DE102018105035B3 - Method and system for monitoring bioreactors - Google Patents

Abstract

Described is a method for monitoring biogas plants, mana) during operation of the biogas plant measures the amount of organic acids and the conductivity, b) the quotient of the amount of organic acids and the conductivity forms and compares with a predetermined setpoint for the quotient , c) and in the event that the quotient of the amount of organic acids and the conductivity exceeds the predetermined setpoint for the quotient by a factor of 1.5 or more, d) records the value. A method is also described for monitoring and Control of biogas plants and a computer program product and a system for carrying out the Verfahren.Das described method is suitable, even in combination with other known early warning indicators biogas plants with any substrate feed optimally lead and monitor.

Description

The present invention relates to a method for monitoring and controlling biogas plants and to a computer program product and a system for carrying out the method.

The fermentation of biogenic raw materials in biogas plants is a complex multi-stage microbial process, in which different microorganisms and groups of microorganisms are involved, some of which are in very close correlation with each other. The metabolic rate of the microorganisms decisively determines both the efficiency of a biogas plant and the process stability. For optimum operation of a biogas plant and its process management, the living conditions for the microorganisms must always be optimally maintained.

A special problem in the process management is the prevention of hyperacidity. This is mainly due to the degradation of the supplied nutrients (substrates) to short-chain organic acids such as acetic acid or propionic acid. An excessively high concentration of these acids leads to a lowering of the pH and, as a result, to an inhibition of the growth of the methanogenic microorganisms. When the pH drops further, the growth is finally stopped and the gas production in the reactor decreases sharply. The system is acidified.

Once hyperacidity has occurred, it is difficult to stabilize the process. Above all, the regeneration requires a lot of time.

Therefore, it is essential for optimal process control to recognize acidification as early as possible and initiate appropriate countermeasures. Suitable measures are, for example, the addition of alkalis to stabilize the pH or to reduce the substrate input.

For optimal process control, the reactor is constantly monitored and all important process parameters such as pH, gas concentrations in the liquid and gaseous phase, methane gas quantities formed in the form of gas formation rate and the space load are observed, measured, recorded and evaluated. With the help of these parameters, the biogas plant is then operated with the aim of increasing and optimizing the space-time yield. Effective process control based on the pH alone is not sufficient because the system is already at a critical stage when the pH drops.

Usually, the sum concentration of the organic acids, more rarely the acid spectrum (by photometry, titration, HPLC or GC), the FOS / TAC value (by titration) and the TS and oTS content as early warning indicators (FWI) and process parameters are determined in the laboratory , For certain biogas plants, the early warning indicators oS / Ca, P / Ca and P to be determined in the laboratory are also suitable DE 10 2008 044 204 A1 or the DE 10 2012 107 410 A1 are described. The ratio of the CH ₄ to the CO ₂ concentration in the biogas, the concentration of the dissolved H ₂ , as well as the parameters pH value, temperature, redox and the electrical conductivity for determining the salinity can be measured online as early warning indicators. It is also known that in some biogas plants the conductivity correlates with the buffer capacity.

It is therefore an object of the present invention to provide further parameters for the early detection of hyperacidity in a bioreactor, which are reliable and easy to determine and which make it possible to counteract impending hyperacidity at a very early stage.

The object of the invention is achieved by a method according to the main claim. Advantageous embodiments of the method are characterized in the dependent subclaims.

1. a) während des Betriebs der Biogasanlage die Menge an organischen Säuren und die Leitfähigkeit misst,
2. b) den Quotienten aus der Menge an organischen Säuren und der Leitfähigkeit bildet und mit einem vorgegebenen Sollwert für den Quotienten vergleicht,
3. c) und für den Fall, dass der Quotient aus der Menge an organischen Säuren und der Leitfähigkeit den vorgegebenen Sollwert für den Quotienten um den Faktor 1,5 oder mehr überschreitet,
4. d) den Wert aufzeichnet.

