 recovery Methods 0.000 title claims description 125
- 239000000463 material Substances 0.000 title claims description 83
- 238000000034 method Methods 0.000 title claims description 50
- 238000004519 manufacturing process Methods 0.000 title claims description 12
- 239000000378 calcium silicate Substances 0.000 claims description 82
- 229910052918 calcium silicate Inorganic materials 0.000 claims description 82
- OYACROKNLOSFPA-UHFFFAOYSA-N calcium;dioxido(oxo)silane Chemical compound [Ca+2].[O-][Si]([O-])=O OYACROKNLOSFPA-UHFFFAOYSA-N 0.000 claims description 76
- 239000011575 calcium Substances 0.000 claims description 44
- 239000007788 liquid Substances 0.000 claims description 42
- 239000010802 sludge Substances 0.000 claims description 32
- 239000002245 particle Substances 0.000 claims description 30
- 238000006243 chemical reaction Methods 0.000 claims description 26
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 25
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 25
- 239000004571 lime Substances 0.000 claims description 25
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 24
- 229910052791 calcium Inorganic materials 0.000 claims description 24
- 239000002351 wastewater Substances 0.000 claims description 24
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 20
- 239000002002 slurry Substances 0.000 claims description 20
- 239000011148 porous material Substances 0.000 claims description 19
- 229910052588 hydroxylapatite Inorganic materials 0.000 claims description 18
- XYJRXVWERLGGKC-UHFFFAOYSA-D pentacalcium;hydroxide;triphosphate Chemical compound [OH-].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O XYJRXVWERLGGKC-UHFFFAOYSA-D 0.000 claims description 18
- 239000002994 raw material Substances 0.000 claims description 18
- 239000002244 precipitate Substances 0.000 claims description 14
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 13
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 12
- 239000002253 acid Substances 0.000 claims description 8
- 238000001914 filtration Methods 0.000 claims description 7
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 6
- 238000000354 decomposition reaction Methods 0.000 claims description 6
- 238000001556 precipitation Methods 0.000 claims description 6
- 229910001854 alkali hydroxide Inorganic materials 0.000 claims description 5
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 claims description 3
- 230000002378 acidificating effect Effects 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 2
- 238000005054 agglomeration Methods 0.000 claims 1
- 230000002776 aggregation Effects 0.000 claims 1
- 235000012241 calcium silicate Nutrition 0.000 description 76
- 230000000052 comparative effect Effects 0.000 description 25
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 21
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 17
- 239000000047 product Substances 0.000 description 16
- 239000000243 solution Substances 0.000 description 16
- MXZRMHIULZDAKC-UHFFFAOYSA-L ammonium magnesium phosphate Chemical compound [NH4+].[Mg+2].[O-]P([O-])([O-])=O MXZRMHIULZDAKC-UHFFFAOYSA-L 0.000 description 15
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 15
- 239000000920 calcium hydroxide Substances 0.000 description 15
- 235000011116 calcium hydroxide Nutrition 0.000 description 15
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 15
- 229910052567 struvite Inorganic materials 0.000 description 15
- 230000000704 physical effect Effects 0.000 description 11
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- -1 ammonium ions Chemical class 0.000 description 10
- 229910000019 calcium carbonate Inorganic materials 0.000 description 10
- 238000005345 coagulation Methods 0.000 description 10
- 230000015271 coagulation Effects 0.000 description 10
- 239000000843 powder Substances 0.000 description 10
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 10
- 235000012239 silicon dioxide Nutrition 0.000 description 10
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 9
- 230000035484 reaction time Effects 0.000 description 9
- 238000003756 stirring Methods 0.000 description 9
- 239000002686 phosphate fertilizer Substances 0.000 description 8
- 238000004062 sedimentation Methods 0.000 description 8
- 239000007787 solid Substances 0.000 description 8
- 230000007423 decrease Effects 0.000 description 7
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 6
- 239000006227 byproduct Substances 0.000 description 6
- 239000013078 crystal Substances 0.000 description 5
- 230000029087 digestion Effects 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 230000009257 reactivity Effects 0.000 description 5
- 238000000926 separation method Methods 0.000 description 5
- 239000010865 sewage Substances 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 239000001506 calcium phosphate Substances 0.000 description 4
- 229910000389 calcium phosphate Inorganic materials 0.000 description 4
- 235000011010 calcium phosphates Nutrition 0.000 description 4
- 239000003337 fertilizer Substances 0.000 description 4
- 239000005416 organic matter Substances 0.000 description 4
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- QORWJWZARLRLPR-UHFFFAOYSA-H tricalcium bis(phosphate) Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O QORWJWZARLRLPR-UHFFFAOYSA-H 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 3
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 3
- ABLZXFCXXLZCGV-UHFFFAOYSA-N Phosphorous acid Chemical compound OP(O)=O ABLZXFCXXLZCGV-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 239000003513 alkali Substances 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 238000002425 crystallisation Methods 0.000 description 3
- 238000003795 desorption Methods 0.000 description 3
- 238000005755 formation reaction Methods 0.000 description 3
- MKTRXTLKNXLULX-UHFFFAOYSA-P pentacalcium;dioxido(oxo)silane;hydron;tetrahydrate Chemical compound [H+].[H+].O.O.O.O.[Ca+2].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[O-][Si]([O-])=O.[O-][Si]([O-])=O.[O-][Si]([O-])=O.[O-][Si]([O-])=O.[O-][Si]([O-])=O.[O-][Si]([O-])=O MKTRXTLKNXLULX-UHFFFAOYSA-P 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 description 2
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 2
- 239000001110 calcium chloride Substances 0.000 description 2
- 229910001628 calcium chloride Inorganic materials 0.000 description 2
- 239000000292 calcium oxide Substances 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 230000018044 dehydration Effects 0.000 description 2
- 238000006297 dehydration reaction Methods 0.000 description 2
- 229910001425 magnesium ion Inorganic materials 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 239000010456 wollastonite Substances 0.000 description 2
- 229910052882 wollastonite Inorganic materials 0.000 description 2
- 229910014497 Ca10(PO4)6(OH)2 Inorganic materials 0.000 description 1
- 229910021532 Calcite Inorganic materials 0.000 description 1
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- 229910017958 MgNH Inorganic materials 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- ILRRQNADMUWWFW-UHFFFAOYSA-K aluminium phosphate Chemical compound O1[Al]2OP1(=O)O2 ILRRQNADMUWWFW-UHFFFAOYSA-K 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229910052586 apatite Inorganic materials 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- 229940043430 calcium compound Drugs 0.000 description 1
- 150000001674 calcium compounds Chemical class 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000003093 cationic surfactant Substances 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 239000000701 coagulant Substances 0.000 description 1
- 230000002860 competitive effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000004567 concrete Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000030609 dephosphorylation Effects 0.000 description 1
- 238000006209 dephosphorylation reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000004889 fertilizer analysis Methods 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 239000011381 foam concrete Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 150000002505 iron Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910000398 iron phosphate Inorganic materials 0.000 description 1
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 description 1
- 238000002386 leaching Methods 0.000 description 1
- 229910001629 magnesium chloride Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 150000007522 mineralic acids Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 125000001477 organic nitrogen group Chemical group 0.000 description 1
- 239000003002 pH adjusting agent Substances 0.000 description 1
- VSIIXMUUUJUKCM-UHFFFAOYSA-D pentacalcium;fluoride;triphosphate Chemical compound [F-].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O VSIIXMUUUJUKCM-UHFFFAOYSA-D 0.000 description 1
- 229940085991 phosphate ion Drugs 0.000 description 1
- 238000011002 quantification Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000007655 standard test method Methods 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
- 238000009849 vacuum degassing Methods 0.000 description 1
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A40/00—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
- Y02A40/10—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in agriculture
- Y02A40/20—Fertilizers of biological origin, e.g. guano or fertilizers made from animal corpses
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- Separation Of Suspended Particles By Flocculating Agents (AREA)
- Removal Of Specific Substances (AREA)
- Fertilizers (AREA)
Description
本発明は、消化汚泥脱離液など、リンを高度に含む有機性排液からリンをリン酸肥料として回収することができるリン回収資材およびリン回収方法に関する。 The present invention relates to a phosphorus recovery material and a phosphorus recovery method capable of recovering phosphorus as a phosphate fertilizer from an organic effluent containing a high amount of phosphorus, such as a digested sludge detachment liquid.
