JPS60244400A - Digestion state dummy apparatus of anaerobic digestion process - Google Patents

Abstract

PURPOSE:To estimate a digestion state with good accuracy without requiring labor, by successively renewing the coefficient in an operation equation and an org. acid forming ratio by using the amounts of methane gas and carbon dioxide generated in a digestion gas and the concns. of the org. substance and org. acid in said digestion tank. CONSTITUTION:A stock material is subjected to anaerobic fermentation in a digestion tank 1, and the flow amount of the generated digestion gas and the concn. of methane gas are measured by a flow meter 9 and an analyzer 10 while the measured values are sent to an input circuit 4. The concns. of organic acid and org. substance in the digestion tank 1 are respectively measured by densitometers 18, 20 to be sent to the input circuit 4. Various data sent to the input circuit 4 by this method are respectively selected to be inputted to operators 11, 12 and operation circuits 13, 14, 15 and the coefficient in a predetermined operation equation is successively renewed. This renewed coefficient is inputted to an operation and estimation circuit 5 and the data of the input circuit 4 are also inputted thereto and successively renewed data are displayed on a display apparatus through an output circuit 6.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention involves inputting a raw material containing organic matter such as sewage sludge,
The present invention relates to a digestion state simulator that calculates and predicts the future state of digestion in an anaerobic digestion process that produces methane gas through anaerobic fermentation.

[Conventional technology]

Conventionally, there has been a device of this type as shown in FIG. In terms of internal pressure, 1 is an anaerobic digestion tank, and raw materials containing organic matter are guided into the digestion tank 1 through pipe a. In the digestion tank 1, organic substances in the raw materials are decomposed by acid-producing microorganisms present in the digestion tank 1 and become organic acids. The organic acid is further decomposed by methanogenic microorganisms and becomes methane gas and carbon dioxide gas. The raw material after the digestion treatment is discharged to the outside of the digestion tank 1 through the piping. Gas generated by the digestion process is extracted from pipe C. 2 is an input information measuring device installed in the piping. 3 is an input device for simulated input information. 4 is an input circuit, and the outputs of the measuring device 2 and the input device 3 for simulated input information are connected to the signal line 28, respectively.
．． 38. Reference numeral 5 denotes an arithmetic prediction circuit, to which the output of the input circuit 4 is connected via a signal line 4sK.

6 is an output circuit, to which the output of the arithmetic prediction circuit 5 is connected. Further, 7 is a ratio setting device, the output of which is connected to the input circuit 4 through a signal line 7s.

Next, the operation will be explained.

First, the content of calculations in the calculation prediction circuit will be explained. Next, an example of this arithmetic expression is shown.

5a va-=KaIISa(Lvo-Lvn)'V-QII
Sa −−”−(2)1 dNH.

v1117=QIINt(l life NHO+Y?@/Lvl
IKa・5a-(Lvo-tvn)-v-(3)GC
O2a=YCO2/LvlIKaaS”・(jvo-t
vn)・V・・・・・・・・・・・・・・・・・・
...(4) dLa.

■--=QeLai threat LaO+frWL7・Ka・Sa
・(LvO-Lvn)・vat -Knl”Sm”(LaO-Lan)””””””””
”(s)am V' = YcH4Aa・KmlISm(Lao-Lan
)・V-QIISm--(61t GeH4=YcH4/L, aIIKmlISm-(La
o-Lan) Fist v ・・・・・・・・・・・・・・・
(7) Gco2m=Yco2A3・Km@Sm・(La
o-Lan)・v −−−−−−−・−=(8JdAl
k.

