EP2935558A2 - Système de conversion d'énergie - Google Patents

Système de conversion d'énergie

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Publication number
EP2935558A2
EP2935558A2 EP13831821.7A EP13831821A EP2935558A2 EP 2935558 A2 EP2935558 A2 EP 2935558A2 EP 13831821 A EP13831821 A EP 13831821A EP 2935558 A2 EP2935558 A2 EP 2935558A2
Authority
EP
European Patent Office
Prior art keywords
bioreactor
hydrogen
methane
gas
containing gas
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP13831821.7A
Other languages
German (de)
English (en)
Inventor
Ulrich Schmack
Doris Schmack
Monika Reuter
Hans Winter
Martina Beissinger
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Microbenergy GmbH
Original Assignee
Microbenergy GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Microbenergy GmbH filed Critical Microbenergy GmbH
Publication of EP2935558A2 publication Critical patent/EP2935558A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M21/00—Bioreactors or fermenters specially adapted for specific uses
    • C12M21/04—Bioreactors or fermenters specially adapted for specific uses for producing gas, e.g. biogas
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M23/00—Constructional details, e.g. recesses, hinges
    • C12M23/36—Means for collection or storage of gas; Gas holders
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M23/00—Constructional details, e.g. recesses, hinges
    • C12M23/40—Manifolds; Distribution pieces
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M29/00—Means for introduction, extraction or recirculation of materials, e.g. pumps
    • C12M29/06—Nozzles; Sprayers; Spargers; Diffusers
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M29/00—Means for introduction, extraction or recirculation of materials, e.g. pumps
    • C12M29/24—Recirculation of gas
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M29/00—Means for introduction, extraction or recirculation of materials, e.g. pumps
    • C12M29/26—Conditioning fluids entering or exiting the reaction vessel
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M41/00—Means for regulation, monitoring, measurement or control, e.g. flow regulation
    • C12M41/30—Means for regulation, monitoring, measurement or control, e.g. flow regulation of concentration
    • C12M41/34—Means for regulation, monitoring, measurement or control, e.g. flow regulation of concentration of gas
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M41/00—Means for regulation, monitoring, measurement or control, e.g. flow regulation
    • C12M41/48—Automatic or computerized control
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M43/00—Combinations of bioreactors or fermenters with other apparatus
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M43/00—Combinations of bioreactors or fermenters with other apparatus
    • C12M43/04—Bioreactors or fermenters combined with combustion devices or plants, e.g. for carbon dioxide removal
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M47/00—Means for after-treatment of the produced biomass or of the fermentation or metabolic products, e.g. storage of biomass
    • C12M47/12—Purification
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/30—Wastewater or sewage treatment systems using renewable energies
    • Y02W10/33—Wastewater or sewage treatment systems using renewable energies using wind energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/30—Wastewater or sewage treatment systems using renewable energies
    • Y02W10/37—Wastewater or sewage treatment systems using renewable energies using solar energy

Definitions

  • the invention relates to an energy conversion system.
  • renewable energies for power generation is currently gaining in importance.
  • the energy transition away from fossil fuels and nuclear energy to renewable energy sources calls for increased use of renewable energy sources for power generation such as wind power, solar energy, hydropower or geothermal energy.
  • renewable energy sources for power generation such as wind power, solar energy, hydropower or geothermal energy.
  • wind power and solar energy there are pronounced weather-related and daily and seasonal fluctuations in power generation.
  • wind turbines must be shut down in the event of strong wind to prevent overloading the power grids.
  • valuable capacity from renewable energy sources is not used.
  • cheaper surplus electricity could be provided in times when there is a surplus of electricity in connection with insufficient demand from the electricity consumers.
  • Regenerative hydrogen is produced by means of electrolysis using wind or solar power.
  • This regenerative hydrogen along with carbon dioxide derived from power plant exhaust gases, is converted into liquid or gaseous hydrocarbons in a modified Fischer-Tropsch process in a hydrogenation plant, either burned and emitted in power plants or used as fuel for vehicles.
  • WO 2010/1 15938 A1 an energy supply system is shown which converts regeneratively generated electricity from wind or solar energy partially via electrolysis into hydrogen, which is then reacted together with carbon dioxide in a methanation to methane.
  • the carbon dioxide comes either from power plant exhaust gases, from the air or from biomass.
  • separated C0 2 from a biogas plant or C0 2 -containing synthesis gas from the biomass gasification can be used.
  • the methane-containing gas synthesized synthetically by the use of catalysts is fed into a gas supply network via a gas supply device in the form of an additional or replacement gas.
  • 4,883,753 describes high-yield methane production in a continuous culture system as a bioreactor in which thermophilic methane bacteria of the species Methanobacterium thermoautotrophicum are used.
  • a high methane yield is achieved by a high gas input to H 2 and C0 2 is used, wherein the gas transfer rate is supported by very high stirring speeds in the fermenter.
  • WO 2008/094282 A1 describes a biological system for producing methane from hydrogen and carbon dioxide using a bacterial culture containing at least one type of methanogenic bacteria.
  • the carbon dioxide comes from an industrial process, while the hydrogen u.a. can be obtained by electrolysis using cheap excess current.
  • Higher methane yields are achieved by increased temperature, high stirring rates, high gas input, or special reactor types such as stratified or cascading reactors.
  • WO 201 1/000084 A1 also discloses a system for producing a methane-rich gas, in which the electrolysis of water is carried out with the formation of hydrogen and oxygen directly in a bioreactor containing electrochemically active anaerobic microorganisms. Anode and cathode are not separated by a membrane, so that the oxygen from the electrolysis is entered into the system.