嫌気性消化は嫌気性微生物を用いて汚泥中の有機物をメタンと二酸化炭素に変換することにより減量するプロセスである。脱水過程で生じる脱離液は高濃度の溶解性リンを含んでおり、その大部分はリン酸イオン（ＰＯ4 3-）として溶存している。また、有機性の窒素は大部分がアンモニアに変換されるので、高濃度のアンモニウムイオン（ＮＨ4 +）を含んでいる。通常、消化汚泥脱離液は汚水処理プロセスに返流されるが、これが汚水処理系における窒素やリンの負荷を高め、放流水中の窒素濃度やリン濃度を高めてしまう結果となる。 Anaerobic digestion is a process that reduces the amount of organic matter in sludge by converting it to methane and carbon dioxide using anaerobic microorganisms. The desorbed liquid produced in the dehydration process contains a high concentration of soluble phosphorus, most of which is dissolved as phosphate ions (PO 4 3− ). Organic nitrogen contains a high concentration of ammonium ions (NH 4 + ) because most of it is converted to ammonia. Normally, the digested sludge detachment liquid is returned to the sewage treatment process, which increases the load of nitrogen and phosphorus in the sewage treatment system, resulting in an increase in the nitrogen concentration and phosphorus concentration in the effluent water.
また、汚泥中に含有されるリン酸イオン、マグネシウムイオン、アンモニウムイオンが配管中において、リン酸マグネシウムアンモニウム（ＭｇＮＨ4ＰＯ4・６Ｈ2Ｏ：ＭＡＰと云う）を生成し、特に近年の下水処理施設の高度処理化に伴い、生物学的脱リン法を適用された汚泥は嫌気性消化によってリン酸イオン濃度が高くなり、ＭＡＰによるスケーリングが深刻である。 Also, phosphate ions, magnesium ions, and ammonium ions contained in sludge produce magnesium ammonium phosphate (MgNH 4 PO 4 .6H 2 O: MAP) in the pipe, especially in recent sewage treatment facilities. With advanced treatment, sludge to which biological dephosphorization is applied has a high phosphate ion concentration due to anaerobic digestion, and scaling by MAP is serious.
そこで、嫌気性消化工程の後の消化脱離液にマグネシウムイオンを添加してリン酸マグネシウムアンモニウム（ＭＡＰ）結晶を析出させて脱リンするＭＡＰ晶析法と呼ばれる処理方法が行なわれている。回収されたＭＡＰはリン酸と窒素を含む化成肥料として農業利用することができる。 Therefore, a treatment method called a MAP crystallization method is performed in which magnesium ions are added to the digestion and detachment solution after the anaerobic digestion step to precipitate magnesium ammonium phosphate (MAP) crystals for dephosphorylation. The collected MAP can be used in agriculture as a chemical fertilizer containing phosphoric acid and nitrogen.
しかし、従来のＭＡＰ法は、ｐＨ調整剤としての水酸化ナトリウムや添加剤として塩化マグネシウム等の薬品コストが嵩むと云う問題がある。また、水中のリンをＭＡＰの固体粒子として回収する際に、生成した微細なＭＡＰ粒子が処理水と共に流出してＭＡＰの回収率が低下し、これが処理水槽中に蓄積される等の問題があった。具体的には、ＭＡＰ法は比較的ＳＳ濃度が小さく、例えば３０００mg/L程度において有効であり、高濃度の汚泥中に含まれる微細なＭＡＰ粒子はほとんど回収されず、汚泥とともに処分されるので、窒素とリンの回収技術としては問題があった。 However, the conventional MAP method has a problem that chemical costs such as sodium hydroxide as a pH adjuster and magnesium chloride as an additive increase. In addition, when recovering phosphorus in water as MAP solid particles, the generated fine MAP particles flow out together with the treated water, reducing the MAP recovery rate and accumulating this in the treated water tank. It was. Specifically, the MAP method has a relatively small SS concentration, and is effective at, for example, about 3000 mg / L, and the fine MAP particles contained in the high-concentration sludge are hardly recovered and disposed of with the sludge. There was a problem with nitrogen and phosphorus recovery technology.
ＭＡＰ晶析法の上記問題を解消する手段として、例えば、特開２００２−３２６０８９号公報には、流動層リアクター内の結晶が外部に流出しないような速度で原水および循環水を上向流で通水することが記載されている。流動層リアクターの場合、リアクター内で結晶成長が進むように操作条件を設定すれば、微細な核を発生させずにＭＡＰ粒子を回収することができるが、実際は局所的な過飽和度の生成によって微細な核の発生を避けることができず、このためリン回収率が低下し、また原水および循環水、薬剤のショートパスによる結晶表面以外での核化によるリン回収率の低下等の問題がある。 As means for solving the above-mentioned problem of the MAP crystallization method, for example, Japanese Patent Application Laid-Open No. 2002-326089 discloses that raw water and circulating water are passed upwardly at such a speed that crystals in the fluidized bed reactor do not flow outside. It is described to be watered. In the case of a fluidized bed reactor, MAP particles can be recovered without generating fine nuclei if the operating conditions are set so that crystal growth proceeds in the reactor. Therefore, there is a problem in that the phosphorus recovery rate is lowered, and the phosphorus recovery rate is reduced due to nucleation other than the crystal surface due to a short path of raw water, circulating water, and chemicals.
リンを除去する他の方法として凝集沈殿法が知られている。凝集沈殿法は、カルシウム、アルミニウム、鉄など、リンと不溶性沈殿を生成する無機凝集剤を排水に添加し、沈殿を分離除去する方法である。しかし、凝集剤としてアルミニウム塩や鉄塩を添加する方法では、生成したリン酸アルミニウム、リン酸鉄が植物に利用されないため、肥料等に再利用するのは困難である。また、凝集剤として消石灰、塩化カルシウム等のカルシウム化合物を添加する法では、生成するリン酸カルシウムは植物に利用されやすい形態であるので、これを肥料等として再利用するためには好適な方法である。しかし、この方法では、生成したリン酸カルシウムは微細粒子のため、濾過や沈降分離などの固液分離が難しく、また生成したケーキの含水率が高くハンドリングが困難であると云う問題がある。 As another method for removing phosphorus, a coagulation precipitation method is known. The coagulation precipitation method is a method in which an inorganic coagulant that forms an insoluble precipitate with phosphorus, such as calcium, aluminum, or iron, is added to waste water, and the precipitate is separated and removed. However, in the method of adding an aluminum salt or iron salt as a flocculant, the produced aluminum phosphate and iron phosphate are not used in plants, and therefore, it is difficult to reuse them as fertilizers. Further, in the method of adding a calcium compound such as slaked lime or calcium chloride as a flocculant, the generated calcium phosphate is in a form that can be easily used by plants, so it is a suitable method for reusing it as fertilizer. However, in this method, since the produced calcium phosphate is fine particles, there is a problem that solid-liquid separation such as filtration and sedimentation separation is difficult, and the moisture content of the produced cake is high and handling is difficult.
これら従来の方法を解決する手段として、珪酸カルシウムを主成分とする脱リン剤を使う方法が種々提案されている。例えば、特開昭６１−２６３６３６号公報（特許文献１）にはＣａＯ/ＳｉＯ2モル比が１.５〜５の範囲内にある珪酸カルシウム水和物を主成分とする水処理剤が記載されている。また、特公平２−２０３１５号公報（特許文献２）には空隙率５０〜９０％の独立気泡を有する珪酸カルシウム水和物からなる脱リン材が記載されている。特開平１０−２３５３４４号公報（特許文献３）には珪酸カルシウム水和物を主成分とした直径数ミリ程度の球状または中空状に成形した脱リン材が記載されている。さら、特開２０００−１３５４９３号公報（特許文献４）には珪灰石を用いた脱リン方法が提案されている。
従来の珪酸カルシウムを主成分とする脱リン材を用いる方法は、回収物の脱水性や有機物混入の問題はある程度回避できるものの、リンとの反応速度が遅いため、回収物のリン濃度を上げるためには長い反応時間を必要とする。特に、消化汚泥脱離液を対象とした場合には、含有するリンと珪酸カルシウム類の反応速度が非常に遅く、実用に適さない。 Although the conventional method using a dephosphorization material mainly composed of calcium silicate can avoid the problems of dehydration of collected materials and organic matter contamination to some extent, the reaction rate with phosphorus is slow, so that the phosphorus concentration of the collected materials is increased. Requires a long reaction time. In particular, when digested sludge desorbed liquid is used as a target, the reaction rate of the contained phosphorus and calcium silicates is very slow, which is not suitable for practical use.
また、回収されるリン含有物はク溶性リン酸の含有量が１５％に満たないため、肥料公定法で定める副産りん酸肥料に該当せず、リン酸肥料として利用することができない。ク溶性リン酸の含有量を１５％以上に高めるには処理装置の容積を大きくする必要があり、コストアップを招くため実用的ではない。 Moreover, since the content of phosphorus to be recovered is less than 15% in the content of soluble phosphoric acid, it does not fall under the by-product phosphate fertilizer defined by the official fertilizer law and cannot be used as phosphate fertilizer. In order to increase the content of the soluble phosphoric acid to 15% or more, it is necessary to increase the volume of the processing apparatus, which increases the cost, and is not practical.