V--=Q・Alki-Q”Alko-YA, ni/NH
@yNH/Lv-b-sa4vo-tyn)・Vt-YAIk/ALa+La/LvWork・5a-(Punishment-Lv
n)・v-chi・Sm-Km@Sm・(Lao-Lan)
・V) ・・・・・・・・・・・・・・・・・・・・・
(9) pH-10g (Alko-0,8560,83
・Lao)1ag((X)2)1+IOg(0-88/
Kc)・・・・・・・・・(10) However, Q: Raw material flow rate (m5/day) V: Tank volume (m) Lv: Organic matter concentration (P/7) Ka: Reaction rate constant in the acid fermentation process (t/F/da
Y) LVn: Concentration of non-biodegradable organic matter (fP/fP) N
H: Ammonia nitrogen concentration (■/J) YN, /LV: Production ratio of ammonia nitrogen to unit organic matter decomposition amount (
■/ton) GCO2a ``Rate of carbon dioxide generation during acid fermentation process (
Nm3/day) La: Organic acid concentration (m9/day) Km: Reaction rate constant in the methane fermentation process (m37N
m5/day) Sa: Concentration of acid-producing microorganisms in terms of the amount of decomposed organic matter (De/?) Sm: Concentration of methane-producing microorganisms in terms of the amount of methane gas generated (
Nm 7m) YL, ¥'LV: Organic acid generation ratio to organic matter decomposition amount (In9/1) Lan: Non-biodegradable organic acid concentration (mp/-IYC
H4/La ``Methane generation ratio to organic acid decomposition amount (
Nm / Immediately) GeH4” Methane gas generation rate (Nm 7 days) 0002m
``The rate of carbon dioxide production in the methane fermentation process (Nm3
/day) Alk: Alkalinity (■/-13) YAl/NH: Production ratio of alkalinity to the amount of ammonia nitrogen produced (da/rn9) YAll, /La: Production ratio of alkalinity to the amount of decomposed organic acid concentration (Y/~) pH: pH (CO2)1: Carbon dioxide concentration in liquid phase (■/4) Kc:
Carbonic acid dissociation constant subscript i: Subscript 0 indicating the input raw material: YCO2/LV indicating the raw material in the digestion tank ``Ratio of carbon dioxide gas production to the amount of decomposed organic matter (Nm' / t) 7i1 CO2/La ``The production of carbon dioxide gas to the amount of organic acid decomposition Ratio (Nm/■) In the above calculation formula, the reaction process of the anaerobic digestion process is simplified as shown in FIG. That is, the organic matter in the input raw materials is first decomposed by acid-producing microorganisms in the acid fermentation process, producing organic acids, carbonic acid residue, and ammonia nitrogen. Next, in the methane fermentation process, organic acids are decomposed by methanogenic microorganisms to produce methane gas and carbon dioxide gas. The alkalinity in the digestion tank is determined from the ammonia nitrogen and organic acid concentration, and the pH in the digestion tank is
It is determined from the alkalinity in the digester and the dissociation equilibrium of carbonic acid in the liquid phase in the septic tank.

Equation (1) is a mass balance equation regarding the amount of organic matter in anaerobic digestion. The left side of equation (1) is the rate of change of the organic matter in the digester, and the first to third on the right side of equation (1) are
The terms indicate the amount of organic matter input into the digester, the amount of organic matter withdrawn from the digester, and the amount of organic matter decomposed in the digester, respectively.

Similarly K, (2), (3), (5), (6)
, (Equation 91 is a material balance equation for the amount of acid-producing microorganisms, a material balance equation for the amount of ammonia nitrogen, a material balance equation for the amount of organic acids, a material balance equation for the amount of methane-producing microorganisms, and a material balance equation for alkalinity. .

(4).

Equations (7), (8), and (to) are arithmetic expressions for calculating the carbon dioxide gas production rate, methane gas production rate, carbon dioxide production rate in the methane fermentation process, and pH in the digestion tank, respectively. Furthermore, the third term on the right side of equation (1) and the fourth term on the right side of equation (5) are reaction rate rings that indicate the reaction rate in the acid fermentation process and the reaction rate in the methane fermentation process, respectively.

