DE102010043630A1 - Method for increasing concentration of methane biogas, comprises supplying hydrogen and a liquid hydrolyzate in a methane level to a two-stage biogas process or supplying the hydrogen to a methane reactor above the hydrolyzate - Google Patents

Abstract

The method for increasing concentration of methane biogas from biogas plant, comprises supplying hydrogen and a liquid hydrolyzate in a methane level of a two-stage biogas process or supplying the hydrogen to a methane reactor (3) above the hydrolyzate, and diverting the hydrolyzate at the lower end of the methane reactor so that the methane reactor is dived into process technology in a lower column (32) flow throughable with hydrolyzate that represents the part of the methane reactor between inlet and outlet of the hydrolyzate and in an upper column (31). The method for increasing concentration of methane biogas from biogas plant, comprises supplying hydrogen and a liquid hydrolyzate in a methane level of a two-stage biogas process or supplying the hydrogen to a methane reactor (3) above the hydrolyzate, and diverting the hydrolyzate at the lower end of the methane reactor so that the methane reactor is dived into process technology in a lower column (32) flow throughable with hydrolyzate that represents the part of the methane reactor between inlet and outlet of the hydrolyzate and in an upper column (31), which represents the part of the methane reactor between gas supply and gas discharge. The lower column of the methane reactor contains immobilized acetotrophe methanogens, which are formed through the biogas from the hydrolyzate, and the upper column of the methane reactor contains suspended and/or immobilized hydrogenotrophic methanogens. The hydrogen is supplied at the lower end of the upper column in fine distribution and flows through upper column towards top. The biogas formed in the lower column is led into the upper column. The carbon dioxide present in the upper column with the hydrogen is converted to methane through suspended and/or immobilized hydrogenotrophic methanogens. The hydrogen supplied to the methane reactor is regained itself by ion exchange, electrolysis or chemical and biochemical reactions from the methane level. The hydrogen supplied to the methane reactor is regained from hydrolysis gas (2) of a mesophilic, thermophilic or hyper-thermophilic operated hydrolysis of the total biogenic feedstock or a fraction. The hydrogen and the carbon dioxide are supplied from hydrolysis gas so that the hydrogen in the resulting biogas is 3 vol.%. Independent claims are included for (1) a methane reactor for producing biogas; and (2) a biogas plant for two-stage production of biogas.

Description

The invention relates to a method, a plant and a methane reactor for increasing the methane concentration of the biogas from biogas plants.

The production of biogas from renewable raw materials, bioavailable waste and other input materials is carried out with the help of biogas plants in which microorganisms make a biochemical conversion of these substances into biogas, consisting of the main components methane and carbon dioxide.

The conversion of biodegradable substances (hereinafter referred to as biogenic substances) into biogas takes place via several biochemical steps, hydrolysis, acidogenesis, acetogenesis and methanogenesis.

In hydrolysis, water-soluble constituents are dissolved out of the biogenic substances and, as a result of several types of extracellular enzymes, non-water-soluble biogenic substances are decomposed into water-soluble, generally low molecular weight, substances. To accelerate certain degradation processes and so-called Fremdenzyme can be used. In the following acidogenesis, the substances dissolved in the hydrolysis are converted into lower organic acids, such as lower fatty acids and amino acids. In acetogenesis, the organic acids are converted to acetic acid to form CO ₂ . The products of acetogenesis are converted to methane in methanogenesis with the help of methane-forming bacteria (hereinafter called methanogens).

These processes take place in single-stage biogas plants in temporal and spatial juxtaposition. In two-stage procedures, the sub-steps of hydrolysis and acidogenesis (first stage) of the sub-steps acetogenesis and especially methanogenesis (second stage) are separated apparatus and process technology. As a result, a better controllability and a higher stability of the method are achieved. In common usage, the first stage of the two-stage biogas process is often referred to only as hydrolysis and the second stage as a methane stage. The hydrolysis takes place in the so-called hydrolysis reactor, the methanation in the methane reactor. The aqueous solution leaving the hydrolysis is commonly referred to as hydrolyzate. In the following, this simplistic language is also used.

In the hydrolysis reactor, the degradation of the biogenic substances to lower organic acids takes place to form a hydrolysis gas which contains hydrogen and carbon dioxide as main components. The thermal conditions of the hydrolysis in this case have a significant influence on the chemical composition of the hydrolysis gas. Thus, in thermophilic and hyperthermophilic conditions, an increased proportion of hydrogen in the hydrolysis gas is detected. The maximum formation of hydrogen can be observed after 1-3 days, this then falls again. The hydrolysis gas is usually removed from the process. A process-technical use of the hydrolysis gas is currently not carried out.

In the methane reactor, methanogenesis according to the current state of knowledge can take place in two ways, the acetotrophic and the hydrogenotrophic transformation. In the acetotrophic conversion, methane with carbon dioxide as a by-product is formed from acetic acid. In the hydrogenotrophic conversion, the formation of methane from hydrogen and carbon dioxide with water as a by-product takes place according to the following formula (1): 4H ₂ + CO ₂ → CH ₄ + 2H ₂ O (1)

Both processes take place in conventional single and multi-stage biogas plants without previously controllable preference in parallel. So far, it has been assumed that the majority of the resulting methane is formed by the acetotrophic conversion, and the hydrogenotrophic conversion accounts for only a small proportion of methane formation.

Both the acetotrophic conversion and the hydrogenotrophic conversion are carried out by a biocenosis of corresponding microorganisms, the acetotrophic methanogens or the hydrogenotrophic methanogens. Recently, it has been found that in the methane stage of two-stage plants there are large populations and a high diversity of such microorganisms that undergo the hydrogenotrophic transformation.

The concentration of the main energy carrier methane contained in the resulting biogas fluctuates between 45% and 70% for one-stage plants, depending on the type of feedstock. In two- and multi-stage plants, methane concentrations between 50% and 80% can be achieved.

These methane concentrations are suitable without subsequent process steps to increase the concentration of methane for the operation of gas engines or turbines. Depending on the required gas quality, however, higher methane concentrations are required for feeding into the gas network or for use as fuel.

According to the prior art, methane concentrations above 80% can not be obtained biologically in technical biogas plants be generated. Therefore, various chemical, physical or physicochemical methods are used to remove all or part of the carbon dioxide while minimizing methane losses. The carbon dioxide is then either released into the atmosphere or chemically bound. This can lead to the loss ("slippage") of a part of the methane. These methods are technically well established and have proven to be practical, but their application is associated with higher investment costs, a significant energy consumption and possibly a consumption of chemicals.

The optimization of the process for the formation of biogas with high methane concentrations on biological way is therefore also of high economic importance.

There are proposals known to provide the hydrogenotrophic bacterial conversion of carbon dioxide and hydrogen from external sources to biogas. In the patent JP 200-152 799 For this purpose, a gas mixture consisting of hydrogen and carbon monoxide, used from a pyrolysis.

According to the patent JP 06-169 783 Hydrogen is obtained by electrolysis and converted to methane with additionally supplied carbon dioxide. This methane is then burned and the resulting carbon dioxide is again converted together with the above-mentioned hydrogen to methane. However, this process becomes energetically meaningful only if recyclable products, such as corrinoids, are obtained.

In the patent FR 2 537 992 A1 Hydrogen is fed to a one-stage, discontinuous fermenter. There was an increase in methane production, which stabilized after about 40 hours. However, the described process can not be applied in a continuous biogas process, since the increased hydrogen partial pressure inhibits the conversion of propionic acid into acetic acid and thus prevents the acetotrophic conversion.

The patent US 3,383,309 A describes a discontinuous biogas process (digested digester) into which hydrogen is introduced. This hydrogen is obtained from the biogas produced by a reformer, but can alternatively come from external sources. The purpose of this hydrogen feed is to increase the activity of the methane-forming microorganisms to significantly shorten the residence time of the digested sludge. The supply of hydrogen and the associated energy yield provides the necessary energy for the degradation of the organic acids. An increase in the methane yield or the methane concentration is not provided and according to current knowledge, the patent was filed in 1964, with this process also not possible.

The patent US 4 696 746 B1 describes a methane production process with higher efficiency and methane yield. The methane production is operated in two independent methane reactors, methane reactor I for the acetotrophic conversion ("methane phase I") and methane reactor II for the hydrogenotrophic conversion ("methane phase II"). In the methane reactor I, the liquid hydrolyzate is fed and converted to biogas. In the methane reactor II, the hydrolysis gas is introduced without pretreatment or after separation of carbon dioxide, from which biogas is also formed there. In one embodiment, at least part of the effluent from methane reactor I liquid is fed into the methane reactor II, in addition to the hydrolysis gas is introduced. An increase in the methane content of the biogas, which was caused by acetotrophic conversion in the methane reactor I, does not occur.