  • WO 2012/1 10252 A1 discloses a system for storing electrical energy in the form of methane, which uses electricity from renewable and non-renewable energies for hydrogen production. The hydrogen is introduced together with carbon dioxide into a reactor containing methanogenic microorganisms which then produce methane.
  • US 3,383,309 describes a process for improved sewage sludge degradation.
  • fatty acid-containing organic wastes are better degraded when a portion of the resulting methane-containing fermentation gas is converted by gas reforming into hydrogen and carbon monoxide and then the hydrogen-containing gas thus formed is recirculated into the anaerobic fermenter for digester gas formation.
  • the invention is based on the object of providing an energy conversion system which allows excess electricity, which can not be fed into the grid, to be converted into a chemical energy carrier which can be temporarily stored.
  • bio-methane gas produced in the bioreactor biological gas produced in the bioreactor
  • biomethane biological gas
  • biogas biological gas produced in the bioreactor
  • electrolysis unit biologically treated sewage treatment plant
  • electrolysis system biologically treated sewage treatment plant
  • the present invention provides an energy conversion system.
  • the energy conversion system comprises an electrolysis unit for the electrochemical generation of hydrogen and oxygen from water, a connection to the public power grid for supplying the electrolysis unit with electrical energy, an anaerobic bioreactor of a sewage treatment plant, wherein the bioreactor comprises a discharge device for the removal of a methane-containing gas produced in the bioreactor, a supply device for the supply of electrochemically generated in the electrolysis unit hydrogen in the anaerobic bioreactor of the sewage treatment plant, a control unit for Control and regulation of the supply of hydrogen in the anaerobic bioreactor of the treatment plant and for controlling and regulating the removal of the methane-containing gas produced in the bioreactor and a device for utilization and / or storage of the withdrawn from the bioreactor methane-containing gas.
  • the energy conversion system according to the invention may comprise one or more control units.
  • the control and regulation of the supply of hydrogen and the control and regulation of the removal of the methane-containing gas produced in the bioreactor of the sewage treatment plant can thus be carried out by a single control and regulation unit or by two separate control and regulating units.
  • the present invention also includes a method of converting energy with the steps
  • one or more control and regulation units can be used in the method according to the invention.
  • the control and regulation of the supply of hydrogen and the control and regulation of the removal of the methane-containing gas produced in the bioreactor of the sewage treatment plant can thus be carried out by a single control and regulation unit or by two separate control and regulating units.
  • the energy conversion system according to the present invention is based on a special embodiment of the "power to gas" technology.
  • an electrolysis device for generating hydrogen and oxygen from water
  • an anaerobic bioreactor of a sewage treatment plant for the production of methane-containing gas with an outlet for the biomethane-containing gas produced in the bioreactor
  • a return device for the return of carbon dioxide into the bioreactor of a sewage treatment plant if appropriate, a return device for the return of carbon dioxide into the bioreactor of a sewage treatment plant
  • a distribution device for the fine distribution of H 2 optionally a distribution device for the fine distribution of H 2 , a device for utilization and / or storage of the biomethane-containing gas produced in the bioreactor,
  • a control and regulating device for controlling and regulating the gas flows into the reactor and the gas flow from the reactor.
  • the energy conversion system according to the invention can efficiently use the unused power surplus capacity due to fluctuations in electricity production and electricity demand at times when cheap surplus electricity is available on the market to form methane-rich gas of hydrogen and carbon dioxide, which then serves as a chemical energy source or temporary storage.
  • the present invention shows a way of forming additional methane from favorable current present on the electricity market at certain times via the intermediate stage of conversion into hydrogen in the anaerobic bioreactor of a sewage treatment plant using the microorganisms already present there, in order to fluctuate a usage of this to reach accumulating excess current and even to decrease negative control energy.
  • the production of additional methane by way of biological methanation is integrated directly into a sewage treatment plant or wastewater treatment plant
  • the existing infrastructure of a sewage treatment plant can be widely used, so that only a few additional devices such as the electrolyser or the hydrogen injection must be added to the system.
  • a carbon dioxide source for biological methanation In the biogas produced under conventional conditions, there is already sufficient residual CO 2 (about 20 to 45% of the digester gas volume) available that can be used for the formation of additional methane, the carbon dioxide for the biol Ogic methanation thus comes, in contrast to the physically technical catalytic process, but also to biological processes that work with cultures of hydrogenotrophic methanogenic bacteria, directly from the energy conversion system itself and does not need to be supplied externally.
  • Boundary conditions are, in particular, electricity prices and the availability of cheap surplus electricity, the difference in electricity prices from renewable sources compared to conventional electricity sources, the price of natural gas and the prices and technical development of electrolysis systems.
  • an electrolyzer which produces the hydrogen for introduction into the anaerobic reactor of the sewage treatment plant, only electricity is used which can be obtained at a lower price than the current electricity market price.
  • Suitable for this is electricity that is produced in the market as surplus electricity, especially if from the renewable energy sources wind power or solar power can not be fed into the grid due to overload of the power grid.
  • the fluctuating current sources would alternatively have to be regulated, so that the excess current would be lost.
  • Negative balancing power becomes necessary when the electricity load, ie the electricity demand in the electricity grid, is lower than predicted by the grid operators, so that there is a risk of grid instability.
  • the participant In order to be able to participate in the control energy market, the participant must provide a certain power (currently 5 MW), with which he can take power from the grid. Since the participants in the control energy market can join forces, the individual participant does not necessarily have to guarantee a power reduction of 5 MW.
  • the transmission system operator provides power data every fifteen minutes for the secondary control energy market.
  • the provision of negative control power with a maximum activation time of 5 minutes (secondary control) will be paid to the pantograph in excess of the service price. Since the working price for the actually retrieved electricity is very low or costs nothing at all, and may even be remunerated extra, this also results in a source of cheap electricity, for which there is otherwise no demand in the electricity grid.
