JP5265588B2 - Methane fermentation method - Google Patents

Methane fermentation method Download PDF

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JP5265588B2
JP5265588B2 JP2010011774A JP2010011774A JP5265588B2 JP 5265588 B2 JP5265588 B2 JP 5265588B2 JP 2010011774 A JP2010011774 A JP 2010011774A JP 2010011774 A JP2010011774 A JP 2010011774A JP 5265588 B2 JP5265588 B2 JP 5265588B2
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methane fermentation
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茂 丸山
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Metawater Co Ltd
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    • YGENERAL 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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Description

本発明は、長期にわたって、有機性廃棄物を安定してメタン発酵処理できるメタン発酵方法に関する。   The present invention relates to a methane fermentation method capable of stably treating methane fermentation of organic waste over a long period of time.

メタン発酵処理は、有機性廃棄物を嫌気性下でメタン菌により発酵処理して有機性廃棄物をメタンガスに転換するもので、有機性廃棄物をバイオガスと水とに分解して大幅に減量することができる。しかも、副産物として生成するメタンガスをエネルギーとして回収できるメリットがある。   Methane fermentation treatment is an anaerobic treatment of organic waste with methane bacteria to convert the organic waste into methane gas. The organic waste is decomposed into biogas and water to greatly reduce the amount of waste. can do. In addition, there is a merit that methane gas generated as a by-product can be recovered as energy.

ところで、メタン発酵処理では、処理中にメタン発酵槽内の発酵液が発泡することがあった。発泡が生じる原因としては、発酵液の粘度増加、有機性廃棄物からの発泡性物質の混入などがある。例えば、濃縮された下水余剰汚泥は、高分子凝集剤を含んでいる場合がある。濃縮された下水余剰汚泥を多量に含む有機性廃棄物をメタン発酵処理した場合、高分子凝集剤の作用で発酵液が高粘度になり易く、撹拌を目的に行われるバブリングにより発泡が生じ易かった。発泡が穏やかな場合は特に問題無いが、発泡が激しくなると、泡界面が上昇してバイオガスの回収経路などに泡などが進入して配管を閉塞したり、泡が圧力計などの計測器具に付着して誤作動の原因となったり、損傷する問題があった。   By the way, in the methane fermentation treatment, the fermentation liquid in the methane fermentation tank may foam during the treatment. Causes of foaming include an increase in the viscosity of the fermentation broth and the incorporation of foaming substances from organic waste. For example, the concentrated sewage surplus sludge may contain a polymer flocculant. When organic waste containing a large amount of concentrated sewage surplus sludge was subjected to methane fermentation, the fermentation liquor was likely to become highly viscous due to the action of the polymer flocculant, and foaming was likely to occur due to bubbling performed for the purpose of stirring. . If foaming is mild, there is no problem, but if foaming becomes severe, the foam interface will rise and foam will enter the biogas recovery path and block the pipe, or the foam will become a measuring instrument such as a pressure gauge. There was a problem of sticking and causing malfunction or damage.

メタン発酵槽内の発泡を検知する方法としては、メタン発酵槽内に泡の上面レベルを検知する泡検出電極を垂設して発泡を検知する方法(特許文献1の段落番号0017,図2参照)がある。この方法は、発酵液の伝導性を利用し、発酵液が発泡して液面が上昇し液面検出電極に接触すると電流が流れて発泡を検知するものであるが、液面検出電極に発酵液が付着することがあった。   As a method of detecting foaming in the methane fermentation tank, a method of detecting foaming by suspending a foam detection electrode for detecting the upper surface level of the foam in the methane fermentation tank (see paragraph number 0017 of FIG. 2 and FIG. 2). ) This method utilizes the conductivity of the fermentation broth, and when the fermentation broth foams and the liquid level rises and contacts the liquid level detection electrode, current flows to detect foaming. The liquid sometimes adhered.

また、メタン発酵槽内に圧力センサを設け、圧力変化を測定して発泡を検出する方法(特許文献1の段落番号0035,図5参照)がある。しかしながら、発泡に伴う圧力変化は微小で、ノイズ的なものであり、検出精度は低かった。更には、圧力上昇を検知した時点では、泡が既に配管内に入り込んでしまっている状態である場合が多かった。   In addition, there is a method for detecting foaming by providing a pressure sensor in the methane fermenter (see paragraph number 0035 of FIG. 5 and FIG. 5). However, the pressure change due to foaming was minute and noise-like, and the detection accuracy was low. Furthermore, when the pressure increase is detected, there are many cases where the bubbles have already entered the pipe.

特開平8−299998号公報JP-A-8-299998

本発明の目的は、メタン発酵槽内の発泡を精度よく検知し、配管や計測器等を損傷することなく発泡を抑制することが可能なメタン発酵方法を提供することにある。   An object of the present invention is to provide a methane fermentation method capable of accurately detecting foaming in a methane fermentation tank and suppressing foaming without damaging pipes or measuring instruments.

上記目的を達成するにあたり、本発明のメタン発酵方法の第1は、有機性廃棄物をメタン発酵槽内に投入し、高温メタン菌によりメタン発酵するメタン発酵方法であって、前記メタン発酵槽内の発酵液の液面よりも上方の温度を計測し、前記メタン発酵槽内の発酵液のバブリング開始前の前記温度と、バブリング停止直後の前記温度との温度差が、正常運転に基づく前記温度差よりも大きい場合にメタン発酵槽内の発泡を抑制する制御を行うことを特徴とする。
また、本発明のメタン発酵方法の第2は、有機性廃棄物をメタン発酵槽内に投入し、高温メタン菌によりメタン発酵するメタン発酵方法であって、前記メタン発酵槽内の発酵液の液面よりも上方の温度を計測し、前記メタン発酵槽内の発酵液のバブリングを開始し、その後バブリングを停止した時、前記温度がバブリング開始前の温度まで低下するのに要する時間が、正常運転時に温度低下するまでに要する時間よりも長い場合に、メタン発酵槽内の発泡を抑制する制御を行うことを特徴とする。
In achieving the above object, the first of the methane fermentation methods of the present invention is a methane fermentation method in which organic waste is introduced into a methane fermentation tank and methane fermentation is performed using high-temperature methane bacteria, the temperature above the temperature than the liquid level of the fermentation liquid was measured, and the temperature before bubbling initiation of the fermentation liquid in the methane fermentation tank, the temperature difference between the temperature immediately after bubbling stopped, based on the normal operation of the and performing control to suppress foaming of the methane fermentation tank is greater than the difference.
The second of the methane fermentation methods of the present invention is a methane fermentation method in which organic waste is introduced into a methane fermentation tank and methane fermentation is performed using high-temperature methane bacteria, and the liquid of the fermentation liquid in the methane fermentation tank When the temperature above the surface is measured and bubbling of the fermented liquid in the methane fermenter is started and then bubbling is stopped, the time required for the temperature to drop to the temperature before bubbling starts is normal operation. In some cases, control is performed to suppress foaming in the methane fermentation tank when it is longer than the time required for the temperature to drop.