These calculation formulas can be calculated using
This can be easily solved using the Unge-Kutta method or the like. That is, the actual input information to the digester is measured by the measuring device 2, and sent to the input circuit 4 via the signal line 2S, and further K, signal I! ! The signal is input to the arithmetic prediction circuit via 4s.

In addition, when calculating and predicting using simulated input information, the facility operator inputs the simulated input information from the input device 3 of the simulated input information to the input circuit 4K, further K, and the signal via the signal line 3S. It is input to the arithmetic prediction circuit 5 via the line 4s.

On the other hand, the coefficients in the calculation formula, such as the reaction rate constant, are inputted from the ratio setting device 7, inputted to the input circuit 4 via the signal line 7S, and further inputted to the calculation prediction circuit 5 via the signal line 4s. In the arithmetic prediction circuit 5, ) tunge-Kut
Solve each of the arithmetic expressions shown using the ta method or the like. The future product amount and concentration of the digestion process, which is the calculation result, is shown on the signal line 5S.
The data is sent to the output circuit 6 via the 1000K, and further sent to the display device (not shown) K where it is displayed in the form of a time series chart or the like. Based on the calculation results, the facility operator determines operating conditions such as the amount of raw materials to be input, and operates the facility.

Since the conventional digestion state simulator was configured as described above, the coefficients in the calculation equation change based on changes in the properties of the input raw materials, so if these coefficients are fixed at constant values over a long period of time, Simulation prediction accuracy decreases.

For this reason, in order to have facility operators change operating conditions such as input raw materials based on incorrect prediction results.

This often caused abnormalities in the digestion conditions, making it difficult to operate the digester stably.

In addition, with conventional equipment, it takes a lot of time and effort to conduct laboratory-scale experiments at regular intervals to determine and update these coefficients.
The drawback was that it required a lot of effort.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and uses the amount of methane gas generated from the digestion tank, the amount of carbon dioxide gas, K, the concentration of organic matter in the digestion tank, and the concentration of organic acids in the digestion tank. The coefficients in the reaction rate term that indicate the reaction rate of the fermentation process, the coefficients in the reaction rate term that indicate the reaction rate of the acid fermentation process, and the ratio of organic acid production to unit organic matter decomposition amount are updated sequentially, and calculation prediction accuracy is good,
Another object of the present invention is to provide a device for simulating the state of digestion in an anaerobic digestion process, which can eliminate the need to update coefficients based on experiments.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. Second
In the figure, 21 and 8 are an organic matter concentration meter and an organic acid concentration meter, respectively, installed in the digestion tank 1, and their outputs are connected to a signal line 21s.

It is connected to the input circuit 4 by 8S. 9 and 10 are a gas flow meter and a gas analyzer equipped with piping cVc for drawing out the generated digestion gas, respectively, and their outputs are connected to the input circuit 4 by signal lines 9s and IQs, respectively.
It is connected to the. 11 and 12 are arithmetic units for calculating the concentration of acid-producing microorganisms in terms of removed organic matter and the concentration of methane-producing microorganisms in terms of amount of generated methane gas, and the outputs of the input circuit 4 are connected by signal lines 11s and 12s, respectively. There is. 13, 14.15 are the organic acid production ratio YLa/Lv per amount of organic matter removed from the psicess value for a certain period from the present to the past, and the coefficient in the reaction rate term indicating the reaction rate in the formic acid fermentation process according to each equation , a calculation circuit for calculating a coefficient in a reaction rate term indicating a reaction rate in a methane fermentation process.

In the arithmetic circuit 131C, the output of the input circuit 4 is connected to the signal line 13s.
It is connected by K. In the arithmetic circuit 141C, the outputs of the arithmetic unit 11 and the input circuit 4 are connected to the signal line 16S.

14s K. The arithmetic circuit 15 receives the output of the arithmetic unit 12 and the input circuit 4 as a signal 1117s.