There is still a high demand for biogas production plants with increased methane yield.

The object of the invention is to provide a process, a plant and a methane reactor, with which the enrichment of methane in the biogas by biological means, ie in the biogas process itself, is possible in order to minimize further purification of the biogas.

• – Wasserstoff wird einem Methanreaktor der Methanstufe oberhalb des Hydrolysats zugeleitet,
• – das Hydrolysat wird unterhalb der Wasserstoffzufuhr aus dem Methanreaktor abgeleitet. So ist der Methanreaktor prozesstechnisch in eine mit Hydrolysat durchströmte Untersäule, die den Teil des Methanreaktors zwischen Einlass und Auslass des Hydrolysats darstellt, und eine Obersäule, die den Teil des Methanreaktors zwischen Gaszuleitung und Gasableitung darstellt, eingeteilt. Die Untersäule des Methanreaktors enthält immobilisierte acetotrophe Methanbildner, durch die aus dem Hydrolysat Biogas gebildet wird. Die Obersäule des Methanreaktors enthält suspendierte und/oder immobilisierte hydrogenotrophe Methanbildner, die Biogas durch Umwandlung von Kohlendioxid und Wasserstoff bilden.
• – Der Wasserstoff wird am unteren Ende der Obersäule feinverteilt zugeführt und strömt durch die Obersäule nach oben.
• – Das in der Untersäule gebildete Biogas wird in die Obersäule geleitet, wodurch das darin enthaltene Kohlendioxid in der Obersäule mit dem dort zugeführten Wasserstoff durch suspendierte und/oder immobilisierte hydrogenotrophe Methanbildner zu Methan umgewandelt wird.

According to the invention, the object is achieved by a method for increasing the methane concentration of the biogas from biogas plants, in which hydrogen and hydrolyzate are fed to a methane stage of a two-stage biogas process. The process according to the invention is characterized by the following steps:

• Hydrogen is fed to a methane reactor of the methane stage above the hydrolyzate,
• - The hydrolyzate is derived below the hydrogen supply from the methane reactor. Thus, the methane reactor is procedurally divided into a hydrolyzate-flowed sub-column, which represents the part of the methane reactor between the inlet and outlet of the hydrolyzate, and a top column, which is the part of the methane reactor between gas supply and gas discharge. The lower column of the methane reactor contains immobilized acetotrophic methanogens, by which biogas is formed from the hydrolyzate. The top column of the methane reactor contains suspended and / or immobilized hydrogenotrophic methanogens which form biogas by conversion of carbon dioxide and hydrogen.
• - The hydrogen is fed finely distributed at the lower end of the upper column and flows up through the upper column.
• - The biogas formed in the sub-column is passed into the upper column, whereby the carbon dioxide contained therein is converted in the upper column with the hydrogen supplied there by suspended and / or immobilized hydrogenotrophic methanogen to methane.

In the process for increasing the methane concentration of the biogas from biogas plants, hydrogen and hydrolyzate are fed to a methane stage of a two-stage biogas process. Preferably, hydrogen is supplied in a process according to the invention with a volume flow of at least 72 liters per day.

In the context of the invention, a two-stage biogas process is understood to mean an apparatus-specific hydrolysis stage in which the biogenic starting materials are first hydrolyzed, and methane stage, in which the conversion of the liquid hydrolyzate to biogas is carried out by microorganisms.

In a method according to the invention are used as biogenic feedstocks solids, especially renewable raw materials selected from corn, corn silage, cereals and its by-products, landscape care, tree and shrub or biogenic residues, especially biowaste from the separate collection and residual waste with a high proportion of organic origin.

According to the invention, the methane stage comprises at least one methane reactor. The hydrolyzate liquid and the hydrogen are fed to the methane reactor in the process according to the invention so that two reaction zones are formed in the methane reactor. In this case, the acetotrophic conversion of the constituents of the hydrolyzate liquid to methane preferably proceeds in a reaction zone, the sub-column through which flows. In the other reaction zone, the top column, through which the supplied hydrogen flows, preferably the hydrogenotrophic conversion of carbon dioxide and hydrogen to methane takes place. For this, the hydrogen is fed to the methane reactor above the hydrolyzate liquid, preferably immediately above it. Hydrogen is supplied in pure form or as part of a gas mixture with at least 2 vol .-% hydrogen content.

Hydrolyzate liquid is preferably removed below the feed line of the hydrolyzate from the methane reactor. Preferably, the hydrolyzate liquid is removed at the lower end of the methane reactor. This results in a flow of the hydrolyzate between the location of the Hydrolysatzuleitung and the point of Hydrolyysatableitung. This area through which it flows is also referred to herein as the sub column of the methane reactor.

The sub-column of the methane reactor contains acetotrophic methanogens, which are preferably immobilized on packing materials with which the methane reactor is equipped in the area of the sub-column. The acetotrophic methanogens are preferably present in the form of a biofilm. This is understood to mean a film which, apart from the microorganisms, mainly contains water, which forms hydrogels with metabolic products of the microorganisms, so that the biofilm has a mucilaginous consistency.

The acetotrophic methanogens form biogas in the methane reactor from the constituents of the hydrolyzate liquid supplied. Due to the flow of the hydrolyzate through the sub-column, the starting materials of the biochemical reactions contained in the hydrolyzate are transported to the surface of the packing and thus to the microorganisms.

The hydrolyzate is passed through the sub-column. The flow is due to the difference in height between liquid supply and liquid discharge of the reactor effected (in the case that the liquid discharge is arranged below the supply line) and / or by pumping the hydrolyzate liquid through the methane reactor.

The biogas formed in the methane reactor is discharged at the top of the reactor. The area of the methane reactor between the point at which the hydrogen is fed in and the place where the biogas is taken off is called the top column of the methane reactor. The hydrogen is fed finely distributed at the lower end of the upper column and rises in the upper column. The biogas, which is formed in the lower part of the methane reactor by acetotrophic conversion, rises in the methane reactor and also flows through the top column. As a result, the hydrogen flows through the upper column together with the biogas formed in the sub-column.

The upper column is, like the lower column, filled with hydrolyzate. The hydrolyzate contained in the top column is largely at rest, since the top column is traversed exclusively by the gas bubbles of the rising biogas and the introduced hydrogen. A liquid-side flow through the upper column does not take place because the part of the methane reactor, which forms the upper column, has no supply and discharge lines for liquid. Therefore, in methane reactors in which a method according to the invention is carried out, the liquid lines are arranged below the gas lines, so that the sub-column in the lower part of the methane reactor and the upper column is located in the upper part of the methane reactor. The conditions that are present in the upper column due to the low flow only due to the rise of the gas, advantageously promote the settlement of hydrogenotrophic methanogen. These are very shear-prone and therefore find in the low-flow environment of the upper column before good growth conditions. Since the growth of hydrogenotrophic methanogens proceeds very slowly and therefore the nutrient requirement is not high, the nutrient supply from the sub-column, caused by the flow of the rising gas bubbles, sufficient.

In the upper column, the carbon dioxide of the rising biogas and the hydrogen come into contact with the hydrogenotrophic methanogens suspended and / or immobilized in the hydrolyzate liquid, through the metabolism of which methane is formed. In a preferred embodiment of the invention, the hydrogenotrophic methanogens are immobilized in the upper column on packing.

In the sub-column biogas is formed by acetotrophic methanogen from the hydrolyzate, which rises as gas bubbles in the sub-column and thus enters the upper column. In the upper column, the carbon dioxide contained in the biogas is converted with the supplied hydrogen by the suspended in the upper column and / or immobilized hydrogenotrophic methanogen to methane.

Preferably, the inventive method is carried out so that hydrogen and carbon dioxide are particularly long contained in the top column to ensure effective conversion to methane. This is preferably ensured by suitable designs of the methane reactor, in particular by internals which increase the run length of the gas, preferably meander-shaped deflecting plates and / or wire knits. Alternatively or in combination, this is ensured by a suitable choice of reactor height.

Particularly preferably, alternatively or in combination with the aforementioned embodiments, a circulation operation of the biogas in the methane reactor in the region of the upper column is carried out. For this purpose, the biogas, which is derived from the methane reactor, fed to the methane reactor above the Hydrolyatsatzufuhr again. Possibly. this cycle operation is repeated at least once. Particularly preferably, the biogas is conducted a total of three times the area of the upper column of the methane reactor. As a result, it is advantageously possible to achieve a methane concentration in the biogas of more than 80% by volume.

Depending on the biogenic feedstock, the biogas discharged by the process from the methane reactor still contains small amounts of undesired accompanying gases, in particular water vapor, hydrogen sulfide, ammonia, siloxanes or nitrogen compounds. These are preferably separated in a subsequent process according to the requirements of the intended use. A preferred method of separation is the condensation of the water vapor and the disposal of the condensate.