  • any stream suitable for use in the process according to the invention is not demanded at the respective time in the power grid and is therefore suitable for storage in a "power to gas" process Electricity available when there is a current over-capacity in the public power grid
  • the power conversion system must have a connection to the power grid and advantageously have a network regulator, which branches off in accordance with power from the grid at times in which favorable electricity, in particular surplus electricity from renewable energy sources or from the need for negative control power available.
  • the energy conversion system has an electrolyzer, which is not part of a conventional sewage treatment plant.
  • electrolysis systems are known from the prior art.
  • electrolysers which operate on the principle of alkaline electrolysis or with a polymer electrolyte membrane (PEM electrolysis). Since the power for the electrolysis is discontinuously available, in particular electrolysers are suitable, which have short response times for hydrogen production and possibly low costs in standby mode.
  • Electrolyzers suitable for the process according to the invention are those in which the hydrogen produced is produced under pressure, since this has a positive effect on the directly subsequent introduction of the hydrogen into the anaerobic bioreactor. Preference is given to systems which operate at a pressure of 0 to 30 bar.
  • the dimensioning of the electrolysis system depends on the size of the existing anaerobic bioreactor of the sewage treatment plant.
  • the methane-containing sewage gas from the digester of the sewage treatment plant consists of about 20 to 45% of carbon dioxide, which can be converted with the electrolytically produced hydrogen in the digester by biological methanation to biomethane.
  • the maximum necessary rate of hydrogen production (m 3 / h ⁇ 1 ) is calculated from the production of sewage gas (m 3 / h ⁇ 1 ) multiplied by the proportion of carbon dioxide in the sewage gas and a factor of 4 for the reaction equation for the conversion of H 2 and C0 2 to CH 4 (GI.1).
  • the electrolysis power can be chosen correspondingly lower. Since common electrolysis systems operate with an efficiency of about 70 - 80%, the waste heat generated during the electrolysis operation can be used by the anaerobic bioreactor of the sewage treatment plant, for example via a Heat exchanger for heating the digested sludge is supplied.
  • the oxygen obtained in the electrolysis of water can be used to provide for the utilization of the biomethane-containing gas for improved combustion of the gas in a CHP or other gas burner, or the oxygen is released into the atmosphere.
  • the requirements on the quality of the hydrogen produced are significantly lower in the process according to the invention than, for example, in the production of hydrogen for a catalytic methanization for the production of synthetic methane or for use in fuel cells, but also for methane production with culture systems of methanogenic microorganisms, so here cheaper electrolysis systems can be used.
  • the generated hydrogen for biological methanation in a digester may contain both moisture and small amounts of oxygen, for example less than 2%, or other trace gases.
  • the hydrogen introduced here contains no carbon monoxide, which would inhibit the methane synthesis by the methanogenic microorganisms.
  • the power supply system optionally has a buffer for the electrolytically generated hydrogen.
  • the dimensioning of the electrolysis system should be chosen so that no more H 2 is produced than in the digestion tower with the residual C0 2 present can be converted by the microorganisms to biomethane.
  • the utilization of the methane-containing biogas produced takes place in the form of a gas feed into the gas network, this may only contain a small proportion of H 2 , currently about 5%. In this scenario, it may also be beneficial to cache additionally produced hydrogen locally.
  • Common hydrogen storage systems are known systems from the prior art, such as compressed gas cylinders, liquid gas storage or metal hydride storage.
  • a central component of the energy conversion system according to the invention is an anaerobic bioreactor of a sewage treatment plant for the production of methane-containing gas or a digestion tower.
  • Digesters of sewage treatment plants are usually egg-shaped containers with dimensions up to 50 m in height and a volume of several thousand m 3 .
  • Devices connected to the digester are a digested sludge feed with a corresponding pump, a heating device for heating the digested sludge, optionally a recirculation or ring line for circulating the digested sludge, a discharge line for digested sludge, a floating sludge discharge and a foam destroyer in the upper part of the digester.
  • Digesters have a device for discharging the produced methane-containing fermentation gas.
  • digested sludge which consists of the primary sludge or primary sludge, which originates from the primary clarifier and the excess sludge, which comes from the aerobic activated sludge tank or the secondary clarifier.
  • This mixture of excess sludge and primary sludge is also called raw sludge.
  • the digestion towers are not completely filled with digested sludge, so that there is a volume of biogas above the digested sludge.
  • Digester gas from anaerobic methane formation in a digester usually contains 55 to 80% methane and is formed at a moderate temperature in the range of 25 ° C to 45 ° C. The remaining portion is carbon dioxide and small amounts of hydrogen sulfide and hydrogen.
  • the process according to the present invention works well at the moderate temperatures that already prevail in sewage treatment plants.
  • the previously unused amount of carbon dioxide in the digester gas is used as a carbon source for the biological methanation with the help of electrolytically generated hydrogen, which is generated in the availability of cheap excess flow through an electrolyzer and then introduced into the digester.
  • electrolytically generated hydrogen which is generated in the availability of cheap excess flow through an electrolyzer and then introduced into the digester.
  • the complete carbon dioxide in the digester gas can be converted to methane, so that in the optimal case practically pure methane gas is produced.
  • the method according to the present invention more methane is produced in total and less carbon dioxide is formed than is normally present in the digester gas of a conventional sewage treatment plant.
  • the residual hydrogen present is not lost energy, but can also be used in a suitable utilization of the resulting methane-containing biogas.
  • the hydrogen is generated from electricity which can not otherwise be fed into the grid, any increase in the methane content in the digester gas produced is advantageous for the chemical storage of electrical energy, even if portions of hydrogen or carbon dioxide remain in the biomethane-containing gas so produced.
