JP2012024696A - Purification of biogas, and method of recovering phosphorus in waste liquid - Google Patents

Purification of biogas, and method of recovering phosphorus in waste liquid Download PDF

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JP2012024696A
JP2012024696A JP2010165690A JP2010165690A JP2012024696A JP 2012024696 A JP2012024696 A JP 2012024696A JP 2010165690 A JP2010165690 A JP 2010165690A JP 2010165690 A JP2010165690 A JP 2010165690A JP 2012024696 A JP2012024696 A JP 2012024696A
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phosphorus
biogas
methane fermentation
waste liquid
iron
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Masakazu Kuroda
正和 黒田
Megumi Yuzawa
恩 湯沢
Masato Komori
正人 小森
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Yamato Co Ltd
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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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
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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
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    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
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Abstract

PROBLEM TO BE SOLVED: To provide a method of removing/recovering a phosphorous content included in waste liquid as phosphate, and removing hydrogen sulfide included in biogas obtained by methane fermentation, in methane fermentation treatment.SOLUTION: The method is used for removing hydrogen sulfide in biogas and removing/recovering phosphorus in waste liquid, in methane fermentation treatment characterized by precipitating and removing phosphorus as iron phosphate by immersing a composite material of iron in waste liquid containing phosphorus generated by methane fermentation in methane fermentation treatment of organic waste, removing hydrogen sulfide in biogas as iron sulfide by bringing the suspension of the iron phosphate into contact with biogas including hydrogen sulfide generated by methane fermentation, and recovering a phosphoric acid solution generated there as a water-soluble phosphate by being reacted with calcium hydroxide and/or magnesium hydroxide.

Description

本発明は、メタン発酵によって得られるバイオガスの精製とメタン発酵により生ずる廃液中に含まれるリン分を同時に除去・回収する方法に関する。   The present invention relates to a method for purifying biogas obtained by methane fermentation and simultaneously removing and recovering phosphorus contained in waste liquid produced by methane fermentation.

近年、地球温暖化に起因すると考えられるさまざまな環境問題が顕在化するようになって、化石燃料への依存を極力少なくするため、廃棄植物などの農林業等において発生する種々の廃棄物や畜産廃棄物などの有機性廃棄物を原料として、嫌気性細菌によるメタン発酵処理を利用して得られるバイオメタンガスをエネルギー源の一つとして利用することが試みられている。   In recent years, various environmental problems thought to be caused by global warming have become apparent, and in order to reduce dependence on fossil fuels as much as possible, various wastes and livestock produced in agricultural and forestry industries such as waste plants Attempts have been made to use biomethane gas obtained by using methane fermentation treatment with anaerobic bacteria as an energy source, using organic waste such as waste as a raw material.

このメタン発酵で生産されるメタンガスを主成分とするバイオガス中には、数１００〜３，０００ｐｐｍ程度の硫化水素を含有しており、この硫化水素が燃焼することにより硫黄酸化物になることや腐食性があることから、バイオガスを利用するためにはこの硫化水素を除去する必要がある。また、メタン発酵処理で生成する廃液中にはリンを含んでいるためこのまま放流することは環境への影響上から好ましくなく、この廃液中のリンの除去も必要となる。   Biogas mainly composed of methane gas produced by this methane fermentation contains about several hundred to 3,000 ppm of hydrogen sulfide, and when this hydrogen sulfide burns, it becomes sulfur oxide. Since it is corrosive, it is necessary to remove this hydrogen sulfide in order to use biogas. Further, since the waste liquid produced by the methane fermentation treatment contains phosphorus, it is not preferable to discharge it as it is because of the influence on the environment, and it is also necessary to remove the phosphorus in the waste liquid.

この硫化水素の除去法(脱硫法)として、主として次の乾式脱硫、湿式脱硫及び生物脱硫の３つの方法がある。
(イ)乾式脱硫法
酸化鉄など金属系の脱硫剤により硫化水素を除去する。湿式方式に比べ水処理の必要がなく、取扱が簡便なことから広く普及しており、除去率は９０％以上である。脱硫剤の酸化鉄は硫化鉄となり、吸着力が次第に低下していくため、定期的な交換が必要であり、２基を並列で設置する場合が多くコストが高くなる（例えば、特許文献１、２参照）。 There are mainly the following three methods of removing hydrogen sulfide (desulfurization method): dry desulfurization, wet desulfurization, and biological desulfurization.
(B) Dry desulfurization method Hydrogen sulfide is removed with a metal-based desulfurization agent such as iron oxide. Compared to the wet method, there is no need for water treatment, and it is widely used because it is easy to handle, and the removal rate is 90% or more. Since the iron oxide of the desulfurizing agent becomes iron sulfide and the adsorptive power gradually decreases, periodic replacement is necessary, and there are many cases where two units are installed in parallel, which increases the cost (for example, Patent Document 1, 2).