メタン発酵槽内の発酵液の液面よりも上方の温度を計測し、メタン発酵槽内の発酵液のバブリング開始前の前記温度と、バブリング停止直後の前記温度との温度差が、正常運転に基づく前記温度差よりも大きいか、あるいは、メタン発酵槽内の発酵液のバブリングを開始し、その後バブリングを停止した時、メタン発酵槽内の発酵液の液面よりも上方の空間の温度がバブリング開始前の温度まで低下するのに要する時間が、正常運転時に温度低下するまでに要する時間よりも長い場合は、泡の上面レベルが温度を検出した位置よりも上部にあると推測できる。このため、本発明によれば、メタン発酵槽内の発酵液の液面よりも上方の温度を計測し、メタン発酵槽内の発酵液のバブリング開始前の前記温度と、バブリング停止直後の前記温度との温度差が、正常運転に基づく前記温度差よりも大きいか、あるいは、メタン発酵槽内の発酵液のバブリングを開始し、その後バブリングを停止した時、メタン発酵槽内の発酵液の液面よりも上方の空間の温度がバブリング開始前の温度まで低下するのに要する時間が、正常運転時に温度低下するまでに要する時間よりも長いことを検知したら、メタン発酵槽内の発泡を抑制する制御を行うことにより、配管閉塞や各種計測機器の損傷等のトラブルの発生を抑制でき、メンテナンスコストを低減できる。 Measure the temperature above the liquid level of the fermentation broth in the methane fermentation tank, and the temperature difference between the temperature before the start of bubbling of the fermentation liquid in the methane fermentation tank and the temperature immediately after the bubbling stop is normal operation. When the bubbling of the fermentation liquid in the methane fermentation tank is started and then bubbling is stopped, the temperature of the space above the liquid level of the fermentation liquid in the methane fermentation tank is bubbled. When the time required to decrease to the temperature before the start is longer than the time required to decrease the temperature during normal operation, it can be assumed that the upper surface level of the bubble is above the position where the temperature is detected. Therefore, according to the present invention, the temperature above the liquid level of the fermentation liquid in the methane fermentation tank is measured, and the temperature before the start of bubbling of the fermentation liquid in the methane fermentation tank, and the temperature immediately after the bubbling stops when the temperature difference is greater than the temperature difference based on normal operation of the, or to start the bubbling of the fermentation liquid in the methane fermentation tank, when subsequently stopped bubbling, the liquid level of the fermentation liquor of the methane fermentation tank Control that suppresses foaming in the methane fermenter when it is detected that the time required for the temperature of the space above it to drop to the temperature before the start of bubbling is longer than the time required for the temperature to drop during normal operation As a result, troubles such as blockage of pipes and damage to various measuring devices can be suppressed, and maintenance costs can be reduced.

本発明のメタン発酵方法は、メタン発酵槽内の発酵液の液面よりも上方であって、高さ方向に異なる複数の位置の温度を計測することが好ましい。この態様によれば、メタン発酵槽内の泡の上面レベルを精度よく検知できるので、発泡状態に応じた最適な発泡の抑制制御を実施することができる。   In the methane fermentation method of the present invention, it is preferable to measure temperatures at a plurality of positions above the liquid level of the fermentation liquid in the methane fermentation tank and different in the height direction. According to this aspect, since the upper surface level of the foam in the methane fermentation tank can be detected with high accuracy, it is possible to carry out optimal foam suppression control according to the foaming state.

本発明のメタン発酵方法は、メタン発酵槽内の発酵液の組成を変更することにより前記発泡を抑制することが好ましい。   The methane fermentation method of the present invention preferably suppresses the foaming by changing the composition of the fermentation broth in the methane fermentation tank.

本発明のメタン発酵方法は、メタン発酵槽内の発酵液中の高分子凝集剤及び/又は粘性菌の量を低減することにより前記発泡を抑制することが好ましい。   The methane fermentation method of the present invention preferably suppresses the foaming by reducing the amount of the polymer flocculant and / or viscous bacteria in the fermentation broth in the methane fermentation tank.

本発明のメタン発酵方法は、消泡剤を含む有機性廃棄物をメタン発酵槽に供給して前記発泡を抑制することが好ましい。   In the methane fermentation method of the present invention, it is preferable to suppress the foaming by supplying an organic waste containing an antifoaming agent to the methane fermentation tank.

本発明のメタン発酵方法は、メタン発酵槽内上方の気相部から散水して前記発泡を抑制することが好ましい。   In the methane fermentation method of the present invention, it is preferable to sprinkle water from the upper gas phase in the methane fermentation tank to suppress the foaming.

本発明のメタン発酵方法は、前記発泡を槽外に取り出して前記発泡を抑制することが好ましい。   In the methane fermentation method of the present invention, the foaming is preferably taken out of the tank to suppress the foaming.

本発明によれば、メタン発酵槽内の発酵液の液面よりも上方の温度を計測し、メタン発酵槽内の発酵液のバブリング開始前の前記温度と、バブリング停止直後の前記温度との温度差が、正常運転に基づく前記温度差よりも大きいか、あるいは、メタン発酵槽内の発酵液のバブリングを開始し、その後バブリングを停止した時、メタン発酵槽内の発酵液の液面よりも上方の空間の温度がバブリング開始前の温度まで低下するのに要する時間が、正常運転時に温度低下するまでに要する時間よりも長い場合は、泡の上面レベルが温度を検出した位置よりも上部にあると推測できるので、このような状態を検知したら、メタン発酵槽内の発泡を抑制する制御を行うことにより、配管閉塞や各種計測機器の損傷等のトラブルの発生を抑制でき、メンテナンスコストを低減できる。 According to the present invention, the temperature above the liquid level of the fermentation broth in the methane fermentation tank is measured, and the temperature before the start of bubbling of the fermentation broth in the methane fermentation tank and the temperature immediately after the bubbling is stopped. The difference is greater than the temperature difference based on normal operation , or when the bubbling of the fermentation broth in the methane fermentation tank is started and then stopped, the level above the liquid level of the fermentation broth in the methane fermentation tank If the time required for the space temperature to drop to the temperature before the start of bubbling is longer than the time required for the temperature to drop during normal operation , the upper surface level of the foam is above the position where the temperature was detected. Therefore, if such a state is detected, the occurrence of troubles such as piping blockage and damage to various measuring instruments can be suppressed by performing control to suppress foaming in the methane fermenter. Nsukosuto can be reduced.