本発明は、従来のリン回収資材およびリン回収方法における上記問題を解決したものであり、排水等からリンを回収する際に、大型の装置を必要とせず、回収物を副産りん酸肥料として利用することができるリン回収資材およびリン回収方法を提供する。 The present invention solves the above-mentioned problems in conventional phosphorus recovery materials and phosphorus recovery methods, and does not require a large apparatus when recovering phosphorus from wastewater or the like, and the recovered product is used as a by-product phosphate fertilizer. Provided are phosphorus recovery materials and phosphorus recovery methods that can be used.
本発明は、以下に示す構成によって上記課題を解決したリン回収資材に関する。
〔１〕消化汚泥脱離液に含まれるリンの回収に用いられる凝集沈殿用のリン回収資材であって、平均粒子径(メジアン径)１０μm以上〜１５０μm以下、ＢＥＴ比表面積８０m2/ｇ以上、細孔容積０.５cm3/ｇ以上、遊離石灰含有量１０％未満、Ｃａ/Ｓｉモル比０.８以上〜１.８以下の多孔質および非晶質の珪酸カルシウム水和物からなり、リン回収物のク溶性リン酸が１５％以上であることを特徴とするリン回収資材。
This invention relates to the phosphorus collection | recovery material which solved the said subject with the structure shown below.
[1] Phosphorus recovery material for coagulation sedimentation used for recovery of phosphorus contained in digested sludge desorption liquid, having an average particle diameter (median diameter) of 10 μm to 150 μm, a BET specific surface area of 80 m 2 / g or more, pore volume 0.5 cm 3 / g or more, free lime content of less than 10%, Ca / Si molar ratio of 0.8 or more to 1.8 or less porous and made of amorphous calcium silicate hydrate, phosphorus A phosphorus recovery material characterized in that the recovered product has a soluble phosphonic acid content of 15% or more .
また、本発明は以下に示す構成からなるリン回収資材の製造方法に関する。
〔２〕珪酸原料と石灰原料とを水性スラリーとし、その水熱反応によって珪酸カルシウム水和物を生成させ、これを濾別し乾燥して珪酸カルシウム水和物からなるリン回収資材を製造する方法において、上記水性スラリーに水酸化アルカリを添加して水熱反応させることによって多孔質および非晶質の珪酸カルシウム水和物からなるリン回収資材を製造することを特徴とするリン回収資材の製造方法。
Moreover, this invention relates to the manufacturing method of the phosphorus collection | recovery material which consists of a structure shown below.
[2] A method for producing a phosphorus recovery material comprising calcium silicate hydrate by forming an aqueous slurry of a silicate raw material and a lime raw material, generating a calcium silicate hydrate by hydrothermal reaction, filtering it and drying it In which a phosphorus recovery material comprising porous and amorphous calcium silicate hydrate is manufactured by adding an alkali hydroxide to the aqueous slurry and causing a hydrothermal reaction. .
また、本発明は以下に示す構成からなるリン回収方法に関する。
〔３〕リン含有排水にリン回収資材を添加してリン含有沈殿物を生成させ、これを濾別してリンを回収する方法において、リン含有排水が消化汚泥脱離液であり、リン回収資材として平均粒子径(メジアン径)１０μm以上〜１５０μm以下、ＢＥＴ比表面積８０m 2 /ｇ以上、細孔容積０.５cm 3 /ｇ以上、遊離石灰含有量１０％未満、Ｃａ/Ｓｉモル比０.８以上〜１.８以下の多孔質および非晶質の珪酸カルシウム水和物からる請求項１に記載するリン回収資材を用いることを特徴とするリン回収方法。
〔４〕消化汚泥脱離液にリン回収資材を添加すると共に酸を添加して該液のｐＨを酸性側にし、珪酸カルシウム水和物の逐次的な分解でカルシウムを溶出させ、該液中のリンと反応させて珪酸カルシウム水和物粒子表面にヒドロキシアパタイトを生成せしめ、この沈殿物を分離してリンを回収する上記[３]のリン回収方法。
〔５〕上記[３]または上記[４]のリン回収方法において、反応終了時のｐＨが８.０以上〜９.０未満になるように酸を添加するリン回収方法。
〔６〕リン回収資材の使用量が、排水中のリン含有量に対して、Ｃａ／Ｐモル比が１.５以上〜２.５以下である上記[３]〜上記[５]の何れかに記載するリン回収方法。
〔７〕処理温度が１０℃以上〜１００℃未満である上記[３]〜上記[６]の何れかに記載するリン回収方法。
Moreover, this invention relates to the phosphorus collection | recovery method which consists of a structure shown below.
[3] In a method of adding phosphorus recovery material to phosphorus-containing wastewater to generate a phosphorus-containing precipitate, and filtering this to recover phosphorus, the phosphorus-containing wastewater is digested sludge detachment liquid, and average as phosphorus recovery material Particle diameter (median diameter) 10 μm to 150 μm, BET specific surface area 80 m 2 / g or more, pore volume 0.5 cm 3 / g or more, free lime content less than 10%, Ca / Si molar ratio 0.8 or more A phosphorus recovery method using the phosphorus recovery material according to claim 1, comprising a porous and amorphous calcium silicate hydrate of 1.8 or less .
[4] Adding phosphorus recovery material to the digested sludge desorption liquid and adding acid to bring the pH of the liquid to the acidic side, and eluting calcium by sequential decomposition of calcium silicate hydrate, The phosphorus recovery method according to the above [3], wherein it is reacted with phosphorus to form hydroxyapatite on the surface of calcium silicate hydrate particles, and the precipitate is separated to recover phosphorus.
[5] The phosphorus recovery method of [3] or [4], wherein an acid is added so that the pH at the end of the reaction is 8.0 or more and less than 9.0.
[6] Any of the above [3] to [5], wherein the amount of phosphorus recovery material used is such that the Ca / P molar ratio is 1.5 or more and 2.5 or less with respect to the phosphorus content in the waste water. A method for recovering phosphorus described in 1.
[7] The phosphorus recovery method according to any one of [3] to [6] above, wherein the treatment temperature is 10 ° C. or higher and lower than 100 ° C.
本発明のリン回収資材は、多孔質度が高く、好ましくは遊離石灰含量が１０％未満であって、Ｃａ/Ｓｉモル比が０.８〜１.８の非晶質珪酸カルシウム水和物からなるので、消化汚泥脱離液に添加して液中のリンを沈澱化する際に、競合する炭酸カルシウム生成反応が起こり難く、従来から知られている珪酸カルシウム水和物や消石灰など他の石灰質資材よりも高いリンの回収率を得ることができる。また、得られたリン回収物の濾過性等の物性も良好で、低コストで消化汚泥脱離液中のリンを回収することができる。 The phosphorus recovery material of the present invention is an amorphous calcium silicate hydrate having a high degree of porosity, preferably having a free lime content of less than 10% and a Ca / Si molar ratio of 0.8 to 1.8. Therefore, when adding to digested sludge desorbing liquid to precipitate phosphorus in the liquid, competing calcium carbonate formation reaction is unlikely to occur, and conventionally known calcium silicate hydrates and other calcareous substances such as slaked lime A higher phosphorus recovery rate than the material can be obtained. Moreover, physical properties such as filterability of the obtained phosphorus recovery product are good, and phosphorus in the digested sludge desorbing liquid can be recovered at low cost.
また、本発明のリン回収資材はリンとの反応性が高いので、消化汚泥脱離液中のリンと短時間に反応しリン含有量の高い沈殿物を生成することができ、ク溶性リン酸１５％以上の沈殿物を回収することができる。これは副産りん酸肥料として利用することができ、回収物を再資源化することができる。 In addition, since the phosphorus recovery material of the present invention is highly reactive with phosphorus, it can react with phosphorus in the digested sludge detachment liquid in a short time to produce a precipitate having a high phosphorus content, and is soluble in phosphoric acid. More than 15% of the precipitate can be recovered. This can be used as a by-product phosphate fertilizer, and the recovered material can be recycled.
以下、本発明を実施形態に基づいて具体的に説明する。なお、％は単位固有の場合を除き質量％である。 Hereinafter, the present invention will be specifically described based on embodiments. In addition,% is mass% except the case intrinsic | native to a unit.
〔リン回収資材〕
本発明のリン回収資材は、消化汚泥脱離液に含まれるリンの回収に用いられる凝集沈殿用のリン回収資材であって、平均粒子径(メジアン径)１０μm以上〜１５０μm以下、ＢＥＴ比表面積８０m2/ｇ以上、細孔容積０.５cm3/ｇ以上、遊離石灰含有量１０％未満、Ｃａ/Ｓｉモル比０.８以上〜１.８以下の多孔質および非晶質の珪酸カルシウム水和物からなり、リン回収物のク溶性リン酸が１５％以上であることを特徴とするリン回収資材である。
[Phosphorus recovery materials]
The phosphorus recovery material of the present invention is a phosphorus recovery material for coagulation sedimentation used for recovery of phosphorus contained in the digested sludge detachment liquid, and has an average particle diameter (median diameter) of 10 μm to 150 μm and a BET specific surface area of 80 m. Porous and amorphous calcium silicate hydrate with 2 / g or more, pore volume 0.5cm 3 / g or more, free lime content less than 10%, Ca / Si molar ratio 0.8 to 1.8 It is a phosphorus recovery material characterized in that it contains 15% or more of the soluble phosphoric acid of the phosphorus recovery product .