The hydrogen which is fed to the methane reactor above the hydrolyzate liquid preferably originates from an external source, from an upstream or downstream process of the biogas process or from the methane stage itself.

Preferred external sources are gas reservoirs or gas cylinders. Preferably, the hydrogen is contained in pure form in the external sources.

Hydrogen can be produced in small quantities (less than 2% by volume) in the methane reactor from dissolved monomers and polymers such as amino acids, fatty acids and sugars, which are introduced into the methane reactor, by fermentative (acidogenic and acetogenic) microorganisms. By recycling the biogas, which is taken from the methane reactor, into the methane reactor above the hydrolyzate liquid, it is also possible in this way to use hydrogen, which was obtained in the methane stage of the two-stage biogas process, in the process according to the invention. Possibly. is the hydrogen from the biogas previously separated or enriched,

If the supplied hydrogen comes from a preceding or next stored process of the biogas process or from the methane stage itself, it is present as part of a gas mixture. In the supply of hydrogen, which is part of a gas mixture, the hydrogen is previously preferably enriched by ion exchange, electrolysis or biochemical reactions in the gas mixture or separated from the other components of the gas mixture. As a result, hydrogen concentrations of 5 to 80 vol .-% are usually achieved, which are fed to the methane reactor.

Preferably, hydrogen is supplied to the hydrolysis gas formed in the hydrolysis step of the biogas process. In this case, hydrogen is particularly preferably recovered from the hydrolysis gas of a thermophilic or hyperthermophilic hydrolysis and supplied to the methane reactor.

In the embodiment of the method according to the invention, wherein the hydrogen from the Hydrogenysis gas is fed to the methane reactor, hydrogen is obtained from the hydrolysis of the entire biogenic feedstock or a portion thereof depending on the hydrogen demand and then fed to the methane reactor. In this case, hydrogen is preferably fed from a mesophilic (30-37 ° C), thermophilic (50-55 ° C) or hyperthermophilic (> 55 ° C) operated hydrolysis. Hydrogen is more preferably fed from a thermophilic or hyperthermophilic hydrolysis.

To obtain hydrogen from the hydrolysis gas, the proportion of associated gases, in particular carbon dioxide, in the hydrolysis gas is preferably initially minimized by a customary purification process. In this case, the proportion of CO _{2 in} the hydrolysis gas is preferably minimized by an adsorption-desorption process, preferably using the different adsorption properties of hydrogen and carbon dioxide in molecular sieves.

If the methane content of the biogas, which is formed by the acetotrophic conversion from the hydrolyzate in the region of the bottom column of the methane reactor, is already high and is preferably more than 60% by volume, carbon dioxide is also preferably passed from the hydrolysis gas into the methane reactor. This is accomplished by controlling the level of carbon dioxide in the hydrolysis downstream purification, and containing at least 3% by volume of carbon dioxide in the gas mixture and hydrogen and carbon dioxide together being fed to the methane reactor. Complete removal of the carbon dioxide from the hydrolysis gas is technically practically unrealizable, so that in processes according to the invention in which hydrogen is fed from the hydrolysis gas to the methane reactor, it is also necessary to pass an at least small amount of carbon dioxide into the methane reactor.

The supply of hydrogen into the methane reactor takes place in finely divided form above the feed line of the hydrolyzate. The hydrogen is fed as close as possible over the hydrolyzate liquid in order to increase the run length of the gas in the methane reactor.

The hydrogen is fed to the methane reactor so that the hydrogen content in the biogas, which is derived from the methane reactor is minimal (maximum 3 vol .-%). In a process according to the invention, the maximum amount of hydrogen fed is such that the molar amount of hydrogen is fed at most in the stoichiometric ratio according to formula (1) to the molar amount of available carbon dioxide. In this case, the amount of hydrogen introduced is preferably regulated so that carbon dioxide is present in the stoichiometric excess in the methane reactor in order to convert as much hydrogen as possible. In the event that the demand for carbon dioxide is not completely covered by the amount of CO ₂ generated in the sub-column, therefore, the CO ₂ from the hydrolysis gas is used for the reaction and fed together with the hydrogen at the lower end of the upper column finely divided. This CO ₂ is advantageously already in contact with the H ₂ , so that mass transfer processes, which are necessary in the use of CO ₂ - from the sub-column, omitted.

The CO ₂ content in the hydrolysis gas can be controlled with the measured value of the H ₂ sensor. The control preferably takes place via a control of the residence time in the CO ₂ separation. The CO ₂ content from the hydrolysis gas is advantageously used to achieve the highest possible conversion of hydrogen to methane.

The invention also includes a methane reactor suitable for use in two-stage biogas processes.

The methane reactor according to the invention contains at least two liquid lines, one of which represents the liquid feed line (also referred to herein as "inlet") and the liquid discharge line (also referred to herein as "outlet"). The liquid lines preferably comprise corresponding valve elements which permit the liquid flow in the direction of the interior of the methane reactor in the liquid supply line and a guidance of the liquid out of the methane reactor during the liquid discharge. Furthermore, the methane reactor according to the invention comprises at least two gas lines, one of which represents the gas supply line and a gas discharge (also referred to herein as "biogas discharge").

• – die Gaszuleitung ist oberhalb der Flüssigkeitszuleitung und der Flüssigkeitsableitung angeordnet,
• – die Flüssigkeitsableitung ist bevorzugt unterhalb der Flüssigkeitszuleitung angeordnet,
• – die Gasableitung ist oberhalb der Gaszuleitung, Flüssigkeitszuleitung und Flüssigkeitsableitung angeordnet, vorzugsweise ist die Gasableitung oberhalb aller am Methanreaktor enthaltenen Leitungen angeordnet.

The liquid and gas lines of the methane reactor are arranged on the methane reactor in the vertical direction as follows:

• The gas supply line is arranged above the liquid supply and the liquid discharge,
• The liquid discharge is preferably arranged below the liquid supply line,
• - The gas discharge is arranged above the gas supply line, liquid supply and liquid discharge, preferably the gas discharge is arranged above all lines contained in the methane reactor.

The liquid discharge is preferably arranged at the lower end of the methane reactor. The vertical distance between the liquid feed and the liquid discharge of the methane reactor according to the invention is preferably less than half the vertical extent of the methane reactor (total height), in particular between ½ and 1/8 of the total height of the methane reactor. Is preferred the supply line formed as a lance for the fine distribution of the hydrogen-containing gas.

The gas discharge is preferably arranged at the upper end of the methane reactor. Particularly preferably, the lines are arranged with respect to the vertical extent of the methane reactor as follows: the gas discharge is in the upper third, the liquid discharge is arranged in the lower third. The liquid feed line is arranged from the lower end of the methane reactor in the vertical direction preferably at most halfway up the methane reactor.

Due to this special arrangement of the lines, certain reaction zones set in operation of the methane reactor, which are characterized by their flow characteristics. The area between liquid supply and liquid discharge is traversed during operation with liquid. The methane reactor according to the invention is preferably equipped with packing under the gas supply line. The region of the methane reactor, which is located below the gas feed line and includes the liquid lines, is also referred to herein as the sub column of the methane reactor. In this case, the liquid feed line is preferably arranged in the upper part of the sub-column, so that the liquid feed line is arranged directly below the gas feed line of the methane reactor.

The area of the methane reactor, which is located between the gas inlet and the gas outlet, is not flowed through during operation on the liquid side. A flow through this area is caused by rising gas. This area between gas supply and gas discharge is also referred to herein as the upper column of the methane reactor.

A plant-technical separation between the areas of the upper column and lower column of the methane reactor is not absolutely necessary. However, the two regions of the methane reactor must be designed so that both an exchange of liquid between the upper column and sub-column is possible, and that a gas transfer is possible at least from the sub-column in the direction of the upper column.

Preferably, a sieve bottom is arranged between the liquid feed and the gas feed of the methane reactor.

In the region of the upper column of the methane reactor according to the invention, a hydrogen sensor is attached. This is preferably arranged below the gas discharge at the methane reactor.

Preferably, the region of the upper column of the methane reactor according to the invention is also equipped with internals. The internals serve to increase the contact surface and facilitate the mass transfer from the liquid phase into the gas phase and vice versa, thus causing intensive contact of hydrogen and carbon dioxide in the gas phase of the methane reactor.

The gas supply, which is used for supplying the hydrogen in the methane reactor, is preferably designed so that a throttling of the gas stream is possible. The gas supply is preferably regulated by the measured value of the hydrogen sensor of the methane reactor.

In the area of the sub-column of the methane reactor according to the invention is equipped with packing. The fillers are designed so that they are suitable for immobilization of microorganisms.

Preferably, the gas discharge of the methane reactor is connected to a gas supply line via which the biogas removed from the methane reactor is fed again to the reactor, so that the withdrawn biogas can be recycled. The gas discharge is either directly connected to the gas supply line, through which the hydrogen is also fed into the methane reactor. Alternatively, the gas discharge is connected to a further gas supply line of the methane reactor, which is preferably also located above the liquid supply.

