JP2005319388A - Method for setting operation condition of methane fermentation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for setting the optimum operation conditions in a methane fermentation system. <P>SOLUTION: In a reaction system where the amount V<SB>30</SB>of a waste charged into a methane fermentation tank 10 is equal to the discharged material amount V<SB>40</SB>from in-tank waste 20 in the methane fermentation tank, the change speed dVS/dt of the amount VS of in-tank organic material in the in-tank waste, the input speed VS<SB>in</SB>of organic material to the methane fermentation tank, the discharge speed VS<SB>out</SB>of organic material from the methane fermentation tank and the gas generation speed dG/dt of gas generating from the in-tank waste are determined and, based on them, the growth speed (dV<SB>21A</SB>/dt)g of methane fermentation sludge 21A is calculated. Thereafter, a first discharge speed F<SB>1</SB>of discharge material of such an extent as not to change the in-tank waste amount V is calculated on the basis of a waste input speed F<SB>in</SB>, the growth speed and the gas generation speed. Subsequently, methane fermentation sludge concentration X in the methane fermentation tank is calculated on the basis of the in-tank waste amount, the growth speed and the first discharge speed and, in accordance with the methane fermentation sludge concentration X, the operation condition is set. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for setting operating conditions of a methane fermentation system.

  There is a methane fermentation treatment method as an energy recovery type biological treatment method. The methane fermentation treatment method is widely used for various industrial wastewater treatments including excess sludge digestion in sewage treatment plants.

  Methane fermentation treatment methods include so-called standard and efficient types that use methane fermentation sludge containing methane bacteria and the like (hereinafter referred to as conventional types), and UASB that uses granular sludge called granules ( There are upflow anaerobic sludge blanket method and EGSB (expanded granular sludge blanket) method.

  The UASB and EGSB methods are highly loaded, and solids impede the growth of granules, so they are not suitable for digesting wastes with high solids concentrations.

  On the other hand, the conventional methane fermentation treatment method is suitable for the treatment of waste having a high solid matter concentration, and is used for digestion of excess sludge in a sewage treatment plant. In recent years, examples of use for food waste, organic solid waste in livestock factories, livestock waste, etc. are increasing due to the activation of a recycling society and the prohibition of ocean dumping.

  Here, in the methane fermentation system using the methane fermentation treatment method, the organic load is set as the operation condition. Conventionally, when setting this organic matter load, it was performed with respect to the solid matter concentration in the methane fermenter. This is ideally set for methane fermentation sludge concentration, but it is difficult to measure or estimate only methane fermentation sludge from a mixture of methane fermentation sludge and undigested waste. That's why. Therefore, conventionally, an organic load is set for the solid matter in the methane fermentation tank, and thereafter, the operation is performed based on the experience and intuition of the operator.

  On the other hand, as a technique for automating the methane fermentation process without depending on the experience and intuition of such an operator, for example, there is a processing system described in Patent Document 1.

In this processing system, the methane fermentation system is controlled as follows. Using the amount of organic waste supplied to the methane fermenter and the solid concentration in the methane fermenter, calculate the estimated amount of biogas produced by methane fermentation and the estimated time required to reach the estimated value. . And the biogas production amount and measurement time which were actually measured are compared with the said estimated value and estimated time. The supply amount of organic waste to the methane fermentation tank is adjusted based on the comparison result and the pH detection value in the solid-liquid separation unit that separates the solid component and the liquid component flowing out from the methane fermentation tank.
JP 2003-39052 A

  However, even in the system described in Patent Document 1, the solid matter concentration in the methane fermentation tank is measured, but the concentration itself of the methane fermentation sludge contained in the solid matter is not determined. Therefore, when organic load is set with respect to the solid substance in the methane fermenter in which the undigested solid substance is also mixed, it may become overloaded and methane fermentation may not advance.

  Therefore, even if the system is controlled according to the amount of biogas produced, methane fermentation may stop. In the system described in Patent Document 1, pH is measured so that methane fermentation does not stop, and the amount of waste to be input is adjusted. However, even if the pH is kept neutral, when the concentration of the organic acid is high (for example, exceeding 1000 ppm), methane fermentation may stop or shift to hydrogen fermentation. Therefore, even in the treatment system described in Patent Document 1, it is difficult to optimally operate the methane fermentation system.

  An object of the present invention is to provide a method for setting optimum operating conditions in a methane fermentation system.

  The inventor conducted intensive research on a method for setting optimum operating conditions in a methane fermentation system, and found the following.

  1stly, this inventor discovered that the waste amount in a tank changes, since the waste in a methane fermentation tank will lose | disappear from the inside of a methane fermentation tank as gas, if digested with methane fermentation sludge. Second, the present inventor has found that the concentration of methane fermentation sludge can be derived by measuring the change in the amount of waste in the tank produced by methane fermentation. The present invention has been made based on these findings.

  That is, the method for setting the operating conditions of the methane fermentation system according to the present invention is a method for setting the operating conditions of the methane fermentation system that decomposes the organic matter to be treated contained in the waste in the methane fermentation tank using the methane fermentation sludge. In the reaction system in which the input waste amount of input waste to be input to the methane fermentation tank is the same as the extracted waste amount extracted from the in-tank waste in the methane fermentation tank, The rate of change in the amount of organic matter in the tank, the rate at which the organic matter contained in the input waste is charged into the methane fermentation tank, the rate at which the extracted organic matter contained in the withdrawal is withdrawn from the methane fermentation tank The extraction rate and the gas generation rate of the gas generated from the waste in the tank by methane fermentation are obtained, and the measurement is performed based on the change rate, the organic matter input rate, the organic matter extraction rate, and the gas generation rate. Calculate the growth rate of the methane fermentation sludge in the fermenter and the first extraction speed for extracting the extract so as not to change the amount of waste in the tank. And calculating the methane fermentation sludge concentration in the methane fermentation tank based on the amount of waste in the tank, the growth rate, and the first extraction rate. To do.

  In the above method, first, in the reaction system in which the amount of waste input to the methane fermenter and the amount of withdrawn material extracted from the methane fermenter are the same, the change rate, organic material input rate, organic material extraction rate, and gas generation rate described above are set. Ask. Next, the growth rate of methane fermentation sludge is calculated based on them. Subsequently, a first extraction rate is calculated based on the waste input rate, the growth rate, and the gas generation rate. By pulling out the drawn material at the first drawing speed, the amount of waste in the tank is maintained substantially constant.

  And the methane fermentation sludge density | concentration is calculated based on the waste amount in a tank, a growth rate, and a 1st extraction speed.

  As described above, the methane fermentation sludge concentration is calculated by determining the change rate, the organic matter input rate, the organic matter extraction rate, and the gas generation rate. Therefore, it is possible to set the organic substance load in the methane fermentation system (in other words, the amount of organic substance input to the methane fermentation tank) using the methane fermentation sludge concentration involved in methane fermentation among the waste in the tank.