本発明のリン回収資材は、珪酸カルシウム水和物が水中のリンと反応して一般式〔Ｃａ10(ＰＯ4)6(ＯＨ)2〕によって表される難溶性のリン酸カルシウム（ヒドロキシアパタイト）を生成する。この沈殿物を排水から分離することによってリンを排水から回収することができる。 In the phosphorus recovery material of the present invention, calcium silicate hydrate reacts with phosphorus in water to form poorly soluble calcium phosphate (hydroxyapatite) represented by the general formula [Ca 10 (PO 4 ) 6 (OH) 2 ] To do. Phosphorus can be recovered from the wastewater by separating the precipitate from the wastewater.
本発明のリン回収資材の粒径は、リンの回収効率を高め、濾過性および沈降性の良い回収物を得るために、平均粒子径(メジアン径)１０μm〜１５０μmであるものが好ましい。平均粒子径が１０μmより小さいと濾過性および沈降性に劣り、リン回収後の固液分離が難しくなる。一方、リン回収資材の平均粒径が１５０μmより大きいと、液との接触面積の低下からリン回収能力が低下する。 The particle diameter of the phosphorus recovery material of the present invention is preferably an average particle diameter (median diameter) of 10 μm to 150 μm in order to increase the recovery efficiency of phosphorus and obtain a recovered product with good filterability and sedimentation. If the average particle size is smaller than 10 μm, filterability and sedimentation are poor, and solid-liquid separation after phosphorus recovery becomes difficult. On the other hand, if the average particle size of the phosphorus recovery material is larger than 150 μm, the phosphorus recovery capability decreases due to the decrease in the contact area with the liquid.
本発明のリン回収資材は、細孔容積０.５cm3/ｇ以上、ＢＥＴ比表面積８０ｍ2/ｇ以上の多孔質珪酸カルシウム水和物である。細孔容積０.５cm3/ｇ以上であれば概ね比表面積８０ｍ2/ｇ以上であり、この多孔質度の珪酸カルシウム水和物はリンとの反応速度が速く、短時間で消化汚泥脱離液中のリンを回収することができる。具体的には、実施例１〜２に示すように、反応時間６０分のリン回収率は約６５％以上、反応時間１２０分のリン回収率は約７５％以上である。 The phosphorus recovery material of the present invention is a porous calcium silicate hydrate having a pore volume of 0.5 cm 3 / g or more and a BET specific surface area of 80 m 2 / g or more. If the pore volume is 0.5 cm 3 / g or more, the specific surface area is approximately 80 m 2 / g or more, and this porous calcium silicate hydrate has a high reaction rate with phosphorus, and digestion sludge is released in a short time. Phosphorus in the liquid can be recovered. Specifically, as shown in Examples 1-2, the phosphorus recovery rate for a reaction time of 60 minutes is about 65% or more, and the phosphorus recovery rate for a reaction time of 120 minutes is about 75% or more.
一方、珪酸カルシウム水和物の細孔容積が０.５cm3/ｇ未満および比表面積が８０ｍ2/ｇ未満のものはリンとの反応性が低く、例えば、比較例１〜２に示すように、反応時間６０分のリン回収率は約５０％未満、反応時間１２０分のリン回収率は６０％以下であり、反応時間が２４０分でもリン回収率は約６０％程度である。 On the other hand, calcium silicate hydrate having a pore volume of less than 0.5 cm 3 / g and a specific surface area of less than 80 m 2 / g has low reactivity with phosphorus. For example, as shown in Comparative Examples 1 and 2 The phosphorus recovery rate for a reaction time of 60 minutes is less than about 50%, the phosphorus recovery rate for a reaction time of 120 minutes is 60% or less, and even if the reaction time is 240 minutes, the phosphorus recovery rate is about 60%.
さらに、本発明のリン回収資材は非晶質の珪酸カルシウム水和物である。ここで非晶質の珪酸カルシウム水和物とは、Ｘ線回折分析において、トバモライトやゾノトライト
のような明瞭な回折像を示さず、２９.４°において不明瞭なメインピークを有する回折像を与える珪酸カルシウム水和物である。結晶質の珪酸カルシウム水和物に比べて、非晶質の珪酸カルシウム水和物はリンとの反応速度が高い。
Furthermore, the phosphorus recovery material of the present invention is amorphous calcium silicate hydrate. Here, the amorphous calcium silicate hydrate does not show a clear diffraction image like tobermorite or zonotolite in X-ray diffraction analysis, but gives a diffraction image having an unclear main peak at 29.4 °. Calcium silicate hydrate. Compared to crystalline calcium silicate hydrate, amorphous calcium silicate hydrate has a higher reaction rate with phosphorus.
例えば、比較例１（非晶質珪酸カルシウム水和物）と比較例３（結晶質珪酸カルシウム水和物）に示すように、これらは平均粒子径、細孔容積、比表面積が類似しているが、反応性は大幅に異なり、非晶質の比較例１は反応時間６０分のリン回収率は約５０％であるのに対して、結晶質の比較例３は反応時間６０分のリン回収率は約１５％程度である。 For example, as shown in Comparative Example 1 (amorphous calcium silicate hydrate) and Comparative Example 3 (crystalline calcium silicate hydrate), these are similar in average particle diameter, pore volume, and specific surface area. However, the reactivity is significantly different, and the comparative example 1 of amorphous has a phosphorus recovery rate of about 50% for the reaction time of 60 minutes, whereas the comparative example 3 of crystalline has the phosphorus recovery of the reaction time of 60 minutes. The rate is about 15%.
本発明のリン回収資材において、珪酸カルシウム水和物に含有される遊離石灰は１０％未満であることが好ましい。遊離石灰量が１０％より多いとリンとの反応率が低下する。 In the phosphorus recovery material of the present invention, the free lime contained in the calcium silicate hydrate is preferably less than 10%. When the amount of free lime is more than 10%, the reaction rate with phosphorus decreases.
本発明のリン回収資材において、珪酸カルシウム水和物のカルシウムとケイ素のモル比（Ｃａ/Ｓｉ）は０.８以上〜１.８以下が好ましい。Ｃａ/Ｓｉモル比が１.８を上回ると多孔質度が低下し、かつ遊離石灰含量が１０％以上となり、リンとの反応性が低下する。一方、Ｃａ/Ｓｉモル比が０.８未満では回収物のヒドロキシアパタイトの含量が低下し、ク溶性リン酸１５％以上という副産りん酸肥料の要件を満足できなくなる。 In the phosphorus recovery material of the present invention, the calcium to silicon molar ratio (Ca / Si) of the calcium silicate hydrate is preferably 0.8 or more and 1.8 or less. When the Ca / Si molar ratio exceeds 1.8, the degree of porosity decreases and the free lime content becomes 10% or more, and the reactivity with phosphorus decreases. On the other hand, when the Ca / Si molar ratio is less than 0.8, the content of hydroxyapatite in the recovered product is lowered, and the by-product phosphate fertilizer requirement of 15% or more of soluble phosphoric acid cannot be satisfied.
本発明のリン回収資材は、珪酸カルシウム水和物が水中に含まれるリンと反応してリン酸カルシウム（ヒドロキシアパタイト）を生成する。このヒドロキシアパタイトの生成に必要なカルシウムは、他からカルシウムを添加することなく、珪酸カルシウム水和物のリン酸による逐次的な分解によって供給される。そのため、液中のカルシウムの初期濃度は低く、ヒドロキシアパタイトの過飽和度も液全体としては低い状態が維持される。 In the phosphorus recovery material of the present invention, calcium silicate hydrate reacts with phosphorus contained in water to produce calcium phosphate (hydroxyapatite). Calcium necessary for the production of this hydroxyapatite is supplied by sequential decomposition of calcium silicate hydrate with phosphoric acid without adding calcium from others. Therefore, the initial concentration of calcium in the liquid is low, and the supersaturation degree of hydroxyapatite is kept low as the whole liquid.
さらに、珪酸カルシウム水和物の分解にともなって、カルシウムイオンが多孔質の細孔を通じて粒子表面に供給されるため、ヒドロキシアパタイトの結晶化は珪酸カルシウム水和物粒子の表面のみで起こる。そのため、凝集沈殿法のカルシウム源として本発明の珪酸カルシウム水和物を用いると、該水和物表面にヒドロキシアパタイトが堆積し、微細なヒドロキシアパタイト粒子が液中に遊離することなく、従って、濾過性および沈降性の良いケーキを得ることができる。 Furthermore, as calcium silicate hydrate is decomposed, calcium ions are supplied to the particle surface through porous pores, so that crystallization of hydroxyapatite occurs only on the surface of the calcium silicate hydrate particles. Therefore, when the calcium silicate hydrate of the present invention is used as a calcium source for the coagulation precipitation method, hydroxyapatite is deposited on the surface of the hydrate, and fine hydroxyapatite particles are not released in the liquid. Cake having good property and sedimentation can be obtained.