（ロ）湿式脱硫法
ガス中の硫化水素をアルカリ水による洗浄によりあるいは高圧水に吸収させて除去する方式である。アルカリ水の水酸化ナトリウム溶液の濃度調整や水処理が必要であり、高圧水による吸収では加圧が必要であること、また広いスペースも必要であり、除去率は高いが高コストとなる（例えば、特許文献３参照）。 (B) Wet desulfurization method In this method, hydrogen sulfide in the gas is removed by washing with alkaline water or by absorbing it in high-pressure water. It is necessary to adjust the concentration of sodium hydroxide solution and water treatment of alkaline water. Absorption with high-pressure water requires pressurization, and also requires a large space, resulting in a high removal rate but high cost (for example, And Patent Document 3).

（ハ）生物脱硫法
硫黄酸化細菌の働きによりガス中の硫化水素を除去する方法で、発酵槽内に少量の空気を注入する方式と、反応塔を設置し担体を充填させて除去する方式がある。除去後の硫化水素濃度が、数百ｐｐｍ程度にとどまることもあることから、乾式脱硫を後段に設置する場合もあり、維持管理が複雑で、高い除去率が必ずしも得られない（例えば、特許文献 ４〜６、非特許文献１参照）。 (C) Biological desulfurization method This method removes hydrogen sulfide in gas by the action of sulfur-oxidizing bacteria. There are two methods: a method in which a small amount of air is injected into the fermenter and a method in which a reaction tower is installed and packed with a carrier. is there. Since the hydrogen sulfide concentration after removal may remain at several hundred ppm, dry desulfurization may be installed in the subsequent stage, so that maintenance is complicated and high removal rates are not necessarily obtained (for example, patent documents) 4-6, refer nonpatent literature 1).

また、廃液中のリンの除去方法として、次のリン酸塩沈殿法、吸着法、リン酸鉄沈殿分離法及びリン酸塩回収法がある。
（イ）リン酸塩沈殿法
リン分を水酸化マグネシウムとアンモニアと反応させてリン酸マグネシウムアンモニウムを生成させる方法（ＭＡＰ法）や、リン分を水酸化カルシウムと反応させてヒドロキシアパタイトを生成させる方法（ＨＡＰ法）のような難溶性の塩を生成させ、沈殿分離して回収する方法である（例えば、非特許文献２参照）。ＭＡＰ法もＨＡＰ法も、いずれも廃液中に多量の薬液を注入してリン酸塩を形成させる方法であり、高純度の塩を生成するには複雑な液調整が必要で、コストも高くなる。 In addition, as a method for removing phosphorus in the waste liquid, there are the following phosphate precipitation method, adsorption method, iron phosphate precipitation separation method, and phosphate recovery method.
(I) Phosphate precipitation method A method in which phosphorus is reacted with magnesium hydroxide and ammonia to produce magnesium ammonium phosphate (MAP method), or a method in which phosphorus is reacted with calcium hydroxide to produce hydroxyapatite. This is a method in which a sparingly soluble salt such as (HAP method) is produced, separated by precipitation, and recovered (for example, see Non-Patent Document 2). Both the MAP method and the HAP method are methods in which a large amount of chemical solution is injected into the waste liquid to form phosphate, and complex liquid adjustment is required to produce a high-purity salt, which increases costs. .

（ロ）吸着法
ジルコニウムフェライトのようなリンを吸着する吸着剤により回収する方法である。吸着剤による方法は、アルカリでリンを脱着するため、吸着処理した後に廃液性状の調整が必要となり、薬液使用量も多く高コストである（例えば、特許文献７参照）。 (B) Adsorption method This is a method of recovery using an adsorbent that adsorbs phosphorus such as zirconium ferrite. In the method using an adsorbent, phosphorus is desorbed with an alkali, so that it is necessary to adjust the properties of the waste liquid after the adsorption treatment, and the amount of chemical solution used is large and the cost is high (for example, see Patent Document 7).

（ハ）リン酸鉄沈澱分離法
リンを含有する液中で鉄を溶解させ、難溶性のリン酸鉄を生成させ、沈殿分離して回収する方法である。リン酸鉄を生成させる方法は、薬液が不要で簡便であるが、リン酸鉄の用途がないことが隘路になっている（例えば、特許文献８，９参照）。 (C) Iron phosphate precipitation separation method This is a method in which iron is dissolved in a liquid containing phosphorus to form poorly soluble iron phosphate, which is separated by precipitation and recovered. The method for producing iron phosphate is simple because it does not require a chemical solution, but there is no use for iron phosphate (see, for example, Patent Documents 8 and 9).

（ニ）リン酸塩回収法
リン酸を含む廃液に凝集剤の塩化鉄を加えて沈殿物を得る方法である。沈殿物のリン酸鉄は水に溶解しないので、リン酸鉄に強いアルカリ溶液(水酸化ナトリウムあるいは水酸化カルシウム溶液でpＨ＝１２以上)を加えて、さらに塩化カルシウムあるいは塩化マグネシウム、硫酸マグネシウム、硫酸アンモニウムのいずれかの塩を加えて、リン酸塩を得ている。リン酸塩を分離して排出される強いアルカリ排水はリサイクルも可能であるが、環境への排出には中和が必要であり、薬剤使用量が多く、コストが高いという問題がある（例えば、特許文献１０参照）。 (D) Phosphate recovery method This is a method of obtaining a precipitate by adding iron chloride as a flocculant to a waste liquid containing phosphoric acid. Since iron phosphate in the precipitate does not dissolve in water, a strong alkaline solution (pH = 12 or more with sodium hydroxide or calcium hydroxide solution) is added to iron phosphate, and further calcium chloride or magnesium chloride, magnesium sulfate, ammonium sulfate. Add any of the salts to get the phosphate. Strong alkaline effluent discharged by separating phosphate can be recycled, but neutralization is necessary for discharge to the environment, and there is a problem that the amount of chemicals used is high and the cost is high (for example, (See Patent Document 10).

