EP2162526A1

EP2162526A1 - Biogas plant with solids fermentation and methane production in the recirculating percolate tank

Info

Publication number: EP2162526A1
Application number: EP07856639.5A
Authority: EP
Inventors: Michael Feldmann
Original assignee: Meissner Jan A
Current assignee: Meissner Jan A
Priority date: 2007-06-27
Filing date: 2007-12-12
Publication date: 2010-03-17
Also published as: EP2167631B1; HUE027343T2; DE202007019678U1; ES2558364T3; WO2009000305A1; EP2927309B1; EP2927308A1; WO2009000309A1; EP2927309A1; DE202007019668U1; US9963665B2; DE202007019537U1; EP2160458B1; US20100285556A1; DE102007029700A1; EP2927308B1; WO2009000309A8; EP2160458A1; EP2167631A1; DK2167631T3

Abstract

There is shown a biogas plant and a process for the production of biogas by the anaerobic bacterial solids fermentation process. The biogas plant comprises a multiplicity of fermenters of the garage type, at least one recirculating percolate tank (RPT) which is connected to at least one associated fermenter for receiving percolate, with the RPT being connected to the biogas system and having a volume amounting to at least 5%, preferably at least 7%, especially preferably at least 10% and in particular at least 12% of the volume of the fermenter(s) to which it is connected for receiving percolate.

Description

Michael Feldmann F30376PCT (Y)

Biogas plant with fermentation of solids and methane production in the percolate circulation tank

The present invention relates to a biogas plant, in particular a biomass power plant and a method for biogas production by the Feststoffvergärungsverfahren.

The established technology for the production of biogas is currently the so-called wet fermentation plants, of which more than 3500 are currently in use in Germany. These are only about 20 plants for solid fermentation (also known as dry fermentation) of renewable raw materials. According to the recently published final report "Monitoring to the effect of the amended Renewable Energy Sources Act (EEG) on the development of electricity production from biomass", which was commissioned by the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), the dry fermentation still has not reached the stage of marketability. The plants in operation are considered to be demonstration plants (see page 52, Figure 5-2 of the final report).

In the generic biogas plant is a biogas plant for the production of biogas by the solidification process with a plurality of fermenters of the garage type and at least one percolate circulation tank (PUT), which is connected to at least one associated fermenter for receiving percolate. Percolate is a liquid that exits the digestate during dry fermentation. This percolate is collected at the bottom of a fermenter and passed into the at least one percolate tank. From this at least one Perkolatumlauftank the percolate is then passed back into the fermenter, there to soak the fermentation mass, because without water, the biochemical processes can not occur.

It is an object of the present invention to increase the performance of conventional biogas plants and to improve a process for producing biogas by the solidification process, in such a way that the methane yield over conventional biogas plants and processes is higher. This object is achieved in that the at least one PUT is connected to the biogas system and has a volume which is at least 5%, preferably at least 7%, more preferably at least 10% and in particular at least 12% of the volume of that fermenter or that fermenter with which he is connected to receive percolate.

The biogas plant of the present invention is thus characterized by a relatively large PUT and further characterized in that the PUT is connected to the biogas system.

In known biogas plants of the type mentioned, the PUT - if present at all - designed to be much smaller than in the invention. So far, the only function of the PUT is to collect percolate and provide enough percolate to spray the contents of the fermenter so that the pumps used to pump the percolate will not suck in air. The methane formation occurs almost exclusively in the (garage) fermenters.

In contrast, in the biogas plant of the invention, the PUT is made substantially larger than in the prior art, and it is also connected to the biogas system. The inventor has recognized that with a sufficient size of the PUT a very significant methane yield can be generated in the PUT and therefore the PUT is also connected to the biogas system.

Due to the size of the PUT and the achievable by this residence time of circulating percolate in PUT is achieved that set in the PUT an increased concentration of acetogenic and methanogenic bacteria, while adjusting in Garagenfermenter an increased concentration of fermentative or hydrolytic and acidogenic bacteria. This means that the hydrolysis of the biomass into simple organic building blocks and the acidogenesis of these simple organic building blocks takes place in the fermenter first. Acicogenesis leads to methanogenic substrates and acetogenic substrates, which are then partially washed out by the percolate and passed with the percolate into the PUT. In the PUT, the acetogenic and methanogenic bacteria, which process the products of the hydrogenated and acidogenic bacteria (essentially various organic acids), preferentially settle, whereby methane is also and especially produced in the PUT. The PUT acts in a sense as a "methane reactor". This local separation of the stages of fermentation is only a tendency, but of course also in the garage fermenter acetogenesis and methanogenesis take place. However, the acetogenic and methanogenic bacteria find better living conditions in the PUT than in the fermenter. In particular, the methanogenic bacteria in the fermenter suffer from "acid spikes", ie a transient, sharp drop in the pH which always occurs when new fresh mass is introduced into the fermenter. The reason for these acid spikes in the Guresasseauffrischung is inter alia in the course taking place AutoHydrolyse, in the acids contained in the plant material or in the residual water of the plants are dissolved in water. The problem here is in particular that the methanogenic bacterial strains usually have the longest reproduction times of all bacteria involved and tend to provide the methanogenic bacteria with long reproduction times higher methane yields than those with short reproduction times. This means that the particularly methane-yielding bacteria in the fermenter would prefer a relatively long fermentation cycle, but this is not optimal for the total yield of the biomass power plant, as explained in more detail below. In contrast, in the PUT, the methanogenic bacteria can settle and multiply in conditions that are more favorable to them, thus leading to a high methane yield in the PUT.

In an advantageous development, a plurality of PUTs are provided which are interconnected by a percolate line, in particular a percolate ring line. Preferably, the ratio of fermenters to PUTs is at least 3: 1, and more preferably at least 5: 1. This means that the percolate from several fermenters is fed into one and the same PUT. In particular, this means that percolate, which originates from a fermenter in which a fermentation liquor has just taken place, and thus the pH has dropped, is mixed with percolate from other higher pH fermenters, thus curbing acid peaks, which causes the Living conditions for the acetogenic and methanogenic bacteria in the PUT significantly improved. It is particularly advantageous if the Perkolatzuflüsse coming from different fermenters are mixed together before they are introduced into a PUT.

Preferably, the at least one PUT is arranged in a PUT cycle, in which percolate, which runs through a drain from a fermenter, must pass through at least one PUT before it is reintroduced into a fermenter. This will ensure that the acids contained in the percolate are degraded by the acetogenic and methanogenic bacteria in the PUT and the percolate is introduced less acidic in the fermenter or the fermenter. This prevents the fermenters from over acidifying or makes it possible to feed the fermenters more frequently and in larger quantities with fresh, still unfermented material. This in turn reduces the required size of the system and saves a considerable amount of investment costs.

The at least one PUT is preferably heatable in order to be able to produce the optimum conditions for the acetogenic and methanogenic bacteria in the PUT.

In a particularly advantageous development, artificial settlement areas for methanogenic bacteria are installed in the at least one PUT. Such settlement areas may be formed by one or more of the following: racks in which towel, carpet or drapery-type fabrics can be hung, basket-like structures or hollow balls of acid-proof plastic, in particular those filled with smaller objects, lamellar structures made of plastic, heaps of objects with large surfaces, in particular woodchips or straw, and / or nets or other containers with openings filled with woodcarvers. In this case, means are preferably provided which prevent floating of these objects, so that the settlement areas for the methanogenic bacteria are always immersed in percolate. Through these settlement areas, an increased population of methanogenic bacteria can be obtained, which significantly increases the biogas yield in the PUT.