  Further, in the method for setting the operating conditions of the methane fermentation system according to the present invention, the methane fermentation system has a concentration means for concentrating the extract drawn from the methane fermentation tank to form concentrated sludge, and the concentrated sludge When returning at least a part of the waste to the methane fermentation tank, the second extraction speed for extracting the extract so as not to change the amount of waste in the tank, the return speed of the concentrated sludge to the methane fermentation tank, and the waste input speed And calculating the methane fermentation sludge concentration in the methane fermentation tank based on the amount of waste in the tank, the growth rate, the second extraction speed, the return speed, and the concentration rate of the concentration means. It is preferable.

  In this case, when at least a part of the concentrated sludge formed by the concentration means is returned into the methane fermentation tank, the return speed of the concentrated sludge to the methane fermentation tank, the waste input speed, and the gas generation speed Based on this, the second drawing speed is calculated. By extracting the extracted material at the second extraction speed, the amount of waste in the tank is maintained substantially constant even when at least a part of the concentrated sludge is returned into the methane fermentation tank.

  And the methane fermentation sludge density | concentration in a methane fermentation tank is computed based on the amount of waste in a tank, a proliferation rate, a 2nd extraction speed, a return speed, and a concentration rate.

  When returning the concentrated sludge, the methane fermentation sludge is also returned to the methane fermentation tank because the concentrated sludge also contains methane fermentation sludge. Therefore, the methane fermentation sludge concentration is maintained high.

  And if the methane fermentation sludge density | concentration in a methane fermenter is maintained high, it will become possible to throw in many organic substances (in other words, high load operation is possible).

  In addition, the method for setting the operating conditions of the methane fermentation system according to the present invention is to set the operating conditions of the methane fermentation system that decomposes the organic matter to be treated contained in the waste in the methane fermentation tank using the methane fermentation sludge. In a reaction system in which the input waste amount of input waste to be input to the methane fermentation tank is the same as the extraction amount of the extract drawn from the in-tank waste in the methane fermentation tank, The rate of change in the amount of organic matter in the tank in the product, the rate of input of organic matter contained in the input waste into the methane fermentation tank, the rate of introduction of organic matter in the extract, and the rate of extraction of the extracted organic matter contained in the extract from the methane fermentation tank The organic matter extraction rate and the gas generation rate of the gas generated from the waste in the tank by methane fermentation are obtained, and based on the change rate, the organic matter input rate, the organic matter extraction rate, and the gas generation rate Including the step of calculating the growth rate of the methane fermentation sludge in the fermenter, characterized in.

  Even in the above method, first, in the reaction system in which the amount of waste input to the methane fermenter and the amount of extract to be extracted from the methane fermenter are the same, the change rate, the organic matter input rate, the organic matter extraction rate, and the gas generation rate described above are set. Ask. Next, the growth rate of methane fermentation sludge is calculated based on them.

  When the growth rate is calculated in this way, it is possible to calculate the drawing speed for pulling out the drawn material so that the amount of waste in the tank becomes constant using the growth rate. And it is possible to calculate a methane fermentation sludge density | concentration based on the extraction speed | rate, the waste amount in a tank, and a proliferation rate. If the methane fermentation sludge concentration is calculated in this way, the volume load can be set for the methane fermentation sludge concentration.

  In addition, it is possible to take measures and operations to maintain a high methane fermentation sludge concentration in the methane fermentation tank.

  In addition, the method for setting the operating conditions of the methane fermentation system according to the present invention is to set the operating conditions of the methane fermentation system that decomposes the organic matter to be treated contained in the waste in the methane fermentation tank using the methane fermentation sludge. The amount of input waste in a reaction system in which the input waste amount of input waste to be input to the methane fermentation tank is the same as the extracted amount of the extract extracted from the in-tank waste in the methane fermentation tank , Input organic matter concentration, concentration of input organic matter in input waste, amount of waste in tank, amount of extracted material, concentration of extracted organic material, concentration of extracted organic matter in extract, and generated from waste in tank by methane fermentation The method includes measuring a gas generation amount of gas and calculating a methane fermentation sludge concentration in the methane fermentation tank based on the measurement values.

  In the above method, first, in a reaction system in which the amount of waste input to the methane fermentation tank is the same as the amount of extract to be extracted from the methane fermenter, the amount of input waste, the concentration of input organic matter, the amount of waste in the tank, the amount of extract, Measure organic matter concentration and gas generation amount. And the methane fermentation sludge density | concentration is computed from those values.

  Therefore, the volume load in the methane fermentation system can be set based on the methane fermentation sludge concentration involved in methane fermentation among the waste in the tank.

  Further, in the method for setting the operating conditions of the methane fermentation system according to the present invention, the methane fermentation system has a concentration means for concentrating the extract drawn from the methane fermentation tank to form concentrated sludge, and the concentration means When at least a part of the concentrated sludge is returned to the methane fermentation tank, the return amount of the concentrated sludge to the methane fermentation tank is measured, and the input waste amount, input organic substance concentration, in-tank waste amount, withdrawn substance amount, withdrawn organic substance concentration It is desirable to include a step of calculating the methane fermentation sludge concentration in the methane fermentation tank based on the gas generation amount, the return amount, and the concentration rate of the concentration means.

  In this case, when at least a part of the concentrated sludge formed by the concentration means is returned to the methane fermentation tank, the amount of concentrated sludge returned to the methane fermentation tank is measured, and the amount of waste input and the concentration of input organic matter are measured. The methane fermentation sludge concentration is calculated on the basis of the amount of waste in the tank, the amount of extracted material, the concentration of extracted organic matter, the amount of gas generated, the amount of return, and the concentration rate.

  When returning the concentrated sludge, the methane fermentation sludge is also returned to the methane fermentation tank because the concentrated sludge also contains methane fermentation sludge. Therefore, the methane fermentation sludge concentration is maintained high.

  And if the methane fermentation sludge density | concentration in a methane fermenter is maintained high, it will become possible to throw in many organic substances (in other words, high load operation is possible).

  According to this invention, the methane fermentation sludge density | concentration in the waste in a tank in a methane fermentation tank is calculated. Therefore, the operating conditions of the methane fermentation system can be optimized using the methane fermentation sludge concentration.

  Preferred embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or corresponding parts are denoted by the same reference numerals.

(First embodiment)
Drawing 1 is a mimetic diagram showing the composition of an example of a methane fermentation system. The methane fermentation system 1 in FIG. 1 is operated under the operating conditions set by the setting method according to the present embodiment.