一方、従来の凝集沈殿法において、消石灰や塩化カルシウムなどのカルシウム溶解度の高い化合物を用いた場合は、これらを投入した直後に液中のカルシウム濃度は非常に高いレベルに達するため、リン酸イオンと瞬時に反応してヒドロキシアパタイトの過飽和度は非常に高まり、液中にヒドロキシアパタイトの微細結晶が遊離して多数生成する。そのため、生成したケーキは濾過性に劣り、固液分離が困難になる。また、含水率が高いだけでなく、下水処理場の処理水のように有機物を多量に含有している場合は、有機物と共沈するため回収物の純度が低くなる。 On the other hand, when a compound with high calcium solubility such as slaked lime or calcium chloride is used in the conventional coagulation sedimentation method, the calcium concentration in the solution reaches a very high level immediately after the addition of these, so phosphate ions and It reacts instantaneously and the supersaturation degree of hydroxyapatite is greatly increased, and a large number of hydroxyapatite fine crystals are liberated in the liquid. Therefore, the produced cake is inferior in filterability, and solid-liquid separation becomes difficult. Moreover, not only has a high water content, but also contains a large amount of organic matter such as treated water in a sewage treatment plant, the purity of the recovered product is lowered because it co-precipitates with the organic matter.
また、本発明の珪酸カルシウム水和物と異なる軽量気泡コンクリート、珪灰石、造粒成形した珪酸カルシウム水和物などを用いた場合にも、排水中のリンをヒドロキシアパタイトとして回収することができるが、これらの珪酸カルシウム水和物は多孔性に劣り、排水中のリンと反応する表面積が小さいため、反応速度が遅い。 In addition, even when lightweight cellular concrete, wollastonite, granulated calcium silicate hydrate, etc., which are different from the calcium silicate hydrate of the present invention are used, phosphorus in waste water can be recovered as hydroxyapatite. These calcium silicate hydrates are inferior in porosity and have a low reaction rate because they have a small surface area that reacts with phosphorus in the waste water.
例えば、軽量気泡コンクリートはトバモライトを主体とした珪酸カルシウム化合物中に独立気泡を多く含む性状であって連続気泡を持たないため、生成した多孔質体の多孔性が劣り、全細孔容積は０.２cm3/ｇ程度である。また、造粒成形した珪酸カルシウム水和物は連続気泡を持つが、全細孔容積は０.２cm3/ｇ程度である。従って、これらの珪酸カルシウム水和物はリンとの反応速度が遅く、リンを回収するための時間が長くかかるため、これらの珪酸カルシウム水和物を用いて凝集沈殿法を行なうことは実際的ではない。 For example, lightweight aerated concrete is a property containing many closed cells in a calcium silicate compound mainly composed of tobermorite and does not have open cells, so the porosity of the produced porous body is inferior and the total pore volume is 0. It is about 2 cm 3 / g. The granulated and molded calcium silicate hydrate has open cells, but the total pore volume is about 0.2 cm 3 / g. Therefore, since these calcium silicate hydrates have a slow reaction rate with phosphorus and it takes a long time to recover phosphorus, it is not practical to perform a coagulation precipitation method using these calcium silicate hydrates. Absent.
本発明のリン回収資材は、高濃度のアンモニウムイオンおよび炭酸イオンを含むリン含有排液に対して特に有効であり、例えば、消化汚泥脱離液からリンを高い率で回収することができる。消化汚泥脱離液は高濃度のアンモニウムイオンおよび炭酸イオンが溶存しており、従来の珪酸カルシウム水和物を用いた凝集沈殿法では、反応時間が長く、迅速にリンを回収することができず、副産りん酸肥料の要件であるク溶性リン酸１５％以上の沈澱物を回収することができない。一方、本発明のリン回収資材はリンとの反応性が高いので、消化汚泥脱離液から短時間にリンを回収することができ、ク溶性リン酸１５％以上の沈殿物を回収できるので、これを副産りん酸肥料として利用することができる。 The phosphorus collection | recovery material of this invention is especially effective with respect to the phosphorus containing drainage containing high concentration ammonium ion and carbonate ion, for example, can collect | recover phosphorus with a high rate from digested sludge desorption liquid. Digested sludge leaching solution contains high concentrations of ammonium ions and carbonate ions, and the conventional coagulation sedimentation method using calcium silicate hydrate has a long reaction time and cannot recover phosphorus quickly. In addition, it is not possible to recover a precipitate of 15% or more soluble phosphonic acid, which is a requirement for by-product phosphate fertilizer. On the other hand, since the phosphorus recovery material of the present invention has high reactivity with phosphorus, it can recover phosphorus in a short time from the digested sludge detachment liquid, and can collect precipitates of 15% or more soluble phosphonic acid, This can be used as a by-product phosphate fertilizer.
〔リン回収資材の製造方法〕
本発明のリン回収資材として用いる珪酸カルシウム水和物は、珪酸原料と石灰原料とを水性スラリーとし、その水熱反応によって珪酸カルシウム水和物を生成させ、これを濾別し乾燥して珪酸カルシウム水和物からなるリン回収資材を製造する方法において、上記水性スラリーに水酸化アルカリを添加して水熱反応させ、多孔質および非晶質の珪酸カルシウム水和物を生成させることによって製造することができる。珪酸原料が非晶質の形態であれば、１００℃未満の温度で合成することも可能である。
[Method of manufacturing phosphorus recovery material]
The calcium silicate hydrate used as the phosphorus recovery material of the present invention is an aqueous slurry of a silicate raw material and a lime raw material, and a calcium silicate hydrate is produced by hydrothermal reaction thereof, which is filtered and dried to obtain calcium silicate. In the method for producing a phosphorus recovery material comprising a hydrate, it is produced by adding an alkali hydroxide to the aqueous slurry and causing a hydrothermal reaction to produce porous and amorphous calcium silicate hydrate. Can do. If the silicic acid raw material is in an amorphous form, it can be synthesized at a temperature of less than 100 ° C.
珪酸原料と石灰原料からなる水性スラリーに添加する水酸化アルカリ溶液としては、例えば、水酸化ナトリウム、水酸化カリウムのようなアルカリ金属水酸化物であれば特に限定されず、これらは単独で用いてもよく、２種以上の混合物として用いてもよい。上記水性スラリーに適量の水酸化アルカリを添加して水熱反応させることによって、細孔容積０.５cm3/ｇ以上、ＢＥＴ比表面積８０ｍ2/ｇ以上の多孔質珪酸カルシウム水和物を得ることができる。 The alkali hydroxide solution added to the aqueous slurry composed of the silicic acid raw material and the lime raw material is not particularly limited as long as it is an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, and these are used alone. It may also be used as a mixture of two or more. A porous calcium silicate hydrate having a pore volume of 0.5 cm 3 / g or more and a BET specific surface area of 80 m 2 / g or more is obtained by adding an appropriate amount of alkali hydroxide to the aqueous slurry and causing a hydrothermal reaction. Can do.
添加するアルカリ水溶液の濃度は０.１〜１％が好ましい。アルカリ水溶液の濃度が０.１％未満では細孔容積を大きくする効果が発揮されず、一方、アルカリ水溶液の濃度を１％より高くしてもアルカリの添加効果は頭打ちであり、コストアップを招くので望ましくない。 The concentration of the alkaline aqueous solution to be added is preferably 0.1 to 1%. If the concentration of the aqueous alkali solution is less than 0.1%, the effect of increasing the pore volume will not be exhibited. So undesirable.
〔リン回収方法〕
リン含有排水に、本発明の珪酸カルシウム水和物を添加してヒドロキシアパタイトを生成させ、この沈殿を分離することによって、リンを回収する凝集沈殿法において、処理液のｐＨがアルカリ性であると、珪酸カルシウム水和物との効率的な反応が進行しない。本発明のリン回収資材は、他からカルシウムを添加することなく、排水(消化汚泥脱離液)に含まれるリン酸による珪酸カルシウム水和物の逐次的な分解によってカルシウムを溶出させ、排水中のリンと反応させて珪酸カルシウム水和物の表面にヒドロキシアパタイトを生成させる。ここで液のｐＨが中性以上であると珪酸カルシウムの逐次的な分解が十分に進行しない。そこで、他の酸、例えば塩酸、硫酸、硝酸等の無機酸、酢酸などの有機酸を添加してｐＨを酸性側にすることによって、珪酸カルシウム水和物の分解を促すとよい。
[Phosphorus recovery method]
In the coagulation precipitation method in which phosphorus is recovered by adding the calcium silicate hydrate of the present invention to phosphorus-containing wastewater to produce hydroxyapatite and separating this precipitate, the pH of the treatment liquid is alkaline, Efficient reaction with calcium silicate hydrate does not proceed. The phosphorus recovery material of the present invention elutes calcium by sequential decomposition of calcium silicate hydrate with phosphoric acid contained in the waste water (digested sludge detachment liquid) without adding calcium from others, It reacts with phosphorus to produce hydroxyapatite on the surface of calcium silicate hydrate. Here, if the pH of the liquid is neutral or higher, the sequential decomposition of calcium silicate does not proceed sufficiently. Therefore, it is preferable to promote decomposition of calcium silicate hydrate by adding another acid, for example, an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid, or an organic acid such as acetic acid to make the pH acidic.