15B. The outputs of the arithmetic circuits 13, 14, 15 are connected to signal lines 18g, 19s, and 19s, respectively.
Operator by 20s! It is connected to the llu circuit 5.

Next, the operation will be explained. According to the present invention, (1) Instruments used in the gas phase, such as digester gas flowmeters and gas analyzers, are superior in terms of maintainability and reliability than densitometers, etc., which are used by being immersed in digestive fluid. ■ As shown in the calculation formula, the gas production rate is proportional to the reaction rate in the methane fermentation process and acid fermentation process, and can be directly measured. Therefore, the methane production rate and carbon dioxide production rate are the reaction rate constants. This is the main information when updating. Of the various coefficients in the θ calculation formula, simply updating the coefficients in the term indicating the reaction rate in the acid fermentation process and methane fermentation process and the organic acid production ratio (YLa/Lv) in terms of removed organic matter can solve practical problems. It is possible to simulate the state of digestion with unprecedented accuracy.

An example of a coefficient updating method will be shown below. Updating the coefficient in the reaction rate term in the arithmetic expression indicating the reaction rate in the methane production process is achieved by solving equation (7). In other words, by transforming equation (7) into the following equation, the reaction can be calculated using the methane gas production rate ('CH4), the methane-producing microorganism concentration (Sm), and the organic acid concentration in the digester (Lad) for a certain period in the past. The coefficients Km, LaO in the velocity term can be defined.

The methane gas production rate (GeH4) is calculated as the product of the digestion gas flow rate and the methane gas concentration in the digestion gas.

The digestion gas flow rate and methane gas concentration are measured by the digestion gas flow meter 9 and the digestion gas analyzer 101C, respectively. The organic acid concentration (Lao) in the digestion tank is measured by an organic acid concentration meter 8. The measured values of the digestion gas flow rate, methane gas concentration, and organic acid concentration are measured through signal lines 9s and 10a, respectively.

8SK is sent to the input circuit 4 and input to the arithmetic circuit 15 via the signal line 15s. The methane gas generation ratio YcH4/I, ac to the amount of decomposed organic acid is set in the ratio setting device 7, sent to the input circuit 4 via the signal line 7S, and further inputted to the arithmetic circuit 15 via the signal line 15S. Ru. The methane-producing microorganism concentration (sm) is
Methane gas production rate, source ÷ - s - ++) K As shown, the concentration of methane-producing microorganisms in terms of the amount of generated methane gas can be calculated.

Here, k, +1: Time G: Amount of digestive gas generated between time k and +1 □ a: +10 between time k and K, the concentration of methane gas generated and other symbols are as already shown.

The measured value of the raw material flow rate Q is measured by the input information measuring device 2 and sent to the input circuit 4 via the signal line 2S. The digestion gas flow rate G and the methane gas concentration a are measured by the digestion gas flowmeter 9 and the gas analyzer 10, and the signal line 9s
, 103 to the input circuit 4. These signals are further input to the arithmetic unit 12 via a signal line 128. The arithmetic unit 12 performs the calculation of equation (12), and the result of the calculation is input to the calculation circuit 15 via the signal line 17s.

The arithmetic circuit 15 substitutes the information from the signal lines 15s and 17s into equation (11) to obtain the coefficient K m + L a
Calculate n. The coefficients Km and Lan, which are the calculation results, are sent to the calculation prediction circuit 5 through the signal line 20S.

Updating the coefficient in the reaction rate term in the arithmetic expression indicating the reaction rate in the acid production process is achieved by solving <7), +81 and equation (4). That is, (7),
(81 (4) can be modified and rearranged as shown below: methane gas production rate (GeH4), carbon dioxide production rate (GCO2m+GCO2a), acid-producing microorganism concentration (Sa ), and organic matter concentration in the digester ( LVO) can be used to determine the coefficients Ka and LVn in the reaction rate term.