In an advantageous development, a channel structure is formed in the at least one PUT such that percolate, which enters the PUT at an entrance, is guided to its exit along a flow path whose length is at least three times, preferably at least six times, the largest dimension of the PUT. During the passage of percolate through the PUT, the acetogenic and methanogenic bacteria degrade acid so that the pH of the percolate gradually increases. Through the channel structure is achieved that results in a quasi-continuous flow of percolate along the channel, so that set along the channel on average different pH values of the percolate. Specifically, this means that the pH in a channel section near the entrance to the PUT will be lower than in a channel section located near the exit of the PUT. This in turn means that the diverse methanogenic bacterial strains will settle there within the channel structure where their optimal acidity is present. Methanogenic bacteria strains that are more sensitive to acids will tend to settle at the end of the channel structure, while bacterial strains that can withstand lower pH levels will settle closer to the entrance area of the PUT. Overall, the various acedogenic and methanogenic bacterial strains thus find their optimal living conditions and thus increase the methane yield.

Preferably, the channel structure in the PUT is designed such that the biogas which is produced in the PUT, is led to its exit into the biogas system in the channel system above the flow path of the percolate.

Preferably, the at least one PUT accesses, in particular gas-tight closable hatches, through which it is accessible to operating personnel. The PUT may have a foil roof. Alternatively, however, a solid roof, for example made of concrete, may be provided. In this case, the PUT is then connected to a compensating gas storage for biogas.

In an advantageous development, a device is provided which is suitable for producing an oxygen content of from 0.2% to 2.5%, preferably from 0.5% to 1%, in the gas atmosphere of the PUT. This oxygen content allows sulfur bacteria to settle in the airspace of the PUT that biologically bind the harmful sulfur compounds (eg H ₂ S, COS, CS ₂ ) produced during anaerobic bacterial digestion. This is extremely advantageous because such sulfur compounds, in particular hydrogen sulfide, in biogas can lead to significant problems in the use of gas. For example, corrosion on the equipment and / or on the motors due to the formation of sulfuric acid or sulfuric acids. Other problems that can arise from such sulfur compounds are the acidification of the engine oil and the inhibition of the fermentation process. In addition, even concrete fermenters can be affected by corrosion when hydrogen sulfide oxidizes in the air and sulfuric acid is formed. Finally, the combustion of hydrogen sulfide produces sulfur dioxide, which causes problems on the exhaust side. Furthermore, it is imperative that the biogas be desulphurized before the injection of methane into the natural gas grid. Desulfurization of biogas is therefore extremely advantageous for material technology and microbiological reasons. Preferably, artificial settlement areas for sulfur bacteria are arranged in the at least one PUT. These settlements should be arranged so that the sulfur bacteria have contact with the medium to be purified, ie the biogas, access to the oxygen in the gas atmosphere of the PUT to oxidize the sulfur, access to water for the microbiological process and access to nutrients for your own growth. Water and nutrients are found in the percolates of the sulfur bacteria. The settlement areas for sulfur bacteria are therefore preferably arranged such that they are temporarily wetted by the percolate in the PUT within the expected fluctuation of the level of the percolate in the PUT and are temporarily exposed to the biogas.

Alternatively, settlement areas for sulfur bacteria can be located above the percolate level in the PUT and sprayed with percolate.

In addition, artificial settlement areas for sulfur bacteria can also be installed in the garage fermenters as described above. To make contact with the medium to be purified, i. The biogas produced in the garage fermenter should have access to oxygen in the garage atmosphere of the garage fermenter, access to water and access to nutrients, should the additional settlement areas between the percolation nozzles and the digestate be installed. This can e.g. in such a way that open containers (such as nets) filled with woodchips or other material with large surfaces are hung on the fermenter cover or placed on the fermentation mass in mat form. As a result, the desulfurization performance of the latent sulfur bacteria increases to a very considerable extent. In contrast to the gauze blanket, which also has a large surface area, the surface of the man-made settlement area is not destroyed every time a fermentation takes place, but is retained for the next fermentation cycle, which means that the population of sulfur bacteria does not have to rebuild itself over and over again Size is present from the beginning. As a result, the desulfurization performance increases again.

In an advantageous development, the biogas plant comprises a press, which is suitable, already angegorene fermented mass, which is retrieved in the course of a Gärmassenauffrischung from the fermenter and used as seed for the fresh mass, squeeze so that the liquid phase passed into at least one PUT and the solid phase can be mixed with the fresh mass. This makes it possible to increase the nutrient content of the percolate with the same amount of substrate used. When expressing the fermented mass nutrient Substances released that would remain in the plant structures without this mechanical processing of the digestate and thus disposed of.

In particular, it is advantageous not only to perform this pressing once, but to completely repress or durchzuwalken the entire inoculation material with each Gärmassenauffrischung. It is advantageous if only about 20% of the digestate is disposed of and about 80% remain as an anesthetic agent. As a result, an increased proportion of the substrates passes through the fermentation process several times. This increased proportion is thus pressed out several times and whipped through, which further increases the nutrient yield and thus the nutrient content in the percolate and thus the methane production.

In an advantageous development, at least one outlet is provided in the bottom of the PUT, through which percolate can be discharged from the PUT, wherein the diameter of the outlet is so large that dry substance, which has settled as a silt at the bottom of the PUT, during deflation of the Percolate is flushed through the at least one outlet. In addition or as an alternative, pipes with nozzle-like outlets can be installed around the bottom in the PUT, which stir up the silt before it is flushed away through the outlets. This reduces the effort involved in manual cleaning of the PUT or can even be completely eliminated.

Preferably, the flow rate of the percolate along the above-mentioned flow path in the PUT is on average less than 4 cm per second, and more preferably less than 2.5 cm per second. A suitable flow rate can be achieved by matching the channel structure to the percolate volume. The particular advantage of the limited flow rate of the percolate is that shear forces in the percolate can be avoided, which could rupture flakes of acetogenic and methanogenic bacteria. Close proximity between the acetogenic bacteria that produce hydrogen and the methanogenic bacteria that consume hydrogen is important to the process so that they can efficiently exchange the hydrogen. Therefore, it is advantageous if the flakes of acetogenic and methanogenic bacteria are retained in the PUT.

In an advantageous embodiment, the percolate persists on average four to twelve hours, preferably an average of five to seven hours in the PUT. This dwelling Times in the PUT are advantageous both with regard to the methane yield in the PUT and with regard to the fermentation process in the fermenter.

Preferably, the digestate in the fermenter is so far enriched with loose material, such as straw, that increases the ability of the digestate, percolate, increased to a capacity of at least 0.75 m ³ percolate per 1 m ² fermenter base and day. In a preferred method for biogas production thus at least 0.75 m ³ percolate per 1 m ² Fermentergrundfläche and day are sprayed on the fermentation mass in the fermenter.

In a particularly advantageous embodiment, the percolate in PUT at 30 ° C to 40 ° C, preferably 33 ° C to 37 ⁰ C held. This temperature range provides for knowledge of the inventor, an ideal compromise between the preferred temperatures of the acetogenic and methanogenic bacteria (between 32 ⁰ C and 42 ° C) and the preferred temperatures of the acidogenic bacteria in the fermenter is (between 25 ° C and 35 ° C), in which the percolate flows back. Overall, the best biogas yields are expected in this temperature range.