The present invention is therefore a method for monitoring biogas plants, wherein one

1. a) measuring the amount of organic acids and the conductivity during operation of the biogas plant,
2. b) the quotient of the amount of organic acids and the conductivity forms and compares with a predetermined setpoint for the quotient,
3. c) and in the event that the quotient of the amount of organic acids and the conductivity exceeds the predetermined setpoint for the quotient by a factor of 1.5 or more,
4. d) records the value.

It is preferred in the process according to the invention that the calcium concentration and / or the phosphate concentration are additionally measured in step a).
Preference is furthermore given to a process according to the invention, wherein in step b) the quotient of the amount of organic acids and the calcium concentration and / or the quotient of the phosphate concentration and the calcium concentration is additionally formed and a desired value for the respective quotient given for the respective quotients compares and / or compares the phosphate concentration with a predetermined setpoint for the phosphate concentration.

It is particularly preferred that in step c) the factor for exceeding the setpoint for the quotient of organic acids and the calcium concentration is 2.5 or higher, for the quotient of the phosphate concentration and the calcium concentration is 1.5 or higher, and for the phosphate concentration 2 or higher.
By measuring other parameters (calcium concentration, phosphate concentration) it is possible to identify additional known early warning indicators to better monitor the biogas process.

Preference is given to a method according to the invention in which, when at least one predetermined setpoint value is exceeded by the respective predetermined factor, measures are initiated against the expected overacidification of the biogas process.

It is particularly preferred that the measures against the expected hyperacidity are selected from the supply of the pH-increasing chemical compounds, the supply of trace elements and the reduction of the supply of substrates.

Furthermore, it is preferred according to the invention to carry out the measurements at regular intervals and / or continuously. Carrying out the continuous measurement is advantageous if the measured values can be determined online. So a continuous measurement is possible. In other measuring methods, in particular in titration methods, a measurement at certain intervals is advantageous, since the sample preparation and sample measurement requires a certain amount of time.

But it is also preferable that the regular intervals are between one hour and one day long. This is advantageous for smaller biogas plants, since a continuous and / or online measurement leads to a high cost and thus is no longer profitable for such biogas plants. However, since the pre-warning times are several days, a daily measurement of the relevant parameters is indicated for cost reasons and still leads to a monitoring of the biogas plant according to the invention.

Particularly preferred is a method according to the invention in which the values of the measurements are continuously recorded. This ensures that the respective quotient formation can take place continuously and thus also the change of the quotients over a long period of time can be continuously monitored. The thus continuously recorded values and quotients can then be evaluated by means of suitable statistical methods known to the person skilled in the art and processed and evaluated in a corresponding computer program product.

The subject of the present invention is therefore also a computer program product, which is directly loadable into an internal memory of a computing unit and software code or parts thereof, which are executable for performing the method steps according to one of the preceding claims, when executing the computer program product on a computing unit.

1. a) mindestens eine Recheneinheit,
2. b) mindestens einen Datenübertragungsbus, welcher mit externen Peripheriegeräten der Biogasanlage verbunden ist,
3. c) mindestens eine interne Datenbank,
4. d) mindestens eine Überwachungs- und/oder Steuerungssoftware zur Analyse der aus den externen Peripheriegeräten übermittelten Messwerten und Daten, und
5. e) mindestens ein Endgerät zur Visualisierung von Informationen.

A further subject of the present invention is also a system for monitoring and controlling biogas plants, comprising

1. a) at least one computing unit,
2. b) at least one data transfer bus which is connected to external peripherals of the biogas plant,
3. c) at least one internal database,
4. d) at least one monitoring and / or control software for analyzing the measured values and data transmitted from the external peripherals, and
5. e) at least one terminal for visualizing information.

Particularly preferred according to the invention is a system according to the invention in which the monitoring and / or control software is a computer program product according to the invention.

Also particularly preferred is a system according to the invention, in which a data output bus and / or control bus is furthermore provided, which is adapted to initiate measures against the expected hyperacidity. This is particularly advantageous because it allows the appropriate measures against the expected hyperacidity can be automatically made. In this case, the computer program product is designed in such a way that it can independently determine the respectively optimum measure by means of the parameters recorded in current methods or parameters determined and learned from previous methods and execute the optimal measure or combination of measures.