  The methane fermentation system 1 is a system that processes organic waste such as garbage, food waste, and livestock waste by methane fermentation. As shown in FIG. 1, the methane fermentation system 1 includes a methane fermentation tank 10.

  FIG. 2 is a schematic diagram showing the flow of waste in the methane fermentation system 1.

  Referring to FIGS. 1 and 2, the methane fermenter 10 is charged with waste containing organic matter through a line L1. Moreover, a part of the waste 20 in the tank is extracted from the methane fermentation tank 10 through the line L2. Hereinafter, the waste that is input to the methane fermentation tank 10 is referred to as input waste 30, and a part of the in-tank waste 20 that is extracted from the methane fermentation tank 10 is referred to as extracted material 40.

  FIG. 3 is a chart showing the configuration of the input waste 30, the in-tank waste 20, and the withdrawn product 40.

  The state of the methane fermentation system 1 at a specific time will be described with reference to FIGS. 2 and 3. The input waste 30 includes an input organic substance 31 and an input inorganic substance 32. The tank waste 20 includes a tank organic substance 21 and a tank inorganic substance 22. The organic matter 21 in the tank contains methane fermentation sludge 21A in which methane bacteria exist and is involved in methane fermentation, and an organic matter 21B to be digested by the methane fermentation sludge 21A. In the case where the methane fermentation system 1 is operated continuously or semi-continuously, the organic matter 21B to be treated includes a stage before digestion by methane fermentation and an undigested one.

  The drawn product 40 includes a drawn organic material 41 and a drawn inorganic material 42. The extracted organic matter 41 includes methane fermentation sludge 41A and undigested organic matter 41B. When the methane fermentation system 1 is operated in a steady state to be described later, the drawn product 40 and the in-tank waste 20 have substantially the same composition.

In addition, although the input waste 30, the waste 20 in the tank, and the extract 40 contain liquid components, they are not shown for simplicity. Further, in FIG. 2, the hatched lines are for distinguishing organic substances, inorganic substances, methane fermentation sludge, and the like. Further, the in-tank waste amount V in FIG. 3 is, for example, an amount of so-called solids (Total Solid: TS) left by drying the in-tank waste 20 at about 110 ° C. Similarly, the input waste amount V ₃₀ and the withdrawn amount V ₄₀ are solid amounts. Further, the amount of organic matter VS in the tank is a so-called VTS (Volatile Total Solid) amount which is generated by burning the waste 20 in the tank at, for example, 600 ° C. Similarly, the input organic matter amount V ₃₁ and the extracted organic matter amount V ₄₁ are VTS amounts.

In this embodiment, unless otherwise specified, the waste to be subjected to methane fermentation is a waste having a relatively high solid concentration (for example, 10,000 mg / l, that is, 10 kg / m ³ or more).

  The methane fermentation process in the methane fermentation system 1 is performed as follows. That is, first, the input waste 30 is introduced into the methane fermentation tank 10 through the line L1. When the methane fermentation system 1 is operated, the methane fermentation sludge 21 </ b> A is previously placed in the methane fermentation tank 10 as seed sludge in order to cause the input waste 30 introduced into the methane fermentation tank 10 to undergo methane fermentation.

  In the methane fermentation tank 10, the organic matter 21B to be treated is digested with the methane fermentation sludge 21A. Here, when the organic matter 21B to be processed is decomposed by methane bacteria (in other words, methane fermentation), a gas 50 (see FIG. 1) containing methane as a main component is generated. Examples of the component of the gas 50 include sulfur compounds such as methane, carbon dioxide, hydrogen, hydrogen sulfide, and nitrogen. However, when methane fermentation proceeds appropriately, the components of the gas 50 are mainly methane and carbon dioxide.

  A part of the decomposed organic matter 21B becomes methane fermentation sludge 21A containing methane fermentation related bacteria. Therefore, the methane fermentation sludge 21 </ b> A grows in the methane fermentation tank 10.

  When the methane fermentation is proceeding in the methane fermentation tank 10 as described above, the extract 40 is extracted from the line L2.

In the methane fermentation treatment as described above, it is necessary to appropriately set the input waste amount V ₃₀ that is the amount of the input waste 30 so that the methane fermentation does not stop. For example, if more than the amount that can be treated with the methane fermentation sludge 21A in the methane fermentation tank 10 is introduced, the progress of methane fermentation is likely to stop.

  Conventionally, the input waste amount depends on the solid matter concentration in the methane fermentation tank 10, in other words, the amount of the organic substance 21 in the tank relative to the in-tank waste 20, or the total amount of the organic substance 21 in the tank and the inorganic substance 22 in the tank. Was set. However, since the solid matter of the in-tank waste 20 has the configuration shown in FIG. 3, even if the solid matter concentration is high, the concentration of methane fermentation sludge involved in methane fermentation is not always high. Therefore, the operation of the methane fermentation system 1 is not operated under optimal operation conditions, and methane fermentation sometimes stops.

The operation condition setting method according to the present embodiment can calculate the methane fermentation sludge concentration X in the methane fermentation tank 10 and set the amount of waste V ₃₀ input to the methane fermentation tank 10 based on the methane fermentation sludge concentration X. Characterized by points.

Hereinafter, a method for setting the operating conditions of the methane fermentation system 1 will be described. When setting the operating conditions, first, an extract 40 having the same amount as the amount of input waste 30 to be input to the methane fermentation tank 10 (that is, the input waste amount V ₃₀ shown in FIG. 3) is extracted from the methane fermentation tank 10. A reaction system is formed in which the amount of extracted waste V ₃₀ is the same as the amount of extracted waste V ₄₀ (see FIG. 3). In the present embodiment, unless otherwise specified, the quantity means weight as shown in FIG.

ここで、(dVS/dt)cは、槽内有機物２１が消化される速度である。以下では、(dVS/dt)cを実質有機物消化速度と称す。(dV_21A/dt)gは、メタン発酵汚泥２１Ａの増殖速度である。また、Gは、メタン発酵により発生したガス５０のガス発生量であり、dG/dtはガス発生速度である。なお、水分の蒸発、メタンガス及び炭酸ガスの液中溶解、微量のガスの発生などを考慮すると左辺と右辺とは厳密には等しいとは限らないが、ここでは簡単のために左辺と右辺とは等しいものとする。 When methane fermentation proceeds in the methane fermentation tank 10, a part of the organic matter 21 in the tank in the methane fermentation tank 10 is digested to generate gas 50, and the methane fermentation sludge 21A grows. Therefore, the following equation holds.

Here, (dVS / dt) c is the rate at which the organic matter 21 in the tank is digested. Hereinafter, (dVS / dt) c is referred to as a substantial organic matter digestion rate. (dV _21A / dt) g is the growth rate of the methane fermentation sludge 21A. G is a gas generation amount of the gas 50 generated by methane fermentation, and dG / dt is a gas generation rate. It should be noted that the left side and the right side are not necessarily exactly the same when considering the evaporation of moisture, the dissolution of methane gas and carbon dioxide gas, the generation of a small amount of gas, etc. It shall be equal.