特開２００４−４１９８号公報Japanese Patent Laid-Open No. 2004-4198 特開２００５−３４２６１１号公報JP 2005-342611 A 特開２００６−８３１５６号公報JP 2006-83156 A 特開２００６−１４３７７９号公報Japanese Patent Laid-Open No. 2006-143779 特開２００６−１４３７８０号公報JP 2006-143780 A 特開２００６−１４３７８１号公報JP 2006-143781 A 特開２００９−１３６７８４号公報JP 2009-136784 A 特開２００７−２６８３３８号公報JP 2007-268338 A 特開２００９−２７６０３９号公報JP 2009-276039 A 特開２００８−１９５５５８号公報JP 2008-195558 A

大槻研司、守恵信、脇田正彰「生物脱硫法によるメタン発酵バイオマスガスの硫化水素の除去」、東海畜産学会報、第16巻46-48（2005）Kenji Ohtsuki, Masanobu Mori, Masaaki Wakita “Removal of Hydrogen Sulfide from Methane Fermentation Biomass Gas by Biological Desulfurization”, Tokai Livestock Research Institute, Vol. 16, 46-48 (2005) 荻野隆生、平島 剛「下水汚泥からのリン回収プロセスの開発」、環境資源工学、第52巻，172-182(2005)Takao Kanno and Tsuyoshi Hirashima “Development of phosphorus recovery process from sewage sludge”, Environmental Resource Engineering, Vol.52, 172-182 (2005) 藤貫正、五十嵐俊雄、細越千恵子「栃木県葛生地区炭酸塩岩石の地球化学的研究」、地質調査所月報、第33巻、第4号、187−206(1982)Tadashi Fujinuki, Toshio Igarashi, Chieko Hosukoshi “Geochemical Study of Carbonate Rocks in the Kuzuu District, Tochigi Prefecture”, Geological Survey Monthly, Vol. 33, No. 4, 187-206 (1982)

乾式脱硫法では、酸化鉄にバイオガスを接触させると、ガス中の硫化水素が酸化鉄と反応し、硫化鉄が生成されることにより脱硫される。このような硫化水素による硫化鉄の生成は、酸化鉄の他に塩化第１鉄、塩化第２鉄、リン酸鉄などでも可能である。特に、リン酸鉄の反応による方法は、広く行なわれている鉄を利用した簡便な水中のリン除去で生成されたものを利用可能であるが、生成物であるリン酸鉄は利用されていない。   In the dry desulfurization method, when biogas is brought into contact with iron oxide, hydrogen sulfide in the gas reacts with iron oxide to produce iron sulfide, which is desulfurized. Such generation of iron sulfide by hydrogen sulfide is possible with ferrous chloride, ferric chloride, iron phosphate and the like in addition to iron oxide. In particular, the method based on the reaction of iron phosphate can be performed by simple removal of phosphorus in water using iron, but the product iron phosphate is not used. .

本発明は、上記したような従来の方法の問題点を解決し、メタン発酵処理を行う際に発生する廃液中に含まれるリン分を、従来適当な利用方法が見出されていなかったリン酸鉄に代わって、肥料等に利用の可能性のある水溶性のリン酸塩として回収すると同時に、メタン発酵で得られるバイオガス中に含まれる硫化水素を除去し、硫化水素を含まないバイオガスを得る方法を提供するものである。   The present invention solves the problems of the conventional methods as described above, and phosphoric acid for which phosphorus contained in waste liquid generated when methane fermentation treatment is performed has not been found in the prior art. Instead of iron, it is recovered as a water-soluble phosphate that can be used for fertilizer, etc., and at the same time, it removes hydrogen sulfide contained in biogas obtained by methane fermentation, and removes biosulfide-free biogas. It provides a method of obtaining.

本発明者らは、上記のような課題を解決すべく鋭意研究の結果、メタン発酵処理によって発生する廃液を鉄と接触させることによって、廃液中のリン分を水に難溶性のリン酸鉄として分離し、この難溶性のリン酸鉄を利用してメタン発酵により得られるバイオガス中の硫化水素を除去する方法を見出し、本発明を完成した。即ち、本発明は、廃液中のリン酸鉄によりバイオガス中の硫化水素を除去すると同時に、併せて廃液中に含まれるリン酸鉄を水溶性のリン酸塩として回収する方法を提供するものである。   As a result of earnest research to solve the above-mentioned problems, the present inventors brought the waste liquid generated by the methane fermentation treatment into contact with iron, thereby converting the phosphorus content in the waste liquid into poorly soluble iron phosphate in water. A method for separating and removing hydrogen sulfide in biogas obtained by methane fermentation using this hardly soluble iron phosphate was found, and the present invention was completed. That is, the present invention provides a method for removing hydrogen sulfide in biogas with iron phosphate in waste liquid and simultaneously recovering iron phosphate contained in waste liquid as water-soluble phosphate. is there.