Normally, fermentation liquor replenishment takes place every 28 days in solid fermentation processes in garage fermenters. This is the fermentation cycle time recommended, for example, by "Bio-Ferm", a solid-state fermentation equipment manufacturer, however, the inventor has recognized that plant performance can be significantly increased if the fermentation cycles significantly over the 28-day standard in the prior art For this purpose, the inventor has carried out simulations of the gas yield as a function of the fermentation cycle times and related these to the used digestate, whereby the inventor has recognized that the capacity of the biogas plant can be drastically increased if the digestate per fermenter is changed every six to six months The shortening of the fermentation cycle increases the average volume load of the fermenter of the biogas plant with fresh organic matter (volume load) .In particular, the inventor was able to determine that the biogas plant (ie the one provided by the fermenters) Vol by reducing the fermentation cycle time at the same power can be about 50% smaller than is the case with conventional biogas plants of the solid-state fermentation type, which drastically reduces the investment costs. An even further reduction of the fermentation cycle time does not lead to improved results, since the increased Fresh fermented mass will deliver its optimum gas yield only after three to four days. However, the possibility of shortening the fermentation cycles depends essentially on the spatial displacement of part of the acetogenesis and methanogenesis into the PUTs described above.

Preferably, the number of fermenters in the biogas plant is between 12 and 24, more preferably between 16 and 20, and there are two daily Gährassenunterfrischungen made in the entire biogas plant. In this conception, therefore, the same day-to-day work for the refreshment of the fermentation gas, which must be carried out by the operating staff of the biogas plant, is carried out on a daily basis, so that the optimum fermentation cycle can also be practically realized.

Preferably, the fresh mass is heated prior to introduction into the fermenter. Additionally or alternatively, the fresh mass is subjected to a weakly aerobic prehydrolysis prior to introduction into the fermenter. By this measure, the required residence time for the substrate in the fermenter, whereby the fermenter can be loaded more frequently and with more fresh mass and the system performance, ie, the room capacity in kg oTS / m ³ fermenter space / day is increased. For the same gas yield, therefore, fewer fermenters must be built so that the productivity and efficiency of the plant is increased.

Preferably, the refreshment of the fermentation mass comprises the following steps: removing the fermentation mass from the fermenter, replacing a part of the fermentation mass with fresh mass, and

Introducing the fresh mass supplemented by digestate into the fermenter, wherein the again introduced into the fermenter, fermented in the previous fermentation cycle fermentation mass (the so-called inoculation) is pressed before mixing with fresh mass so that a liquid phase is formed in at least one PUT can be passed, and a solid phase is formed, which can be mixed with the fresh mass.

Preferably, 13% to 60% of the fermentation mass is discharged into a post-fermenter, and the fresh mass fraction is preferably 22% to 69% of the fermentation mass newly introduced into the fermenter. This particularly advantageous method of restoring the odoriferous substance is suitable in turn, especially in the context of the relatively large PUTs and their function as a methane reactor.

In an advantageous development, the biogas plant comprises a device for the chemical, mechanical and / or thermal digestion of ligninous and / or fibrous renewable raw materials, in particular of straw.

The particular advantage of straw is that it is generally a residue which, for example, is produced in cereal production anyway and is therefore available in sufficient quantities. While most so-called energy crops grown specifically for power generation compete for limited agricultural land with crops for food and feed production, straw as a fermentation substrate is one of the few exceptions to this competition for available arable land.

However, there is currently a technical prejudice against the use of straw as a fermentation substrate. In fact, it is currently believed by experts that the biogas yield of straw is too low for economic biogas production. For example, the article "Energetic Utilization of Straw - Possibilities and Limitations" by D. Peisker, T. Hering and Dr. med. H. Vetter of the Thuringian State Office for Agriculture from February 2007 categorically excluded the use of straw on the basis of anaerobic bacterial degradation (see page 3 of the cited article). The reason for the opinion that straw is not suitable for anaerobic bacterial fermentation is due to its high lignin content. The lignin, which is indigestible for the bacteria involved in fermentation, blocks the bacteria from reaching the cellu- lose and therefore causes the fermentation process and thus the biogas production to progress only very slowly. For this reason, straw currently plays no role as a substrate in biogas production, but rather is considered useless.

Deviating from this technical prejudice, however, the inventor has found that quite large quantities of biogas can be obtained from straw if it is chemically, mechanically and / or thermally digested before fermentation. In the following, a variety of methods are presented, with which the straw can be opened up and the gas yield can be significantly increased. It should be noted that everything in the following discussion with specific reference to straw and is also considered in the context of other lignin and / or fiber-containing renewable raw materials.

In an advantageous embodiment, the device for mechanical digestion comprises a device for cutting, chopping and / or grinding lignin and / or fibrous raw materials, in particular a hammer mill or straw mill.

Additionally or alternatively, the device for the digestion of lignin- and / or fibrous renewable raw materials, in particular straw, comprises a device for saturated steam treatment. A device for saturated steam treatment preferably comprises a pressure vessel and means adapted to generate a water vapor in the pressure vessel, with a pressure which is between 20 and 30 bar, and a temperature which is between 180 ° C and 250 ° C. Saturated steam treatment takes place at the pressures and temperatures described and typically lasts for 5 to 15 minutes. The function of the saturated steam treatment will be described using the example of wheat straw.

Wheat straw consists of about 40% cellulose, 23% arabinoxylan (hemicellulose) and 21% lignin, with all three major components forming a densely packed structure. The main obstacle to the biochemical utilization of cellulose and hemicellulose is lignin, which is indigestible to microorganisms and blocks the bacteria from accessing cellulose and hemicellulose. In the case of saturated steam treatment, the ligininstructures are softened or melted, but essentially not released from the stalks during the relatively short treatment time. After the saturated steam treatment, the lignin solidifies again. However, when the lignin solidifies, lumped droplet-like lignin structures are formed which leave enough interstices through which firstly aqueous organic acids and then the bacteria can reach the cellulose and arabinoxylan, which decompose them by the known four-stage anaerobic fermentation.

In the saturated steam treatment described here, the lignin is thus changed primarily in its microscopic structure, but it is not dissolved out of the straws. In particular, the structure of the straws remains as such. This represents a difference to the thermal pressure hydrolysis, which under fundamentally similar conditions, However, it is carried out for longer periods, and in which a real hydrolysis takes place, that is, a dissolution of previously solid or dry substances in water. Thermal pressure hydrolysis dissolves the structure of the straw and results in a syrupy suspension.

In an advantageous development, the device for the digestion of ligninous and / or fibrous renewable raw materials, in particular straw, comprises a container for soaking the same before the saturated steam treatment, for example in water. When the soaked raw material is subjected to a saturated steam treatment, the drawn-in water evaporates abruptly, causing tearing of lignocellulosic structures and making the cellulose even more accessible to the bacteria.

Alternatively to the saturated steam treatment, grinding can be carried out, for example, in a hammer mill. This form of disruption mechanically destroys the lignin structures. The inventor has found that the biogas yield increases significantly with the degree of grinding. In fact, results in a particle range of 2 cm to 0.1 mm, a methane yield, which decreases approximately linearly compared to the logarithm of the particle size. The degree of grinding therefore preferably corresponds to at least one sieve hole size of 8 mm, particularly preferably 1 mm. The proportion of straw that can be ground for mechanical digestion depends on the degree of grinding. With a fine grinding degree, corresponding to a sieve hole size of 1 mm, it does not make sense to grind all the straw, because otherwise a dough-like pulp would form, which sticks to the fermentation mass and prevents percolation.