また、リン含有排水が消化汚泥脱離液の場合には、高濃度に含まれる炭酸イオンとリン回収資材のカルシウムが炭酸カルシウムを生成し、リンとカルシウムの反応が抑制される傾向がある。この炭酸カルシウム生成反応は、液のｐＨが高いほど迅速に進むため、この反応を抑制してリンとカルシウムの反応をスムースに進めるためには、でき得る限りｐＨを低く保つほうが良い。 Further, when the phosphorus-containing wastewater is digested sludge detachment liquid, carbonate ions contained in a high concentration and calcium of the phosphorus recovery material generate calcium carbonate, and the reaction between phosphorus and calcium tends to be suppressed. Since this calcium carbonate production reaction proceeds more rapidly as the pH of the solution is higher, it is better to keep the pH as low as possible in order to suppress this reaction and smoothly advance the reaction between phosphorus and calcium.
具体的には、酸の添加量は反応終了時のｐＨが８.０以上〜９.０未満になる量が好ましい。消化汚泥脱離液の場合は、高濃度に含有される炭酸イオンとアンモニウムイオンの緩衝作用によって、酸を添加してもｐＨの変動が少ないので、珪酸カルシウム水和物を添加する前のｐＨが５.０〜８.０、より望ましくは６.０〜７.０の範囲になるように酸を添加すれば、反応終了時のｐＨが８.０以上〜９.０未満にすることができ、効率のよいリン回収を行なうことができる。 Specifically, the amount of acid added is preferably such that the pH at the end of the reaction is from 8.0 to less than 9.0. In the case of digested sludge detachment liquid, there is little fluctuation in pH even when acid is added due to the buffering action of carbonate ions and ammonium ions contained in high concentration, so the pH before adding calcium silicate hydrate is If an acid is added so as to be in the range of 5.0 to 8.0, more preferably 6.0 to 7.0, the pH at the end of the reaction can be adjusted to 8.0 or more and less than 9.0. Efficient phosphorus recovery can be performed.
また、リン回収資材の使用量は、排水中に含まれるリンに対して、珪酸カルシウム水和物のカルシウムのモル比（Ｃａ/Ｐ）が１.５以上〜２.５以下の範囲が好ましい。このモル比が２.５より高いと未反応の珪酸カルシウム化合物が残留し、アパタイトの生成量が不十分となるため、回収物中のリン濃度が低下する。一方、このモル比が１.５より低いとリンの溶解度が高くなり、十分な回収率が得られなくなる。 Moreover, the usage-amount of phosphorus collection | recovery material has the preferable molar ratio (Ca / P) of calcium silicate hydrate with respect to the phosphorus contained in waste water in the range of 1.5 or more and 2.5 or less. If this molar ratio is higher than 2.5, an unreacted calcium silicate compound remains and the amount of apatite produced becomes insufficient, so that the phosphorus concentration in the recovered product is lowered. On the other hand, if the molar ratio is lower than 1.5, the solubility of phosphorus becomes high, and a sufficient recovery rate cannot be obtained.
本発明のリン回収方法において、処理温度は高い方が効率的なリン回収が可能である。処理温度の上限は限定されないが、加熱コスト等を勘案すれば工業的にみて１０℃以上〜１００℃以下、より好ましくは２５℃以上〜７０℃以下が適当である。また、液を攪拌して反応速度を促進することができる。処理時間は、本発明のリン回収資材を用いれば１〜２時間程度で十分である。 In the phosphorus recovery method of the present invention, the higher the processing temperature, the more efficient phosphorus recovery is possible. Although the upper limit of processing temperature is not limited, if heating cost etc. are taken into consideration, it is industrially 10 to 100 degreeC, More preferably, 25 to 70 degreeC is suitable. Moreover, the reaction rate can be accelerated by stirring the liquid. About 1 to 2 hours is sufficient for the processing time if the phosphorus recovery material of the present invention is used.
以下に本発明の実施例を比較例と共に示す。なお、製造したリン回収資材ならびにリン回収品の物性は下記測定方法によって求めた。 Examples of the present invention are shown below together with comparative examples. In addition, the physical property of the manufactured phosphorus collection | recovery material and phosphorus collection | recovery goods was calculated | required with the following measuring method.
〔細孔容積、比表面積〕１５０℃で１時間真空脱気を行なった試料につき、日本ＢＥＬ社装置(BELSORP-mini)を用い、窒素吸着法（ＢＪＨ法）により測定した。
〔平均粒子径〕レーザー回折式粒度分布測定装置(堀場製作所製品：LA-300)を用いて測定した。
〔Ｘ線回折像〕
ミニフレックスＸ線回折装置(理学社製)を用い、Ｃｕ管球、管電圧３０ｋＶ、管電流１５mＡ、サンプリング幅０.０２°、スキャンスピード４°/分の条件で測定した。
[Pore volume, specific surface area] A sample subjected to vacuum degassing at 150 ° C for 1 hour was measured by a nitrogen adsorption method (BJH method) using a Japan BEL apparatus (BELSORP-mini).
[Average particle diameter] The average particle diameter was measured using a laser diffraction particle size distribution analyzer (Horiba, Ltd. product: LA-300).
[X-ray diffraction image]
Measurement was performed using a mini-flex X-ray diffractometer (manufactured by Rigaku Corporation) under the conditions of Cu tube, tube voltage 30 kV, tube current 15 mA, sampling width 0.02 °, and scan speed 4 ° / min.
〔遊離石灰〕セメント協会標準試験方法「遊離酸化カルシウムの定量方法」によって遊離石灰含量を定量した。
〔ク溶性リン酸〕肥料分析法に基づき、１ｇのサンプルを２％クエン酸で３０℃、１時間振盪し、溶解したリン酸をバナドモリブデン酸アンモニウム法で定量した。
〔濾過時間〕沈降濃縮スラリー２５０mlをφ１５０mmのヌッチェで濾過したときの所要時間である。
[Free lime] Free lime content was quantified according to the Cement Association standard test method "Quantification method of free calcium oxide".
[Cu-soluble phosphoric acid] Based on the fertilizer analysis method, a 1 g sample was shaken with 2% citric acid at 30 ° C for 1 hour, and the dissolved phosphoric acid was quantified by the ammonium vanadomolybdate method.
[Filtration time] This is the required time when 250 ml of sedimented concentrated slurry was filtered through a Nutsche of φ150 mm.
〔実施例１〕
珪酸原料（平均粒径２０μmの非晶質シリカ粉）と消石灰をＣａ/Ｓｉモル比０.８になるように調合し、水−固形分比８相当分の０.４％水酸化ナトリウム溶液を加え、オートクレーブ中で攪拌しながら１８０℃、４時間水熱反応を行なった。生成した珪酸カルシウム水和物スラリーを濾過、乾燥して、珪酸カルシウム水和物からなるリン回収資材を得た。この物性値を表１に示す。
一方、下水処理場由来の嫌気性消化汚泥にカチオン性界面活性剤を２００mg/Lの割合で添加し、３５００rpmで２０分間遠心分離して、リンを含有した消化汚泥脱離液を得た。この液の分析値を表２に示す。
次に、この消化汚泥脱離液５０００mlに硫酸を添加してｐＨを６.６に下げた後、液中のリンに対してＣａ／Ｐモル比が２.００になる量のリン回収資材を上記脱離液に添加し、室温（２５℃）で４時間攪拌してリンの回収を行なった。一定時間毎にスラリーをサンプリングし、濾液のリンをバナドモリブデン酸アンモニウム法で定量し、リンの回収率を求めた。その結果を図１に示す。終了後スラリーを自然沈降濃縮し、沈殿を濾過・乾燥してリン回収物を得た。回収品の物性ならびに分析値を表３に示す。
[Example 1]
Silicic acid raw material (amorphous silica powder having an average particle size of 20 μm) and slaked lime were prepared so that the Ca / Si molar ratio was 0.8, and a 0.4% sodium hydroxide solution corresponding to a water-solid content ratio of 8 was prepared. In addition, a hydrothermal reaction was carried out at 180 ° C. for 4 hours while stirring in an autoclave. The produced calcium silicate hydrate slurry was filtered and dried to obtain a phosphorus recovery material consisting of calcium silicate hydrate. The physical property values are shown in Table 1.