(4) formula, (8) formula, Gco2a+Gco2n8Yco2/La″KmIIS
m fist (IJao-Ian) -V+YcQt2/Lv@
KamSa@CLVO-LVn)@V-...-(13)
From equations (13) and (7), -KaIISa@(jvo-Lvn)eV = (14
) (14), the total carbon dioxide production rate (Gco2a + Gco2m) is calculated as the product of the digestion gas flow rate and the carbon dioxide concentration in the digestion gas. The digestion gas flow rate and carbon dioxide concentration are measured by a digestion gas flow meter 9 and a digestion gas analyzer 10, respectively. Methane gas production rate G. Regarding H4, it is the same as described above. The organic matter concentration (I, vo) in the digestion tank is measured by an organic matter concentration meter 21. Digestion gas flow rate, methane gas concentration,
The measured values of carbon dioxide concentration and organic matter concentration are on the signal line 9s.
, 10s, 21s to the input circuit 4,
Further, the signal is input to the arithmetic circuit 14 through the signal line 14s. Methane gas generation ratio YcHt to amount of decomposed organic acid
/l, a, carbon dioxide generation ratio Y to amount of decomposed organic acid
. o2/La, ratio Y of carbon dioxide gas generation to the amount of decomposed organic matter. 02/LV is set in the ratio setting device 7IC, sent to the input circuit 4 via the signal line 7s, and further inputted to the arithmetic circuit 14 via the signal line 14sK.

The concentration of acid-producing microorganisms (Sa) can be calculated by calculating the concentration of acid-producing microorganisms in terms of the amount of removed organic matter, as shown by measurements of the raw material flow rate, the organic matter concentration in the input raw materials, and the organic matter concentration in the digester.

5a(k+1)=Sa(k)+3(Lvi-4,vo)
-q 5a(k) "・--" (16)■ Measured value of raw material flow rate Q and organic matter concentration L in input raw material
vi is measured by the input information measuring device 2 and sent to the input circuit 4 via the signal line 2S. The organic matter concentration Lvo in the digestion tank is measured by the organic matter concentration meter 21 and sent to the input circuit 4 via the signal line 218. These signals are further input to the arithmetic unit 11 through the signal line 11sK. The arithmetic unit 11 performs the arithmetic operation of equation (16), and the result of the arithmetic operation is input to the arithmetic circuit 14 via the signal line '16s. In the arithmetic circuit 14, the information from the signal lines 168 and 143 is substituted into equation (15) to obtain the coefficients Ka and LVO.
Calculate. The coefficient KiLVO, which is the calculation result, is on the signal line 1.
98K is sent to the arithmetic prediction circuit 5.

Organic acid production ratio YLa/r, v of decomposed and removed organic matter
The update of (41, (5), (7), (s)
This is accomplished by solving the equation. That is, (4)
, (5) , +71 , (If we transform and rearrange the sJ formula into 5 as shown below, we can obtain the methane gas production rate (GeF4) and the carbon dioxide production rate (Goo2a+G
o82m), the organic acid concentration in the input raw material (Lai), and the organic acid concentration in the digestion tank (Lao), it is possible to determine the organic acid production ratio YLa//Lv based on the amount of organic acid removed.