即ち、本発明は、以下の内容をその要旨とする発明である。
（１）有機性廃棄物のメタン発酵処理において、メタン発酵により発生するリンを含む廃液に鉄の複合材料を浸漬させてリンをリン酸鉄として沈澱除去し、このリン酸鉄の懸濁液をメタン発酵により発生した硫化水素を含むバイオガスと接触させて硫化鉄としてバイオガス中の硫化水素を除去するとともに、ここで生成するリン酸溶液を水酸化カルシウム及び／又は水酸化マグネシウムと反応させて水溶性のリン酸塩として回収することを特徴とする、メタン発酵処理におけるバイオガスの精製と廃液中のリンの回収方法。
（２）水酸化カルシウム及び／又は水酸化マグネシウムの代わりに、又はこれに加えてドロマイトを使用することを特徴とする、前記（１）に記載のメタン発酵処理におけるバイオガスの精製と廃液中のリンの回収方法。
（３）生成したリン酸溶液に水酸化カルシウム及び／又は水酸化マグネシウムを加えてｐＨを８〜９に調整することを特徴とする、前記（１）又は（２）に記載のメタン発酵処理におけるバイオガスの精製と廃液中のリンの回収方法。 That is, the present invention has the following contents.
(1) In the methane fermentation treatment of organic waste, the iron composite material is immersed in a waste solution containing phosphorus generated by methane fermentation to precipitate and remove phosphorus as iron phosphate. It is brought into contact with a biogas containing hydrogen sulfide generated by methane fermentation to remove hydrogen sulfide in the biogas as iron sulfide, and the phosphoric acid solution produced here is reacted with calcium hydroxide and / or magnesium hydroxide. A method for purifying biogas and recovering phosphorus in waste liquid in a methane fermentation process, characterized in that it is recovered as a water-soluble phosphate.
(2) Use of dolomite instead of or in addition to calcium hydroxide and / or magnesium hydroxide in the methane fermentation treatment according to (1) above and in the waste liquid How to recover phosphorus.
(3) In the methane fermentation treatment according to (1) or (2), the pH is adjusted to 8 to 9 by adding calcium hydroxide and / or magnesium hydroxide to the generated phosphoric acid solution. Biogas purification and recovery of phosphorus in waste liquid.

本発明の方法によれば、メタン発酵処理にて発生するバイオガス中に含まれる硫化水素などの硫黄分を、同じメタン発酵処理にて生ずる廃液中に含まれるリンと鉄との反応を利用して得られたリン酸鉄と接触させることによって硫化鉄として固定し、除去することができる。更に、メタン発酵処理にて生ずる廃液中に含まれるリンも、従来有効な利用方法が見出せなかったリン酸鉄などの形態のものを、最終的にリン酸カルシウム、リン酸マグネシウム、リン酸マグネシウムアンモニウムなどの水溶性のリン酸塩の形で回収することができ、これらのリン酸塩が肥料として有利に利用することができる。即ち、メタン発酵処理で得られるバイオガスの有害物質である硫黄分を、同じメタン発酵処理の廃液中のリン分を利用して除去できることと、更にこのリン分がリン酸塩として回収できるので、肥料に有利に使用できるというメリットを有する。   According to the method of the present invention, the sulfur content such as hydrogen sulfide contained in the biogas generated in the methane fermentation treatment is used by utilizing the reaction between phosphorus and iron contained in the waste liquid produced in the same methane fermentation treatment. It can be fixed and removed as iron sulfide by bringing it into contact with the iron phosphate obtained. Furthermore, the phosphorous contained in the waste liquid produced by the methane fermentation treatment is also in a form such as iron phosphate, for which an effective use method has not been found in the past, such as calcium phosphate, magnesium phosphate, and magnesium ammonium phosphate. It can be recovered in the form of water-soluble phosphates, and these phosphates can be advantageously used as fertilizers. That is, the sulfur content that is a harmful substance of biogas obtained by methane fermentation treatment can be removed using the phosphorus content in the waste liquid of the same methane fermentation treatment, and further this phosphorus content can be recovered as a phosphate, It has the merit that it can be used advantageously for fertilizer.

本発明のバイオガスの精製と廃液中のリンの回収方法の全体の工程を示すフローチャートである。It is a flowchart which shows the whole process of the purification method of the biogas of this invention, and the collection | recovery method of the phosphorus in a waste liquid.

本発明は、有機性廃棄物を原料として、メタン発酵によってメタンガスを主成分とするバイオガスを生産するに際して、メタン発酵により発生する廃液中に含まれるリン分を水に難溶性のリン酸鉄として分離し、この難溶性のリン酸鉄を利用して同じメタン発酵により得られるバイオガス中に含まれる硫化水素を除去する方法である。   The present invention uses organic waste as a raw material, and when producing biogas mainly composed of methane gas by methane fermentation, phosphorus contained in the waste liquid generated by methane fermentation is used as iron phosphate that is hardly soluble in water. This is a method of separating and removing hydrogen sulfide contained in biogas obtained by the same methane fermentation using this hardly soluble iron phosphate.