  • the anaerobic bioreactor of the treatment plant has a discharge device for the methane-containing biogas formed.
  • This discharge device is located in the gas space of the reactor above the digested sludge in the upper part of the bioreactor. In a preferred embodiment, it is a pipeline which can be shut off by means of a valve.
  • measuring devices for the composition of the methane-containing biogas formed in particular measuring devices for measuring the content of CH 4 , C0 2 , H 2 , 0 2 , N 2 and H 2 S.
  • the content of N 2 and H 2 S is not relevant for the control and regulation of the gas flows, it is preferably to measuring devices for determining the content of CH 4 and / or C0 2 and / or H 2 and / or 0 2.
  • the measurement of the oxygen content is safety relevant because of Explosion limits of hydrogen / oxygen mixtures, but also to control an anaerobic atmosphere for biological methanation.
  • the discharge device has measuring devices for determining the Amount of withdrawn methane-containing gas, such as gas meters or Gas Wegmess Erasmus.
  • An essential component of the energy conversion system according to the invention in a modification of a conventional sewage treatment plant is a supply device for the supply of hydrogen in the anaerobic bioreactor of the sewage treatment plant.
  • This supply device connects the output for the hydrogen formed by the electrolyzer with the hydrogen inlet in the anaerobic bioreactor of the sewage treatment plant.
  • the supply device is a gas line capable of receiving hydrogen at the pressure at which it is provided by the electrolyzer.
  • the feeding device enters the anaerobic bioreactor in such a way that the supplied hydrogen is introduced directly into the digested sludge, ie preferably in the lower part of the digester.
  • the supplied hydrogen is distributed as finely as possible by a corresponding fine distribution system on the feeder in order to achieve a good gas-to-liquid transfer, which A prerequisite for the most complete implementation of the hydrogen by the methanogenic microorganisms is.
  • the prior art discloses various systems for introducing gas, such as nozzles, sprinklers or injection pipes, static mixing systems, injectors, pressure-relief systems, perforated hoses or two-dimensional components, cartridges, frits, plates or components of sintered materials or membranes ,
  • gas such as nozzles, sprinklers or injection pipes, static mixing systems, injectors, pressure-relief systems, perforated hoses or two-dimensional components, cartridges, frits, plates or components of sintered materials or membranes .
  • the electrolytic hydrogen delivery device is not directly connected to the anaerobic bioreactor, but the hydrogen is introduced through a suitable delivery system into a raw slurry feed line which is transported into the anaerobic bioreactor.
  • the feed line for the raw sludge is a pressure line and the raw sludge is introduced into the anaerobic bioreactor via a pumping system.
  • the hydrogen introduction system is, in particular, a multiphase pump, a static mixer or, more preferably, a dynamic mixer.
  • a filter device for coarse impurities can be connected upstream.
  • the hydrogen introduction system is housed in a gassing container and the hydrogen is introduced in a bypass to the supply line for raw sludge, since the hydrogen to be introduced is not continuously available.
  • the bypass for the introduction of hydrogen is preferably released via controllable valves for a raw sludge feed into the digestion tower as soon as hydrogen is available for the introduction.
  • the energy conversion system according to the invention uses the carbon dioxide which is present within the system of the sewage treatment plant and which is not converted to methane in conventional operation. Thus, no external carbon dioxide is added to the digester for methanation. Since the method according to the invention only uses excess flow for the hydrogen production and subsequent methanation, which is not continuously available, it is not possible at least temporarily during operation of the system to completely reduce the carbon dioxide content of the resulting methane-containing biogas. Depending on the utilization of the resulting methane-containing biogas, the C0 2 portion must be partially removed, so that within the energy conversion system, a carbon dioxide gas is obtained, which can be used for further biological methanation with hydrogen.
  • the methane content must be at least 95%, so that existing carbon dioxide must be removed before the gas feed in a gas treatment plant. This carbon dioxide can be recycled within the system in the digester, so that it can be methanized together with supplied hydrogen.
  • a recovery of the methane-containing biogas for example via a cogeneration unit (CHP) instead, where it comes to the conversion of the gas into electricity and heat, a proportion of residual carbon dioxide is not critical. In times when there is an excess of electricity in the grid, the CHP can not feed in electricity; At the same time, however, surplus electricity is available for water electrolysis. If the methane-containing biogas is not used for the energy requirements within the energy supply system, it is favorable in this scenario to temporarily store the methane and carbon dioxide-containing biogas in a gas storage or returned to the fermenter instead of directly using the CHP, so that it at certain times comes to a recirculation of carbon dioxide or carbon dioxide-containing gas in the digester of the sewage treatment plant.
  • CHP cogeneration unit
  • the C0 2 -containing exhaust gas which is produced in the CHP or in a gas burner, within the energy conversion system be returned to the digester for biological methanation.
  • the carbon dioxide or carbon dioxide gas recirculation device is a pipeline with a port which introduces the appropriate gas into the bioreactor of the treatment plant.
  • the connection is preferably located in the region of the digester, in which the digested sludge is located, ie in the lower area.
  • the return device relates the carbon dioxide or carbon dioxide-containing gas in preferred embodiments, for example, from the biogas upgrading plant, from the line for methane-containing biogas, from the exhaust gas of the CHP or from a possible memory.
  • the return device for the return of carbon dioxide or carbon dioxide - containing gas into the bioreactor of a sewage treatment plant is equipped with valves which control the gas flow both at the connection to the bioreactor and at the C0 2 source.
  • Gas meters, gas analyzers and an appropriate control and control device control the gas flow for the carbon dioxide-containing gas.