ここで、VS_inは、有機物投入速度である。有機物投入速度とは、投入廃棄物３０に含まれる投入有機物３１のメタン発酵槽１０への投入速度である。VS_outは、有機物引抜速度である。有機物引抜速度とは、引抜物４０に含まれる引抜有機物４１のメタン発酵槽１０からの引抜速度である。なお、式（２）は、ガス発生速度dG/dtを一定（すなわち、定数）とみなしてよい場合に成立する式である。ガスの発生は、槽内有機物２１がメタン発酵により消化されることに由来する。したがって、ガス発生速度が定数とみなせる場合、(dV_21A/dt)gも定数とみなせる。そのため、VS_outもほぼ定数である必要がある。すなわち、式（２）は、ガス発生速度dG/dt及び有機物引抜速度VS_outを定数とみなしてよい場合に成立している。 When attention is paid to the change in the weight of the organic matter in the methane fermentation tank 10, the weight of the organic matter released out of the methane fermentation tank 10 as the gas 50 out of the organic matter 21 in the tank is reduced. Therefore, the following equation holds.

Here, VS _in is an organic substance input speed. The organic substance input speed is the input speed of the input organic substance 31 contained in the input waste 30 to the methane fermentation tank 10. VS _out is the organic extraction speed. The organic matter drawing speed is a drawing speed of the drawn organic matter 41 contained in the drawn matter 40 from the methane fermentation tank 10. Expression (2) is an expression that is established when the gas generation rate dG / dt may be regarded as constant (that is, a constant). Generation | occurrence | production of gas originates in the organic substance 21 in a tank being digested by methane fermentation. Therefore, when the gas generation rate can be regarded as a constant, (dV _21A / dt) g can also be regarded as a constant. Therefore, VS _out needs to be almost constant. That is, Expression (2) is established when the gas generation rate dG / dt and the organic matter extraction rate VS _out may be regarded as constants.

と表される。 From equation (2), the growth rate is

It is expressed.

  Here, dVS / dt is obtained by measuring the waste amount V in the tank every appropriate time and calculating the rate of change. This is due to the following reason.

That is, the input waste amount V ₃₀ and the withdrawn amount V ₄₀ are the same, and when the methane fermentation is not progressing, the in-tank waste amount V is constant. However, in the methane fermentation tank 10, the organic matter 21B to be treated is digested by methane fermentation. Thereby, a part of the organic substance 21 in the tank is released out of the reaction system as the gas 50. Therefore, the amount of organic matter 21 in the tank is reduced.

  The change in the weight of the organic matter 21 in the tank appears as a change in the waste amount V in the tank. Therefore, the change rate dVS / dt of the organic matter amount VS in the tank can be obtained by measuring the waste amount V in the tank, for example, every day and obtaining the change rate thereof. The in-tank waste amount V may be obtained by, for example, measuring the methane fermentation tank 10 in which the in-tank waste 20 is put with a load cell and subtracting the weight of the methane fermentation tank 10 from the measured value. This is because “the reduction amount of organic matter ≈ the generation amount of methane + the generation amount of carbon dioxide gas” is established, that is, the reduction of the waste 30 in the tank due to the methane fermentation is almost derived from the gasification of the organic matter. This is the case.

  As described above, dVS / dt can be obtained from the change rate of the waste amount V in the tank, but may be as follows. That is, the organic substance concentration P in the tank, which is the concentration of the organic substance 21 in the tank in the methane fermentation tank 10 (see FIG. 3), is measured every predetermined time. Then, the tank waste amount V is multiplied by the tank organic matter concentration P to calculate the tank organic matter amount VS. Then, the time change is obtained to obtain dVS / dt. The organic substance concentration P in the tank can be measured, for example, by loss on ignition (sewage test method).

Further, the organic substance input speed VS _in of the input organic substance amount V ₃₁ can be calculated by measuring the input organic substance concentration S _in which is the concentration of the input organic substance 31 _in the input waste ₃₀ and the input waste quantity V ₃₀ .

More specifically, first, the input waste amount V ₃₀ and the input organic matter concentration S _in are measured every predetermined time (for example, one day). Then, by multiplying the input waste amount V ₃₀ and the measured value of the input organic substance concentration S _in , the input organic substance amount V ₃₁ per predetermined time is calculated. The rate of change, that is, the organic material input speed VS _in is calculated from the amount of organic material input V ₃₁ per predetermined time.

Further, the organic matter withdrawal speed VS _out is obtained by measuring the withdrawal amount V ₄₀ and the withdrawal organic matter concentration Q, which is the concentration of the withdrawal organic matter 41 in the withdrawal matter 40, and calculating the change over time. The input waste amount V ₃₀ and the withdrawn amount V ₄₀ can be measured by a weight measuring device such as a load cell. Also, it charged organic concentration S _in and pulling organic matter concentration Q can measure the forward cheat method sewage test method (VTS).

  Moreover, since the gas generation amount G from the methane fermentation tank 10 can also be measured by, for example, a gas meter or the like, the gas generation rate dG / dt can also be obtained from the time change of the measured value.

As described above, the change rate dVS / dt of the organic substance amount VS in the tank, the organic substance input speed VS _in , the organic substance extraction speed VS _out, and the gas generation speed dG / dt are obtained experimentally. Therefore, the growth rate (dV _21A / dt) g of the methane fermentation sludge 21A is obtained from the equation (3) based on the change rate dVS / dt, the organic matter input rate VS _in , the organic matter extraction rate VS _out and the gas generation rate dG / dt. Calculated.

As described above, Expression (2) or Expression (3) is an expression that is established when the gas generation rate dG / dt and the organic matter extraction rate VS _out can be regarded as constants. Therefore, when the gas generation rate dG / dt and the organic matter extraction rate VS _out can be regarded as constants, the growth rate (dV _21A / dt) g is calculated based on the measurement values obtained by performing the above various measurements.

Further, the substantial organic matter digestion rate (dVS / dt) c is calculated by substituting the gas generation rate dG / dt and the calculated growth rate (dV _21A / dt) g into the equation (1).

By the way, when the amount of the waste 20 in the tank is extremely reduced from the initial amount, the methane fermentation sludge amount V _21A also decreases. When the amount of methane fermentation sludge V _21A decreases, the initial load of the experiment is not maintained. Therefore, the growth rate (dV _21A / dt) g of the methane fermentation sludge 21A changes. Therefore, when calculating the growth rate (dV _21A / dt) g, the change rate dVS / dt, the organic substance input rate VS _in during the period in which the volume of the waste 20 in the tank is maintained at the initial volume as much as possible, It is preferable to use an organic matter extraction rate VS _out and a gas generation rate dG / dt.