本発明のメタン発酵方法に用いるメタン発酵装置を表す概略構成図である。It is a schematic block diagram showing the methane fermentation apparatus used for the methane fermentation method of this invention. 実施例1における温度センサT1の計測値の経時変化を示す図表である。6 is a chart showing a change with time of a measurement value of a temperature sensor T1 in Example 1. 実施例1において、発泡が生じなかった場合の温度センサT1の計測値の経時変化を示す図表である。In Example 1, it is a graph which shows a time-dependent change of the measured value of temperature sensor T1 when foaming does not arise. 実施例1において、発泡が生じた場合の温度センサT1の計測値の経時変化を示す図表である。In Example 1, it is a graph which shows a time-dependent change of the measured value of temperature sensor T1 when foaming arises.

本発明のメタン発酵方法に用いるメタン発酵槽について、図1を用いて説明する。   The methane fermentation tank used for the methane fermentation method of this invention is demonstrated using FIG.

メタン発酵槽1は、有機性廃棄物を、槽内に存在する高温メタン菌等の嫌気性微生物の作用によりメタン発酵処理してメタンガスを含むバイオガスを発生させるものである。メタン発酵槽1内には、嫌気性微生物を担持させる目的で固定ろ床、流動ろ床などの担体を装填してもよい。担体を装填することにより、高温メタン菌等が担体に担持されて槽内に高温メタン菌を多量に留めることができ、有機性廃棄物のメタン発酵処理効率を高めることができる。   The methane fermentation tank 1 generates biogas containing methane gas by subjecting organic waste to methane fermentation treatment by the action of anaerobic microorganisms such as high-temperature methane bacteria present in the tank. The methane fermentation tank 1 may be loaded with a carrier such as a fixed filter bed or a fluidized filter bed for the purpose of supporting anaerobic microorganisms. By loading the carrier, high-temperature methane bacteria and the like are supported on the carrier and a large amount of high-temperature methane bacteria can be retained in the tank, and the efficiency of methane fermentation treatment of organic waste can be improved.

メタン発酵槽1の上側部には、有機性廃棄物供給源から伸びた有機性廃棄物供給ラインL1が接続している。この有機性廃棄物供給ラインL1を通して槽内に有機性廃棄物が供給される。   An organic waste supply line L1 extending from an organic waste supply source is connected to the upper side of the methane fermentation tank 1. The organic waste is supplied into the tank through the organic waste supply line L1.

メタン発酵槽1の側壁には、上流側から発酵液循環ポンプP1とヒータ2とが介装された循環ラインL2が併設されている。この循環ラインL2の上流は、メタン発酵槽1の底部付近に開口し、下流はメタン発酵槽1の発酵液液面レベル付近に開口している。   On the side wall of the methane fermentation tank 1, a circulation line L <b> 2 in which a fermentation liquid circulation pump P <b> 1 and a heater 2 are interposed is provided from the upstream side. The upstream of the circulation line L2 opens near the bottom of the methane fermentation tank 1, and the downstream opens near the fermentation liquid level of the methane fermentation tank 1.

メタン発酵槽1の上部には、メタン発酵槽1内で発生したメタンガスを含むバイオガスを取出すバイオガス取出しラインL3が連結している。このバイオガス取出しラインL3の先端は、図示しないバイオガスホルダやバイオガス利用設備などに連結するバイオガス回収ラインL4と、バイオガスの少なくとも一部を発酵液中にバブリングできるようにその先端部が発酵液中の下方で開口して配置されたバブリングラインL5とに分岐している。このバブリングラインL5には、バブリングポンプP2が介装されている。   Connected to the upper part of the methane fermentation tank 1 is a biogas extraction line L3 for extracting biogas containing methane gas generated in the methane fermentation tank 1. The leading end of the biogas extraction line L3 is fermented so that at least a part of the biogas can be bubbled into the fermentation broth, and a biogas recovery line L4 connected to a biogas holder or a biogas utilization facility (not shown). It branches off to a bubbling line L5 that is open at the bottom of the liquid. A bubbling pump P2 is interposed in the bubbling line L5.

メタン発酵槽1の下方には、槽内の発酵汚泥を系外に排出する、発酵汚泥引き抜きポンプP3を介装した発酵汚泥排出ラインL6が設けられている。   Below the methane fermentation tank 1, there is provided a fermentation sludge discharge line L <b> 6 interposing a fermentation sludge extraction pump P <b> 3 that discharges the fermentation sludge in the tank out of the system.

メタン発酵槽1内の発酵液の液面よりも上方の空間(以下、上部空間10ともいう)には、温度センサT1が設置されている。温度センサT1としては、例えば、測温抵抗体、熱伝対等が挙げられる。   A temperature sensor T <b> 1 is installed in a space above the liquid level of the fermentation liquid in the methane fermentation tank 1 (hereinafter also referred to as the upper space 10). Examples of the temperature sensor T1 include a resistance temperature detector and a thermocouple.

温度センサT1は、メタン発酵槽1の天板1aから0〜0.3m下方であって、かつ、発酵液の最高液面よりも0.1m以上上方に配置されていることが好ましい。なお、発酵液面は、有機性廃棄物の投入および発酵液の引き抜きにより変動する。温度センサT1をこのように配置することで、検出誤差の発生を抑制しつつ、泡がバイオガス取出しラインL3に入り込む前に発泡を抑制し易くなる。   It is preferable that the temperature sensor T1 is 0 to 0.3 m below the top plate 1a of the methane fermentation tank 1 and 0.1 m or more above the highest liquid level of the fermentation broth. The fermentation liquid level varies depending on the input of organic waste and the extraction of the fermentation liquid. By disposing the temperature sensor T1 in this way, it is easy to suppress foaming before the bubbles enter the biogas extraction line L3 while suppressing the occurrence of detection errors.

次に、本発明のメタン発酵方法について説明する。   Next, the methane fermentation method of the present invention will be described.