  • a corresponding device for utilizing and / or storing the methane-containing biogas produced in this way which contains at least a portion of methane which reacts to the reaction of electrolysis hydrogen with residual sludge contained in the digested sludge, forms part of the energy conversion system according to the invention.
  • C0 2 goes back.
  • all recycling and / or storage facilities from the prior art are suitable, which can use the resulting from excess flow additionally produced biomethane.
  • certain embodiments for recovery appear particularly suitable.
  • the methane-containing biogas produced according to the invention is processed so that it can be stored directly in the natural gas network.
  • a natural gas methane-containing biogas is fed into the natural gas grid as a substitute gas for natural gas, the so-called SNG gas (synthetic or substitute natural gas).
  • SNG gas synthetic or substitute natural gas
  • This is particularly suitable for larger sewage treatment plants with a biogas production from about 250 m 3 per hour in question.
  • the surplus stream used for the electrolysis of water is completely converted into combustible gas, that is to say into a chemical energy store, which can then be stored in the existing natural gas network and thus uses the existing infrastructure of the gas network as storage.
  • the biomethane-containing gas must meet certain requirements, which are based on the respectively applicable feed-in guidelines (eg DVGW worksheets G260 and G262 in Germany), such as a methane content of more than 95% and a hydrogen content of less than 5%.
  • methane-containing gas can be generated that meets these requirements.
  • devices for biogas treatment and subsequent gas conditioning eg calorific value adjustment
  • the separated carbon dioxide from the biogas treatment can optionally be returned to the methanation in the anaerobic bioreactor.
  • the produced methane-containing biogas is burned within the energy conversion system for energy.
  • gas engines, gas turbines or micro gas turbines or gas burners are suitable.
  • Particularly suitable is their use in plants with combined heat and power, which simultaneously generate electricity and heat such as a combined heat and power plant (CHP). Since the requirements for the gas quality are significantly lower than for feeding into the natural gas grid, a complex biogas treatment, in particular the C0 2 separation, is generally unnecessary.
  • the methane-containing biogas formed according to the process of the present invention contains Less to no C0 2 , but more methane, so that the calorific value during combustion is significantly greater, so more electricity and heat can be generated.
  • the additional energy gain from increased methane production and possibly additional hydrogen can reduce the external energy consumption of a wastewater treatment plant.
  • the excess stream used for the electrolysis of water is intermediately converted into a biogas with an increased methane content, that is, into a chemical energy store.
  • the fact that the gas is consumed within the system again, the return power in this case is disconnected from the mains, so it can be done at any time independently.
  • the electricity additionally generated from the methane formed with the addition of hydrogen and the additionally generated heat can be used externally.
  • the generated heat can be used for nearby external consumers (eg commercial users, public infrastructure such as swimming pools) or fed into a district heating network.
  • the generated power can be fed into the power grid in a suitable manner. For the current share, this is in principle a reconversion of the excess current used.
  • the power from the reconversion is preferably fed into the power grid when there is an increased power demand and thus favorable electricity market conditions, for example when retrieving positive control energy in the event of an unforeseen increased power load.
  • the power supply is controlled by a network controller.
  • the energy conversion system is designed to use excess flow for hydrogen synthesis as well as biological methanation of the hydrogen thus produced in a wastewater treatment plant. Therefore, the power conversion system must have appropriate control devices to operate efficiently. Particularly suitable for this purpose are computer-aided control devices from the state of the art.
  • Central control variable for the control and regulation of the plant is the gas composition of the methane-containing biogas formed in the anaerobic bioreactor in conjunction with the amount of methane-containing biogas produced.
  • In the area of the biogas outlet from the anaerobic bioreactor there are appropriate measuring devices for the composition of the methane-containing biogas formed, in particular for measuring the content of CH 4 , C0 2 , H 2 , 0 2 , N 2 and H 2 S.
  • the discharge device has measuring devices for determining the amount of methane-containing gas produced, such as gas meters or gas flow meters.
  • the inventively provided (s) one (or more) control and regulation unit (s) provides for a reduction of the C0 2 content of the digester gas or for a complete methanation of the internal system residual C0 2 with H 2 and thus over a conventional Wastewater treatment plant for an increased methane production rate.
  • a primary controlled variable in this system is the C0 2 content of methane-containing biogas.
  • the amount of hydrogen supply to the anaerobic bioreactor is optionally limited by the fact that not enough hydrogen can be formed with the aid of the electrolyzer, because there is not enough surplus electricity from the power grid, which is regulated by a mains regulator.
  • hydrogen may be resorted to for methanation, which has been cached in the energy supply system in times when excess hydrogen has been produced.
  • the H 2 content in the starting gas from the anaerobic bioreactor As a second controlled variable in addition to the C0 2 content of the methane-containing biogas, the H 2 content in the starting gas from the anaerobic bioreactor. The largest possible proportion of this hydrogen is to be converted into methane together with the internal C0 2 , which then serves as a chemical energy carrier or buffer.
  • a certain proportion of hydrogen can be tolerated in the produced methane-containing biogas or can be usefully recycled. Depending on the further utilization of the methane-containing biogas, this proportion may be greater (eg in the case of utilization in the CHP plant) or smaller (eg in the case of direct gas feed-in). If the proportion of H 2 in the produced methane-containing biogas is too high, there is a negative feedback on the hydrogen production rate in the electrolyzer or a proportion of the hydrogen produced is not introduced into the anaerobic bioreactor, but intermediately stored.
  • the methane content of the methane-containing biogas produced is not exclusive in this system as a controlled variable, since a 4-fold molar excess of hydrogen is advantageously used for the methanation of C0 2 with H 2 on the basis of the chemical reaction equation. If the hydrogen is only converted into methane to a certain extent, there is a volume of residual hydrogen in the starting gas in terms of volume that, if appropriate, the proportion of methane decreases numerically, although in total more methane was produced. The total amount of methane produced is then calculated from the proportion of methane in connection with the total amount of biogas, which is determined by gas meters or gas flow meters.