• 1 die lineare Abhängigkeit der elektrischen Leitfähigkeit, der Pufferkapazität (TAC) ○ und dem gelösten Carbonat ♦ für die Übersäuerungsexperimente 1 bis 3 bei pH > 6,5;
• 2 den Verlauf der Betriebsparameter pH-Wert (♦), org. Säuren (▲), Gasbildungsrate (+) und dem Verhältnis aus organischen Säuren zur elektrischen Leitfähigkeit (A/elCon) (●) bei steigender Raumbelastung (- - - - -) bis zur vollständigen Übersäuerung an Tag 54. Der FWI A/elCon warnt bereits ab Tag 47 vor einer drohenden Prozessstörung. Übersäuerungszeitraum:
  
• 3 den Verlauf des pH-Wertes (♦), des FOS/TAC (■) und des Verhältnisses aus organischen Säuren zur Leitfähigkeit (A/elCon) (●) bei der Simulation einer Übersäuerung einer Klärschlamm- und organische Abfällevergärenden Biogasanlage durch Zugabe von Essigsäure; und
• 4 eine schematische Darstellung eines Systems zur Überwachung und Steuerung von Biogasreaktoren.

The present invention will be explained in more detail with the accompanying drawings. It shows:

• 1 the linear dependence of the electrical conductivity, the buffer capacity (TAC) ○ and the dissolved carbonate ♦ for the hyperacidity experiments 1 to 3 at pH>6.5;
• 2 the course of the operating parameters pH value (♦), org. Acids (▲), gas formation rate (+) and the ratio of organic acids to electrical conductivity (A / elCon) (●) with increasing volume load (- - - - -) until complete overacidification on day 54. The FWI A / elCon warns already starting from day 47 before an impending process disturbance. Acidification period:
  
• 3 the course of the pH value (♦), the FOS / TAC (■) and the ratio of organic acids to conductivity (A / elCon) (●) in the simulation of a hyperacidity of a sewage sludge and organic waste fermentation biogas plant by the addition of acetic acid; and
• 4 a schematic representation of a system for monitoring and control of biogas reactors.

The inventors refer to the novel early warning indicator (FWI) according to the invention with A / elCon, where A stands for organic acids (Acids) and elCon for electrical conductivity (Conductivity). The term organic acids used herein is also referred to by the abbreviation "oS". Thus, the abbreviations "A" and "oS" are to be considered equivalent.

The inventors have now made a total of four early warning indicators available to optimally monitor biogas plants. Each of the early warning indicators is able to identify the impending acidification of the biogas production process. However, since the composition of the substrates of biogas plants can be very different and the composition can change over the course of the fermentation process, since, for example, other substrates are added, it is advantageous to determine several early warning indicators simultaneously. With the present invention, this is easily possible because some parameters determined in the fermentation liquor, alone or in combination with other parameters, are suitable for use as an early warning indicator.

The on-line measurement of calcium concentrations by fluorescence spectroscopy using calcium-specific optodes is known. These and other optodes are for example in the WO 2013/107895 A1 described. Also, online measuring devices for the phosphate concentration are already known. Such systems are sold, for example, by the company WTW Scientific Technical Workshops GmbH. Also available are TOC analyzers, which can be used for online measurement. Titration machines for FOS / TAC measurements and for the determination of organic acids are also known and can continuously take samples and analyze them by means of robotics. Likewise, there are suitable sensors for measuring the conductivity, which can be used in aqueous media. Such sensors are also suitable for online measurements. Therefore, a continuous measurement of all relevant parameters of the biogas process is technically possible and particularly preferred according to the invention.

The values of the respective parameters, such as phosphate, calcium, organic acids and / or conductivity, which are important for the early-warning indicators, are determined by means of a computer. The corresponding quotient of these contents is determined accordingly and further processed by means of a computer. These measurements can be repeated at predetermined intervals and further processed and stored. From these values, a baseline is preferably calculated, which is used as the basis for determining the threshold value for triggering the alarm. Out of that way The resulting series of measured values then determines a tendency and generates a signal when the threshold value is reached. Such methods for processing such measured values are known to those skilled in the field of measurement and control technology. The creation of a computer program product to be used for this purpose is also known per se to the person skilled in the art.