In an alternative embodiment, the straw may be cut and / or chopped to a particle length of less than 5 cm, preferably less than 2 cm. For example, this can be done at harvest time, because with modern balers straw bales can be pressed out of stalks, which are only about 4 cm long.

Alternatively, however, the straw can also be digested in a bale shape, which in particular substantially facilitates its transport and handling, as explained in more detail below. Since the structure is preserved, for example, of straw taps under the saturated steam treatment, even straw bales retain their shape under the saturated steam treatment and can be transported easily and efficiently after this. A particular advantage of bales is furthermore that they can be layered at the bottom in a garage fermenter, which can increase the filling level of the fermenter. In principle, the filling level of the fermenter is limited by the fact that, starting at a certain height of the substrate in the fermenter, the pressure at its bottom becomes so high that the substrate becomes too compacted to allow percolate to seep through. However, straw bale layers, which are introduced into a fermenter at the bottom, are far more pressure-stable than conventional fermentation substrates. Even under the load of the overgrown digestate, the straw bale layer is still permeable to percolate, so that the usual filling level in the fermenter can still be filled up on the straw bale layer. The fermenters can therefore be constructed higher than usual by the height of the straw bale position, which reduces proportionate fermenter-specific technology costs (gate, gas technology, sensors, flaps and openings, percolate nozzles, drains, piping, etc.) and the efficiency of the biogas plant as a whole elevated. Preferably, the straw bales are dissolved after being layered in the fermentor by removing the yarn with which they are held together.

Further explanations for the digestion of ligninous and / or fibrous renewable raw materials are given in patent application PCT / EP2007 / 006681, the priority of which is claimed in this application.

In an advantageous development, the biogas plant comprises a device for dehydrating and pelleting fermentation residues, which is suitable for processing fermentation residues into fuel pellets and / or fuel briquettes. The processing of fermentation residues into fuel pellets is in turn particularly attractive when ligninous and / or fibrous renewable raw materials, in particular straw, are used as the fermentation substrate. In this case, the lignin contained in the digestate has the advantage that it melts during pelleting, solidifies again when cooling the pellets and thus leads to relatively solid pellets or briquettes, which are a valuable fuel. Even assuming that the methane yield of straw is less than that of other fermentation substrates, the energy balance of the biogas plant as a whole is extremely advantageous because a valuable fuel is produced in addition to the power and heat generated. Further details on the energy balance when fuel pellets or briquettes are produced from digestate can be found in patent application PCT / EP2007 / 009809, the priority of which is claimed in this application. If such a device is provided for dehydrating and pelleting of fermentation residues, it is again advantageous to increase the throughput of fermentation substrate, ie in particular to shorten the fermentation cycle. This is in turn made possible by the above-mentioned, compared to the prior art enlarged PUTs. In this respect, there is therefore a technical connection between the PUTs according to a development of the invention and the digestate pelleting. However, fermentation residue pelleting is also possible in embodiments with conventional PUTs.

The biogas plant and the device for producing fuel pellets can be structurally combined or spatially separated from one another.

The biogas plant preferably comprises a device for washing out or eluting the fermentation residues. By washing and elution harmful substances such as chlorine, potassium, sulfur and nitrogen from the digestate are washed out. This leads to an improved quality of the fuel pellets or briquettes, so that these, optionally with further conditioning, can obtain regular fuel quality. In an advantageous embodiment, the device for leaching is formed by a thermophil-operated digestate bunker, which is described in more detail below.

Preferably, at least 30% by weight of the dry matter of the fresh mass is straw, and more preferably at least 75% by weight. It may be pure straw or straw, which is contained in solid manure, whose dry matter is about 75% also made of straw. In a particularly advantageous development, 30 to 90% by weight of the dry substance of the fresh mass consist of pure straw, 10 to 70% by weight of solid manure, and 0 to 30% by weight of other substrates. This ensures that the fermentation residue pellets consist predominantly of straw, are easy to produce due to the relatively high lignin content and are well suited for firing. In addition, the urea in the solid manure already leads to a very significant chemical digestion of the straw when it is mixed with the solid manure.

The device for dehydrating and pelleting the digestate preferably comprises a device for mechanically dehydrating it, in particular a screw press or a decanter. With such a screw press, it is possible to reduce the water content of the fermentation residues to, for example, 45% to 55%. The after treatment with In particular, the remaining water content of the screw press is low enough that it can be dried to a sufficient degree of dryness using pelletizing using the waste heat of the existing gas engines. Another advantage of the mechanical dehydration is that the water is dissolved out of the digestate with dissolved therein for combustion harmful substances such as chlorine, nitrogen, sulfur, potassium chloride and / or silicates. If the fermentation residues were only dehydrated by thermal drying, a much greater proportion of these harmful substances would remain in the fermentation residues.

Preferably, the means for dehydrating and pelletizing further comprises a drying device, which is preferably a convective belt dryer. As mentioned above, the drying device is preferably operated with waste heat from at least one gas engine of the biogas plant. Preferably, the belt dryer is a low temperature belt dryer whose temperature does not exceed 180 ° C, preferably 140 ° C. Due to the low temperature, no dioxins and furans are produced during drying. With such a belt dryer, the water content of the digestate can be reduced to, for example, 7 to 13%. Alternatively, the drying device can be formed by a drum dryer with contact drying, which can also operate at temperatures not exceeding 180 ° C, preferably 140 ° C.

The device for dehydrating and pelleting preferably comprises a device for comminuting the at least mechanically pressed and optionally already dried fermentation residues. Preferably, this device is formed by a hammer mill or a straw mill.

Preferably, the dehydrating and pelletizing device further comprises a conditioning device suitable for adding one or more of the following to the shredded and at least partially dehydrated and / or dried fermentation residues: cereal flour, molasses, starch, quicklime, steam, wood chips and / or sawdust. The addition of cereal flour and / or molasses and / or starch increases the strength of the fermentation residue pellets. By steaming the mass to be pelleted, it becomes supple and can be pelleted better. An addition of quicklime improves the ash softening behavior of the pellets when they are burned. By adding wood chips and sawdust, the burning properties of the pellets are further improved, in particular especially with regard to burning behavior, ash formation and emissions, so that the pellets can even be used in domestic pellet heating systems. In addition, the at least partially dehydrated and / or dried fermentation residues, a nitrogen-binding agent, in particular a nitrogen reducing reducing agent, hydrated lime, oil press cake, such as those resulting from the production of rapeseed or pumpkin seed oil, calcium, magnesium and / or aluminum are added. The oil press cakes increase the calorific value of the pellets, calcium, magnesium and aluminum can improve the burning behavior.

Finally, the device for dehydrating and pelleting preferably comprises a pelleting press which is suitable for pressing the comminuted and dehydrated fermentation mass into pellets or briquettes.

Preferably, at least some of the said components of the dehydrating and pelleting device are connected by mechanical and / or pneumatic conveying systems.