  • H 2 recovery from the separated gas from the biogas upgrading makes sense, if sufficient H 2 is available from surplus stream.
  • H 2 -containing biogas can be recirculated before being recycled into the fermenter.
  • For the utilization of the methane-containing biogas in a CHP with reconversion and feeding the stream into the power grid is an additional regulation via the mains regulator in the power supply in the sense that preferably only current is fed when it is needed. Otherwise, the methane-containing biogas is not utilized in the cogeneration unit, but temporarily stored.
  • Fig. 1 An energy conversion system with supply of hydrogen in one
  • Fig. 2 An energy conversion system with supply of hydrogen in one
  • FIGS. 3A, 3B plots the gas formation rates and the space load of a hydrogen utilization with sewage sludge samples in a continuous experimental fermenter.
  • Fig. 4A, 4B plot the gas composition of the formed methane-containing
  • Wastewater treatment plant in the methanation of supplied hydrogen.
  • FIG. 1 shows by way of example an energy conversion system with supply of hydrogen into a digestion tower of a sewage treatment plant and subsequent utilization of the resulting methane-containing gas by gas direct injection into the natural gas grid.
  • From the power grid 1 is provided via a power regulator 2 via the power supply 3 of the electrolysis device 4 each current for water hydrolysis available when the power grid excess current is available, which can be obtained at low prices.
  • the hydrogen produced in the electrolysis device 4 is supplied via the hydrogen supply line 5 completely or proportionately into the anaerobic bioreactor 6 of the sewage treatment plant in the sewage sludge area via a fine distribution system or stored in a hydrogen storage 7.
  • the quantitative supply of hydrogen is by appropriate Shut-off valves and a three-way valve regulated.
  • the waste heat of the electrolyzer 4 is fed via a heat exchanger 8 to the anaerobic bioreactor 6 for heating the sewage sludge.
  • the biogas line 9 leads via a valve to the biogas upgrading device 12.
  • the measuring devices 10 for analyzing the gas quality and the amount of gas produced methane-containing biogas and a control and regulating device 1 1 , This regulates the hydrogen flow into the anaerobic bioreactor via the electrolysis device 4 and the hydrogen storage 7 on the basis of the results of the measuring devices and the specifications for controlling the gas quality.
  • the biogas treatment 12 is regulated and optionally introduced via the line for carbon dioxide recirculation 13 in biogas processing and separated from the biogas C0 2 introduced into the anaerobic bioreactor 6 in the sewage sludge, so that it is available for further methanation , If the gas quality is already sufficiently good for direct injection as substitute gas, so that it is possible to dispense with biogas upgrading, the control and regulating device 11 can control a bypass to the biogas upgrading via a further biogas line (not shown).
  • the biogas produced can also be fed back into the anaerobic bioreactor via a further biogas line 14 before it is fed into the biogas upgrading 12, ie it can be recirculated.
  • Treated biogas from the biogas upgrading 12 is supplied via a further gas line 15 of the biogas conditioning device 16.
  • Figure 2 shows an energy conversion system with supply of hydrogen in a digester of a sewage treatment plant and subsequent recovery of the resulting methane-containing gas in a device for combined heat and power such a CHP.
  • From the power grid 1 is provided via a power regulator 2 via the power supply 3 of the electrolysis device 4 each current for water hydrolysis available when the power grid excess current is available, which can be obtained at low prices.
  • the hydrogen produced in the electrolysis device 4 is supplied via the hydrogen supply line 5 into the anaerobic bioreactor 6 of the sewage treatment plant in the region of the sewage sludge.
  • the quantitative supply of hydrogen is regulated by the hydrogen production from the electrolyzer 4.
  • the waste heat of the electrolyzer 4 is fed via a heat exchanger 8 to the anaerobic bioreactor 6 for heating the sewage sludge.
  • In the digested sludge area is a device for removing the digestate in a fermentation residue storage 23, in which the digestate drying takes place.
  • the biogas line 9 leads via a valve to a biogas storage 24 and from there into a CHP 25 as a gas utilization device.
  • the measuring devices 10 Arranged between the biogas outlet on the digester and the CHP are the measuring devices 10 for analyzing the gas quality and the amount of gas produced by the methane-containing biogas and a control and regulating device 11. This regulates the hydrogen flow into the anaerobic bioreactor 6 via the electrolysis device 4 on the basis of the results of the measuring devices and the specifications for controlling the gas quality.
  • the biogas utilization in the CHP 25 is regulated on the basis of the measurement results and, if appropriate, C0 2 deficiency in the fermenter via the gas line 26 carbon dioxide from the exhaust gas of the CHP in the anaerobic bioreactor 6 in the sewage sludge introduced so that it is available for further methanation. Otherwise, the exhaust gas is released via the line 27.
  • the biogas produced can also be fed back into the anaerobic bioreactor before being fed into the biogas storage 24 via a further biogas line 14, ie be recirculated, for example if there is a high residual hydrogen content, but the electrolyzer simultaneously produces little or no hydrogen.
  • the gas composition in the biogas storage 24 of the gas composition of each currently discharged from the digester via the biogas line 9 gas may differ, it makes sense to install at the biogas outlet of the biogas storage 24 more gas measuring devices (not shown).
  • the utilization of methane-containing biogas in CHP 25 produces both electricity and heat.
  • the produced stream can be used within the sewage treatment plant via the line 29, for example, for the ventilation of the aerobic activated sludge basin 19 via compressed air pumps. Excess sludge from the activated sludge tank 19 is fed via the line 20 to the digester. In addition to using the electricity produced within the treatment plant this can also be fed into the power grid 1.