The gas feed of the methane reactor is preferably connected to a source of hydrogen. Preferred hydrogen sources are selected from an external gas reservoir, a gas line, which are connected to a reactor of upstream or downstream process, in particular a gas line which is connected to at least one hydrolysis reactor or a gas line which is connected via a plant for hydrogen enrichment with the methane reactor ,

The methane reactor is preferably designed in the region of the top column so that rising gas requires a long residence time in the reactor before it is discharged at the gas outlet. For the methane reactor in the upper column is preferably designed as a tubular reactor.

The region of the upper column of the methane reactor according to the invention preferably has a minimum volume of 160 liters. In this case, the region of the top column of the methane reactor preferably has a length of at least 5 meters. The methane reactor according to the invention is preferably designed such that under normal conditions (101.325 Pa and 273.15 K) a gas charge of at least 0.45 m ^{3 of} hydrogen per cubic meter of the liquid volume in the region of the upper column of the methane reactor is possible.

Alternatively or in combination, the methane reactor according to the invention comprises internals in the region of the upper column, which serve to extend the path of the ascending gas bubbles. For this purpose, the methane reactor according to the invention preferably contains meander-shaped deflecting plates and / or wire knits in the region of the upper column.

An inventive methane reactor is preferably a component of a biogas plant which is suitable for carrying out a two-stage biogas process. Therefore, the invention also includes a plant for two-stage production of biogas (also simplified herein "biogas plant") containing at least one methane reactor according to the invention and at least one hydrolysis reactor. Furthermore, the biogas plant according to the invention contains at least one liquid store, which is connected to the liquid discharge of the methane reactor.

Hydrolysis reactors which are contained in biogas plants according to the invention are preferably solid percolators with which solid biogenic substances are degraded by sprinkling with an aqueous liquid. In principle, any hydrolysis reactors known from the prior art are suitable as constituents of biogas plants according to the invention. A hydrolysis reactor, which is contained in a biogas plant according to the invention, comprises a liquid feed, a liquid discharge and a gas discharge via which the hydrolysis gas formed during the hydrolysis is removed from the hydrolysis reactor. The biogas plant according to the invention preferably contains at least two parallel hydrolysis reactors which are preferably operated at different times. This ensures advantageous continuous liquid and gas production in the hydrolysis step.

Hydrolysis stage and methane level of the biogas plant according to the invention are connected to one another on the liquid side. The system is designed so that the liquid flow from the hydrolysis stage runs into the methane stage. For the liquid discharge of a hydrolysis reactor is connected to the liquid feed of a methane reactor according to the invention. In this case, a liquid reservoir is preferably arranged between the hydrolysis reactor and the methane reactor, which serves to store the hydrolyzate liquid.

Preferably, liquid escaping from the methane reactor is fed to the sprinkling via the liquid store of the hydrolysis stage.

Preferably, the biogas plant according to the invention contains a biogas storage, which is connected to the gas discharge of a methane reactor according to the invention.

In a preferred embodiment of a biogas plant according to the invention, the hydrolysis stage is also connected on the gas side to the methane stage. For this purpose, a hydrolysis reactor has a gas discharge line which is connected to the gas supply line of the methane reactor according to the invention. Hydrogen from the hydrolysis stage is fed into the methane reactor via this gas line. Since preferably the proportion of carbon dioxide in the hydrolysis gas is minimized before the feed line to the methane reactor, the biogas plant according to the invention preferably contains a plant for CO ₂ separation, which is arranged between a hydrolysis reactor and a methane reactor and is connected on the gas side via corresponding lines to the reactors. Preferably, the plant comprises a gas storage, which is arranged between the plant for CO ₂ capture and the methane reactor and the gas side is connected to these via corresponding gas lines.

In a further preferred embodiment of a biogas plant according to the invention, the biogas plant contains a plant for the provision of hydrogen from an external source, preferably a gas reservoir containing hydrogen. The plant for providing hydrogen from an external source is connected to the gas supply of a methane reactor according to the invention.

The biogas plant according to the invention and the methane reactor according to the invention are operated as follows:
Before the methane reactor is put into operation, first a colonization of the individual reaction zones of the methane reactor (upper and lower column) takes place in the so-called run-in phase. To colonize the methane reactor an anaerobic inoculation of the methane reactor is carried out by a liquid inoculum containing acetotrophic and hydrogenotrophic methanogen, is introduced into the methane reactor and is discharged at the liquid discharge again. The methane reactor is filled after introduction of the inoculum with the inoculum liquid which flows between the inlet and outlet through the region of the sub-column.

Depending on the living conditions found in the upper and lower columns of the methane reactor, the corresponding biocenoses are formed for the microorganisms introduced. In this case, the region of the upper column is predominantly colonized by acetotrophic methanogens due to the low flow predominantly by hydrogenotrophic methanogen and the sub-column flowed through. Already in the start-up phase, gas formation takes place in the methane reactor. Due to the rising gas bubbles, which reach from the area of the sub-column in the region of the top column of the methane reactor, hydrogenotrophic methanogens are carried to the area of the top column. Hydrogenotrophic methanogens have a particularly high susceptibility to shear, and therefore immobilize only very poorly in the flow-through sub-column. The upper column is only very slightly flowed through by the rising gas bubbles and therefore offers good growth conditions for hydrogenotrophic microorganisms. The inoculum used is preferably manure or sewage sludge. These liquids naturally contain a diverse composition of various microorganisms.

At the end of the run-in phase, a biocenosis with hydrogenotrophic methanogens has formed in the upper column and a biocenosis in the lower column with acetotrophic methanogens, which are preferably present in the form of a biofilm.

During the run-in phase, a gradual admixing of hydrolyzate liquid to the inoculum occurs, allowing the microorganisms to adapt to the altered environmental conditions with the altered nutrient content present in the hydrolyzate as opposed to the inoculum.

As soon as the proportion of inoculum at the liquid fed to the methane reactor is zero, exclusively hydrolyzate is passed into the methane reactor and the run-in phase is ended. There now takes place the operating phase in which biogas is formed from the hydrolyzate liquid and supplied hydrogen, which has an increased methane content. The supply of hydrogen is preferably carried out at the beginning of the inoculation.

A hydrolysis reactor is filled with biogenic substances which are hydrolyzed within the hydrolysis reactor. The hydrolysis is preferably carried out under thermophilic conditions, that is to say at temperatures of 50-55 ° C. or under hyperthermophilic conditions, ie at temperatures of more than 55 ° C. In doing so, the degree of degradation of the biogenic starting material advantageously increases, and hydrogen is increasingly formed during the hydrolysis, which is present in amounts which can be used in process engineering.

The hydrolysis gas formed in the hydrolysis leaves the hydrolysis reactor via a gas line. The liquid hydrolyzate is recovered via the liquid discharge as free of solids as possible. The hydrolyzate is optionally fed via a liquid storage the methane reactor via the liquid feed line. The hydrolyzate flows between the liquid feed and the liquid discharge through the bottom of the methane reactor and leaves the methane reactor via the liquid discharge. The liquid leaving the methane reactor is directed to a liquid reservoir. From there, the liquid is either removed from the process or fed to a hydrolysis reactor via its liquid feed line.

In the methane reactor, the hydrolyzate flows through the sub-column between the liquid feed and the liquid discharge. The acetotrophic methanogens contained in the sub-column form from the components of the hydrolyzate biogas, which contains methane and carbon dioxide. This rises as gas bubbles upwards and inevitably enters the top column of the methane reactor and passes this until it is removed at the gas discharge of the methane reactor.

Through the gas supply of the methane reactor, which is arranged above the liquid supply, finely divided hydrogen is supplied, which rises in the upper column. The hydrogenotrophic methanogens contained in the top column of the methane reactor form methane from introduced hydrogen and the carbon dioxide, which is formed in the rising biogas, which was formed by the acetotrophic conversion in the lower column of the reactor. This advantageously results in an increase in the methane concentration in the biogas.

At the hydrogen sensor, which is located in the methane reactor in the region of the upper column (preferably at the upper end of the upper column), the hydrogen concentration in the biogas is monitored. The hydrogen supply to the methane reactor is preferably regulated on the basis of the measurement signal of the hydrogen sensor. In this case, the supplied hydrogen stream is adjusted so that at elevated hydrogen concentration present at the sensor of the methane reactor supplied hydrogen stream is throttled.