必要により前処理した有機性廃棄物を、有機性廃棄物供給ラインL1からメタン発酵槽1内に供給する。例えば、塵芥、生ごみ、家畜糞尿、下水汚泥などの有機性廃棄物の場合、上水と混合し、粉砕・破砕などの前処理を行うことが好ましい。また、油脂排液、ステアリン酸やパルミチン酸等のような油脂分を多く含む有機性廃棄物の場合は、65〜80℃に加温して可溶化する前処理を行うことが好ましい。   If necessary, the pretreated organic waste is supplied into the methane fermentation tank 1 from the organic waste supply line L1. For example, in the case of organic waste such as dust, garbage, livestock manure, sewage sludge, it is preferable to mix with clean water and perform pretreatment such as crushing and crushing. In the case of an organic waste containing a large amount of oil and fat such as fat and oil drainage, stearic acid and palmitic acid, it is preferable to carry out a pretreatment that is heated to 65 to 80 ° C. and solubilized.

メタン発酵槽1では、槽内に供給された有機性廃棄物を、槽内に存在する高温メタン菌等の嫌気性微生物によりメタン発酵する。槽内の発酵液は、発酵液循環ポンプP1を連続的または間欠的に作動して循環ラインL2から一定流量で引き抜き、ヒータ2にて50〜55℃に加温した後、メタン発酵槽1へ返送する。これにより、槽内の発酵液が循環され、発酵液上面に形成されたスカム等が破壊されると共に、メタン発酵槽1内の発酵液温度が、約50〜55℃に均一化される。なお、槽内の発酵液は、供給された有機性廃棄物と同量の発酵液が、発酵汚泥排出ラインL6から引き抜かれ、槽内には常時一定量の発酵液が満ちている。   In the methane fermentation tank 1, the organic waste supplied in the tank is subjected to methane fermentation by anaerobic microorganisms such as high-temperature methane bacteria present in the tank. The fermented liquid in the tank is continuously or intermittently operated from the fermenting liquid circulation pump P1 and drawn out from the circulation line L2 at a constant flow rate, heated to 50 to 55 ° C. by the heater 2, and then transferred to the methane fermentation tank 1. Return it. Thereby, the fermented liquor in the tank is circulated, the scum formed on the upper surface of the fermented liquid is destroyed, and the temperature of the fermented liquid in the methane fermenter 1 is made uniform at about 50 to 55 ° C. In addition, as for the fermented liquid in a tank, the same amount of fermented liquid as the supplied organic waste is pulled out from the fermentation sludge discharge line L6, and a constant amount of fermented liquid is always filled in the tank.

有機性廃棄物をメタン発酵した際に発生したバイオガスは、バイオガス取出しラインL3から槽外に取り出し、バイオガス回収ラインL4を経てバイオガスホルダ等に送り、一部はバブリングラインL5を経てメタン発酵槽1に返送し、発酵液のバブリングに使用する。なお、発酵液のバブリングは、常時行う必要はなく、間欠的に行っても良い。例えば、メタン発酵槽1内に有機性廃棄物を供給直後は、発酵液の汚泥濃度が均一化されていないので、メタン発酵槽1内に有機性廃棄物を供給中または供給直後にバイオガスによるバブリングを行って、発酵液の有機性廃棄物の汚泥濃度の均一化を図ることが好ましい。   Biogas generated during methane fermentation of organic waste is taken out of the tank from the biogas extraction line L3, sent to the biogas holder, etc. via the biogas recovery line L4, and partly methane fermentation via the bubbling line L5. Return to tank 1 and use for bubbling fermentation broth. It should be noted that bubbling of the fermented liquid is not always required, and may be performed intermittently. For example, immediately after supplying organic waste into the methane fermentation tank 1, the sludge concentration of the fermentation liquid is not uniformized. It is preferable to make the sludge concentration of the organic waste of the fermentation liquid uniform by bubbling.

このようにしてメタン発酵処理を実施していると、発酵液の粘度増加、有機性廃棄物からの発泡性物質の混入などの要因によって、発酵液が発泡することがあった。特に、バイオガスによるバブリング直後に発泡が生じる場合が多かった。
そこで、本発明では、メタン発酵槽内の上部空間10の温度を計測し、該温度が正常運転に基づく温度上昇幅よりも大きいか、あるいは、温度上昇の持続時間が正常運転に基づく温度上昇持続時間よりも長いことを検知したら、メタン発酵槽内の発泡を抑制する制御を行う。
When the methane fermentation treatment is carried out in this manner, the fermentation liquid may foam due to factors such as an increase in the viscosity of the fermentation liquid and mixing of foamable substances from organic waste. In particular, foaming often occurred immediately after bubbling with biogas.
Therefore, in the present invention, the temperature of the upper space 10 in the methane fermentation tank is measured and the temperature is larger than the temperature increase width based on normal operation, or the temperature increase duration is based on normal operation. If it detects that it is longer than time, control which suppresses foaming in a methane fermentation tank will be performed.

ここで、高温メタン菌によるメタン発酵では、メタン発酵槽内の発酵液はおよそ50〜55℃に保たれている。これに対し、メタン発酵槽内の上部空間10は、外気温により変動するが、およそ20〜45℃程度である。   Here, in the methane fermentation by high-temperature methane bacteria, the fermentation liquor in the methane fermentation tank is maintained at about 50 to 55 ° C. On the other hand, the upper space 10 in the methane fermenter varies depending on the outside air temperature, but is about 20 to 45 ° C.

このように高温メタン菌によるメタン発酵の場合、発酵液と、メタン発酵槽1内の上部空間10は、温度差が大きいため、発酵液の発泡が激しくなって、泡の上面レベルが徐々に上昇していき、泡の上面が温度センサT1に接触すると、温度センサT1による検出値が急激に上昇する。なお、温度センサT1による検出値は、日中と夜間、夏場と冬場等外気温の影響を受けて変化するが、かかる外気温の影響による変化は、発泡による温度上昇に比べて極めて小さい。更には、外気温の影響による温度変化は徐々に変化するのに対し、発泡による温度上昇は突発的である。このように、外気温の影響による温度変化と、発泡による温度変化とは著しく異なる。また、発酵液をバイオガスでバブリングすると、発酵液面から発酵液の液温まで加温されたバブリングガスが放出されるので、バブリング中は一時的に温度センサT1による検出値は発酵液の温度近くまで上昇するが、バブリングを停止すると、発酵液の液面からのバブリングガスの放出が停止するので、直ちに温度が低下する。このような温度変化パターンが「正常運転」の状況の一例である。これに対し、発泡による温度上昇の場合、温度センサT1に泡が常時接触しているので、バブリングに伴う温度上昇の持続時間よりも長い。このように、バブリングに基づく温度上昇の持続時間と、発泡に基づく温度上昇の持続時間は著しく異なる。このような温度変化パターンが「正常運転」からはずれた状況の一例である。   Thus, in the case of methane fermentation by high-temperature methane bacteria, since the temperature difference between the fermentation liquid and the upper space 10 in the methane fermentation tank 1 is large, foaming of the fermentation liquid becomes intense and the upper surface level of the bubbles gradually increases. Then, when the upper surface of the bubble comes into contact with the temperature sensor T1, the value detected by the temperature sensor T1 rises rapidly. The value detected by the temperature sensor T1 changes under the influence of outside air temperature such as daytime and nighttime, summertime and wintertime, but the change due to the influence of the outside air temperature is extremely small compared to the temperature rise due to foaming. Furthermore, while the temperature change due to the influence of the outside air temperature changes gradually, the temperature rise due to foaming is sudden. Thus, the temperature change due to the influence of the outside air temperature is significantly different from the temperature change due to foaming. Further, when bubbling the fermentation broth with biogas, the bubbling gas heated from the surface of the fermentation broth to the temperature of the fermentation broth is released. Therefore, during the bubbling, the temperature sensor T1 temporarily detects the temperature of the fermentation broth. Although it rises to near, when the bubbling is stopped, the release of the bubbling gas from the surface of the fermentation broth stops, so the temperature immediately decreases. Such a temperature change pattern is an example of a “normal operation” situation. On the other hand, in the case of the temperature rise due to foaming, the bubble is always in contact with the temperature sensor T1, and therefore, it is longer than the duration of the temperature rise accompanying bubbling. Thus, the duration of the temperature rise based on bubbling is significantly different from the duration of the temperature rise based on foaming. This is an example of a situation where such a temperature change pattern deviates from “normal operation”.