Next, the drawing speed of the drawn material 40 is optimized. This is due to the following reason. That is, a part of the in-tank waste 20 becomes a gas 50 when it is digested and goes out of the system. Therefore, in the reaction system in which the input waste amount V ₃₀ and the withdrawn amount V ₄₀ are equal, the in-tank waste amount V gradually decreases. As a result, the operation of the methane fermentation system 1 may not be possible. Therefore, it is necessary to optimize the extraction speed so that the waste amount V in the tank in the methane fermentation tank 10 does not change.

Since a certain amount of the drawn product is withdrawn by pulling out a predetermined time, to optimize the extraction rate is equivalent to optimizing the pulling amount V _40.

  Hereinafter, a method for setting the drawing speed will be described.

が成り立つ。ここで、F_inは、投入廃棄物３０の廃棄物投入速度である。Fは、引抜物４０の引抜速度である。 First, paying attention to the weight balance in the methane fermentation system 1 of FIG.

Holds. Here, F _in is a waste input rate of the input waste 30. F is the drawing speed of the drawn material 40.

となる。ガス発生速度dG/dtも式（３）の場合と同様に実験的に求められる。更に、メタン発酵汚泥２１Ａの増殖速度(dV_21A/dt)gは、式（３）により算出される。したがって、廃棄物投入速度F_in、ガス発生速度dG/dt及び増殖速度(dV_21A/dt)gに基づいて、式（５）から第１引抜速度F₁が算出される。 Assuming that the extraction speed F when the waste amount V in the tank does not change is the first extraction speed F ₁ , dV / dt = 0 at the first extraction speed F ₁ . Therefore, equation (4) becomes

It becomes. The gas generation rate dG / dt is also obtained experimentally as in the case of the equation (3). Further, the growth rate (dV _21A / dt) g of the methane fermentation sludge 21A is calculated by the equation (3). Therefore, the first extraction speed F ₁ is calculated from the equation (5) based on the waste input speed F _in , the gas generation speed dG / dt, and the growth speed (dV _21A / dt) g.

In addition, when the volume change of the waste 20 in the tank cannot be ignored, the gas generation rate dG / dt and the change rate dVS / dt of the organic matter amount VS in the waste 20 in the tank are obtained. It is desirable to correct the volume of (dV _21A / dt) g and dG / dt in Equation (5). This is because a more preferable first drawing speed F ₁ can be set.

Subsequently, the methane fermentation sludge concentration X in the methane fermentation tank 10 is calculated using the growth rate (dV _21A / dt) g and the first extraction rate F ₁ calculated by the equations (3) and (5). .

が成り立つ。ここで、dX/dtはメタン発酵汚泥濃度Xの変化速度である。X_outは、図３に示すように引抜物４０中のメタン発酵汚泥濃度である。なお、X_outは、実質的にXに等しい。また、V・(d(V_21A/V)/dt)gは、（dV_21A/dt）gに相当する。 In methane fermentation system 1, paying attention to the material balance regarding methane fermentation sludge concentration X,

Holds. Here, dX / dt is the rate of change of the methane fermentation sludge concentration X. _Xout is the methane fermentation sludge concentration in the extract 40 as shown in FIG. X _out is substantially equal to X. V · (d (V _21A / V) / dt) g corresponds to (dV _21A / dt) g.

In the steady state where the methane fermentation sludge concentration X can be regarded as constant, dX / dt≈0. On the other hand, the growth rate (dV _21A / dt) g and the first drawing rate F ₁ are calculated from the equations (3) and (5). Moreover, the waste amount V in the tank is a measurable amount. Therefore, the methane fermentation sludge concentration X can be calculated from Equation (6) based on the waste amount V in the tank, the growth rate (dV _21A / dt) g, and the first extraction rate F ₁ . Note that the above-described steady state means a state in which certain conditions are “material balance-like” and “bioreactive”.

  Next, a non-steady state, that is, a case where the methane fermentation sludge concentration X in the methane fermentation tank 10 changes with time will be described. In this case, the equation (6) is a differential equation regarding the time t of X.

  Therefore, X can be obtained as a function of time by solving Equation (6) for X.

ここで、X_out≒Xである。また、Vは上述したように計測可能であり、また、F₁は、実験的に求めることができる。V・(d(V_21A/V)/dt)gは増殖速度(dV_21A/dt)gに相当しており、式（３）より算出される。したがって、式（７）の微分方程式をXについて解くことが可能である。 More specifically, for the methane fermentation sludge concentration X, equation (6) is modified as follows.

Here, X _out ≈X. V can be measured as described above, and F ₁ can be obtained experimentally. V · (d (V _21A / V) / dt) g corresponds to the growth rate (dV _21A / dt) g and is calculated from the equation (3). Therefore, the differential equation of equation (7) can be solved for X.

  Thus, regarding the unsteady state, by obtaining X as a function of time, the convergence value of X when the steady state is assumed can be obtained.

  In the case of a waste having a high solid matter concentration, a so-called residence time in which the waste stays in the methane fermentation tank is long (10 days to several tens of days). For this reason, it is not known whether the vehicle is optimally operated after several hundred days. Therefore, even if the methane fermentation can be operated without stopping for about one month at the beginning, there is a risk that, for example, after one year, the concentration of methane fermentation sludge decreases and the operation cannot be performed. For this reason, it has been difficult to apply the methane fermentation treatment to waste having a high solid concentration.

  On the other hand, in the operation condition setting method of the present embodiment, as described above, the X in the unsteady state is calculated from the equation (7), and the convergence value, that is, the value in the case where it can be regarded as the steady state is obtained. And a load is set with respect to the methane fermentation sludge density | concentration in the case where it can be considered that it is a steady state, equipment design is carried out from the beginning so that operation can be performed with the load, and the load is operated as a rated load. Therefore, it is possible to operate optimally in the future with short-term data without performing a long-term (one year or more) preliminary test.

  In addition, each value calculated above, for example, methane fermentation sludge density | concentration X etc., can be made into a more exact value with the following method. That is, first, the operating condition of the methane fermentation system 1 is set based on the calculated value. And the methane fermentation system 1 is drive | operated according to the set driving | running condition, and a driving | running condition is correct | amended according to deviation with measurement.

  As described above, in the method for setting the operating conditions of the methane fermentation system 1 according to the present embodiment, the material balance and the biological reaction are constant in the methane fermentation tank 10 that has conventionally been difficult to measure and estimate. The methane fermentation sludge concentration X can be calculated. Therefore, it is possible to determine the load on the methane fermentation system 1 based on the methane fermentation sludge concentration X in the methane fermentation tank 10.