If the supplied hydrogen originates from the hydrolysis gas of the hydrolysis stage, the hydrolysis gas is taken off via the gas discharge of the hydrolysis reactor and fed to the methane reactor via its gas supply line. The hydrolysis is carried out preferably thermophilic, at 50-55 ° C, or hyperthermophilic, at more than 55 ° C. For the separation of carbon dioxide from the hydrolysis gas, this preferably passes through the plant for CO ₂ separation, in which carbon dioxide is separated from the hydrolysis gas and removed from the process. Preferably, the plant for CO ₂ capture performs an adsorption-desorption process, in particular a pressure swing adsorption in zeolites or molecular sieves.

The enriched hydrogen is fed from the plant for CO ₂ separation via the gas feed of the methane reactor to the methane reactor. Since the hydrogen is preferably formed in the first phase of the hydrolysis, this is preferably over transferred a gas storage in the methane reactor or possibly initially stored therein.

When operating several hydrolysis reactors, these are preferably operated in parallel and charged with biogenic substances at different times. In this way, a continuous production of hydrolyzate and hydrolysis gas is ensured.

The hydrogen supplied to the methane reactor rises in the methane reactor and passes through the top column, where the supplied hydrogen and the carbon dioxide contained in the methane reactor are converted to methane by the hydrogenotrophic methanogens in the top column of the methane reactor.

In order to achieve an additional accumulation of methane in the biogas, in one embodiment, in addition to the hydrogen of the hydrolysis gas and carbon dioxide of the hydrolysis gas is passed into the methane reactor. A control of the carbon dioxide content is implemented by a reduction of the residence time of the hydrolysis gas in the plant for CO ₂ separation or by the appropriate choice of the pressure level in this apparatus.

The methane-enriched biogas rises in the upper column of the methane reactor and is discharged from the methane reactor via the gas discharge.

Due to the preferred embodiments of the methane reactor according to the invention, the residence time of the rising gas in the region of the upper column of the methane reactor is increased, which promotes an increase in the methane content in the biogas.

Due to the biogas discharge at the upper end of the upper column escapes the biogas, which is preferably passed into a biogas storage.

The advantage of the method according to the invention is that the carbon dioxide, which is formed as by-product in the acetotrophic methane formation, is used as a carbon source for the formation of methane in a hydrogenotrophic conversion. In conventional processes, the carbon dioxide from the biogas is usually removed and released into the atmosphere. Especially promoted in a method according to the invention reaction of the carbon dioxide formed in the acetotrophic conversion to methane, an enrichment of methane in the biogas and thus an increased methane concentration is advantageously achieved. The biological enrichment is carried out in a structurally and process-technically complete unit for minimizing the apparatus-technical effort and the required equipment (especially the energy) in comparison to the prior art.

By minimizing the CO ₂ content of the hydrolysis gas, in particular the CO _{2 of} the biogas, which is formed by the acetotrophic formation of methane, is converted in the methane stage in the hydrogenotrophic conversion. This leads advantageously to an enrichment of methane in the biogas.

Another advantage of the supply of hydrogen from the hydrolysis in a methane reactor is that the process engineering and investment costs for the separation of carbon dioxide from the biogas is lower in such a method, as in processes in which the methane content in the biogas only in a downstream process after the biogas has been discharged from the methane reactor. The volume flow of the hydrolysis gas is substantially lower than the volume flow of the biogas of a biogas plant. Therefore, the structural design of the process for carbon dioxide removal from the hydrolysis gas is smaller and therefore associated with significantly lower investment and operating costs, as a downstream system for carbon dioxide removal from the biogas.

With reference to accompanying drawings embodiments of the invention will be explained in more detail. Show

1 Flow diagram of an example plant with a vertical sub-column and hydrogen production from the hydrolysis gas

2 Flow diagram of an example plant with horizontal sub-column and hydrogen production from the hydrolysis gas

3 Flow chart of an example plant with direct hydrogen feed

4 Flow diagram of an example plant with a vertical sub-column and hydrogen production from the hydrolysis gas and circulation of the biogas

5 Flow diagram of an example plant with a horizontal sub-column and hydrogen production from the hydrolysis gas and circulation of the biogas

6 Flowchart of an example plant with direct hydrogen feed and

Recycling of biogas

Embodiment 1: Plant with vertical sub-column

In the 1 shown plant consists of a hydrolysis reactor ( 1 ), in which the biogenic substances are first hydrolyzed, a plant for removing the CO ₂ from the hydrolysis gas ( 2 ), a methane reactor ( 3 ) and a return water tank ( 4 ).

The methane reactor ( 3 ) has an inlet ( 33 ) and an outlet ( 34 ) for liquid. Between inlet ( 33 ) and outlet ( 34 ) of the methane reactor ( 3 ) this is equipped with packing, this area forms the sub-column ( 32 ). The methane reactor ( 3 ) has a gas supply line ( 35 ) and a gas discharge ( 37 ), wherein the gas supply ( 35 ) above the inlet ( 33 ) is arranged. The gas discharge ( 37 ) is above the gas supply line ( 35 ) and the liquid lines ( 33 . 34 ) arranged. The area between gas supply line ( 35 ) and gas discharge ( 37 ) forms the area of the upper column ( 31 ) of the methane reactor ( 3 ). In the upper column ( 31 ) is a hydrogen sensor ( 36 ) arranged.

The system is operated as follows:
In the start-up phase, an anaerobic inoculation of the methane reactor ( 3 ) with an inoculum of liquid manure or sewage sludge. This is the methane reactor ( 3 ) through the inlet ( 33 ), flows through it and leaves it via the outlet ( 34 ). During the run-in phase, acetotrophic methanogens immobilize preferentially in the area of the sub-column through which ( 32 ), whereas a carryover of the hydrogenotrophic methanogens into the upper column ( 31 ) he follows. During the break-in phase, a gradual increase in the amount of hydrolyzate supplied occurs. At the end of the warm-up phase, in the upper column ( 31 ) a biocenosis of hydrogenotrophic methanogens and in the sub-column ( 32 ) a biocenosis of acetotrophic methanogens, preferably in the form of a biofilm formed.

In the hydrolysis reactor ( 1 ) biogenic solids to short-chain organic acids and alcohols in aqueous solution, the liquid hydrolyzate, and a hydrolysis gas consisting mainly of H ₂ and CO ₂ , converted. The hydrolyzate is removed from the hydrolysis reactor, the methane reactor ( 3 ) at the inlet ( 33 ) and flows through the sub-column ( 32 ) from top to bottom and leaves them at the outlet ( 34 ). It is then returned via the return water tank ( 4 ) in turn fed to the hydrolysis.

In the lower column ( 32 ) is formed from the constituents of the hydrolyzate liquid by the acetotrophic methanogen there biogas, mainly consisting of methane and CO ₂ .

The hydrolysis gas is removed from the hydrolysis reactor ( 1 ) and passes through a plant for CO ₂ removal ( 2 ), where the hydrolysis gas is freed from carbon dioxide, which is discharged from the process. The resulting enriched hydrogen is added to the methane reactor ( 3 ) through the gas supply line ( 35 ), which immediately above the inlet ( 33 ) is arranged.

That in the area of the lower column ( 32 ) of the methane reactor ( 3 ) formed biogas rises in the form of gas bubbles in the lower column ( 32 ) and thus enters the upper column ( 31 ) of the methane reactor ( 3 ). The liquid in the upper column ( 31 ) is only slightly flowed through by the rising gas bubbles of the biogas and the supplied hydrogen.

In the upper column ( 31 ) is a biocenosis of hydrogenotrophic methanogens, which is predominantly suspended. Through this, methane is formed with water as a by-product from the CO _{2 of} the rising biogas and the supplied hydrogen. The hydrogen and the CO ₂ are in this case supplied so that the proportion of H ₂ in the biogas is minimal. This is done by an H ₂ sensor ( 36 ) at the upper end of the upper column ( 31 ) which is connected to the gas supply ( 35 ) or to the gas purification ( 2 ) is coupled.

The biogas with the increased methane content escapes at the upper end of the upper column ( 31 ) by the biogas discharge ( 37 ).

Embodiment 2: Plant with horizontal sub-column

With attached 2 an embodiment of the invention will be explained in more detail. 2 shows a process flow diagram of a plant to increase the methane content of biogas.

In the 2 shown plant consists of a hydrolysis reactor ( 1 ), in which the biogenic substances are first hydrolyzed, a plant for removing the CO ₂ from the hydrolysis gas ( 2 ), a methane reactor ( 3 ) and a return water tank ( 4 ).

The methane reactor ( 3 ) has an inlet ( 33 ) and an outlet ( 34 ) for liquid, which are arranged at the same height of the methane reactor. Between inlet ( 33 ) and outlet ( 34 ) of the methane reactor ( 3 ) this is equipped with packing, this area forms the sub-column ( 32 ). The methane reactor ( 3 ) has a gas supply line ( 35 ) and a gas discharge ( 37 ), wherein the gas supply ( 35 ) above the inlet ( 33 ) is arranged. The Gas discharge ( 37 ) is above the gas supply line ( 35 ) and the liquid lines ( 33 . 34 ) arranged. The area between gas supply line ( 35 ) and gas discharge ( 37 ) forms the area of the upper column ( 31 ) of the methane reactor ( 3 ). In the upper column ( 31 ) is a hydrogen sensor ( 36 ) arranged.