  • a grid controller 2 regulates the power supply, so that is fed only at times when this is economically viable.
  • the heat produced in the CHP can be used via the line 28 preferably within the sewage treatment plant. Via heat exchangers 21, the thermal energy can be supplied to the anaerobic bioreactor, via heat exchangers 22, for example, to the plant for drying fermentation residue 23.
  • Example 1 Batch tests for hydrogen utilization with sewage sludge samples
  • the experimental batches contained either pure hydrogen as gas or a H 2 / C0 2 gas mixture in the volume ratio 4: 1.
  • the hydrogen was replaced by nitrogen.
  • the serum bottles with the sewage sludge samples were incubated for 1 to 3 days at 37 ° C until either no overpressure was measurable or almost constant pressure was reached, so that practically no gas was reacted.
  • 50 ml of gas were taken from the serum bottle with the aid of a syringe and the gas composition in the gas chromatograph was analyzed. Table 1 summarizes the results of this gas measurement.
  • Table 1 Batch tests for hydrogen utilization with sewage sludge samples
  • the metered addition of hydrogen into the digester would be increased and / or throttled the C0 2 return, so that the least possible residual carbon dioxide contained in the produced biogas.
  • the experiments showed that sewage sludge is suitable to convert added hydrogen by biological methanation using the microorganisms contained therein to methane and that it is in principle possible to completely convert existing C0 2 and completely convert added hydrogen into methane.
  • Example 2 Hydrogen utilization with sewage sludge samples in a continuous experimental fermenter
  • Self-built stainless steel fermenters with a total volume of 5.2 l were used for the experiments.
  • 5 l of sewage sludge was initially introduced into the anaerobic fermenters.
  • 250 ml of excess sludge with an OTS content of between 2.2 and 2.8% were added daily through a closable opening at the upper end of the fermenter and a corresponding amount of 250 ml of fermentation substrate was discharged at the lower end of the fermenter, so that a mean residence time for the fermentation substrate of 20 days.
  • the fermenters were operated at a temperature of 39-40 ° C.
  • the H 2 gas was supplied via an open fumigation tube, which introduced the hydrogen directly into the fermentation substrate at the bottom of the fermenter.
  • the gas was metered from a hydrogen cylinder via a mass flow device (Wagner), in which the gas flow in l / h was set.
  • a Milligascounter (Ritter) was used to measure the amount of H 2 gas introduced.
  • At the At the top of the fermenter was the biogas outlet for the methane-containing biogas.
  • the produced biogas was introduced into a gas-tight gas bag and collected here until a sufficiently large amount of gas (4 I) had accumulated to determine the gas composition of the biogas produced in a gas analyzer (Awite).
  • the amount of biogas production in the fermenter was also determined via the gas outlet using a Milligascounter (Ritter).
  • Figures 3A and 4A respectively show the fermenter in which H 2 has been added
  • Figures 3B and 4B show the control fermenters without H 2 addition, respectively.
  • Figures 3A and 3B show on the right axis respectively the volume load of the fermenter with sewage sludge (reference numeral 31).
  • the fermenter with H 2 addition had an average volume load of 1.25 kgoTS / m 3 d
  • the control fermenter an average volume load of 1.19 kgoTS / m 3 d.
  • Reference numeral 32 refers to the amount of gas formed methane-containing biogas
  • reference numeral 33 to the amount of methane gas formed.
  • the fermenter with H 2 feed had on average a biogas formation rate of 1.97 Nl / d, while the control fermenter formed an average of 1.18 Nl / d of biogas.
  • the fermenter with H 2 feed thus formed on average 82% more methane-containing biogas than the control fermenter, this biogas also contains a proportion of unreacted hydrogen, as shown in Figure 4A can be seen.
  • the methane formation rate of the H 2 feed fermenter was 0.9 Nl / d on average, while that of the control fermenter was 0.7 Nl / d on average.
  • the fermenter with H 2 supply about 29% more Methane produces as the control fermenter, meaning that added hydrogen is converted by the microorganisms in the sewage sludge with the existing carbon dioxide into methane.
  • the line labeled 34 in FIG. 3A indicates the supply of H 2 to the fermenter. An average of 1, 76 IH 2 per day was introduced into the fermenter.
  • FIGS. 4A and 4B show the result of the gas analysis of the respectively formed methane-containing biogas in percent of the measured total gas.
  • Reference numeral 41 refers to the methane content
  • reference numeral 42 to the carbon dioxide content
  • reference numeral 43 in Figure 4A to the hydrogen content in the product gas derived from unreacted hydrogen in the experimental fermenter. Due to the relatively low gas formation rates, only about every 2 to 3 days a gas analysis could be carried out, since the gas analyzer presupposed an accumulated amount of gas of about 4 l. In the fermenter with H 2 supply, the residual hydrogen content in the biogas formed averaged 18.8%, the content of methane on average 45.7% and the content of unreacted carbon dioxide 10.7%.
  • the methane content in the biogas was on average 55.0% and the content of carbon dioxide 24.2%. From the measurement of the hydrogen addition in the fermenter and the amount and composition of the gas formed in the fermenter according to the invention could be calculated that on average 63% of the added hydrogen were converted into methane. This corresponds approximately to the measured methane formation rates from FIG. 3.
  • the methane formation rates of 0.9 Nl / d for the fermenter with H 2 supply and of 0.7 Nl / d for the control without H 2 supply correspond to converted to methane formation rates per liter of fermenter volume in each case 0.18 Nl / Id or 0.14 Nl / Id.
  • the fermenter with H 2 supply has a methane yield of 0.04 Nl / dd.
  • the H 2 addition to the fermenter averaged 1.76 l per day, ie 0.35 l per liter of fermenter volume.