From equations (5) and (7), v-△Lao=QeLai-QIILao+YLa/L
veKaIISa-(Lvo-Lvn)lIv(17)
By substituting and rearranging the equation (15) derived from the equation K (4), +7) and the equation (8), in the equation (18), the methane gas production rate (GeH4)
, the total carbon dioxide production rate (GCO2a + GC02m) is
It is measured by the aforementioned digester gas flow meter 9 and digester gas analyzer 10, and is sent to the input circuit 4 via signal lines 9s and IQs. The organic acid concentration Q, ai) in the manned raw material and the input raw material amount (Q) are measured by the input information measuring device 2 and sent to the input circuit 4 by the signal m2SK. The organic acid concentration (Lao) in the digestion tank is measured by an organic acid concentration meter 8 and sent to the input circuit 4 via a signal line 8S. Carbon dioxide generation ratio Y per amount of organic matter removed
CO2/Ll/, the carbon dioxide gas production ratio per removed organic acid amount YCO2/La, and the methane gas production ratio YcH4/La per removed organic acid amount are set by the ratio setting device 7,
The signal is sent to the input circuit 4 via the signal line 7s. These signals are further sent to the arithmetic circuit 13 via a signal line 13S. The arithmetic circuit 13 substitutes these signals into equation (18) to determine the organic acid production ratio YLa/Lv per amount of removed organic matter. The calculation result YLa/Lv is the signal line 1
85 to the arithmetic prediction circuit 5.

While updating the coefficients as shown above, the state of digestion is simulated using the same procedure as shown in FIG. The results of examining these coefficient updating methods through computer simulation using example data are shown in FIGS. 3 and 4, respectively.

Here, the coefficients were updated sequentially using data from the past three days. As shown in FIGS. 3 and 4, the actual measured values and calculated values, both in terms of numerical trends, agree well with an accuracy that does not pose much of a problem in practice.

In the above example, the concentration of methane-producing microorganisms and the concentration of acid-producing microorganisms are calculated by converting them into the amount of methane gas and mass production of removed organic matter, respectively. It is also possible to provide a means to directly measure the concentration (1゜Also, for organic substance concentration and organic acid concentration, it is sufficient if the measurement frequency is at least once a day, and it is possible to manually analyze the concentration in the laboratory and directly input it to the input circuit. You may also input it.

Furthermore, in the above embodiment, the coefficient in the reaction rate term indicating the reaction rate in the acid fermentation process is 3 r Lvn + the coefficient Krr1 in the reaction rate term in the methane fermentation process. Although an example has been shown in which all of L and In are updated, it is also possible to fix the value of I'vn l L'an and update only Ka+Km.

It is also recommended that the newly determined coefficient values be updated while being smoothed.

Further, in the above example, an example was shown in which the reaction rate in the acid fermentation process and the methane fermentation process was a first-order reaction equation proportional to the substrate concentration. Formula and K
Similar effects can be achieved even when using these modified formulas.

In addition, using this device that simulates the digestion conditions of the anaerobic digestion process, the optimal operating conditions such as input amount and digestion temperature will be automatically determined while taking into consideration the thermal efficiency of the digester and the disposal cost of the digested raw materials. If the operability of the digester is determined based on the determined operating conditions, highly efficient operation becomes possible.