The signal generated when reaching the threshold value is then supplied to an output unit. This output unit can generate an optical or acoustic signal, such as a horn actuate. The output unit may preferably forward the signal to an input unit of the process control unit. The aforementioned input unit can also be an integral part of the output unit. Such electronic components are known per se. When the signal of the threshold value is present, the process control unit can then intervene in the reactor in accordance with predetermined decision sequences. It is preferred that addition units for supplying liquid and / or solids are controlled. Such addition units may be pumps such as metering pumps, solids pumps, membrane pumps, etc., solids feeders, and the like.

Substances which can be added include, for example, caustic soda, caustic soda as a solid, quicklime (CaO), liquid or solid alkalis. However, the supply unit can also be controlled so that the supply is reduced or stopped. This is the case, for example, when the substrate entry is to be changed in order to avoid the overacidification. The addition of CaO is preferred, however, since it has been found that a higher volume loading can be achieved by the addition of CaO. Also, the addition of trace elements is particularly preferred. Thus, the growth of the microorganisms required to carry out the biogas process can be promoted, which also leads to a stabilization of the biogas process. Thus, the threat of hyperacidity can be averted.

The following examples illustrate the invention in more detail without limiting the scope of the invention.

example 1

acidification experiments

Three hyperacidity experiments were performed. For this purpose, in each case a bioreactor with a fermentation volume of 20 L at a temperature of 37 ° C was charged with a substrate and fermented, the substrate consisting of 95% corn silage and 5% cattle slurry (based on oTS). The increase in volume was carried out every 8 days by 1 kg oTS m ^-3 d ^-1 .

In the three hyperacidity experiments, which in the 1 shown, that the electrical conductivity of the sludge between pH 6.5 and 8 depends linearly on the total buffer capacity of the sludge and especially on the carbonate buffer. During a stable biogas process, the pH is between 7 and 8. In this pH range, the inorganic carbon is for the most part as charged bicarbonate. With increasing instability of the fermentation process, the associated increase in the concentration of short-chain organic acids and a decrease in the pH, the equilibrium of the buffer shifts to the reaction products carbon dioxide and water. As the concentration of bicarbonate decreases, the electrical conductivity decreases.

In the 2 the course of selected operating parameters of one of the three hyperacidity experiments is shown as an example. The gas formation rate increases with increasing space load. The concentration of organic acids remains low despite increased space load until day 50 and warns from day 51 with acid concentrations above 2 g L ^-1 before an impending process disturbance. The pH value warns by a decrease below 7 as of day 50. The A / elCon warns by a rise of the normal value by a factor of 1.5 already from day 47 and thus one week before the occurrence of the complete hyperacidity on day 54.

Table 1 shows the warning times of selected process parameters and the early warning indicators organic acids, pH, FOS / TAC, biogas yield, oS / Ca, P / Ca, P and A / elCon for the three hyperacidity experiments. The early warning indicators oS / Ca, P / Ca and P also found by the inventors were developed for the co-fermentation of high-fat substrates in waste biogas plants. Since the substrates of agricultural biogas plants have significantly lower levels of fat, there was no characteristic decrease in the calcium concentration before the occurrence of hyperacidity, whereby an impending disturbance was delayed. In comparison, A / elCon warned in two out of three hyperacidity experiments on the earliest. Only in trial 1 There was an earlier increase in the phosphate concentration (P) and thus an earlier warning by the indicators P and P / Ca. Table 1 Comparison of the early warning times of various early warning indicators in the hyperacidity experiments (Exp.) According to Example 1 Exp. Early warning [d] pH biogas yield oS oS / Ca P / Ca P FOS / TAC A / Elcon 1 3 3 3 4 12 9 4 4 2 4 4 3 4 4 3 3 6 3 4 4 4 7 3 3 7 9

Example 2

Simulation of acidification of a sewage sludge and organic waste biogas process

In order to investigate whether the ratio of organic acids to electrical conductivity, in short A / elCon, as an early warning indicator (FWI) indicates an imminent acidification even in wastewater treatment plants and thus can be used as FWI in different plant types, in a laboratory experiment an overacidification of a simulated with sewage sludge and organic wastes operated biogas process.