On the other hand, a cationic surfactant was added to anaerobic digested sludge derived from a sewage treatment plant at a rate of 200 mg / L, and centrifuged at 3500 rpm for 20 minutes to obtain a digested sludge desorbed solution containing phosphorus. The analytical value of this liquid is shown in Table 2.
Next, sulfuric acid is added to 5000 ml of this digested sludge desorbing solution to lower the pH to 6.6, and then a phosphorus recovery material in an amount such that the Ca / P molar ratio is 2.00 with respect to phosphorus in the solution. The phosphorus was recovered by adding to the desorbing solution and stirring at room temperature (25 ° C.) for 4 hours. The slurry was sampled at regular intervals, and phosphorus in the filtrate was quantified by the ammonium vanadomolybdate method to obtain the phosphorus recovery rate. The result is shown in FIG. After completion, the slurry was naturally precipitated and concentrated, and the precipitate was filtered and dried to obtain a phosphorus recovery product. Table 3 shows the physical properties and analytical values of the collected products.
〔実施例２〕
実施例１と同じ珪酸原料（平均粒径２０μmの非晶質シリカ粉）と消石灰を、Ｃａ/Ｓｉモル比１.２になるように調合し、水−固形分比８相当分の０.４％水酸化ナトリウム溶液を加え、オートクレーブ中で攪拌しながら１８０℃、４時間水熱反応を行なった。生成した珪酸カルシウム水和物スラリーを濾過、乾燥して、珪酸カルシウム水和物からなるリン回収資材を得た。この物性値を表１に示す。実施例１と同様な条件でリン含有排水の処理を行なった。その結果を図２および表３に示す。
[Example 2]
The same silicic acid raw material (amorphous silica powder having an average particle size of 20 μm) and slaked lime as in Example 1 were prepared so as to have a Ca / Si molar ratio of 1.2, and a water-solid content ratio of 0.4 equivalent to 0.4. % Sodium hydroxide solution was added and hydrothermal reaction was carried out at 180 ° C. for 4 hours with stirring in an autoclave. The produced calcium silicate hydrate slurry was filtered and dried to obtain a phosphorus recovery material consisting of calcium silicate hydrate. The physical property values are shown in Table 1. The wastewater containing phosphorus was treated under the same conditions as in Example 1. The results are shown in FIG.
〔実施例３〕
実施例１と同じ珪酸原料（平均粒径２０μmの非晶質シリカ粉）と消石灰を、Ｃａ/Ｓｉモル比１.５になるように調合し、水−固形分比８相当分の０.４％水酸化ナトリウム溶液を加え、オートクレーブ中で攪拌しながら１８０℃、４時間水熱反応を行なった。生成した珪酸カルシウム水和物スラリーを濾過、乾燥して、珪酸カルシウム水和物からなるリン回収資材を得た。この物性値を表１に示す。実施例１と同様な条件でリン含有排水の処理を行なった。その結果を図２および表３に示す。
Example 3
The same silicic acid raw material (amorphous silica powder having an average particle size of 20 μm) and slaked lime as in Example 1 were prepared so as to have a Ca / Si molar ratio of 1.5, and a water-solid content ratio of 0.4 equivalent to 0.4. % Sodium hydroxide solution was added and hydrothermal reaction was carried out at 180 ° C. for 4 hours with stirring in an autoclave. The produced calcium silicate hydrate slurry was filtered and dried to obtain a phosphorus recovery material consisting of calcium silicate hydrate. The physical property values are shown in Table 1. The wastewater containing phosphorus was treated under the same conditions as in Example 1. The results are shown in FIG.
〔実施例４〕
珪酸原料（平均粒径２０μmの非晶質シリカ粉）と消石灰を、Ｃａ/Ｓｉモル比１.０になるように調合し、水−固形分比８相当分の０.４％水酸化ナトリウム溶液を加え、温浴中で攪拌しながら９５℃、２０時間反応を行なった。生成した珪酸カルシウム水和物スラリーを濾過、乾燥して、珪酸カルシウム水和物からなるリン回収資材を得た。この物性値を表１に示す。実施例１と同様な条件でリン含有排水の処理を行なった。その結果を図１および表３に示す。
Example 4
Silicic acid raw material (amorphous silica powder with an average particle size of 20 μm) and slaked lime were prepared so that the Ca / Si molar ratio was 1.0, and a 0.4% sodium hydroxide solution corresponding to a water-solid content ratio of 8 And the reaction was carried out at 95 ° C. for 20 hours with stirring in a warm bath. The produced calcium silicate hydrate slurry was filtered and dried to obtain a phosphorus recovery material consisting of calcium silicate hydrate. The physical property values are shown in Table 1. The wastewater containing phosphorus was treated under the same conditions as in Example 1. The results are shown in FIG.
〔比較例１〕
実施例１と同じ珪酸原料（平均粒径２０μmの非晶質シリカ粉）と消石灰を、Ｃａ/Ｓｉモル比０.８になるように調合し、水−固形分比８相当分の水を加え、オートクレーブ中で攪拌しながら１８０℃、４時間水熱反応を行なった。生成した珪酸カルシウム水和物スラリーを濾過、乾燥して、珪酸カルシウム水和物からなるリン回収資材を得た。この物性値を表１に示す。実施例１と同様な条件でリン含有排水の処理を行ない、その結果を図１および表３に示す。
[Comparative Example 1]
The same silicic acid raw material (amorphous silica powder having an average particle size of 20 μm) and slaked lime as in Example 1 were prepared so that the Ca / Si molar ratio was 0.8, and water corresponding to a water-solid content ratio of 8 was added. Then, hydrothermal reaction was carried out at 180 ° C. for 4 hours while stirring in an autoclave. The produced calcium silicate hydrate slurry was filtered and dried to obtain a phosphorus recovery material consisting of calcium silicate hydrate. The physical property values are shown in Table 1. The phosphorus-containing wastewater was treated under the same conditions as in Example 1, and the results are shown in FIG.
〔比較例２〕
実施例１と同じ珪酸原料（平均粒径２０μmの非晶質シリカ粉）と消石灰を、Ｃａ/Ｓｉモル比１.０になるように調合し、水−固形分比８相当分の水を加え、温浴中で攪拌しながら９５℃、２０時間反応を行なった。生成した珪酸カルシウム水和物スラリーを濾過、乾燥して、珪酸カルシウム水和物からなるリン回収資材を得た。この物性値を表１に示す。実施例１と同様な条件でリン含有排水の処理を行なった。その結果を図１および分析値を表３に示す。
[Comparative Example 2]
The same silicic acid raw material (amorphous silica powder having an average particle size of 20 μm) and slaked lime as in Example 1 were prepared so that the Ca / Si molar ratio was 1.0, and water corresponding to a water-solid content ratio of 8 was added. The reaction was carried out at 95 ° C. for 20 hours with stirring in a warm bath. The produced calcium silicate hydrate slurry was filtered and dried to obtain a phosphorus recovery material consisting of calcium silicate hydrate. The physical property values are shown in Table 1. The wastewater containing phosphorus was treated under the same conditions as in Example 1. The results are shown in FIG. 1 and the analysis values are shown in Table 3.
〔比較例３〕
珪酸原料（平均粒径１０μmの珪石粉末）と消石灰を、Ｃａ/Ｓｉモル比０.８になるように調合し、水−固形分比１５相当分の水を加え、オートクレーブ中で攪拌しながら１８０℃、８時間水熱反応を行なった。生成した珪酸カルシウム水和物スラリーを濾過、乾燥して、結晶質の珪酸カルシウム水和物からなるリン回収資材を得た。この物性値を表１に示す。実施例１と同様な条件でリン含有排水の処理を行なった。その結果を図１および表３に示す。
[Comparative Example 3]
A silicic acid raw material (silica stone powder having an average particle size of 10 μm) and slaked lime are prepared so as to have a Ca / Si molar ratio of 0.8. Hydrothermal reaction was performed at ° C for 8 hours. The produced calcium silicate hydrate slurry was filtered and dried to obtain a phosphorus recovery material composed of crystalline calcium silicate hydrate. The physical property values are shown in Table 1. The wastewater containing phosphorus was treated under the same conditions as in Example 1. The results are shown in FIG.
〔比較例４〕
実施例１と同じ珪酸原料（平均粒径２０μmの非晶質シリカ粉）と消石灰を、Ｃａ/Ｓｉモル比２.０になるように調合し、水−固形分比８相当分の０.４％水酸化ナトリウム溶液を加え、オートクレーブ中で攪拌しながら１８０℃、４時間水熱反応を行なった。生成した珪酸カルシウム水和物スラリーを濾過、乾燥して、珪酸カルシウム水和物からなるリン回収資材を得た。この物性値を表１に示す。実施例１と同様な条件でリン含有排水の処理を行なった。その結果を図２および表３に示す。
[Comparative Example 4]
The same silicic acid raw material (amorphous silica powder having an average particle size of 20 μm) and slaked lime as in Example 1 were prepared so as to have a Ca / Si molar ratio of 2.0, and a water-solid content ratio of 0.4 equivalent to 0.4. % Sodium hydroxide solution was added and hydrothermal reaction was carried out at 180 ° C. for 4 hours with stirring in an autoclave. The produced calcium silicate hydrate slurry was filtered and dried to obtain a phosphorus recovery material consisting of calcium silicate hydrate. The physical property values are shown in Table 1. The wastewater containing phosphorus was treated under the same conditions as in Example 1. The results are shown in FIG.