このため、温度センサT1による計測値が、正常運転に基づく温度上昇幅よりも大きいか、あるいは、温度上昇の持続時間が正常運転に基づく温度上昇持続時間よりも長い場合は、泡の上面レベルが、温度センサT1に達したと推測できる。   For this reason, when the measured value by the temperature sensor T1 is larger than the temperature rise width based on normal operation or the duration of temperature rise is longer than the temperature rise duration based on normal operation, the upper surface level of the bubble is It can be estimated that the temperature sensor T1 has been reached.

そこで、温度センサT1にて、このような状態にあることを検知したら、メタン発酵槽1内の発泡を抑制する制御を行うことにより、バイオガス取出しラインL4等の各種配管内に泡が入り込んだり、上部空間10に設置されている各種計測機器等に泡が付着する前に発泡を抑制でき、配管閉塞や各種計測機器の誤作動や損傷等のトラブルの発生を抑制して、メンテナンスコストを低減できる。   Therefore, if the temperature sensor T1 detects that such a state is present, by controlling to suppress foaming in the methane fermentation tank 1, bubbles may enter into various pipes such as the biogas take-out line L4. , Foaming can be suppressed before bubbles are attached to various measuring devices installed in the upper space 10, and maintenance costs are reduced by preventing troubles such as piping blockage and malfunctions and damages of various measuring devices. it can.

また、発泡を検出して発泡の抑制処理を行っても、引き続き発泡が進行した場合や、発泡の進行が急激な場合は、有機性廃棄物の投入を一時的に停止し、上部空間の温度が、正常運転に基づく温度上昇幅の範囲内となるか、あるいは、温度上昇の持続時間が正常運転に基づく温度上昇持続時間の範囲内となったら、有機性廃棄物の投入を再開することが好ましい。再開時に投入する有機性廃棄物の投入量は、定格運転時の50〜90%で行い、発泡が起きなければ定格運転時の投入量に戻すことが好ましい。   In addition, even if foaming is detected and foaming suppression is performed, if foaming continues or if foaming progresses rapidly, the introduction of organic waste is temporarily stopped, and the temperature of the upper space is reduced. However, if the temperature rise is within the range of the temperature rise based on normal operation or the duration of the temperature rise is within the range of temperature rise duration based on the normal operation, the input of organic waste may be resumed. preferable. The input amount of the organic waste to be input at the time of restarting is preferably 50 to 90% of the rated operation, and it is preferable to return to the input amount at the rated operation if foaming does not occur.

発泡の抑制方法としては、特に限定はなく、従来公知の方法を用いることができる。例えば、メタン発酵槽1内の発酵液の組成を変更して発泡を抑制する方法が挙げられる。   The method for suppressing foaming is not particularly limited, and a conventionally known method can be used. For example, the method of suppressing foaming by changing the composition of the fermentation broth in the methane fermentation tank 1 can be mentioned.

前述したように、高分子凝集剤を含んだ有機性廃棄物をメタン発酵処理した場合、高分子凝集剤の作用で発酵液が高粘度になり易く、撹拌を目的に行われるバブリングにより発泡が生じ易くなる傾向にある。また、粘性菌等が増殖して発酵液の粘度が増加することでも、発泡が生じ易くなる。   As described above, when organic waste containing a polymer flocculant is subjected to a methane fermentation treatment, the fermentation liquid tends to become highly viscous due to the action of the polymer flocculant, and foaming occurs due to bubbling performed for the purpose of stirring. It tends to be easier. In addition, foaming easily occurs when viscous bacteria and the like grow and the viscosity of the fermentation liquid increases.

発酵液の組成を変更する方法としては、発酵液中の高分子凝集剤や粘性菌を低減する方法が挙げられる。発酵液中の高分子凝集剤や粘性菌を低減するには、例えば下水余剰汚泥等のような高分子凝集剤を多く含んだ有機性廃棄物の供給量割合を低減する方法や、メタン発酵槽1に供給する有機性廃棄物の固形分濃度を低減してメタン発酵槽1内の発酵液の粘度を希釈すると共に有機性廃棄物負荷を低減する方法等が挙げられる。   Examples of the method for changing the composition of the fermentation broth include a method of reducing polymer flocculants and viscous bacteria in the fermentation broth. In order to reduce polymer flocculants and viscous bacteria in the fermentation broth, for example, a method of reducing the supply rate of organic waste containing a large amount of polymer flocculants such as sewage surplus sludge, methane fermenter And a method of reducing the solid waste concentration of the organic waste supplied to 1 to dilute the viscosity of the fermentation liquor in the methane fermenter 1 and reducing the organic waste load.

また、発酵液の組成を変更する方法の他の例として、消泡剤を含む有機性廃棄物をメタン発酵槽に供給して、消泡剤の作用により発泡を低減させる方法がある。なお、消泡剤は、直接メタン発酵槽1内に導入しても良いが、バイオガスの利用目的等を考慮して、非シリコーン系のエーテル系等の有機系消泡剤を使用することが多い。かかる消泡剤をメタン発酵槽1内に直接添加した場合、嫌気性微生物によって分解されため、効果の発現時間が数時間程度と短く、十分な消泡効果が得られないことがある。   Moreover, as another example of the method of changing the composition of the fermentation broth, there is a method of reducing foaming by supplying an organic waste containing an antifoaming agent to a methane fermentation tank and by the action of the antifoaming agent. The antifoaming agent may be introduced directly into the methane fermenter 1, but in consideration of the purpose of using biogas, an organic antifoaming agent such as a non-silicone ether may be used. Many. When such an antifoaming agent is added directly into the methane fermenter 1, it is decomposed by anaerobic microorganisms, so that the effect onset time is as short as several hours and a sufficient defoaming effect may not be obtained.