〔Effect of the invention〕

As described above, according to the present invention, by using the amount of methane gas generated from the digestion tank, the amount of carbon dioxide gas produced, the concentration of organic matter in the digestion tank, and the concentration of the same organic acid, Since the ratio of organic acid production to the amount of decomposed organic matter is updated sequentially, there is no need for experiments for updating coefficients that require manual labor, and the prediction accuracy is also excellent, which is an extremely excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional device for simulating the state of digestion in an anaerobic digestion process, FIG. 2 is a block diagram of a device for simulating the state of digestion in an anaerobic digestion process according to an embodiment of the present invention, FIG. 4 is a diagram showing the results of calculating and predicting the state of digestion using the simulator of the present invention, and FIG. 5 is a schematic diagram showing the reaction process of the anaerobic digestion process. 1... Anaerobic digestion tank, 2... Input information measuring device,
3... Input circuit for simulated input information, 4... Input circuit,
5... Arithmetic prediction circuit, 6... Output circuit, 7... Ratio setting device, 8... Organic acid concentration meter, 9... Digestion gas flow meter, 10... Gas analyzer, 11 .12...Arithmetic unit, 13°14.15...Arithmetic circuit, 21...Organic substance concentration meter. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Patent applicant Mitsubishi Electric Corporation (2 others): Figure 1 Figure 2 Sado Bi procedural amendment (voluntary) Commissioner of the Japan Patent Office 1. Indication of the case Japanese Patent Application No. 102363/1982 2. Title of the invention Digestion state simulating device for anaerobic digestion process 3, Name of person making the amendment (601) Mitsubishi Electric Corporation Representative Hitoshi Katayama 5, Subject of amendment (1) Scope of claims in the specification (2) Column 6 of Detailed Description of the Invention in the Specification, Contents of Amendment (1) The scope of claims will be amended as shown in the attached sheet. (2) Change "piping b" on page 3, line 20 of the specification to "piping a"
” he corrected. (3) "-Km@Sm・(LaO-Lan)・V)...=(
9) j is r・(Lao-Lan)*v)...---(
9), correct as J. (4) "r (m3/day)" on page 6, line 2 of the specification.
(m3/day)J. (5) FIA specifications, page 6, line 12, page 7, line 5,
"(8m5/day)" in the 7th line of the same page is r(Nm'/da
y) Correct each with J. (6) “cm/Nm 1 day)” on page 6, line 15 of the specification
is corrected to r (m 3 / Nm 5 / day month). (7) "Quality ←" on page 8, line 15 of the specification is corrected to "density". (8) Specification, page 10, line 8 "Each expression shown" on the line (
9) "Acid fermentation process according to each formula" on page 12, lines 15-16 of the specification is corrected to "acid fermentation process." (10) [-Ka @sa ・(LvO-Lvn) ・V −” on page 17, line 3 of the specification
(14) j to r ・Ka*Sa ・(LvO-Lv
n) ・V...(14) Correct as J. (11) "Yes" on page 20, line 3 of the specification.

Claims (1)

[Claims] Input information or simulated input to the anaerobic digestion process, in which raw materials containing organic matter are continuously or intermittently input and subjected to anaerobic acid fermentation and methane fermentation, and the organic matter is decomposed to generate methane gas and carbon dioxide gas. It has an arithmetic prediction circuit that takes information as an input signal and measures the future state of digestion of the process, the amount or concentration of products from the process using an arithmetic expression including a predetermined reaction rate term. In the anaerobic digestion process digestion state simulator that outputs the measured results of this operator, the methane gas production rate of the process, the concentration of methane-producing microorganisms in the digester tank, the methane-producing microorganism concentration in the digester tank, and the methane gas production rate of the process during a predetermined period from the present to the past. Using the values measured by the first means of measuring the internal organic acid concentration or an alternative indicator thereof, calculate the coefficient in the reaction rate term indicating the reaction rate of the methane fermentation process, and output the result of this calculation. a first arithmetic circuit that calculates the rate of methane gas production, the rate of carbon dioxide production, the concentration of acid-producing microorganisms, the concentration of organic matter in the digester, or alternative indicators thereof for a predetermined period from the present to the past; a second calculation circuit that calculates a coefficient in a reaction rate term indicating the reaction rate of the acid fermentation process using the value measured by the second means for measuring the substance, and outputs the calculation result -゛; Methane gas generation amount, carbon dioxide gas generation amount, organic matter and organic acid concentration in the input materials, organic matter and organic acid concentration in the digester, or alternative indicators of these, during a predetermined period from the present to the past. at least one or more third calculation circuit which calculates the generation ratio of organic acid with respect to the unit amount of decomposed organic matter using the value measured by the third means for measuring the amount of organic matter and outputs the calculation result. , the first
- Using the output of the third arithmetic circuit, the coefficient in the reaction rate term indicating the reaction rate of the methane fermentation process in the predetermined arithmetic expression in the arithmetic prediction circuit, and the reaction indicating the reaction rate indicating the acid fermentation process. A digestion state simulating device for an anaerobic digestion process, characterized in that at least one or more of a coefficient in a rate term and a production ratio of organic acid to a unit amount of decomposed organic matter are updated sequentially.