An important development of the invention consists in the way in which the additional process step of digestion of ligninous and / or fibrous renewable raw materials and / or the dehydration and pelleting of digestate residues are integrated into the operation of the biogas plant. The device for pelleting and the device for digesting straw, for example, are economically worthwhile, especially if the throughput of the plant or the biomass power plant is high. However, currently known biomass power plants for solid fermentation (biogas plants) are usually very small as agricultural plants. They have two to six smaller fermenters and achieve an effective electrical output of only 100 to 700 kW. This is partly due to the fact that dry fermentation is generally regarded as not yet ready for the market, but also because of the stepped minimum remuneration of the EEG for injected electricity from straw plants, which drops by up to 15% if a limit of 500 kW is exceeded , In addition, as a result of a greater interpretation of biogas plants with dry fermentation, it is currently argued that the requisite supply of fermentation substrate must be secured in advance over years, in line with Financiers' requirements, and that the operators, who are typically farmers, rely on the want to leave their own renewable resources. By the described biogas plant and the described method according to a development of the invention, which also makes the use of, for example, solid manure and straw economically, the supply of fermentation substrate, however, can be ensured for much larger systems, since, for example, straw accumulates in far greater quantities crops , as it is currently needed, and as it can be transported relatively economically with appropriate (large) technology even over longer distances. On the other hand, the greater the throughput of the biogas plant, the more worth the investment and operating costs for a device for dehydrating and pelleting of digestate and for means for breaking up the straw. A contextual relationship between the pelleting of digestate and the possibility of digesting the straw on the one hand and the size of the biogas plant on the other hand, insofar as the facilities for pelleting of digestate and straw digestion significantly contributes to the supply of larger biogas plants with suitable fermentation substrate, namely to ensure solid manure and / or straw, and on the other hand, the size of the biogas plant and the use of low-priced substrates solid manure and straw makes the investment for the facilities for pelleting and digestion in particular and the large biomass power plant as a whole economically.

In a previously unknown size of biogas plants with, for example, 15 to 30 large garage fermenters and a capacity of over 5 MW, they are described below, the operation of the biogas plant, and in particular the transport of the fermentation substrate and the digestate must be made efficient. A further object is to integrate the fermentation residue pelleting described above and / or the above-described digestion of lignin-containing and / or fibrous renewable raw materials into the operating sequence of the biogas plant.

In an advantageous development, the device for chemical, mechanical and / or thermal digestion of lignin- and / or fibrous renewable raw materials is housed in a delivery and loading area of the biogas plant. The delivery and loading area preferably comprises stationary conveyor technology, which is suitable for demanding fresh material from the delivery and loading area to a fermenter forecourt, from which a plurality of fermenters of the garage type is accessible. While in conventional biogas plants with garage fermenters, the fresh mass and the digestate are transported completely with a wheel loader, according to this further development stationary provided by the technology, through which even large quantities of fresh mass can be efficiently transported to Fermenter forecourt to be introduced from there into the fermenter. Such a stationary conveyor technology also allows the entire biogas plant to be built in, thereby avoiding an unpleasant odor in the environment and making it possible to build and operate the biogas plant also in the vicinity of residential areas and in industrial areas.

If the biogas plant is completely enclosed, the delivery and loading area is effectively an interface between the enclosed interior of the plant and the outside area, and is thus arranged in an outer section of the plant. The fermenter forecourt, however, is centrally located in the plant for logistical reasons. Due to the stationary conveyor technology, the fresh mass or the fermentation substrate can be brought from the delivery and loading area to the fermenter forecourt, without the need for transport vehicles that would generate exhaust gas within the housing area and would also increase the operating costs. Preferably, there is a slight underpressure in the delivery and loading area, so that even when delivering fresh mass and loading of digestate, only little air escapes to the outside, and thus the odor nuisance is minimal.

Preferably, in the delivery and loading area at least one housed delivery bunker for fresh mass. Furthermore, first conveying means are preferably provided, which are suitable for conveying fresh material from the at least one delivery bunker for fresh mass to a fresh-material bunker. These first conveying means may comprise, for example, screw conveyors, elevators and conveyor belts, on which the fresh mass from different delivery bunkers are conveyed to the fresh-material bunker. This has the advantage that the fresh mass is already by the fact that it is mixed from different delivery bunkers on one and the same heap, mixed, so that a later mixing of the fresh mass is unnecessary, or no longer has to be made so intense. In this described fresh mass is not the straw that would need to be digested, but additional fresh mass, as used in previously known biogas plants with solidification.

Furthermore, the delivery and loading area preferably comprises second conveying means, in particular a thrust shield, which are suitable, the fresh mass through the Frischmasse bunker through in the direction of the fermenter forecourt. The fresh-material bunker has a dual function: on the one hand it serves as a transport route from the delivery area to the fermenter forecourt, on the other hand it serves as a buffer for fresh mass. It is important that the fresh mass, which was first introduced into the fresh bunker, leaves this first. This means that the fresh mass that is delivered to the fermenter forecourt is always about the same age and pre-hydrolyzed. This results in a substrate consistency, which is advantageous for the subsequent fermentation.

In addition, the delivery and loading area comprises in an advantageous development of a discharge point for straw, and in particular straw in bale shape. In the discharge site, a crane is preferably provided which is suitable for efficiently gripping and transporting bale material.

In the delivery and loading area preferably as mentioned above, a device for chemical, mechanical and / or thermal digestion of straw is provided, which is of one of the types described above. In particular, the means for digestion as described above may be formed so that the bale shape is maintained so that the pulp pretreated by digestion can be transported in bale form from the delivery and loading area to the fermenter forecourt, which greatly facilitates transport and introduction into the fermenters efficient.

Preferably, third conveying means, in particular roller conveyors or push conveyors, are provided, which are suitable for conveying individual bales or packages of bales along a bale duct to the fermenter forecourt.

In the present advantageous development, therefore, a distinction is made between loose fresh material and bale material. Also, the bale material is very efficiently transported from the periphery to the fermentor forecourt by the third conveyor and bale channel, allowing high throughput with very low operating costs. Preferably, a converter is arranged at the fermenter front near the end of the bale channel, which is suitable to remove packages of bales from the bale channel and handed over to a wheel loader or forklift as a package. As will be explained in more detail below with reference to an exemplary embodiment, it is advantageous to introduce a layer of bale material in each fermenter at the bottom. This can be achieved according to this development of the invention. In turn, it is particularly efficient and quick to do this if suitable packages of bales, for example packages of eight bales, have already been handed over to the wheel loader or forklift truck, which can then be unloaded as they are in the fermenter.

Preferably, the delivery bunker, the fresh bunker and / or the bale duct are heatable, and advantageously by means of waste heat, which is generated by one or more gas engines. By preheating the fresh mass temperature losses are compensated, which arise during the Gärmassenauffrischung the waste material. This will accelerate the reintroduction of biogas production after the refreshment of the digestate. Furthermore, this makes the above-described weakly aerobic prehydrolysis possible, which shortens the time until complete fermentation of the fermentation mass and increases the plant output (the substrate throughput) and thus the economic efficiency.

In an advantageous development, a digestate bunker is provided, which is accessible from the fermenter forecourt for introducing fermentation residues. The digestate bunker preferably contains stationary conveying means which are suitable for transporting fermentation residues through the digestate bunker. In an advantageous development of these stationary conveying means are formed by screw conveyors, which are arranged at the ends of the digestate bunker. The digestate bunker is preferably sized to handle the expected amount of digestate of at least two days.