また、その他の発泡の抑制方法としては、例えば、以下の(1)、(2)の方法がある。
(1)上部空間10の上方に散水装置を設け、上部空間10から散水を行って発泡を低減する方法。散水は、発酵液の一部を取り出して行ってもよく、外部水を用いても良い。外部水を用いて散水を行うことにより発酵液の粘度を希釈することもでき、消泡効果をより高めることができる。
(2)メタン発酵槽1の側壁に吸引ポンプを介装した泡吸引ラインを設け、吸引ポンプを作動してメタン発酵槽1の液面に発生する泡を槽外に取り出す方法。取り出した泡は、破泡カラム等に導入して泡破した後、再度メタン発酵槽1へ返送することが好ましい。取り出した泡を消泡した後、メタン発酵槽1へ返送することにより、メタン発酵槽1内の発酵液面が低下するといったトラブルの発生を防止できる。
Other methods for suppressing foaming include, for example, the following methods (1) and (2).
(1) A method of reducing foaming by providing a watering device above the upper space 10 and spraying water from the upper space 10. Sprinkling may be performed by taking out a part of the fermentation broth or using external water. By spraying using external water, the viscosity of the fermentation broth can be diluted, and the defoaming effect can be further enhanced.
(2) A method of providing a bubble suction line with a suction pump on the side wall of the methane fermentation tank 1 and operating the suction pump to take out bubbles generated on the liquid surface of the methane fermentation tank 1 from the tank. The taken-out foam is preferably returned to the methane fermenter 1 again after being introduced into a foam-breaking column or the like and broken. Generation | occurrence | production of the trouble that the fermentation liquid level in the methane fermentation tank 1 falls can be prevented by returning to the methane fermentation tank 1 after defoaming the taken-out foam.

上記した発泡抑制方法はそれぞれ単独で行っても良く、2種類以上を組み合わせて行ってもよい。発泡が激しい場合や、泡の上面レベルがかなり上昇してきている場合などは、2種類以上の方法を組み合わせて、速やかに消泡することが好ましい。   The above-mentioned foaming suppression methods may be performed alone or in combination of two or more. When foaming is severe, or when the upper surface level of the foam has risen considerably, it is preferable to quickly defoam by combining two or more methods.

なお、この実施形態では、温度センサT1は、上部空間に1か所のみ配置されているが、高さ方向に異なる複数の位置にそれぞれ配置してもよい。温度センサT1を、このように配置することにより、メタン発酵槽1内の泡の上面レベルを精度よく検知できる。このため、例えば、発泡が比較的緩やかな場合は、各方法における強度を弱めて発泡の抑制を行ったり、あるいは、発泡が激しく発泡の上昇速度が速い場合などにおいては、各方法の強度を増したり、複数の方法を組み合わせて発泡抑制を行うなどの措置を行い、現在の発泡状態に応じた最適な発泡抑制を選択でき、ランニングコストの最適化を図ることができる。   In this embodiment, only one temperature sensor T1 is disposed in the upper space. However, the temperature sensor T1 may be disposed at a plurality of different positions in the height direction. By disposing the temperature sensor T1 in this way, the upper surface level of the bubbles in the methane fermentation tank 1 can be accurately detected. For this reason, for example, when foaming is relatively gradual, the strength in each method is weakened to suppress foaming, or in the case where foaming is severe and the foaming rate is high, the strength of each method is increased. In addition, by taking measures such as suppressing foaming by combining a plurality of methods, it is possible to select the optimal foaming suppression according to the current foaming state, and to optimize the running cost.

(実施例1)
図1に示すメタン発酵槽を用い、有機性廃棄物を、600L/日で、12分割して、2時間毎に50Lずつメタン発酵槽1内に投入し、滞留時間を10日の負荷で、高温メタン菌にてメタン発酵を行った。有機性廃棄物としては、固形分濃度が約30000mg/Lの下水処理場の混合汚泥(下水処理場の初沈汚泥と余剰汚泥を固形分比6:4で混合したもの。余剰汚泥には、高分子凝集剤が固形分当たり、1重量%含有している。)を用いた。メタン発酵槽1としては、直径1650mm、高さ3150mmの円筒状の槽を用い、メタン発酵槽の天板1aから140mm下方であって、発酵液の液面から210mm上方の位置に温度センサT1(商品名「FTZ3AS14−010G0,PT−100Ω」富士電機製)を設置した。メタン発酵中、槽内の発酵液の液面高さは2800mmとし、発酵液の温度は55℃とした。また、バブリングラインL5からのバブリングは、有機性廃棄物の供給時に、15m/hの流速で、6分間行った。
上記条件にて、メタン発酵を行い、上部空間の温度変化と、メタン発酵槽内の発泡状態との関係を調べた。なお、メタン発酵槽内の発泡状態は、メタン発酵槽内の様子を上部の観察窓から目視して判断した。このときの、温度センサT1の計測値の経時変化を図2に示す。
Example 1
Using the methane fermenter shown in FIG. 1, organic waste is divided into 12 parts at 600 L / day, and 50 L is charged into the methane fermenter 1 every 2 hours, and the residence time is 10 days. Methane fermentation was performed with high-temperature methane bacteria. As organic waste, the mixed sludge of a sewage treatment plant with a solid content concentration of about 30000 mg / L (a mixture of primary sludge and excess sludge of a sewage treatment plant at a solid content ratio of 6: 4. The polymer flocculant contained 1% by weight per solid content). As the methane fermentation tank 1, a cylindrical tank having a diameter of 1650 mm and a height of 3150 mm is used, and a temperature sensor T1 (at a position 140 mm below the top plate 1a of the methane fermentation tank and 210 mm above the liquid level of the fermentation broth. The product name “FTZ3AS14-010G0, PT-100Ω” manufactured by Fuji Electric) was installed. During methane fermentation, the liquid surface height of the fermentation liquid in the tank was 2800 mm, and the temperature of the fermentation liquid was 55 ° C. Bubbling from the bubbling line L5 was performed at a flow rate of 15 m 3 / h for 6 minutes when supplying the organic waste.
Under the above conditions, methane fermentation was performed, and the relationship between the temperature change in the upper space and the foaming state in the methane fermentation tank was examined. In addition, the foaming state in the methane fermentation tank was judged by visually observing the state in the methane fermentation tank from the upper observation window. FIG. 2 shows the change with time of the measured value of the temperature sensor T1 at this time.