The system is operated as follows:
In the start-up phase, an anaerobic inoculation of the methane reactor ( 3 ) with an inoculum of liquid manure or sewage sludge. This is the methane reactor ( 3 ) through the inlet ( 33 ), flows through it and leaves it via the outlet ( 34 ). During the run-in phase, acetotrophic methanogens immobilize preferentially in the area of the sub-column through which ( 32 ), whereas a carryover of the hydrogenotrophic methanogens into the upper column ( 31 ) he follows. During the break-in phase, a gradual increase in the amount of hydrolyzate supplied occurs. At the end of the warm-up phase, in the upper column ( 31 ) a biocenosis of hydrogenotrophic methanogens and in the sub-column ( 32 ) a biocenosis of acetotrophic methanogens, preferably in the form of a biofilm formed.

In the hydrolysis reactor ( 1 ) biogenic solids to short-chain organic acids and alcohols in aqueous solution, the liquid hydrolyzate, and a hydrolysis gas consisting mainly of H ₂ and CO ₂ , converted. The hydrolyzate is removed from the hydrolysis reactor, the methane reactor ( 3 ) at the inlet ( 33 ) and flows through the sub-column ( 32 ) and leaves it at the outlet ( 34 ). It is then returned via the return water tank ( 4 ) in turn fed to the hydrolysis.

In the lower column ( 32 ) is formed from the constituents of the hydrolyzate liquid by the acetotrophic methanogen there biogas, mainly consisting of methane and CO ₂ .

The hydrolysis gas is removed from the hydrolysis reactor ( 1 ) and passes through a plant for CO ₂ removal ( 2 ), where the hydrolysis gas is freed from carbon dioxide, which is discharged from the process. The resulting enriched hydrogen is added to the methane reactor ( 3 ) through the gas supply line ( 35 ), which above the inlet ( 33 ) is arranged.

That in the area of the lower column ( 32 ) of the methane reactor ( 3 ) formed biogas rises in the form of gas bubbles in the lower column ( 32 ) and thus enters the upper column ( 31 ) of the methane reactor ( 3 ). The liquid in the upper column ( 31 ) is only slightly flowed through by the rising gas bubbles of the biogas and the supplied hydrogen.

In the upper column ( 31 ) is a biocenosis of hydrogenotrophic methanogens, which is predominantly suspended. Through this, methane is formed with water as a by-product from the CO _{2 of} the rising biogas and the supplied hydrogen. The hydrogen and the CO ₂ are in this case supplied so that the proportion of H ₂ in the biogas is minimal. This is done by an H ₂ sensor ( 36 ) at the upper end of the upper column ( 31 ) which is connected to the gas supply ( 35 ) or to the gas purification ( 2 ) is coupled.

The biogas with the increased methane content escapes at the upper end of the upper column ( 31 ) by the biogas discharge ( 37 ).

Embodiment 3: Plant with Direct Hydrogen Supply

With attached 3 an embodiment of the invention will be explained in more detail. 3 shows a process flow diagram of a plant to increase the methane content of biogas.

In the 3 shown plant consists of a hydrolysis reactor ( 1 ), in which the biogenic substances are first hydrolyzed, a plant for the supply of hydrogen from an external source ( 5 ), a methane reactor ( 3 ) and a return water tank ( 4 ).

The methane reactor ( 3 ) has an inlet ( 33 ) and an outlet ( 34 ) for liquid. Between inlet ( 33 ) and outlet ( 34 ) of the methane reactor ( 3 ) this is equipped with packing, this area forms the sub-column ( 32 ). The methane reactor ( 3 ) has a gas supply line ( 35 ) and a gas discharge ( 37 ), wherein the gas supply ( 35 ) above the inlet ( 33 ) is arranged. The gas discharge ( 37 ) is above the gas supply line ( 35 ) and the liquid lines ( 33 . 34 ) arranged. The area between gas supply line ( 35 ) and gas discharge ( 37 ) forms the area of the upper column ( 31 ) of the methane reactor ( 3 ). In the upper column ( 31 ) is a hydrogen sensor ( 36 ) arranged.

The system is operated as follows:
In the start-up phase, an anaerobic inoculation of the methane reactor ( 3 ) with an inoculum of liquid manure or sewage sludge. This is the methane reactor ( 3 ) through the inlet ( 33 ), flows through it and leaves it via the outlet ( 34 ). During the run-in phase, acetotrophic methanogens immobilize preferentially in the area of the sub-column through which ( 32 ), whereas a carryover of the hydrogenotrophic methanogens into the upper column ( 31 ) he follows. During the break-in phase, a gradual increase in the amount of hydrolyzate supplied occurs. At the end of the warm-up phase, in the upper column ( 31 ) a biocenosis of hydrogenotrophic methanogens and in the sub-column ( 32 ) a biocenosis of acetotrophic methanogens, preferably in the form of a biofilm formed.

In the hydrolysis reactor ( 1 ) biogenic solids to short-chain organic acids and alcohols in aqueous solution, the liquid hydrolyzate, and a hydrolysis gas consisting mainly of H ₂ and CO ₂ , converted. The hydrolyzate is removed from the hydrolysis reactor, the methane reactor ( 3 ) at the inlet ( 33 ) and flows through the sub-column ( 32 ) from top to bottom and leaves them at the outlet ( 34 ). It is then returned via the return water tank ( 4 ) in turn fed to the hydrolysis.

In the lower column ( 32 ) Is formed from the constituents of the hydrolyzate liquid through the located there acetotrophen Methanbildner biogas mainly composed of methane and CO _2.

The hydrolysis gas is removed from the hydrolysis reactor ( 1 ) derived.

Hydrogen from the external hydrogen source ( 5 ) is the methane reactor ( 3 ) through the gas supply line ( 35 ), which immediately above the inlet ( 33 ) is arranged.

That in the area of the lower column ( 32 ) of the methane reactor ( 3 ) formed biogas rises in the form of gas bubbles in the lower column ( 32 ) and thus enters the upper column ( 31 ) of the methane reactor ( 3 ). The liquid in the upper column ( 31 ) is only slightly flowed through by the rising gas bubbles of the biogas and the supplied hydrogen.

In the upper column ( 31 ) is a biocenosis of hydrogenotrophic methanogens, which is predominantly suspended. Through this, methane is formed with water as a by-product from the CO _{2 of} the rising biogas and the supplied hydrogen. The hydrogen and the CO ₂ are in this case supplied so that the proportion of H ₂ in the biogas is minimal. This is done by an H ₂ sensor ( 36 ) at the upper end of the upper column ( 31 ) which is connected to the gas supply ( 35 ) or to the gas purification ( 2 ) is coupled.

The biogas with the increased methane content escapes at the upper end of the upper column ( 31 ) by the biogas discharge ( 37 ).

Embodiment 4: Plant with vertical sub-column

In the 4 shown plant consists of a hydrolysis reactor ( 1 ), in which the biogenic substances are first hydrolyzed, a plant for removing the CO ₂ from the hydrolysis gas ( 2 ), a methane reactor ( 3 ) and a return water tank ( 4 ).

The methane reactor ( 3 ) has an inlet ( 33 ) and an outlet ( 34 ) for liquid. Between inlet ( 33 ) and outlet ( 34 ) of the methane reactor ( 3 ) this is equipped with packing, this area forms the sub-column ( 32 ). The methane reactor ( 3 ) has a gas supply line ( 35 ) and a gas discharge ( 37 ), wherein the gas supply ( 35 ) above the inlet ( 33 ) is arranged. The gas discharge ( 37 ) is above the gas supply line ( 35 ) and the liquid lines ( 33 . 34 ) arranged. The area between gas supply line ( 35 ) and gas discharge ( 37 ) forms the area of the upper column ( 31 ) of the methane reactor ( 3 ). In the upper column ( 31 ) is a hydrogen sensor ( 36 ) arranged. The gas discharge ( 37 ) is connected to a gas line ( 38 ), which is used to feed gas into the methane reactor ( 3 ) in the area of the upper column ( 31 ) suitable is. The gas line discharges into the methane reactor ( 3 ) at the level of the gas supply ( 35 ).