The digestate bunker according to the mentioned embodiment of the invention has a fourfold function. First, it serves as a buffer for fermentation residues, and second, it provides the fermentation residue transport device from the central fermentor forecourt to the periphery. The sufficient size of the digestate bunker ensures that the fermentation residues can be stored for at least two days, so that they do not have to be removed on weekends. As a third function, post-fermentation takes place in the digestate bunker and therefore it is connected to the biogas system. Thus, from the digestate further biogas is obtained, which would be lost in a simpler design. As a fourth function, the digestate bunker forms a device for washing out the digestate. Due to the high water content in the digestate bunker harmful substances such as chlorine, nitrogen, sulfur, potassium chloride and silicates are washed out of the fermentation residues, which increases the quality of the fermentation residue pellets as fuel. At the entrance end of the digestate bunker a Schütttrog for fermentation residues is preferably arranged. The digestate can thus be poured directly from the fermenter forecourt into the Schütttrog; they then automatically flow to the periphery by removal at the other end, where they are dehydrated and processed into pellets.

In a simple process for the chemical digestion of straw, the straw is already mixed with other fresh material, preferably with solid manure, days before it is introduced into the fermenter. The urea present in the solid manure can in turn dissolve the lignin and make the cellulose and arabinoxylan accessible for hydrolysis. It is important that additionally or separately provided straw is chemically digested by the urea contained in the solid manure. The mixing of the loose straw with the solid manure would typically take place with a greater time interval before the introduction into the fermenter, preferably a few days. In a very simple embodiment of the invention, layers of solid manure and layers of straw can be set up alternately in the fermenter without a time advance, it also being possible for layers of other, not highly lignified, raw materials to be present therebetween. As a result, the urea of the upper solid manure layer with the percolate can penetrate into the layer containing the lignin-containing straw and at least partially dissolve the two-dimensional lignin structures. It is also possible to mix loose lignin-containing material with the digestate and optionally other renewable raw materials. The acid percolate ensures that the planar lignin structures at least partially dissolve and the material biogas supplies, although not with the yield that can be achieved by the other methods described above for the digestion, in particular the saturated steam treatment and / or grinding ,

Preferably, the inoculation material, which comes together with the fresh mass back into the fermenter, by mixing by means of a mechanical press, such as a screw press, durchgewalst and squeezed, whereby the material is at least partially mechanically digested and also possibly integrated nutrients for the anaerobic , Bacterial fermentation be made available. The screw press can be designed to be mobile, for example, be arranged on a low-loader, so that it can be driven on the fermenter forecourt to the relevant fermenter. Preferably, a concentration of pollutants in the percolate is prevented by a part of the circulating percolate is discharged from the percolate cycle. This is preferably done regularly. In this case, the discharge of a portion of the percolate preferably takes place via the percolate ring line, the part of the percolate being discharged into the fermentation residue bunker and / or into a tank from which the percolate is subsequently disposed of.

For a better understanding of the present invention, reference will now be made to the preferred embodiment illustrated in the drawings, which is described with reference to specific terminology. It should be understood, however, that the scope of the invention should not be so limited since such changes and other modifications to the illustrated biogas plant and method and other applications of the invention as set forth herein are to be considered as current or future knowledge of a relevant art Be considered professional. The figures show embodiments of the invention, namely:

Fig. 1 is an elevational view of a biomass power plant according to a development of the invention of

West,

FIG. 3 is an elevational view of the biomass power plant of FIG. 1 viewed from the south; FIG. 4 is an elevational view of the biomass power plant of FIG. 1 viewed from the east; FIG. 5 is a cross-sectional view Fig. 6 is a plan view of the ground floor of the biomass power plant of Fig. 1, Fig. 7 is an enlarged detail of the plan view of Fig. 6, a power and

Fig. 8 shows an enlarged detail of the plan view of Fig. 6, the one

Delivery and loading area shows,

9 is a plan view of the upper floor of the biomass power plant of FIG. 1; FIG. 10 is a cross-section through a garage fermenter of the biomass power plant of FIGS. 1 to 9;

11 is a schematic representation of a channel structure formed within a PUT.

12 is a schematic perspective view of a PUT with packing for the settlement of methanogenic and acetogenic bacteria, 13 shows a schematic cross-sectional representation of a PUT with settlement structures for methanogenic and acetogenic bacteria and with settling structures for sulfur bacteria,

14 shows a further schematic cross-sectional view of a PUT with settlement structures for methanogenic and acetogenic bacteria and with settling structures for sulfur bacteria,

15 shows a schematic representation of a PUT with the associated fermenters and lines,

Fig. 16 is a schematic representation of the fermenter forecourt and the fermenter of

Basic section of the biogas plant of Fig. 1 to 9, in which the Guresassenauffrischung is illustrated and

17 is a block diagram of essential components of a device for dehydrating and pelleting digestate.

In the following, a biomass power plant (BMKW) 10 as an embodiment of a biogas plant according to a development of the invention will be described in detail. 1 to 4 show four exterior views of the BMKW 10 and Fig. 5 is a cross section of the same. In Fig. 6, the floor plan of the ground floor of the BMKW 10 is shown. Fig. 7 shows an enlarged partial area of the plan of Fig. 10, in which a power and heat generating plant of the BMKW is shown. Fig. 8 shows another partial section of the plan of Fig. 6, in which a delivery and loading area is shown enlarged. 9 shows a plan view of the upper floor of the BMKW 10.

With reference to the plan view of Fig. 6, the BMKW 10 is divided into a base section 12 and an expansion section 14. The base section 12 comprises 18 garage-type fermenters arranged in two rows, in a view of Fig. 5 in a northern and a southern row. Between the two rows of fermenters 16 is a Fermentervorplatz 18, to which the gates 20 of the fermenter 16 open. It should be noted that for the sake of clarity, not all fermenter 16 and fermenter ports 20 are provided with reference numerals in the figures.

Furthermore, the base portion 12 comprises a power and heat generating system 22, which is shown enlarged in Fig. 7 and described in more detail below. It also includes the base section 12 a delivery and loading area 24, which is shown enlarged in Fig. 8 and also described in more detail below.

As can be seen in FIGS. 1 to 6, the entire base section 12 is enclosed by a hall structure to which, in particular, a fermenter forecourt (FVP) -Hallenabschnitt 26 and a delivery and Verladebereichshallenabschnitt 28 belongs, as in particular in Fig. 1, 4 and 5 is clearly visible. The entire hall construction or enclosure of the base section 12 is vented through a large central ventilation system, so that there is always a slight negative pressure relative to the atmospheric pressure inside the hall construction.

The expansion section 14 essentially consists of 11 additional fermenters 16 'and an extension of the FVP hall section 26. The expansion section 14 serves to provide, if necessary, up to 11 additional fermenters 16'. This means that the BMKW 10 would initially be built without the expansion section 14 and put into operation. In operation, it turns out then whether the existing 18 fermenters 16 of the base section 12 produce sufficient biogas to supply the four gas engines (not shown), which are intended for the BMKW 10, under full load with gas. If this is not the case, the corresponding number of fermenters 16 'can be supplemented in the expansion section 14, which can thus also be smaller than shown in Fig. 6. In other words, the BMKW 10 has a modular design that is advantageous for achieving an optimal end configuration because the exact biogas yield depends on a variety of factors, including the nature and availability of the fresh mass, and is not theoretically accurately predictable.