To this end, different amounts of acetic acid were added in five 200 mL digestate fractions from a biogas plant operated with sewage sludge and organic wastes. As the acid concentration increased, the pH decreased. The A / elCon warned already before the pH drops below 7 , by a 3.5-fold increase in baseline, from imminent acidification. The results are in the 3 shown. By comparison, the FWI FOS / TAC already established in practice warned of an impending acidification, but only with a 1.6-fold increase compared to the baseline before the pH dropped below 7.

The results confirm that the A / elCon reliably and early indicates impending process disturbances in waste gas biogas plants.

Example 3

Structure and function of an embodiment of a system according to the invention for monitoring and controlling biogas plants In the 4 is now a system according to the invention 1 for the monitoring and control of biogas reactors in the form of a schematic representation. The system 1 includes at least one arithmetic unit 2 , Such computing units may be personal computers (PCs), laptops, notebooks, smartphones, tablets or tablet computers, and the like. The arithmetic unit 2 can also be connected to another input device via a remote connection. Such remote connections may be Internet applications or cloud-based computer systems.

The arithmetic unit 2 now includes an internal database 8th in which the measured values of the respective parameters determined during operation of the biogas plant, such as the amount of organic acids, conductivity, calcium concentration and phosphate concentration, can be stored. This internal database 8th However, it can also be used to store predetermined setpoint values and to store the determined quotients, in order to provide these to a monitoring and / or control software 9 , or a module containing this software, for further calculation and analysis to provide.

By means of the interface 7 receives the arithmetic unit 2 Access to the data transfer bus 3 via which the data and measured values are transmitted from external peripherals of the biogas plant. Such peripheral devices are, for example, measuring and analyzing devices which record operating parameters of the biogas plant. Such operating parameters are in particular also values of the concentration of ingredients in the fermentation liquid such as the amount of organic acids, calcium concentration, phosphate concentration, pH, temperature, concentration of gases in the fermentation liquid or in the gas space of the Bioreactor of the biogas plant. These gases include in particular hydrogen, carbon dioxide, methane and oxygen. Such peripheral devices are, for example, pH probes, optodes for fluorescence measurement of metals such as calcium, potassium, sodium, titration machines and other on-line analyzers, which serve the ongoing monitoring of the biogas plant. By means of this data transfer bus 3 It is possible to transmit the required measured values continuously and in the internal database 8th to save and with the monitoring / control software 9 evaluate.

By means of the interface 7 can the arithmetic unit 2 but also with a data output and / or control bus 4 be connected. This data output and / or control bus 4 is in turn connected to external peripherals of the biogas plant, these peripherals serve the initiation and control of countermeasures in the event of impending acidification. Such peripheral devices are for example metering devices for the addition of solid, liquid or gaseous substances in the biogas plant. Such substances may be, for example, alkalis such as caustic soda or alkaline solids such as calcium oxide. Also is the data output and / or control bus 4 preferably connected to the substrate adding device for the biogas plant in order to limit or stop the further addition of substrate as a further countermeasure for preventing the overacidification.

the interface 7 can also work with another database 5 be connected to what data 6 contains the biogas plant.

the interface 7 is formed such that the connection to the computing unit 2 can be done over any known data transmission paths. Such data transmission paths are, for example, LAN or WLAN data networks, Internet connections or radio links. Of course, the data can be sent in both directions via the interface 7 be transmitted.

The system 1 further includes an input device 11 which may be, for example, a keyboard or other human interface device (HID). Also this input device 11 is about the interface 7 with the arithmetic unit 2 connected, so that the control and monitoring of the biogas plant can be done remotely.

Furthermore, the system includes 1 still a terminal 10 to output the determined values about the condition of the biogas plant. Also this connection between terminal 10 and arithmetic unit 2 is designed as already for the interface 7 described herein. As terminals 10 find devices that have a monitor or screen for the visual display of the system 1 generated information is suitable. Preferred are laptops, notebooks, smartphones, tablets and tablet computers.