The system is operated as follows:
In the start-up phase, an anaerobic inoculation of the methane reactor ( 3 ) with an inoculum of liquid manure or sewage sludge. This is the methane reactor ( 3 ) through the inlet ( 33 ), flows through it and leaves it via the outlet ( 34 ). During the run-in phase, acetotrophic methanogens immobilize preferentially in the area of the sub-column through which ( 32 ), whereas a carryover of the hydrogenotrophic methanogens into the upper column ( 31 ) he follows. During the break-in phase, a gradual increase in the amount of hydrolyzate supplied occurs. At the end of the warm-up phase, in the upper column ( 31 ) a biocenosis of hydrogenotrophic methanogens and in the sub-column ( 32 ) a biocenosis of acetotrophic methanogens, preferably in the form of a biofilm formed.

In the hydrolysis reactor ( 1 ) biogenic solids to short-chain organic acids and alcohols in aqueous solution, the liquid hydrolyzate, and a hydrolysis gas consisting mainly of H ₂ and CO ₂ , converted. The hydrolyzate is removed from the hydrolysis reactor, the methane reactor ( 3 ) at the inlet ( 33 ) and flows through the sub-column ( 32 ) from top to bottom and leaves them at the outlet ( 34 ). It is then returned via the return water tank ( 4 ) in turn fed to the hydrolysis.

In the lower column ( 32 ) is formed from the constituents of the hydrolyzate liquid by the acetotrophic methanogen there biogas, mainly consisting of methane and CO ₂ .

The hydrolysis gas is removed from the hydrolysis reactor ( 1 ) and passes through a plant for CO ₂ removal ( 2 ), where the hydrolysis gas is freed from carbon dioxide, which is discharged from the process. The resulting enriched hydrogen is added to the methane reactor ( 3 ) through the gas supply line ( 35 ), which immediately above the inlet ( 33 ) is arranged.

That in the area of the lower column ( 32 ) of the methane reactor ( 3 ) formed biogas rises in the form of gas bubbles in the lower column ( 32 ) and thus enters the upper column ( 31 ) of the methane reactor ( 3 ). The liquid in the upper column ( 31 ) is only slightly flowed through by the rising gas bubbles of the biogas and the supplied hydrogen.

In the upper column ( 31 ) is a biocenosis of hydrogenotrophic methanogens, which is predominantly suspended. Through this, methane is formed with water as a by-product from the CO _{2 of} the rising biogas and the supplied hydrogen. The hydrogen and the CO ₂ are in this case supplied so that the proportion of H ₂ in the biogas is minimal. This is done by an H ₂ sensor ( 36 ) at the upper end of the upper column ( 31 ) which is connected to the gas supply ( 35 ) or to the gas purification ( 2 ) is coupled.

The biogas with the increased methane content is added to the methane reactor ( 3 ) at the upper end of the upper column ( 31 ) by the biogas discharge ( 37 ) and at least once via the gas line ( 38 ) into the methane reactor ( 3 ) fed. As a result, further enrichment of the methane in the biogas is advantageously achieved.

Embodiment 5: Plant with horizontal sub-column

With attached 5 an embodiment of the invention will be explained in more detail. 5 shows a process flow diagram of a plant to increase the methane content of biogas.

In the 2 shown plant consists of a hydrolysis reactor ( 1 ), in which the biogenic substances are first hydrolyzed, a plant for removing the CO ₂ from the hydrolysis gas ( 2 ), a methane reactor ( 3 ) and a return water tank ( 4 ).

The methane reactor ( 3 ) has an inlet ( 33 ) and an outlet ( 34 ) for liquid, which are arranged at the same height of the methane reactor. Between inlet ( 33 ) and outlet ( 34 ) of the methane reactor ( 3 ) this is equipped with packing, this area forms the sub-column ( 32 ). The methane reactor ( 3 ) has a gas supply line ( 35 ) and a gas discharge ( 37 ), wherein the gas supply ( 35 ) above the inlet ( 33 ) is arranged. The gas discharge ( 37 ) is above the gas supply line ( 35 ) and the liquid lines ( 33 . 34 ) arranged. The area between gas supply line ( 35 ) and gas discharge ( 37 ) forms the area of the upper column ( 31 ) of the methane reactor ( 3 ). In the upper column ( 31 ) is a hydrogen sensor ( 36 ) arranged. The gas discharge ( 37 ) is connected to a gas line ( 38 ), which is used to feed gas into the methane reactor ( 3 ) in the area of the upper column ( 31 ) suitable is. The gas line discharges into the methane reactor ( 3 ) at the level of the gas supply ( 35 ).

The system is operated as follows:
In the start-up phase, an anaerobic inoculation of the methane reactor ( 3 ) with an inoculum of liquid manure or sewage sludge. This is the methane reactor ( 3 ) through the inlet ( 33 ), flows through it and leaves it via the outlet ( 34 ). During the run-in phase, acetotrophic methanogens immobilize preferentially in the area of the sub-column through which ( 32 ), whereas a carryover of the hydrogenotrophic methanogens into the upper column ( 31 ) he follows. During the break-in phase, a gradual increase in the amount of hydrolyzate supplied occurs. At the end of the warm-up phase, in the upper column ( 31 ) a biocenosis of hydrogenotrophic methanogens and in the sub-column ( 32 ) a biocenosis of acetotrophic methanogens, preferably in the form of a biofilm formed.

In the hydrolysis reactor ( 1 ) biogenic solids to short-chain organic acids and alcohols in aqueous solution, the liquid hydrolyzate, and a hydrolysis gas consisting mainly of H ₂ and CO ₂ , converted. The hydrolyzate is removed from the hydrolysis reactor, the methane reactor ( 3 ) at the inlet ( 33 ) and flows through the sub-column ( 32 ) and leaves it at the outlet ( 34 ). It is then returned via the return water tank ( 4 ) in turn fed to the hydrolysis.

In the lower column ( 32 ) is formed from the constituents of the hydrolyzate liquid by the acetotrophic methanogen there biogas, mainly consisting of methane and CO ₂ .

The hydrolysis gas is removed from the hydrolysis reactor ( 1 ) and passes through a plant for CO ₂ removal ( 2 ), where the hydrolysis gas is freed from carbon dioxide, which is discharged from the process. The resulting enriched hydrogen is added to the methane reactor ( 3 ) through the gas supply line ( 35 ), which above the inlet ( 33 ) is arranged.

That in the area of the lower column ( 32 ) of the methane reactor ( 3 ) formed biogas rises in the form of gas bubbles in the lower column ( 32 ) and get that way into the upper column ( 31 ) of the methane reactor ( 3 ). The liquid in the upper column ( 31 ) is only slightly flowed through by the rising gas bubbles of the biogas and the supplied hydrogen.

In the upper column ( 31 ) is a biocenosis of hydrogenotrophic methanogens, which is predominantly suspended. Through this, methane is formed with water as a by-product from the CO _{2 of} the rising biogas and the supplied hydrogen. The hydrogen and the CO ₂ are in this case supplied so that the proportion of H ₂ in the biogas is minimal. This is done by an H ₂ sensor ( 36 ) at the upper end of the upper column ( 31 ) which is connected to the gas supply ( 35 ) or to the gas purification ( 2 ) is coupled.

The biogas with the increased methane content is added to the methane reactor ( 3 ) at the upper end of the upper column ( 31 ) by the biogas discharge ( 37 ) and at least once via the gas line ( 38 ) into the methane reactor ( 3 ) fed. As a result, further enrichment of the methane in the biogas is advantageously achieved.

Embodiment 6: Plant with Direct Hydrogen Supply

With attached 6 an embodiment of the invention will be explained in more detail. 6 shows a process flow diagram of a plant to increase the methane content of biogas.

In the 3 shown plant consists of a hydrolysis reactor ( 1 ), in which the biogenic substances are first hydrolyzed, a plant for the supply of hydrogen from an external source ( 5 ), a methane reactor ( 3 ) and a return water tank ( 4 ).

The methane reactor ( 3 ) has an inlet ( 33 ) and an outlet ( 34 ) for liquid. Between inlet ( 33 ) and outlet ( 34 ) of the methane reactor ( 3 ) this is equipped with packing, this area forms the sub-column ( 32 ). The methane reactor ( 3 ) has a gas supply line ( 35 ) and a gas discharge ( 37 ), wherein the gas supply ( 35 ) above the inlet ( 33 ) is arranged. The gas discharge ( 37 ) is above the gas supply line ( 35 ) and the liquid lines ( 33 . 34 ) arranged. The area between gas supply line ( 35 ) and gas discharge ( 37 ) forms the area of the upper column ( 31 ) of the methane reactor ( 3 ). In the upper column ( 31 ) is a hydrogen sensor ( 36 ) arranged. The gas discharge ( 37 ) is connected to a gas line ( 38 ), which is used to feed gas into the methane reactor ( 3 ) in the area of the upper column ( 31 ) suitable is. The gas line discharges into the methane reactor ( 3 ) at the level of the gas supply ( 35 ).