定格運転20日後(3月28日まで)は、発泡が生じなかったが、それ以降は、バブリング時に発泡が見られた。図3は発泡が生じなかった場合の温度センサT1の計測値の経時変化を示す図表であり、図は、発泡が生じた場合の温度センサT1の測定値の経時変化を示す図表である。図3に示すように、発泡が生じていない場合は、バブリング開始前の温度センサT1による検出値は約30℃であり、バブリングを行った時点で、一次的に温度センサ T1による検出値が約40℃まで増加したものの、バブリングを停止したら、速やかに温度センサT1による検出値は約30℃まで低下した。 After 20 days of rated operation (until March 28), no foaming occurred, but thereafter foaming was observed during bubbling. FIG. 3 is a chart showing the change over time of the measured value of the temperature sensor T1 when foaming did not occur, and FIG. 4 is a chart showing the change over time of the measured value of the temperature sensor T1 when foaming occurred. As shown in FIG. 3, when bubbling has not occurred, the detected value by the temperature sensor T1 before the start of bubbling is about 30 ° C., and when the bubbling is performed, the detected value by the temperature sensor T1 is temporarily about Although the temperature increased to 40 ° C., when the bubbling was stopped, the value detected by the temperature sensor T1 quickly decreased to about 30 ° C.

一方、発泡が生じている場合は、図4に示す様に、バブリング開始前の温度センサT1による検出値は約35℃であったが、バブリングを行った時点で、一次的に温度センサT1による検出値が約55℃まで増加し、その後バブリングを停止しても約20分間はその状態が継続していた。バブリング直後のメタン発酵槽1内の状態を目視したところ、泡の上面レベルが温度センサT1に達していた。なお、図2において、3月27日の天気は晴れで朝の温度が5℃、日中の温度が23℃であり、外気温は朝昼間で約18℃の温度変化があったが、メタン発酵槽の上部空間10の温度変化は、朝昼間で約10℃であった。メタン発酵槽の上部空間10の朝昼間の温度変化は、発泡に伴う温度変化(約20℃)に比べて小さく、外気温の影響による温度変化と、発泡に伴う温度変化とを明確に区別できた。
そして、発泡を検出したら、滞留時間を12日で1日間運転して、発酵槽内の余剰汚泥に含まれる高分子凝集剤の濃度を下げる措置を行ない、発泡が停止したら(温度センサT1による検出値が50℃を超えなくなったら)、滞留時間を10日に戻して運転した結果、発泡は起こらず、安定な運転ができた。
On the other hand, when foaming has occurred, as shown in FIG. 4, the detected value by the temperature sensor T1 before the start of bubbling was about 35 ° C., but when the bubbling was performed, the temperature sensor T1 primarily The detected value increased to about 55 ° C., and the state continued for about 20 minutes even after the bubbling was stopped. When the state in the methane fermenter 1 immediately after bubbling was observed, the upper surface level of the foam reached the temperature sensor T1. In FIG. 2, the weather on March 27 was sunny, the morning temperature was 5 ° C., the daytime temperature was 23 ° C., and the outside air temperature changed about 18 ° C. in the morning and day. The temperature change in the upper space 10 of the fermenter was about 10 ° C. in the morning and daytime. The temperature change in the morning and daytime of the upper space 10 of the methane fermenter is smaller than the temperature change (about 20 ° C) associated with foaming, and the temperature change due to the outside air temperature can be clearly distinguished from the temperature change associated with foaming. It was.
And if foaming is detected, the residence time is operated for 12 days for 1 day, a measure is taken to reduce the concentration of the polymer flocculant contained in the excess sludge in the fermenter, and when foaming stops (detection by temperature sensor T1) When the value did not exceed 50 ° C.), the operation was performed with the residence time returned to 10 days. As a result, foaming did not occur and stable operation was possible.

(実施例2)
実施例1において、発泡を検出したら投入汚泥中の余剰汚泥の濃度を20%下げて運転を行ったところ、発泡が停止して安定な運転ができた。この希釈により発酵液の濃度や、その組成物質の割合が変化し、「発酵液の組成」が変更された。
(Example 2)
In Example 1, when foaming was detected, the operation was performed by reducing the concentration of excess sludge in the input sludge by 20%. As a result, foaming stopped and stable operation was possible. This dilution changed the concentration of the fermentation broth and the proportion of the compositional substances, and changed the “composition of the fermentation broth”.

(実施例3)
実施例1において、発泡を検出したら投入汚泥を希釈して固形分濃度を25000mg/Lに下げて運転を行ったところ、発泡が停止して安定な運転ができた。この希釈により発酵液の濃度が変化し、「発酵液の組成」変更された。
(Example 3)
In Example 1, when foaming was detected, the input sludge was diluted and the solid content concentration was lowered to 25000 mg / L, and the operation was performed. This dilution changed the concentration of the fermentation broth and changed the “composition of the fermentation broth”.

(実施例4)
上部に散水ノズルが設置されたメタン発酵槽を用い、滞留時間を8日に変更した以外は実施例1と同様に運転した。
定格運転3日後に発泡が生じた。このときの温度センサT1の計測値は、図3と同様の変化パターンを示した。
温度センサT1の計測値で50℃以上の継続時間が10分以上に達した時に散水を開始した。散水は、ノズルより40℃の温水を10L/minで10分間実施した。散水を3回実施した結果、温度センサT1の計測値が50℃以下になり、発泡がなくなった。その後も滞留時間8日で運転すると再度2日後に発泡が起こったが、同様に散水を繰り返し行ったところ、発泡がなくなった。その後、滞留時間を10日に戻し運転した結果、発泡の問題がなく運転できた。
Example 4
Using the methane fermentation tank in which the watering nozzle was installed in the upper part, it operated similarly to Example 1 except having changed the residence time to 8 days.
Foaming occurred after 3 days of rated operation. The measured value of the temperature sensor T1 at this time showed the same change pattern as FIG.
Water spraying was started when the duration of 50 ° C. or more reached 10 minutes or more as measured by the temperature sensor T1. Watering was carried out at 40 L warm water from a nozzle at 10 L / min for 10 minutes. As a result of performing watering three times, the measured value of the temperature sensor T1 became 50 ° C. or less, and foaming disappeared. After that, when the operation was carried out with a residence time of 8 days, foaming occurred again after 2 days. When watering was repeated in the same manner, foaming disappeared. Thereafter, the dwell time was returned to 10 days, and as a result, operation was possible without any foaming problems.