本発明のバイオガスの精製と廃液中のリンの回収方法の全体を図１のフローチャートに示す。以下において、このフローチャートに沿って本発明の方法について説明する。
まず、食品工場廃液、畜産廃液や種々のバイオマス、生ゴミなどの有機性廃棄物を原料として使用して、嫌気性細菌によるメタン発酵反応によりメタンガスを主成分とするバイオガスを生成させる。このバイオガスには通常数１００ｐｐｍ〜３，０００ｐｐｍ程度の硫化水素を含有しているためこのままでは利用することができず、硫化水素を除去する必要がある。 The entire method for purifying biogas and recovering phosphorus in waste liquid according to the present invention is shown in the flowchart of FIG. Hereinafter, the method of the present invention will be described with reference to this flowchart.
First, biogas containing methane gas as a main component is generated by a methane fermentation reaction by anaerobic bacteria using organic wastes such as food factory waste liquid, livestock waste liquid, various biomass, and garbage as raw materials. Since this biogas usually contains hydrogen sulfide of about several hundred ppm to 3,000 ppm, it cannot be used as it is, and it is necessary to remove hydrogen sulfide.

一方、このメタン発酵処理においては廃液が発生するが、この廃液中にリンが含まれているため、この廃液をそのまま環境中に放出することは好ましくなく、これらのリンを除去する必要がある。   On the other hand, in this methane fermentation treatment, waste liquid is generated, but since this waste liquid contains phosphorus, it is not preferable to release this waste liquid into the environment as it is, and it is necessary to remove these phosphorus.

図１に示すフローチャートにおいて、本発明の方法は、まず有機性廃棄物をメタン発酵槽において嫌気性細菌を利用してメタン発酵させて、メタンガスを主成分とするバイオガスを生産させる。このバイオガス中には数１００ｐｐｍ〜３，０００ｐｐｍ程度の硫化水素を含有している。メタン発酵処理を行った場合には、これとともにリン分を含む廃液が発生する。   In the flowchart shown in FIG. 1, in the method of the present invention, an organic waste is first subjected to methane fermentation using anaerobic bacteria in a methane fermenter to produce biogas mainly composed of methane gas. This biogas contains hydrogen sulfide of about several hundred ppm to 3,000 ppm. When a methane fermentation process is performed, a waste liquid containing phosphorus is generated.

このメタン発酵によって発生するリンを含む廃液は、これを鉄と接触させて脱リン処理を行うことができる。即ち、このリンを含む廃液の中で鉄を溶解させてリンと反応させ、例えば次式で表わされる反応によって、水に難溶性のリン酸鉄として沈澱させて排液から分離する。
３Ｆｅ２＋＋２ＰＯ４ ３−＝Ｆｅ３（ＰＯ４）２
Ｆｅ３＋＋ＰＯ４ ３−＝ ＦｅＰＯ４ The waste liquid containing phosphorus generated by methane fermentation can be dephosphorized by bringing it into contact with iron. That is, iron is dissolved in the waste liquid containing phosphorus and reacted with phosphorus. For example, it is precipitated as water-insoluble iron phosphate by a reaction represented by the following formula and separated from the effluent.
3Fe 2+ + 2PO 4 3− = Fe 3 (PO 4 ) 2
Fe 3+ + PO 4 3− = FePO 4

この廃液中のリンの鉄による除去方法としては、そのまま鉄材料のみを廃液中に浸漬しても鉄の溶解速度が非常に小さく反応が遅いため、具体的には、例えば、鉄材料を、炭素材料、ステンレススチール、銅又はアルミニウムから選ばれる他の材料と物理的に接触させてなる鉄の複合材料を用いると良い。このような鉄の複合材料を廃液中に浸漬すると鉄の溶解速度が増大し、鉄イオンとリンとの反応が速やかに進行する。詳しくは本発明者ら提出した特許出願（特願２００９−２７６０３９号明細書）の明細書に記載されている。   As a method for removing phosphorus in the waste liquid with iron, even if only the iron material is immersed in the waste liquid as it is, the dissolution rate of iron is very small and the reaction is slow. It is preferable to use an iron composite material in physical contact with another material selected from the materials, stainless steel, copper or aluminum. When such an iron composite material is immersed in the waste liquid, the dissolution rate of iron increases, and the reaction between iron ions and phosphorus proceeds rapidly. Details are described in the specification of a patent application (Japanese Patent Application No. 2009-276039) filed by the present inventors.