The northern and southern fermenter rows are connected by a technology bridge 30, which can be seen in particular in FIGS. 5, 6 and 9. The engineering bridge 30 straddles the FVP 18 at a height that allows wheel loaders, two of which are exemplarily shown in FIG. 5, to pass beneath it even with the bucket fully extended without it being able to contact and damage the engineering bridge.

Referring to FIG. 9, the upper floor of the BMKW 10 comprises three film gas storages 32 in the base section 12 and two further film gas storages 32 'in the dismounting section 14. The film gas storages 32 are good in the cross-sectional views of FIGS. 5 and 15 to recognize. They take on the manner described in more detail below the biogas, which is generated in the fermenters 16 and 16 '.

Furthermore, the upper floor comprises five percolate circulation tanks (PUT) 34 in the base section 12 and four PUTs 34 'in the expansion section 14, which are also clearly visible in the cross-sectional views of FIG. A PUT 34 is located above each of three fermenters 16 and receives percolate from them, which is collected at the bottom of the fermenters and pumped into the PUT 34. The term "percolate" refers to the liquid, manure-like component of the fermentation substance.

Further, located on the upper floor of an exhaust cooling room 31, a southern engineering room 36 and a northern engineering room 38, which are interconnected by the technology bridge 30. In the FVP hall section 26 and in the delivery and loading area Hall section 28 further light bands 40 are arranged.

After a rough overview of the components of the BMKW 10 has been given, the individual sections and components and their operation will be described in detail below.

1st fermenter forecourt

The Fermentervorplatz (FVP) 18 is located in the center of the BMKW 10. It serves as a transport route for fresh mass to the respective fermenters 16, 16 'or of digestate substance from the fermenters 16, 16'. It also serves as a mixing surface on which the content of a fermenter is spread, from which about one-fifth to one-third is taken as digestate and compensated for this withdrawal and resulting from the gasification loss of mass about one-third supplemented by fresh mass and the old fermented mass is mixed. This work can be performed on the FVP 18 by a large wheel loader, as shown schematically in FIG. In the middle of the FVP 18 there is a grated gutter into which seepage fluids and released percolate flow. At the height of the technology bridge 30, the gutter has a collecting shaft (not shown) from which the resulting liquids via a percolate loop (not shown) to one of the PUTs 34 are required.

2. Delivery and loading area

The delivery and loading area 24 is shown in Fig. 8 enlarged in plan. In the embodiment shown, as far as the delivery is concerned, a distinction is made between loose fresh mass and fresh structural mass or fresh bale mass. For the loose fresh mass four delivery bunkers 42 are provided in the embodiment shown, which are housed by the delivery and loading area Hall section 28. A truck can maneuver backwards into the hauled-in delivery bunker and tip or dump the fresh bulk cargo into the delivery bunker 42 there. Since there is a slight underpressure throughout the delivery and loading area 24, hardly any unpleasant odors leave the enclosure to the outside. Each delivery bunker 42 has a downwardly tapered bottom, at the lowest point of which one or more twin flights (not shown) are provided, which requests the fresh meal horizontally to a bucket elevator (not shown) which carries the virgin mass onto a conveyor 44 , or directly to a lower conveyor belt.

From the conveyor belt 44, the fresh mass is dropped into a Frischmassebunker 46. Since the fresh mass is conveyed from four or more different bunkers on the same conveyor belt 44 and thrown onto the same heap in the fresh mass bunker 46, the fresh mass is automatically mixed.

The Frischmassebunker 46 is an elongated chamber that connects the delivery and loading area 24 with the Fermentervorplatz 18, as can be seen in particular in Fig. 6. The Frischmassebunker 46 has a floor and / or wall heating, with the fresh mass is already heated to a temperature of 42 ⁰ C, so that the digestate within a fermenter 16, 16 ', which is supplemented by the fresh mass, is not cooled by this so that the fermentation process after closing the fermenter 16 starts again quickly and possibly even a weakly aerobic prehydrolysis can take place, which shortens the fermentation time and increases the system performance (throughput of fermentation substrate) and the efficiency of the system. The fresh mass bunker 46 has a triple function. First, it serves as an intermediate or buffer for loose fresh mass. On the other hand, it serves as a transport path between the delivery and loading area 24, ie the periphery of the BMKWs 10, and the centrally located Fermentervorplatz 18. For transport is in the Frischmassebunker 46 a push plate or slider arranged (not shown) of each new from above poured bulk loose fresh mass towards the Fermentervorplatz 18 pushes. Then the slide is moved back to make room for new fresh mass. This sliding mechanism ensures that the fresh mass is also pushed out of the fermenter forecourt 18 in the same order in which it was introduced into the fresh-material bunker 46 at the entrance. This means that the fresh mass that reaches the fermentor forecourt 18 is always approximately the same age and therefore of constant quality, which is advantageous for the subsequent fermentation. Finally, a mildly aerobic prehydrolysis takes place in the fresh mass bunker, in which acids contained in the fresh mass begin to act autohydrolytically.

Furthermore, the delivery and loading area 24 comprises a section for the delivery and transport of structural or bale material, in particular for straw. This section for delivering and transporting bale material comprises a preparation space 48, a bale delivery space 50, a digestion area 52 and an intermediate storage 54. In the following, this area of the delivery and loading area 24 will be described with reference to straw as a highly lignified, bale-shaped structural material. but it is understood that this section can also be used for delivery, processing and onward transport of other bale-shaped structural material.

A crane (not shown) is mounted on rails so that it can pick up and drop straw bales in each of the spaces 48-54. The straw bales are delivered to the straw delivery room 50 and efficiently transported by the crane (not shown) to the intermediate storage 54. Before the straw is conveyed to the fermenter forecourt 18, it is pretreated in the digestion region 52, namely digested. The digestion of the straw is necessary because the straw is highly lignified, and the bacteria in the fermenter 16 due to the lignin-crusted cellulose very poorly get to the lignin trapped nutrients. Depending on the embodiment of the BMKW 10, the straw can be digested in different ways in the digestion region 52. For example, the straw can be be mixed by being soaked in a container containing water, a water-alkali solution or a water-acid solution. The soaking causes the lignin, which has largely enclosed the cellulose, to be partially dissolved. After removal from the container, the cellulose is no longer hidden behind a lignin crust, but accessible to the hydrolysis and the bacteria. As a result, the straw which is used in conventional dry fermentation plants at most as a structural material, to a valuable fermentation substrate, which contributes significantly to the biogas development.

However, in an alternative embodiment, the straw in the digestion region 52 may be otherwise disrupted, for example, mechanically using a hammer mill or straw mill, or by being subjected to thermal pressure, i. heated to 180 ° C to 250 ° C for five to ten minutes at high pressure, for example, 20 to 30 bar. This softens the lignin. After the straw has cooled, the lignin solidifies again, but in the form of very small globules with gaps between them, which open the way for the autohydrolytic, organic acids and for the anaerobic bacteria to the nutrients of the straw. Another embodiment is an extension of the thermal printing treatment in which the pressure in the corresponding container is suddenly reduced, whereby the water evaporates in the straw structures and expands very rapidly. The lignin structures are torn and the nutrients for the anaerobic bacteria are exposed.

Provided in the staging area 48 is a roller conveyor 56 onto which individual bales of straw and / or straw bales are laid by the crane (not shown) and which conveys the straw bales to the fermentor forecourt 18 through a straw channel 58 arranged parallel to the fresh meal hopper 46 (see FIG Fig. 6).