(実施例5)
上部に消泡剤の投入口を設けたメタン発酵槽を用い、滞留時間を8日に変更した以外は、実施例1と同様に運転した。
定格運転3日後に発泡が生じた。このときの温度センサT1の計測値は、図3と同様の変化パターンを示した。
温度センサT1の計測値で50℃以上の継続時間が10分以上に達した時に、消泡剤(商品名「ダッポ−H−401」、サンノプコ株式会社製)の20倍希釈液を4.0L注入した。注入後も同様の運転条件で運転した。消泡剤を注入してから2時間後は温度センサT1の計測値は50℃以下であった。4時間後には50℃の継続時間が3分、8時間後には10分を超えたので、再度消泡剤の投入を行った。その後、滞留時間を10日に戻し運転した結果、発泡の問題がなく運転できた。
(Example 5)
The operation was performed in the same manner as in Example 1 except that a methane fermenter provided with a defoamer inlet at the top was used and the residence time was changed to 8 days.
Foaming occurred after 3 days of rated operation. The measured value of the temperature sensor T1 at this time showed the same change pattern as FIG.
When the measured value of the temperature sensor T1 reaches 50 ° C. or more and the duration reaches 10 minutes or more, 4.0 L of a 20-fold diluted solution of an antifoaming agent (trade name “Dappo-H-401”, manufactured by San Nopco Co., Ltd.) Injected. The operation was performed under the same operating conditions after the injection. Two hours after injecting the antifoaming agent, the measured value of the temperature sensor T1 was 50 ° C. or less. After 4 hours, the duration of 50 ° C. was 3 minutes, and after 8 hours, it exceeded 10 minutes. Therefore, the antifoaming agent was charged again. Thereafter, the dwell time was returned to 10 days, and as a result, operation was possible without any foaming problems.

1:メタン発酵槽
2:ヒータ
10:上部空間
L1:有機性廃棄物供給ライン
L2:循環ライン
L3:バイオガス取出しライン
L4:バイオガス回収ライン
L5:バブリングライン
L6:発酵汚泥排出ライン
P1:発酵液循環ポンプ
P2:バブリングポンプ
P3:発酵汚泥引き抜きポンプ
T1:温度センサ
1: Methane fermentation tank 2: Heater 10: Upper space L1: Organic waste supply line L2: Circulation line L3: Biogas extraction line L4: Biogas recovery line L5: Bubbling line L6: Fermented sludge discharge line P1: Fermentation liquid Circulation pump P2: Bubbling pump P3: Fermented sludge extraction pump T1: Temperature sensor

Claims (8)

有機性廃棄物をメタン発酵槽内に投入し、高温メタン菌によりメタン発酵するメタン発酵方法であって、
前記メタン発酵槽内の発酵液の液面よりも上方の温度を計測し、前記メタン発酵槽内の発酵液のバブリング開始前の前記温度と、バブリング停止直後の前記温度との温度差が、正常運転に基づく前記温度差よりも大きい場合にメタン発酵槽内の発泡を抑制する制御を行うことを特徴とするメタン発酵方法。
A methane fermentation method in which organic waste is put into a methane fermentation tank and methane fermentation is performed using high-temperature methane bacteria.
Measure the temperature above the liquid level of the fermentation liquid in the methane fermentation tank, the temperature difference between the temperature before the start of bubbling of the fermentation liquid in the methane fermentation tank and the temperature immediately after the bubbling stop is normal. methane fermentation method and performing control to suppress foaming of the methane fermentation tank is larger than the temperature difference based on driving.
有機性廃棄物をメタン発酵槽内に投入し、高温メタン菌によりメタン発酵するメタン発酵方法であって、A methane fermentation method in which organic waste is put into a methane fermentation tank and methane fermentation is performed using high-temperature methane bacteria.
前記メタン発酵槽内の発酵液の液面よりも上方の温度を計測し、前記メタン発酵槽内の発酵液のバブリングを開始し、その後バブリングを停止した時、前記温度がバブリング開始前の温度まで低下するのに要する時間が、正常運転時に温度低下するまでに要する時間よりも長い場合にメタン発酵槽内の発泡を抑制する制御を行うことを特徴とするメタン発酵方法。Measure the temperature above the liquid level of the fermentation liquid in the methane fermentation tank, start bubbling of the fermentation liquid in the methane fermentation tank, and then stop the bubbling, the temperature to the temperature before the bubbling start The methane fermentation method characterized by performing control which suppresses foaming in a methane fermentation tank, when the time required to fall is longer than the time required for temperature fall at the time of normal operation.
メタン発酵槽内の発酵液の液面よりも上方であって、高さ方向に異なる複数の位置の温度を計測する、請求項1又は2に記載のメタン発酵方法。 The methane fermentation method according to claim 1 or 2 , wherein the temperature at a plurality of positions above the liquid level of the fermentation liquid in the methane fermentation tank and different in the height direction is measured. 前記メタン発酵槽内の発酵液の組成を変更することにより前記発泡を抑制する、請求項1〜3のいずれか1項に記載のメタン発酵方法。 The methane fermentation method according to any one of claims 1 to 3 , wherein the foaming is suppressed by changing a composition of a fermentation broth in the methane fermentation tank. 前記メタン発酵槽内の発酵液中の高分子凝集剤及び/又は粘性菌の量を低減することにより前記発泡を抑制する、請求項1〜のいずれか1項に記載のメタン発酵方法。 The methane fermentation method according to any one of claims 1 to 4 , wherein the foaming is suppressed by reducing an amount of a polymer flocculant and / or viscous bacteria in a fermentation broth in the methane fermentation tank. 消泡剤を含む有機性廃棄物をメタン発酵槽に供給して前記発泡を抑制する請求項1〜のいずれか1項に記載のメタン発酵方法。 The methane fermentation method according to any one of claims 1 to 5 , wherein an organic waste containing an antifoaming agent is supplied to a methane fermentation tank to suppress the foaming. メタン発酵槽内上方の気相部から散水して前記発泡を抑制する請求項1〜のいずれか1項に記載のメタン発酵方法。 The methane fermentation method according to any one of claims 1 to 6 , wherein the foaming is suppressed by sprinkling water from a gas phase portion above the methane fermentation tank. 前記発泡を槽外に取り出して前記発泡を抑制する請求項1〜のいずれか1項に記載のメタン発酵方法。 The methane fermentation method according to any one of claims 1 to 7 , wherein the foaming is taken out of the tank to suppress the foaming.
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