このようにして得られたリン酸鉄を、メタン発酵により発生したバイオガスと接触させると、バイオガス中に含まれる硫化水素は次のような反応により硫化鉄を生成して脱硫されるとともに、リン酸を生成する。バイオガスに含まれる硫化水素の硫黄分は，次の反応式に示すように硫化鉄として固定され、一部は固体硫黄として沈澱して除去される。
２ＦｅＰＯ４＋３Ｈ２Ｓ＝２ＦｅＳ＋２Ｈ３ＰＯ４＋Ｓ
Ｆｅ３（ＰＯ４）２＋３Ｈ２Ｓ＝４ＦｅＳ＋６Ｈ３ＰＯ４＋２Ｓ When the iron phosphate thus obtained is brought into contact with the biogas generated by methane fermentation, the hydrogen sulfide contained in the biogas is desulfurized by generating iron sulfide by the following reaction, Produces phosphoric acid. The sulfur content of hydrogen sulfide contained in biogas is fixed as iron sulfide as shown in the following reaction formula, and a part of it is precipitated and removed as solid sulfur.
2FePO 4 + 3H 2 S = 2FeS + 2H 3 PO 4 + S
Fe 3 (PO 4 ) 2 + 3H 2 S = 4FeS + 6H 3 PO 4 + 2S

ここで生成するリン酸溶液に、水酸化カルシウム、水酸化マグネシウム又はドロマイトを添加してＣａ成分とＭｇ成分を補給するとともに、ｐＨを８〜９に調整すると、次の反応式に示すような反応が進行し、リン酸カルシウム又はリン酸マグネシウムの塩が沈殿し、リン分がリン酸塩として回収できる。ここで回収されたリン塩は肥料として利用することができる。
６ＰＯ４ ３−＋１０Ｃａ２＋２ＯＨ−＝Ｃａ１０（ＯＨ）２（ＰＯ４）６
ＰＯ４ ３−＋Ｍｇ２＋＋Ｈ２Ｏ＝ＭｇＨＰＯ４ When calcium hydroxide, magnesium hydroxide or dolomite is added to the phosphoric acid solution produced here to replenish the Ca and Mg components, and the pH is adjusted to 8-9, the reaction shown in the following reaction formula Advances, calcium phosphate or magnesium phosphate salt is precipitated, and the phosphorus content can be recovered as phosphate. The phosphorus salt recovered here can be used as a fertilizer.
6PO 4 3− + 10Ca 2+ 2OH − = Ca 10 (OH) 2 (PO 4 ) 6
PO 4 3− + Mg 2+ + H 2 O = MgHPO 4

生成するリン酸溶液からのリン酸塩の回収は、溶液のｐＨが８〜９となるように水酸化カルシウム、水酸化マグネシウムのいずれかを加えて調整すればよく、水酸化カルシウム、水酸化マグネシウムに加えて、又はこれに代えてドロマイトを用いても良い。ｐＨ８未満ではリン酸塩があまり生成せず、十分な量で沈澱することがないので、ｐＨ８以上とすることが必要である。   Recovery of phosphate from the resulting phosphoric acid solution may be adjusted by adding either calcium hydroxide or magnesium hydroxide so that the pH of the solution is 8-9. In addition to or instead of this, dolomite may be used. If the pH is less than 8, phosphate is not generated so much and does not precipitate in a sufficient amount.

また、メタン発酵処理で発生する廃液（消化液）は多くの硫化水素とアンモニアを含むので、この廃液（消化液）にリン酸鉄を添加し、この廃液でメタン発酵によるバイオガスを洗浄すればまず硫化水素が除去され、バイオガスを脱硫することができる。さらに、この廃液（消化液）に水酸化カルシウム、水酸化マグネシウム又はドロマイトを加え、ｐＨを８〜９に調整すれば、リン酸マグネシウムアンモニウムの塩が沈殿し、廃液中のリンを回収することができる。回収されたリン塩は肥料として利用できる。
ＰＯ４ ３−＋ＮＨ４＋＋Ｍｇ２＋＋６Ｈ２Ｏ＝ＭｇＮＨ４ＰＯ４・６Ｈ２Ｏ In addition, since the waste liquid (digested liquid) generated by methane fermentation treatment contains a lot of hydrogen sulfide and ammonia, if you add iron phosphate to this waste liquid (digested liquid) and wash the biogas from methane fermentation with this waste liquid First, hydrogen sulfide is removed and biogas can be desulfurized. Furthermore, if calcium hydroxide, magnesium hydroxide or dolomite is added to this waste liquid (digestion liquid) and the pH is adjusted to 8-9, the salt of magnesium ammonium phosphate precipitates and phosphorus in the waste liquid can be recovered. it can. The recovered phosphorus salt can be used as a fertilizer.
PO 4 3− + NH 4+ + Mg 2+ + 6H 2 O = MgNH 4 PO 4 .6H 2 O

なお、ドロマイト、水酸化カルシウムのスラリーに、上記のようにしてメタン発酵の廃液から得たリン酸鉄を混合し、この混合液にメタン発酵のバイオガスを吹き込み洗浄すれば、バイオガスの脱硫ができると同時に、リン酸塩としてリン分を回収することができる。特に、ドロマイトには酸化鉄が含まれており、ドロマイトを加えることは脱硫効果を高める。ドロマイトを焼成した焼成ドロマイトは、ドロマイトに比べ水に溶解しやすく、同様に利用できる。さらに、ドロマイトを摩砕するとドロマイトの複塩構造が破壊され、炭酸カルシウム、炭酸マグネシウムのような単塩に近いものになり、溶解しやすくなる（非特許文献３参照）。   In addition, if the iron phosphate obtained from the waste liquid of methane fermentation as described above is mixed into the slurry of dolomite and calcium hydroxide, and the biogas of methane fermentation is blown into the mixed liquid and washed, biogas desulfurization can be achieved. At the same time, the phosphorus content can be recovered as a phosphate. In particular, dolomite contains iron oxide, and adding dolomite enhances the desulfurization effect. The calcined dolomite obtained by calcining dolomite is easier to dissolve in water than dolomite and can be used in the same manner. Furthermore, when dolomite is ground, the double salt structure of dolomite is destroyed, becoming close to a single salt such as calcium carbonate and magnesium carbonate, and easily dissolved (see Non-Patent Document 3).