  • this should result in a maximum methane yield of 0.09 Nl / d under complete methanation of the hydrogen.
  • a methane yield of 0.04 Nl / Id would correspond to 45% conversion of the introduced hydrogen. Due to the overall small Gas formation rates and the corresponding inaccuracies in the gas analysis, these deviations seem plausible.
  • FIG. 5 shows, by way of example, an energy conversion system with alternative supply of hydrogen to a digester of a sewage treatment plant and subsequent utilization of the resulting methane-containing gas by direct gas injection into the natural gas grid.
  • the illustrated alternative delivery device for introducing the hydrogen into the sewage sludge operates in an analogous manner for an energy conversion system with subsequent utilization of the resulting methane-containing gas in a cogeneration device as shown in FIG.
  • the hydrogen introduction of the hydrogen produced in the electrolyzer 4 via the hydrogen supply line 5 is not directly into the anaerobic bioreactor 6 of the sewage treatment plant, but via a hydrogen injection system 44, the a bypass pipe 45 to sewage sludge line 20, which leads to the anaerobic bioreactor 6, is installed.
  • the sewage sludge line 20 raw sludge is pumped into the anaerobic bioreactor 6, which is fed from a reservoir for excess sludge 46 and a reservoir for primary sludge 47.
  • a static mixer, a multi-phase pump, and especially a dynamic mixer is suitable.
  • a prefilter 48 is installed in the bypass pipe 45.
  • the bypass pipe 45 can be shut off by appropriate valves from the sewage sludge feed line 20 in the anaerobic bioreactor, if no hydrogen is introduced into the sewage sludge (valves not shown).
  • the valve control of the bypass pipe 45 is integrated into the control and regulation of the power conversion system, so that the bypass line 45 is released when hydrogen is to be introduced into the sewage sludge.
  • Example 3 Methanization of supplied hydrogen in the digester of a municipal wastewater treatment plant
  • an electrolyzer for the production of hydrogen with a maximum volume of 30 Nm 3 / h was installed at a municipal wastewater treatment plant.
  • the treatment plant has two digestion towers, each with a volume of 1300 m 3 , and produces a total of approx. 1500 m 3 of digester gas per day or approx. 750 m 3 of digester gas per digestion tower and day.
  • the produced fermentation gas usually has a methane content of about 60% and a carbon dioxide content of about 40%, so that about 450 m 3 of methane are produced per day and digester.
  • the fermentation gas quality should be improved via biological methanation of the electrolytic hydrogen together with the carbon dioxide present in the sewage gas or sewage sludge, so that overall a larger quantity of methane is produced per time.
  • the introduction of hydrogen was technically achieved in such a way that the hydrogen supply did not take place directly into the anaerobic bioreactor itself but through a feed line for the sewage sludge into the digester as in FIG. 5 shown.
  • a mixture of excess sludge and sewage sludge was introduced into the digestion towers as so-called raw sludge.
  • a bypass to this sewage sludge feed hydrogen was introduced into the sewage sludge in a gassing container, which then came together with the introduced hydrogen in the digester.
  • a delivery system for the hydrogen alternatively a static mixer, a dynamic mixer and a multiphase pump were used.
  • a particularly suitable hydrogen introduction system proved to be a dynamic mixer.
  • the gaseous phase hydrogen was introduced into the liquid phase digested sludge such that the two phases were swirled together using energy in rotating mixers.
  • a moderate overpressure can be achieved up to about 5 bar, which proved to be advantageous for the hydrogen input.
  • a relaxation of the medium to normal pressure takes place, so that microbubbles are produced from potentially existing gas bubbles, which in turn cause increased gas transfer into the sewage sludge.
  • the result of the hydrogen supply to the gas quality of the digester gas formed is shown in FIG.
  • the ordinate shows the measured gas qualities as a percentage of the total gas of the digested gas formed.
  • the gas quality was measured on-line with a gas analyzer (Emerson), which is indicated by the solid lines with the filled symbols, and by gas analyzes of gas samples of the methane-containing gas produced in the digester in a gas chromatograph
  • the methane content (circles), the carbon dioxide content (squares) and the hydrogen content (triangles) are plotted in Figure 6.
  • the abscissa represents the time for the hydrogen addition observation period.
  • the gas qualities measured in the exemplary embodiment thus show that the electrolytically produced hydrogen introduced in the anaerobic bioreactor of the sewage treatment plant was almost completely converted into biomethane in a biological methanation and accordingly a methane-containing biogas with a higher methane content and thus higher calorific value was produced.

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Abstract

L'invention concerne un système de conversion d'énergie ayant une unité d'électrolyse (4) pour la production électrochimique d'hydrogène et d'oxygène à partir d'eau, un raccordement au réseau électrique public (1) pour alimenter l'unité d'électrolyse (4) en énergie électrique, un bioréacteur anaérobie (6) d'une station de traitement des eaux usées, le bioréacteur (6) présentant un dispositif d'évacuation (9) pour le soutirage d'un gaz contenant du méthane, formé dans le bioréacteur, un dispositif d'alimentation (5) pour l'alimentation en hydrogène du bioréacteur anaérobie (6) de la station de traitement des eaux usées, une unité de commande et de régulation (11) pour commander et réguler l'alimentation en hydrogène du bioréacteur anaérobie (6) de la station de traitement des eaux usées et pour contrôler et réguler le soutirage du gaz contenant du méthane, formé dans le bioréacteur (6) et un dispositif d'utilisation (18) et/ou de stockage (24) du gaz contenant du méthane, soutiré à partir du bioréacteur.
EP13831821.7A 2012-12-21 2013-12-09 Système de conversion d'énergie Withdrawn EP2935558A2 (fr)

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