  Therefore, long-time operation is possible without stopping methane fermentation during operation of the methane fermentation system 1. Further, the waste 20 in the tank can be decomposed at a uniform digestion rate during operation. In other words, the methane fermentation system 1 can be optimally operated.

  In the operating condition setting method according to the present embodiment, the methane fermentation sludge concentration X is calculated by paying attention to the weight change of the waste 20 in the tank. The ratio of the weight change of the in-tank waste 20 is larger as the solid concentration of the waste to be treated by the methane fermentation treatment method is higher.

  Therefore, the above setting method is particularly effective for a methane fermentation system that processes high-concentration solid waste having a high solid concentration. Furthermore, in the condition setting method of the present embodiment, the steady state methane fermentation sludge concentration X can be estimated by a test of a shorter period. From the above, it becomes possible to perform methane fermentation of high-concentration solid waste, which has been difficult in the past.

By the way, in the above, the process of calculating the methane fermentation sludge density | concentration X is demonstrated in order according to each type | formula. However, if the above process is input to a computer or the like as a program, for example, the input waste amount V ₃₀ , the input organic matter concentration S _in , the waste amount V _in the tank V, the withdrawal amount V ₄₀ , the withdrawal organic matter concentration Q and It is also possible to calculate the methane fermentation sludge concentration X by inputting the gas generation amount G.

(Second Embodiment)
FIG. 4 is a schematic diagram showing the configuration of another example of the methane fermentation system. The methane fermentation system 2 of FIG. 4 is different from the methane fermentation system 1 of the first embodiment in that it has a concentration means 60. In addition, unless otherwise indicated also in this embodiment, the waste to be methane-fermented is a waste having a relatively high solid concentration. In this embodiment, unless otherwise specified, the amount means weight.

  The concentration means 60 concentrates the extract 40 extracted from the methane fermentation tank 10 through the line L2 at a predetermined concentration ratio C. More specifically, the extract 40 is separated into a concentrated sludge 70 that is a solid component and a liquid component. The concentration means 60 is, for example, a decanter, a belt press, a filter press, a membrane, a dryer or the like. The liquid component is drained from the line L3. At least a part of the concentrated sludge (solid component) 70 is returned to the methane fermentation tank 10 through the line L4. Moreover, the solid component which is not returned to the methane fermentation tank 10 is discharged | emitted from the line L5.

  FIG. 5 is a schematic diagram showing the flow of waste with respect to the waste 20 in the tank. Referring to FIG. 5, the concentrated sludge 70 includes an organic substance 71 and an inorganic substance 72. In the organic substance 71, methane fermentation sludge 71A and undigested organic substance 71B are contained. In FIG. 5, diagonal lines are for distinguishing organic substances, inorganic substances and methane fermentation sludge.

  Next, a method for setting operating conditions of the methane fermentation system 2 will be described.

First, as in the first embodiment, the growth rate (dV _21A / dt) g is calculated. That is, first, a reaction system is formed in which the input waste amount V ₃₀ and the withdrawn amount V ₄₀ are the same. Based on the change rate dVS / dt of the organic matter amount VS in the tank, the organic matter input rate VS _in , the organic matter extraction rate VS _out and the gas generation rate dG / dt, the growth rate (dV _21A / dt) g Is calculated.

が成り立つ。ここで、Rは、濃縮汚泥７０のメタン発酵槽１０への返送速度である。式（８）は、第１の実施形態の式（４）に相当する式である。 Next, the extraction speed F of the extract 40 from the methane fermentation tank 10 is optimized. In the methane fermentation system 2, since the concentrated sludge 70 is returned from the concentration means 60, when paying attention to the balance of weight,

Holds. Here, R is the return speed of the concentrated sludge 70 to the methane fermentation tank 10. Expression (8) is an expression corresponding to Expression (4) of the first embodiment.

となる。上述したように廃棄物投入速度F_inは操作パラメータ（運転条件）であり、ガス発生速度dG/dtは実験的に求められる。また、返送速度Rは、返送される濃縮汚泥７０の量である濃縮汚泥量V₇₀(kg)を計測し、その時間変化を求めることで得られる。更に、増殖速度(dV_21A/dt)gは、式（３）より算出される。そのため、第２引抜速度F₂が、廃棄物投入速度F_in、返送速度R、増殖速度(dV_21A/dt)g、ガス発生速度dG/dtに基づいて、式（９）から算出される。 In the present embodiment, if the extraction speed F when the waste amount V in the tank does not change is the second extraction speed F ₂ , dV / dt = 0 in the case of the second extraction speed F ₂ , the equation (8) Is

It becomes. Waste input rate F _in as described above are operating parameters (operating conditions), gas generation rate dG / dt is determined experimentally. The return speed R is obtained by measuring the amount of concentrated sludge V ₇₀ (kg), which is the amount of the concentrated sludge 70 to be returned, and obtaining the change over time. Further, the growth rate (dV _21A / dt) g is calculated from the equation (3). Therefore, the second extraction speed F ₂ is calculated from the formula (9) based on the waste input speed F _in , the return speed R, the growth speed (dV _21A / dt) g, and the gas generation speed dG / dt.

が成り立つ。 Next, in the methane fermentation system 2, paying attention to the material balance regarding the methane fermentation sludge concentration X,

Holds.

In formula (10), C is the concentration factor in the concentration means 60. Also, X _out ≒ X. Further, V · (d (V _21A / V) / dt) g in the equation (10) corresponds to the growth rate (dV _21A / dt) g.

In the equation (10), the in-tank waste amount V can be measured, and the return speed R is experimentally obtained. The concentration ratio C is a measured value. For example, in accordance with the sewage test method, TS and VTS before and after concentration are measured, and how many times the TS and VTS of the extract 40 before concentration are concentrated is calculated. Is required. Further, V · (d (V _21A / V) dt) g corresponds to (dV _21A / dt) g and is calculated from the equation (3). The second drawing speed F ₂ is calculated from the equation (9). And X _out ≒ X. Therefore, the methane fermentation sludge concentration X is calculated from the equation (10) based on the waste amount V in the tank, the growth rate (dV _21A / dt) g, the second extraction rate F ₂ , the return rate R, and the concentration factor C. .

  Here, when calculating X in a steady state, X may be obtained by setting dX / dt to 0. For the unsteady state, X as a function of time t is calculated by solving the differential equation of X.

  It is desirable to set the operation condition of the methane fermentation system 2 based on the calculated value, operate the methane fermentation system 1 according to the set operation condition, and correct the operation condition according to the deviation from the actual measurement. This is the same as in the first embodiment.

  In this embodiment, since the concentrated sludge 70 is returned from the concentration means 60, the methane fermentation sludge concentration X in the methane fermentation tank 10 can be maintained high. Therefore, the methane fermentation system 1 can be operated with a high load, and the system can be downsized.