〔比較例５〕
消石灰粉末を用い、実施例１と同様な条件でリン含有排水の処理を行なった。その結果を図２および表３に示す。
[Comparative Example 5]
Using slaked lime powder, the phosphorus-containing wastewater was treated under the same conditions as in Example 1. The results are shown in FIG.
表１に示すように、珪酸カルシウム水和物を製造する際に水性アルカリを添加して合成した本発明の実施例１と実施例４のリン回収資材は細孔容積および比表面積が大きく、比較例１、比較例２のリン回収資材と比べると約２倍〜４倍である。一方、原料スラリー調整時にアルカリを添加せずに水を用いた比較例１と比較例２のリン回収資材は、細孔容積および比表面積が小さい。このため、図１に示すように、実施例１および実施例４は比較例１および比較例２に比べて短時間に反応が進行しており、リン回収率の向上が顕著である。この結果から、本発明のリン回収資材は液中のリンとの反応性が高く、リンの回収率が高いと考えられる。 As shown in Table 1, the phosphorus recovery materials of Example 1 and Example 4 of the present invention synthesized by adding aqueous alkali when producing calcium silicate hydrate have large pore volume and specific surface area. Compared to the phosphorus recovery material of Example 1 and Comparative Example 2, the amount is about 2 to 4 times. On the other hand, the phosphorus collection | recovery materials of the comparative example 1 and the comparative example 2 which used water, without adding an alkali at the time of raw material slurry adjustment, have a small pore volume and a specific surface area. For this reason, as shown in FIG. 1, the reaction of Example 1 and Example 4 progressed in a shorter time than Comparative Example 1 and Comparative Example 2, and the improvement of the phosphorus recovery rate is remarkable. From this result, it is considered that the phosphorus recovery material of the present invention has a high reactivity with phosphorus in the liquid and a high phosphorus recovery rate.
一方、結晶性の珪酸カルシウム水和物であるトバモライトをリン回収資材として用いた比較例３では、資材の細孔容積、比表面積は比較例１よりも若干大きく、ある程度の多孔性を有しているが、図１に示すようにリンの回収速度は非常に遅い。このことから、結晶質の珪酸カルシウム水和物は、消化汚泥脱離液のリン回収資材としては不適であることがわかる。 On the other hand, in Comparative Example 3 in which tobermorite, which is crystalline calcium silicate hydrate, was used as the phosphorus recovery material, the pore volume and specific surface area of the material were slightly larger than those in Comparative Example 1, and had a certain degree of porosity. However, the recovery rate of phosphorus is very slow as shown in FIG. This shows that crystalline calcium silicate hydrate is unsuitable as a phosphorus recovery material for digested sludge detachment liquid.
表１に示すように、Ｃａ/Ｓｉモル比が高い比較例４は、細孔容積および比表面積は実施例３とほぼ同等であるが、遊離石灰の含有量は１５．１％と高い。その影響により、図２に示すように、比較例４は実施例２および実施例３よりもリン回収率が低い。消石灰粉末を回収資材として用いた比較例５では、さらに回収率が低くなる。 As shown in Table 1, Comparative Example 4 having a high Ca / Si molar ratio has a pore volume and a specific surface area that are substantially the same as Example 3, but has a high free lime content of 15.1%. Due to the influence, as shown in FIG. 2, Comparative Example 4 has a lower phosphorus recovery rate than Examples 2 and 3. In Comparative Example 5 using slaked lime powder as a recovery material, the recovery rate is further reduced.
回収資材中の遊離石灰の量が、リン回収速度に影響を与える理由は、消化汚泥脱離液中に高濃度に含まれる炭酸イオンが遊離石灰と反応して炭酸カルシウムになり、これがリンとの反応を阻害するためである。表２に示したように、消化汚泥脱離液中には炭酸イオンがＣＯ2換算で２１００mg/lと多量に含まれており、カルシウムがリンと反応してヒドロキシアパタイトを生成する反応と、炭酸と反応して炭酸カルシウムを生成する反応が競合的に進む。遊離石灰のカルシウムは、珪酸カルシウム水和物のカルシウムよりも溶解しやすいため、液と回収資材の界面の局部的なｐＨの上昇を引き起こし、ヒドロキシアパタイト生成反応よりも高いｐＨで反応が促進される炭酸カルシウム生成反応が優先することになる。 The reason why the amount of free lime in the recovered material affects the phosphorus recovery rate is that the carbonate ions contained in the digested sludge detachment liquid react with the free lime to form calcium carbonate, which is This is to inhibit the reaction. As shown in Table 2, the digested sludge desorbed solution contains a large amount of carbonate ion at 2100 mg / l in terms of CO 2 , and the reaction of calcium reacting with phosphorus to produce hydroxyapatite, The reaction to produce calcium carbonate in a competitive manner proceeds. Calcium of free lime is more soluble than calcium silicate hydrate, causing a local increase in pH at the interface between the liquid and the recovered material, and the reaction is accelerated at a higher pH than the hydroxyapatite formation reaction. The calcium carbonate production reaction will be prioritized.
実施例１と比較例５におけるリン回収品のＸ線回折像を図３に示す。消石灰をリン回収資材として用いた比較例５では、炭酸カルシウム（カルサイト）のシャープなピークが観察されるのに対し、本発明のリン回収資材を用いた実施例１では、炭酸カルシウムの生成は僅かであり、非晶質なヒドロキシアパタイトのブロードなピークが観察される。このようにリン回収資材の遊離石灰量を低くすることによって、炭酸カルシウムの生成を抑え、効率的にリンを回収することができる。 The X-ray diffraction images of the phosphorus recovery products in Example 1 and Comparative Example 5 are shown in FIG. In Comparative Example 5 using slaked lime as a phosphorus recovery material, a sharp peak of calcium carbonate (calcite) is observed, whereas in Example 1 using the phosphorus recovery material of the present invention, the formation of calcium carbonate is A few, broad peaks of amorphous hydroxyapatite are observed. Thus, by reducing the amount of free lime in the phosphorus recovery material, the production of calcium carbonate can be suppressed and phosphorus can be efficiently recovered.
また、リン回収資材中の遊離石灰含量が増えると、炭酸カルシウム生成反応に消費される分が増えるため、リン回収に働く有効なカルシウム量が減少することになるが、排水中のリン含有量に対して、リン回収資材の使用量を調整し、リンに対するカルシウムのモル比(Ｃａ／Ｐ)を高くすることによって、カルシウムの消費をある程度はカバーすることができる。しかし、遊離石灰含量の増加に応じてリン回収資材の使用量を増していくことは、コスト上昇を招くと同時に、回収品のリン濃度が低下することになるので望ましくない。遊離石灰含量１０％未満のリン回収資材を用い、Ｃａ／Ｐモル比２.５未満でリンを回収すると、リン回収品のリン酸濃度は１５％以上となって好適である。 In addition, when the free lime content in the phosphorus recovery material increases, the amount consumed for the calcium carbonate production reaction increases, so the effective amount of calcium that works for phosphorus recovery decreases. On the other hand, the consumption of calcium can be covered to some extent by adjusting the amount of phosphorus recovery material used and increasing the molar ratio of calcium to phosphorus (Ca / P). However, increasing the amount of phosphorus recovery material used in accordance with the increase in free lime content is undesirable because it increases costs and at the same time decreases the phosphorus concentration of the recovered product. When phosphorus is recovered at a Ca / P molar ratio of less than 2.5 using a phosphorus recovery material having a free lime content of less than 10%, the phosphoric acid concentration of the phosphorus recovery product is preferably 15% or more.
消化汚泥脱離液について、消石灰を用いた従来の石灰凝集沈殿法を適用すると、表３の比較例５に示すように、生成したケーキは濾過性が非常に悪く、含水率が非常に高いケーキになり、濾過による固液分離は実質的に不可能である。一方、本発明の回収資材を用いると、実施例１〜実施例４に示されるように、生成したケーキの濾過性は非常に良く、含水率の低い回収物を得ることができる。 When a conventional lime coagulation method using slaked lime is applied to the digested sludge detachment liquid, as shown in Comparative Example 5 in Table 3, the produced cake has a very poor filterability and a very high moisture content. Thus, solid-liquid separation by filtration is virtually impossible. On the other hand, when the recovered material of the present invention is used, as shown in Examples 1 to 4, the produced cake has very good filterability, and a recovered product having a low water content can be obtained.
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