次に、本発明を実施例によって更に詳しく説明するが、本発明はこれらの実施例によって何ら限定されるものではない。   EXAMPLES Next, although an Example demonstrates this invention in more detail, this invention is not limited at all by these Examples.

図１に示すフローチャートに準拠した実験装置において、メタン発酵槽として上向流嫌気性汚泥床の嫌気槽を用いた。このメタン発酵槽に平均ＢＯＤ濃度３０１４ｍｇ／Ｌ、平均ＳＳ濃度７８０ｍｇ／Ｌの豚舎排水を８０〜１００Ｌ／日で供給して、反応温度を２０〜２５℃に維持してメタン発酵を行った。この豚舎排水の有機物の平均除去率はＢＯＤで凡そ９０％であった。ここで発生したバイオガス(平均メタン含有率６０％、硫化水素濃度２０００〜２７４０ｐｐｍ)は、後の脱硫・リン回収槽に導入した。   In the experimental apparatus based on the flowchart shown in FIG. 1, an anaerobic tank of an upflow anaerobic sludge bed was used as a methane fermentation tank. To this methane fermenter, pig house drainage having an average BOD concentration of 3014 mg / L and an average SS concentration of 780 mg / L was supplied at 80 to 100 L / day, and the reaction temperature was maintained at 20 to 25 ° C. to perform methane fermentation. The average removal rate of organic matter from the piggery effluent was approximately 90% in terms of BOD. The biogas generated here (average methane content 60%, hydrogen sulfide concentration 2000-2740 ppm) was introduced into the subsequent desulfurization / phosphorus recovery tank.

また、メタン発酵処理によって発生した廃液中に含まれるリンの除去のために、２２×３６×０．１ｃｍの鉄のパンチング板に２２×３６×０．５ｃｍの多孔質炭素材を固着した鉄複合材料と、２２×３６×０．１ｃｍの鉄パンチング板とを、互いに１０ｍｍ離して並行に固定して組合せた材料を４組浸漬した脱リン処理槽(有効容積７６Ｌ)を用いた。前述のメタン発酵処理によって発生した廃液の一部をこの脱リン処理槽(有効容積７６Ｌ)に凡そ６０日間連続的に供給し、廃液からの脱窒、脱リン及び脱色処理を行った。この廃液中への鉄複合材料の浸漬処理によって、廃液中に含まれるリンがリン酸鉄となり、汚泥として沈澱して除去された。   In addition, an iron composite in which a porous carbon material of 22 × 36 × 0.5 cm is fixed to an iron punching plate of 22 × 36 × 0.1 cm to remove phosphorus contained in the waste liquid generated by the methane fermentation treatment. A dephosphorization treatment tank (effective volume 76 L) in which four sets of materials in which a material and a 22 × 36 × 0.1 cm iron punching plate were fixed in parallel at a distance of 10 mm and immersed was used. A part of the waste liquid generated by the above methane fermentation treatment was continuously supplied to this dephosphorization treatment tank (effective volume 76 L) for about 60 days to perform denitrification, dephosphorization and decolorization treatment from the waste liquid. By the immersion treatment of the iron composite material in the waste liquid, phosphorus contained in the waste liquid became iron phosphate, which was precipitated and removed as sludge.

次に、５００ｍＬの円筒形の脱硫・リン回収槽に、上記のメタン発酵の廃液処理によって発生したリン酸鉄を含む汚泥１４．２ｇと水３５０ｍＬを入れ、リン酸鉄のスラリーとした。一方、メタン発酵処理で生成したバイオガス (硫化水素濃度２０００〜２７４０ｐｐｍ)の捕集パイプを、この脱硫・リン回収槽の底部に入れ、連続して２日間流通させ、バイオガスの洗浄を行った。洗浄されたガス中の硫化水素濃度は、脱硫・リン回収槽から排出されたガスをガスパックで採取し測定した。このようにして洗浄・脱硫されたバイオガス中の硫化水素濃度は凡そ数ｐｐｍ以下（検知できない）であった。２日間のバイオガス流通を終了後の脱硫・リン回収槽中のスラリーをろ過し、ろ液を８０ｍＬに濃縮して得たろ液のリン濃度は１２１ｍｇ／Ｌであった。この液にｐＨが凡そ１０．５になるまで水酸化カルシウムの飽和水溶液を加え、さらに濃縮してリン酸カルシウム塩を沈殿させて分離した。リン酸塩を分離した後の上澄液のリン濃度（液中に残留しているリン濃度）を測定したところ０．２ｍｇ／Ｌであり、ろ液中のリンの大部分を回収することができた。
なお、ガス中の硫化水素の濃度はガス検知管（ガステックＮｏ．４１）を使用し、液中のリン濃度はハック法によって測定した。 Next, in a 500 mL cylindrical desulfurization / phosphorus recovery tank, 14.2 g of sludge containing iron phosphate generated by the waste liquid treatment of the above methane fermentation and 350 mL of water were put to make an iron phosphate slurry. Meanwhile, a biogas (hydrogen sulfide concentration: 2000 to 2740 ppm) produced by methane fermentation treatment was placed in the bottom of this desulfurization / phosphorus recovery tank and continuously circulated for 2 days to wash the biogas. . The concentration of hydrogen sulfide in the cleaned gas was measured by collecting the gas discharged from the desulfurization / phosphorus recovery tank with a gas pack. The hydrogen sulfide concentration in the biogas cleaned and desulfurized in this way was about several ppm or less (not detectable). The slurry in the desulfurization / phosphorus recovery tank after the 2 days of biogas circulation was filtered, and the filtrate was concentrated to 80 mL. The phosphorus concentration of the filtrate was 121 mg / L. A saturated aqueous solution of calcium hydroxide was added to this solution until the pH reached approximately 10.5, and the solution was further concentrated to precipitate and separate the calcium phosphate salt. When the phosphorus concentration of the supernatant after separating the phosphate (phosphorus concentration remaining in the liquid) was measured, it was 0.2 mg / L, and most of the phosphorus in the filtrate could be recovered. did it.
The concentration of hydrogen sulfide in the gas was measured using a gas detector tube (Gastech No. 41), and the phosphorus concentration in the liquid was measured by the hack method.