By the way, the process of calculating the methane fermentation sludge concentration X in the present embodiment can be input to a computer or the like as a program, for example, and the methane fermentation sludge concentration X can be calculated as in the case of the first embodiment. It is. In this case, as input data, input waste amount V ₃₀ , input organic matter concentration S _in , tank waste amount V, withdrawal amount V ₄₀ , withdrawal organic matter concentration Q, gas generation amount G, concentration factor C, and concentrated sludge The amount V ₇₀ should be entered.

  As mentioned above, although preferred embodiment of this invention was described in detail, it cannot be overemphasized that it is not limited to 1st and 2nd embodiment.

  For example, in the first and second embodiments, the concentration of methane fermentation sludge and the like are calculated by paying attention to the weight balance in the methane fermentation system. However, not only the weight but also the volume change may be noted. However, since the apparent volume may not change even if methane fermentation proceeds, it is preferable to pay attention to the change in weight.

  In the first and second embodiments, the waste having a high solid concentration is described, but the waste is not limited to a high solid concentration. However, as described above, it is preferable that the solid concentration is high from the viewpoint of easily measuring the weight change.

Further, in the first and second embodiments, the expression (2) or the expression (3) is established under the condition that the gas generation rate dG / dt and the organic matter extraction rate VS _out can be regarded as constants. Growth rate (dV _21A / dt) g is calculated. However, it is not always necessary to calculate the growth rate (dV _21A / dt) g based on the measured values when the gas generation rate dG / dt and the organic matter extraction rate VS _out can be regarded as constants. The growth rate (dV _21A / dt) g may be calculated based on the equations when the gas generation rate dG / dt and the organic matter extraction rate VS _out change with time.

However, since the growth rate (dV _21A / dt) g is extremely slow, the conditions under which the gas generation rate dG / dt and the organic matter extraction rate VS _out can be regarded as constants are approximately established. The growth rate (dV _21A / dt) g can be calculated using equation (3).

  The Example of the methane fermentation system 1 of 1st Embodiment is demonstrated. Note that this case corresponds to the case where the concentrated sludge 70 is not returned in the methane fermentation system 2 of the second embodiment.

In Example 1, a methane fermentation test was performed using a commercially available mini jar fermenter (manufactured by Sumitomo Heavy Industries, Ltd.). The volume of the methane fermentation tank 10 was 0.002 m ³ (2 liters). The methane fermentation tank 10 was equipped with a stirring blade for stirring sludge (waste in the tank) in the tank. The stirring blade used was a type capable of stirring slurry sludge.

表１中、固形物濃度は、例えば、１１０℃程度で投入廃棄物を乾燥させて残ったもの（図３中の有機物と無機物）の濃度である。また、投入有機物濃度S_inは、１１０℃で乾燥された固形物を約６００℃で焼いて気体になって出ていったものの濃度である。Ashは灰分を示し、COD_Crは化学的酸素要求量を示している。 As the waste in Example 1, a food production residue discharged from a food factory was used. The composition of the waste is shown in Table 1.

In Table 1, the solid matter concentration is, for example, the concentration of what remains after drying the input waste at about 110 ° C. (organic matter and inorganic matter in FIG. 3). The input organic substance concentration S _in is the concentration of the solid material dried at 110 ° C. and baked at about 600 ° C. to become a gas. Ash indicates ash, and COD _Cr indicates chemical oxygen demand.

  The waste was cut to about several millimeters by a household food processor before being put into the methane fermentation tank 10 so as to facilitate methane fermentation.

Then, the same amount of the drawn material as the amount of the introduced waste was drawn out to form a reaction system in which the amount of the input waste 30 and the amount of the extracted material 40 were the same. In this reaction system, the input waste amount V ₃₀ , the input organic matter concentration S _in , the in-vessel waste amount V, the withdrawn amount V ₄₀ , the withdrawn organic matter concentration Q, and the gas generation amount G were measured.

In this example, the in-tank waste amount V was determined by measuring the methane fermentation tank 10 including the in-tank waste 20 together with the load cell and subtracting the weight of the methane fermentation tank 10. Further, the input waste amount V ₃₀ was measured by an electronic balance, and the input organic matter concentration S _in was measured by a sewage test method. Similarly, the amount V ₄₀ and the organic concentration Q of the extracted organic matter were measured. Further, the gas generation amount G was measured with a gas meter. Measurement was performed every day. FIG. 6 shows the organic matter concentration P in the tank when the organic substance concentration P in the tank is constant. The horizontal axis in FIG. 6 represents the elapsed time while the data is stable, and the vertical axis represents the organic substance concentration P in the tank.

表２中、嫌気汚泥流出量は、メタン発酵汚泥２１Ａがメタン発酵槽１０から流出する速度に相当する。嫌気汚泥発生量は、メタン発酵汚泥２１Ａが発生する速度に相当する。比増殖速度μは(dS/dt)c/Xに相当し、比消費速度νは、(d(V_21A/V)/dt)g/Xに相当する。Y_X/Sは投入有機物３１に対するメタン発酵汚泥の収率である。 Using the measurement values described above, the growth rate (dV _21A / dt) g of the methane fermentation sludge, the first extraction rate F ₁ , the methane fermentation sludge concentration X, and the concentration of the organic matter to be treated by the method shown in the first embodiment. S was calculated. In addition, various microbiological characteristics derived from the methane fermentation sludge concentration X obtained as described above were also calculated. The results are shown in Table 2.

In Table 2, the amount of outflow of anaerobic sludge corresponds to the speed at which the methane fermentation sludge 21A flows out from the methane fermentation tank 10. The amount of anaerobic sludge generated corresponds to the speed at which methane fermentation sludge 21A is generated. The specific growth rate μ corresponds to (dS / dt) c / X, and the specific consumption rate ν corresponds to (d (V _21A / V) / dt) g / X. Y _{X / S} is the yield of methane fermentation sludge with respect to the input organic matter 31.

As shown in Table 2, since the methane fermentation sludge concentration X is 15.2 g / kg (1.5 wt%), a sludge load of 0.5 kg (organic matter) / kg (methane fermentation sludge) / day is applied as an example. It can be estimated that a volume load of 7.6 kg / m ³ / day can be applied. In other words, in the methane fermentation tank 10 of 0.002 m ^3, it is possible to carry out the operation at a volume loading of 7.6kg / m ³ / day.

When the methane fermentation system 1 was actually operated under the above setting conditions, stable operation was possible without accumulation of organic acids up to 7.3 kg / m ³ / day, which was almost equal to the calculation.

  Next, examples of the methane fermentation system 2 of the second embodiment will be described. The configuration of the methane fermentation tank 10 is the same as that in the first embodiment. In the second embodiment, the extract 40 extracted from the methane fermentation tank 10 is concentrated by the concentration means 60. Then, a part of the concentrated sludge 70 is returned to the methane fermentation tank 10. As the concentration means 60, a high-speed centrifuge was used.