Of course, the arithmetic unit includes 2 also devices for the execution of computer programs, which are included in the computer program product according to the invention. By means of this computer program, the inventive method on the arithmetic unit 2 executed and the result on the terminal 10 output.

Of course, according to the invention, the visualization can also take place via the monitor of a data system of the biogas plant. Many biogas plants have data systems and computers which are used, for example, for recording operating parameters. In such biogas plant computer systems, the inventive method can be carried out by means of the computer program product according to the invention and the information can be displayed, for example, on a screen for monitoring and controlling the biogas plant.

The system according to the invention makes it possible to autonomously and fully automatically control biogas plants of any kind, namely online, remotely or manually. By using four different early warning indicator systems biogas plants can be monitored and controlled, which are loaded with different sub-types. These are both substrates from renewable resources (NaWaRo), which are generally low in fat, or even fatty or high-fat raw materials and waste such as these incurred in waste disposal. This also applies to waste in the agricultural sector, especially in animal husbandry, where highly nitrogen-containing and manure-like waste materials are present.

LIST OF REFERENCE NUMBERS

1

system

2

computer unit

3

data transfer bus

4

Data output bus / control bus

5

Database of the biogas plant

6

Data of the biogas plant

7

interface

8th

Internal database

9

Monitoring / control software

10

terminal

11

input device

Claims (13)

Method for monitoring biogas plants, wherein a) during the operation of the biogas plant, the amount of organic acids and the conductivity is measured, b) the quotient of the amount of organic acids and the conductivity forms and compares with a predetermined setpoint for the quotient, c) and in the event that the quotient of the amount of organic acids and the conductivity exceeds the predetermined setpoint for the quotient by a factor of 1.5 or more, d) records the value. Method according to Claim 1 , characterized in that in step a) additionally measures the calcium concentration and / or the phosphate concentration. Method according to at least one of Claims 1 or 2 , characterized in that in step b) additionally forms the quotient of the amount of organic acids and the calcium concentration and / or the quotient of the phosphate concentration and the calcium concentration and compared with a predetermined for the respective quotients setpoint for the respective quotient and / / or comparing the phosphate concentration with a predetermined setpoint for the phosphate concentration. Method according to Claim 3 CHARACTERIZED IN THAT , in step c), the factor for exceeding the target value for the organic acid quotient and the calcium concentration is 2.5 or higher, for the quotient of the phosphate concentration and the calcium concentration is 1.5 or higher, and for the phosphate concentration is 2 or higher. Method, according to at least one of the preceding claims, characterized in that one initiates measures against the expected hyperacidity of the biogas process when exceeding at least one predetermined desired value by the respective predetermined factor. Method according to Claim 5 , characterized in that the measures are selected from the supply of the pH-increasing chemical compounds, the supply of trace elements and the reduction of the supply of substrates. Method according to at least one of the preceding claims, characterized in that the measurements are carried out at regular intervals and / or continuously. Method according to Claim 7 , characterized in that the regular intervals are between one hour and one day long. Method according to at least one of the preceding claims, characterized in that the values of the measurements are continuously recorded. Computer program product, which is directly loadable into an internal memory of a computing unit and software code or parts thereof, which are executable for performing the method steps according to one of the preceding claims, when executing the computer program product on a computing unit. System (1) for monitoring and controlling biogas plants, comprising a) at least one arithmetic unit (2), b) at least one data transmission bus (3), which is connected to external peripherals of the biogas plant, c) at least one internal database (8), d) at least one monitoring and / or control software (9) for analyzing the measured values and data transmitted from the external peripherals, and e) at least one terminal (10) for visualizing information. System, according to Claim 11 , characterized in that the monitoring and / or control software (9) according to a computer program product Claim 10 is. System, according to at least one of Claims 11 or 12 , characterized in that furthermore a data output and / or control bus (4) is provided, which is adapted to initiate measures against the expected hyperacidity.

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