本発明の方法によって、メタン発酵のよって得られるメタンガスを主成分とするバイオガス中に含まれる硫化水素を除去することができ、更に、メタン発酵の廃液中に含まれるリン分も同時に除去して、リン酸塩として回収することができる。従って、この本発明の方法は有機性廃棄物のメタン発酵によるバイオガスの生産に有用であり、さらに副生するリン分もリン酸塩として肥料などに利用することができる。

By the method of the present invention, it is possible to remove hydrogen sulfide contained in biogas mainly composed of methane gas obtained by methane fermentation, and also remove phosphorus contained in waste liquid of methane fermentation at the same time. Can be recovered as phosphate. Therefore, this method of the present invention is useful for the production of biogas by methane fermentation of organic waste, and the by-product phosphorus can also be used as a fertilizer as a phosphate.

Claims (3)

有機性廃棄物のメタン発酵処理において、メタン発酵により発生するリンを含む廃液に鉄の複合材料を浸漬させてリンをリン酸鉄として沈澱除去し、このリン酸鉄の懸濁液をメタン発酵により発生した硫化水素を含むバイオガスと接触させて硫化鉄としてバイオガス中の硫化水素を除去するとともに、ここで生成するリン酸溶液を水酸化カルシウム及び／又は水酸化マグネシウムと反応させて水溶性のリン酸塩として回収することを特徴とする、メタン発酵処理におけるバイオガスの精製と廃液中のリンの回収方法。   In the methane fermentation treatment of organic waste, the iron composite material is immersed in the waste liquid containing phosphorus generated by methane fermentation to precipitate and remove phosphorus as iron phosphate, and this iron phosphate suspension is removed by methane fermentation. It is brought into contact with the generated biogas containing hydrogen sulfide to remove hydrogen sulfide in the biogas as iron sulfide, and the phosphoric acid solution produced here is reacted with calcium hydroxide and / or magnesium hydroxide to dissolve in water. A method for purifying biogas and recovering phosphorus in waste liquid in methane fermentation treatment, wherein the method recovers phosphorus as a phosphate. 水酸化カルシウム及び／又は水酸化マグネシウムの代わりに、又はこれらに加えてドロマイトを使用することを特徴とする、請求項１記載のメタン発酵処理におけるバイオガスの精製と廃液中のリンの回収方法。   The method for purifying biogas and recovering phosphorus in waste liquid according to claim 1, wherein dolomite is used instead of or in addition to calcium hydroxide and / or magnesium hydroxide. 生成したリン酸溶液に水酸化カルシウム及び／又は水酸化マグネシウムを加えてｐＨを８〜９に調整することを特徴とする、請求項１又は２に記載のメタン発酵処理におけるバイオガスの精製と廃液中のリンの回収方法。   The purification and waste liquid of biogas in methane fermentation treatment according to claim 1 or 2, characterized in that calcium hydroxide and / or magnesium hydroxide is added to the produced phosphoric acid solution to adjust the pH to 8-9. Recovery method of phosphorus in the inside.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013187955A1 (en) * 2012-06-15 2013-12-19 Regents Of The University Of Minnesota Hydrothermal carbonization of sewage wastes
CN110143659A (en) * 2019-05-25 2019-08-20 天津金辰博科环保科技发展有限公司 A kind of sewage denitrification and dephosphorization agent and preparation method thereof

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013187955A1 (en) * 2012-06-15 2013-12-19 Regents Of The University Of Minnesota Hydrothermal carbonization of sewage wastes
US9475698B2 (en) 2012-06-15 2016-10-25 Regents Of The University Of Minnesota Hydrothermal carbonization of sewage wastes
CN110143659A (en) * 2019-05-25 2019-08-20 天津金辰博科环保科技发展有限公司 A kind of sewage denitrification and dephosphorization agent and preparation method thereof

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