濃縮手段６０からの濃縮汚泥７０を返送しない場合、実施例１と同様にして算出したメタン発酵槽１０内のメタン発酵汚泥濃度Xは、０．２４wt%程度であった。この場合、容積負荷として約１kg/m³/dayで運転できる程度であった。 Table 3 shows the composition of the input waste 30 to the methane fermentation tank 10.

When the concentrated sludge 70 from the concentration means 60 was not returned, the methane fermentation sludge concentration X in the methane fermentation tank 10 calculated in the same manner as in Example 1 was about 0.24 wt%. In this case, the volume load could be operated at about 1 kg / m ³ / day.

表４に示すバランスが成立している場合、５kg/m³/dayの容積負荷が可能であった。すなわち、濃縮汚泥７０の返送がない場合の５倍の容積負荷での運転が可能であった。 On the other hand, when the concentration means 60 is used, the concentration of methane fermentation sludge determined by the method shown in the second embodiment in consideration of the concentrated sludge amount V ₇₀ and the concentration factor C returned to the methane fermentation tank 10. X was calculated. In this case, the material balance shown in Table 4 was established in the methane fermentation system 2 of Example 2.

When the balance shown in Table 4 was established, a volume load of 5 kg / m ³ / day was possible. That is, it was possible to operate with a volume load five times that when the concentrated sludge 70 was not returned.

It is a schematic diagram which shows the structure of an example of a methane fermentation system. It is a schematic diagram which shows the flow of the waste with respect to the methane fermenter 10 of FIG. It is a chart which shows composition of input waste, waste in a tank, and a withdrawal thing. It is a schematic diagram which shows the structure of the other example of a methane fermentation system. It is a schematic diagram which shows the flow of the waste with respect to the methane fermentation tank 10 of FIG. It is a figure which shows the time change of the organic substance density | concentration P in the tank in the methane fermentation tank 10. FIG.

Explanation of symbols

  1, 2 ... Methane fermentation system, 10 ... Methane fermentation tank, 20 ... Waste in tank, 21 ... Organic substance in tank, 21A ... Methane fermentation sludge, 21B ... Organic substance to be treated, 22 ... Inorganic substance in tank, 30 ... Input waste 31 ... Organic material, 40 ... Extracted material, 41 ... Extracted organic material, 41A ... Methane fermentation sludge in the extracted material, 41B ... Undigested organic material, 50 ... Gas, 60 ... Concentration means, 70 ... Concentrated sludge.

Claims (5)

A method for setting operating conditions of a methane fermentation system that decomposes organic matter to be treated contained in waste in a methane fermentation tank using methane fermentation sludge,
In the reaction system in which the input waste amount of the input waste to be input to the methane fermentation tank and the extraction amount of the extract extracted from the in-tank waste in the methane fermentation tank are the same, the waste in the tank The rate of change in the amount of organic matter in the tank, the rate of organic matter input that is the rate of input of organic matter contained in the input waste into the methane fermentation tank, the rate of extraction of the extracted organic matter contained in the extract from the methane fermentation tank The organic matter extraction rate, and the gas generation rate of the gas generated from the waste in the tank by methane fermentation,
Calculate the growth rate of the methane fermentation sludge in the methane fermentation tank based on the change rate, the organic matter input rate, the organic matter extraction rate and the gas generation rate,
The first extraction speed for extracting the extract so as not to change the amount of waste in the tank is the waste input speed, the growth speed, and the gas generation speed, which are the input speed of the input waste to the methane fermentation tank. Based on
A method for setting operating conditions of a methane fermentation system, comprising a step of calculating a methane fermentation sludge concentration in the methane fermentation tank based on the amount of waste in the tank, the growth rate, and the first extraction rate. The methane fermentation system has a concentration means for concentrating the extract extracted from the methane fermentation tank to form concentrated sludge,
When returning at least a part of the concentrated sludge to the methane fermentation tank, a second extraction speed for extracting the extract so as not to change the amount of waste in the tank is set to the methane fermentation tank of the concentrated sludge. Calculate based on the return speed, the waste input speed, and the gas generation speed,
The method includes a step of calculating a concentration of methane fermentation sludge in the methane fermentation tank based on the amount of waste in the tank, the growth rate, the second extraction rate, the return rate, and the concentration rate of the concentration means. Item 2. A method for setting operating conditions of the methane fermentation system according to item 1. A method for setting operating conditions of a methane fermentation system that decomposes organic matter to be treated contained in waste in a methane fermentation tank using methane fermentation sludge,
In the reaction system in which the input waste amount of the input waste to be input to the methane fermentation tank and the extraction amount of the extract extracted from the in-tank waste in the methane fermentation tank are the same, the waste in the tank The rate of change in the amount of organic matter in the tank, the rate of organic matter input that is the rate of input of organic matter contained in the input waste into the methane fermentation tank, the rate of extraction of the extracted organic matter contained in the extract from the methane fermentation tank The organic matter extraction rate, and the gas generation rate of the gas generated from the waste in the tank by methane fermentation,
An operation condition of the methane fermentation system, comprising a step of calculating a growth rate of methane fermentation sludge in the methane fermentation tank based on the change rate, the organic matter input rate, the organic matter extraction rate, and the gas generation rate. Setting method. A method for setting operating conditions of a methane fermentation system that decomposes organic matter to be treated contained in waste in a methane fermentation tank using methane fermentation sludge,
In the reaction system in which the input waste amount of the input waste to be input to the methane fermentation tank and the extract amount of the extract extracted from the in-tank waste in the methane fermentation tank are the same, the input waste amount, The concentration of the input organic matter in the input waste, the concentration of the input organic matter, the amount of waste in the tank, the amount of the extracted material, the concentration of the extracted organic material in the extracted material, and the concentration of the extracted organic material in the extracted material, Measure the amount of gas generated,
A method for setting operating conditions of a methane fermentation system, comprising a step of calculating a methane fermentation sludge concentration in the methane fermentation tank based on the measured values. The methane fermentation system has a concentration means for concentrating the extract extracted from the methane fermentation tank to form concentrated sludge,
When returning at least a portion of the concentrated sludge from the concentration means to the methane fermentation tank, the amount of the concentrated sludge returned to the methane fermentation tank is measured,
Methane fermentation in the methane fermentation tank based on the input waste amount, the input organic matter concentration, the waste amount in the tank, the withdrawn amount, the withdrawn organic matter concentration, the gas generation amount, the return amount, and the concentration rate of the concentration means The method for setting operating conditions of the methane fermentation system according to claim 4, further comprising a step of calculating a sludge concentration.

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