The system is operated as follows:
In the start-up phase, an anaerobic inoculation of the methane reactor ( 3 ) with an inoculum of liquid manure or sewage sludge. This is the methane reactor ( 3 ) through the inlet ( 33 ), flows through it and leaves it via the outlet ( 34 ). During the run-in phase, acetotrophic methanogens immobilize preferentially in the area of the sub-column through which ( 32 ), whereas a carryover of the hydrogenotrophic methanogens into the upper column ( 31 ) he follows. During the break-in phase, a gradual increase in the amount of hydrolyzate supplied occurs. At the end of the warm-up phase, in the upper column ( 31 ) a biocenosis of hydrogenotrophic methanogens and in the sub-column ( 32 ) a biocenosis of acetotrophic methanogens, preferably in the form of a biofilm formed.

In the hydrolysis reactor ( 1 ) biogenic solids to short-chain organic acids and alcohols in aqueous solution, the liquid hydrolyzate, and a hydrolysis gas consisting mainly of H ₂ and CO ₂ , converted. The hydrolyzate is removed from the hydrolysis reactor, the methane reactor ( 3 ) at the inlet ( 33 ) and flows through the sub-column ( 32 ) from top to bottom and leaves them at the outlet ( 34 ). It is then returned via the return water tank ( 4 ) in turn fed to the hydrolysis.

In the lower column ( 32 ) is formed from the constituents of the hydrolyzate liquid by the acetotrophic methanogen there biogas, mainly consisting of methane and CO ₂ .

The hydrolysis gas is removed from the hydrolysis reactor ( 1 ) derived.

Hydrogen from the external hydrogen source ( 5 ) is the methane reactor ( 3 ) through the gas supply line ( 35 ), which immediately above the inlet ( 33 ) is arranged.

That in the area of the lower column ( 32 ) of the methane reactor ( 3 ) formed biogas rises in the form of gas bubbles in the lower column ( 32 ) and thus enters the upper column ( 31 ) of the methane reactor ( 3 ). The liquid in the upper column ( 31 ) is only slightly flowed through by the rising gas bubbles of the biogas and the supplied hydrogen.

In the upper column ( 31 ) is a biocenosis of hydrogenotrophic methanogens, which is predominantly suspended. Through this, methane is formed with water as a by-product from the CO _{2 of} the rising biogas and the supplied hydrogen. The hydrogen and the CO ₂ are in this case supplied so that the proportion of H ₂ in the biogas is minimal. This is done by a H ₂ - Sensor ( 36 ) at the upper end of the upper column ( 31 ) which is connected to the gas supply ( 35 ) or to the gas purification ( 2 ) is coupled.

The biogas with the increased methane content is added to the methane reactor ( 3 ) at the upper end of the upper column ( 31 ) by the biogas discharge ( 37 ) and at least once via the gas line ( 38 ) into the methane reactor ( 3 ) fed. As a result, further enrichment of the methane in the biogas is advantageously achieved.

After three times the return of the biogas via the gas line ( 38 ) into the methane reactor ( 3 ), a methane content of 86.3% by volume was achieved in the biogas, which was added to the methane reactor ( 3 ) via the gas discharge ( 37 ) was taken. The hydrogen content of the biogas was measured on the hydrogen sensor ( 36 ) and was at most 3% by volume.

LIST OF REFERENCE NUMBERS

(1)

hydrolysis reactor

(2)

Plant for the removal of CO ₂

(3)

methane reactor

(31)

upper column

(32)

pillar

(33)

inlet

(34)

outlet

(35)

gas supply

(36)

H ₂ sensor

(37)

biogas deriving

(38)

gas pipe

(4)

Return water tank

(5)

Plant for the supply of hydrogen from an external source

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 200-152799 [0014]
• JP 06-169783 [0015]
• FR 2537992 A1 [0016]
• US 3383309A [0017]
• US 4696746 B1 [0018]

Claims (14)

A method for increasing the methane concentration of the biogas from biogas plants, in which hydrogen and liquid hydrolyzate are fed to a methane stage of a two-stage biogas process, characterized in that - the hydrogen is fed to a methane reactor of the methane stage above the hydrolyzate and - derived the hydrolyzate at the lower end of the methane reactor is, so that the methane reactor processively into a hydrolyzate flowed sub-column, which is the part of the methane reactor between the inlet and outlet of the hydrolyzate, and a top column, which is the part of the methane reactor between gas supply and gas discharge, divided, the sub-column of the methane reactor contains immobilized acetotrophic methanogen, is formed by the biogas from the hydrolyzate, and the upper column of the methane reactor suspended and / or immobilized hydrogenotrophic methanogen, contains - the hydrogen at the lower end of the O bersäule is fed finely distributed and flows through the upper column, the biogas formed in the lower column is passed into the upper column, whereby the CO ₂ contained therein in the upper column with the hydrogen supplied there by suspended and / or immobilized hydrogenotrophic methanogen to methane becomes. A method according to claim 1, characterized in that the methane reactor supplied hydrogen from an upstream or downstream process or by chemical and physical processes, preferably by ion exchange, electrolysis or chemical and biochemical reactions from the Methanstufe itself is obtained. A method according to claim 1, characterized in that the methane reactor supplied hydrogen from the hydrolysis gas of a mesophilic, thermophilic or hyperthermophilic operated hydrolysis of the entire biogenic feedstock or from a subset thereof is obtained. A method according to claim 3, characterized in that the hydrogen and CO ₂ from the hydrolysis gas is supplied so that the hydrogen content in the biogas formed is at most 3 vol .-%. Method according to one of claims 1 to 4, characterized in that the methane reactor above the hydrolyzate biogas is supplied, which was previously taken from the methane reactor via a gas discharge, which is arranged above the gas supply line for the hydrogen. Method according to one of claims 1 to 5, characterized in that the hydrogen is fed to the methane reactor so that the hydrogen content in the biogas formed is at most 3 vol .-%. Methane reactor ( 3 ) for the production of biogas in two-stage biogas processes with a biogas discharge ( 37 ), an inlet ( 33 ) and an outlet ( 34 ) for liquid and a gas supply ( 35 ), characterized in that - the gas supply ( 35 ) above the inlet ( 33 ) and outlet ( 34 ) of the methane reactor ( 3 ) and - the biogas discharge ( 37 ) above gas supply ( 35 ), Inlet ( 33 ) and outlet ( 34 ) of the methane reactor ( 3 ), so that the methane reactor ( 3 ) in terms of process technology into an upper column ( 31 ) and a sub pillar ( 32 ), whereby the sub-column ( 32 ) the part of the methane reactor ( 3 ) between inlet ( 33 ) and outlet ( 34 ) of the liquid and the upper column ( 31 ) the part of the methane reactor ( 3 ) between gas supply ( 35 ) and biogas derivation ( 37 ), the methane reactor ( 3 ) is designed so that a liquid exchange between upper column ( 31 ) and sub pillar ( 32 ) is possible and a gas exchange at least from the sub-column ( 32 ) in the direction of the upper column ( 31 ) is possible, - the methane reactor ( 3 ) in the area of the sub-column ( 32 ) is equipped with packing, and - wherein the methane reactor ( 3 ) in the area of the upper column ( 31 ) a hydrogen sensor ( 36 ) having. Methane reactor ( 3 ) according to claim 7, characterized in that the outlet ( 34 ) of the methane reactor ( 3 ) in the vertical direction below the inlet ( 33 ) is arranged. Methane reactor ( 3 ) according to claim 7 or 8, characterized in that between inlet ( 33 ) and gas supply ( 35 ) of the methane reactor ( 3 ) a sieve tray is arranged. Methane reactor ( 3 ) according to any one of claims 7 to 9, characterized in that the methane reactor ( 3 ) in the area of the upper column ( 31 ) Contains internals to increase the contact surface, in particular baffles. Methane reactor ( 3 ) according to one of claims 7 to 10, characterized in that the biogas discharge ( 37 ) with a gas line ( 38 ) located above the inlet ( 33 ) into the methane reactor ( 3 ) opens. Methane reactor ( 3 ) according to one of claims 7 to 11, characterized in that the vertical distance between inlet ( 33 ) and outlet ( 34 ) between half and one-eighth of the total height of the methane reactor ( 3 ) is. Biogas plant for the bi-stage production of biogas, comprising at least one methane reactor ( 3 ) according to one of claims 1 to 12, at least one hydrolysis reactor ( 1 ) and at least one liquid reservoir ( 4 ), with the outlet ( 34 ) of the methane reactor ( 3 ), wherein the hydrolysis reactor ( 1 ) via a fluid line with the inlet ( 33 ) of the methane reactor ( 3 ) connected is. Biogas plant according to claim 13, wherein the hydrolysis reactor ( 1 ) has a gas discharge, which via a plant ( 2 ) for CO ₂ separation from the hydrolysis gas, and the plant ( 2 ) for CO ₂ separation from the hydrolysis gas with the gas supply ( 35 ) of the methane reactor ( 3 ) connected is.

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