As can be seen from the above description, both the loose fresh mass and the fresh bale mass are transported by stationary conveyor technology from the delivery and loading area 24 to the fermenter forecourt 18. In particular, make the Frischmassebunker 46 and the straw channel 58, the connection between the central Fermentervorplatz 18 and the peripheral delivery and loading area 24 ready, and this transport is done completely in the housed BMKW 10. The transport with the stationary conveyor technology is suitable for high throughputs and in particular faster, space-saving and cost-effective less expensive than a delivery with wheel loaders. As can be seen from FIG. 6, the straw channel 58 and the fresh-material bunker 46 terminate at a central location of the fermenter forerunner 18, so that the paths between the fermenter-front-side end of the fresh-material bunker 46 or straw channel 58 and the fermenter 16 to be supplied in FIG general are short.

As mentioned above, the digestion of the straw in the digestion region 52 makes it possible to use straw as a fermentation substrate despite its high lignin content. This is extremely advantageous because straw in crop production anyway incurred, and not enough use for this exists. Since the BMKW 10 is designed for renewable raw materials, it makes sense to grow in the vicinity of the BMKW 10 specifically for use in the BMKW 10 suitable raw materials, which, however, are generally not intended for nutrition or as feed. However, this poses a certain conflict of objectives because a certain proportion of the limited land available is always reserved for food production. The use of straw as a fermentation substrate is a very attractive solution, since straw, which is produced as residue during grain production, allows the simultaneous production of food and biomass suitable for use with power plants. In addition, it is possible to produce valuable fuel pellets from straw-containing fermentation residues, as explained in more detail below.

But straw has another advantage. In general, the filling level in fermenters is limited by the pressure at the bottom of the fermenter: this pressure must always be low enough for the fermentation substrate to still be permeable to percolate. If, however, according to an embodiment of the invention, in the lowest layer of each fermenter 16 introduces a layer of straw bales, the entire usual filling level can be layered on this layer of fermentation substance, since the straw bale layer even at the pressure then permeable to Percolate is. This lowermost straw layer thus represents an additional amount of fermentation substrate that can be used in a fermenter, so that the system performance (room capacity measured in new substrate per fermenter and day) is significantly increased.

In an advantageous embodiment of the invention, the straw bales are placed in packages of eight straw bales on the roller conveyor 56, which are two bales wide and four bales high. These packages are transported as a whole through the straw channel 58 and at the End of Fermentervoφlatz 18 by a converter (not shown) lifted and handed over to a wheel loader or forklift, which also receives the packages as a whole or in 2 parts and brings to the fermenter. From these packages can be relatively easily and quickly built said bottom straw bale layer.

As further shown in FIG. 8, a digestate bunker 60 is provided which extends parallel to the fresh meal bunker between the fermentor forecourt 18 and the delivery and loading area 24. The digestate bunker 60 has at its Fermentervorplatz the end facing a Schütttrog 62 for digestate, which forms the entrance into the Gärrestebunker 60. In this Schütttrog 62 fermentation residues are tilted by a wheel loader. From there they are pressed by means of a screw conveyor into the digestate bunker 60. Due to the discontinuous reprints of more and more fermentation residues, the mass is slowly transported through the digestate bin 60 to the other end, where they are transported by further screw conveyors from the digestate bunker 60.

The digestate bunker 60 has a fourfold function. On the one hand, it serves as a transport path between the fermenter forecourt 18 in the center of the BMKW 10 and the delivery and loading area, with similar advantages, as they have been described with respect to the Frischmassebunker 46 and the straw channel 58. On the other hand, the digestate bunker 60 also serves as a thermophilically operated secondary fermenter and acts more or less like another fermenter. Therefore, the digestate bunker 60 is also connected to the biogas system. Third, the digestate bunker 60 serves as a buffer for fermentation residues. It is dimensioned so that it holds at least as many fermentation residues as can be produced on two days. As a fourth function, the digestate bunker forms a device for washing out the digestate. Due to the high water content in the digestate bunker harmful substances such as chlorine, nitrogen, sulfur, potassium chloride and silicates are washed out of the fermentation residues, which increases the quality of the fermentation residue pellets as fuel.

The digestate bin is followed by a conveyor belt 66, with which fermentation residues are first conveyed to a screw press 70 and then to a dehydrating and pelletizing device 64, which will be described separately below. With the screw press 70, a significant portion of the water is squeezed out of the digestate. Together with the water, a significant part of the above-mentioned substances harmful to combustion are removed from the fermentation squeezed out. This represents a significant advantage over a process in which the fermentation residues would only be thermally dried, because in that case substantially more of the harmful substances would remain in the fermentation residues. The squeezed liquid phase is returned as process water in the fermentation residue bunker 60. In an advantageous development, it is previously mechanically and / or chemically treated in order to at least partially remove the said substances which are harmful for the combustion. In particular, an ultrafiltration is suitable, which is connected to a reverse osmosis. In a further advantageous embodiment, a portion of the liquid phase is disposed of, which also takes place pollutant removal.

3. Fermenter and percolate circulation tanks

In Fig. 10, a fermenter 16 is shown in cross section. The fermenter 16 is a conventional garage fermenter except that its ceiling height is higher than usual to accommodate the additional bale of straw on the ground. The fermenter 16 is separated by a gate 20 from the fermenter forecourt 18. In the illustration of FIG. 10, the fermentation mass in fermenter 16 is designated by reference numeral 72.

The fermenter 16 has percolate downcomers 74 on the bottom and a manifold 76 in which the percolate from all the gutters 74 is collected. The collecting channel 76 opens into a siphon shaft 78, from which the collected percolate is lifted by means of a lifting pump 80 and pumped into the percolate circulation tank 34.

A percolate pump 82 pumps the percolate from the percolate flow tank 34 into percolate nozzles 84 located in the area of the ceiling of the fermenter 16 to wet the digestate 72 from above.

A special feature of the illustrated embodiment of the invention is that the percolate circulation tank 34 is formed relatively large. Specifically, the Perkolatumlauftank 34 has a size of 450 m ³ and is intended to supply three fermenters 16. Each fermenter has a floor area of 245 m ² , and with a filling height of 4.25 m, a volume of 1041 m ³ . This means that the ratio of PUT volume to fermentation volume is 14.4%. Such a large percolate circulation tank acts as a kind of methane reactor in which methane is produced in large quantities. Therefore, the percolate circulation tank 34 is also connected to the biogas system. This will be explained in more detail below.

In the percolate circulation tank 34, a level sensor prevents underflow or overflow of predetermined percolate levels. When the maximum level is exceeded, the digestate of the fermenter, which is the next one intended for a refreshment of the fermentation liquor, can be sprayed with the surplus immediately before emptying. Due to the partial disposal of the fermenter content, excess percolate can thus be removed. In addition, all Perkolatumlauftanks 34 via a loop (not shown) connected to each other, so that excess percolate can be passed from one percolate circulation tank in another. When the level in the percolate tank reaches a lower minimum level, the spraying of the fermenter is automatically adjusted and this is displayed in the control room.

The fermenter 16 is coupled to the strong central venting system. The central deaeration system can suck room air into the fermenter from the fermenter forecourt and discharge it into the central deaeration system at the end of the fermenter. This protects the wheel loader driver when refreshing the digestate 72 in the fermenter 16 from breathing in biogas or exhaust gas from the wheel loader. Furthermore, the fermenter via the exhaust gas cooling space 31 is indirectly connected to the exhaust system of the gas engines (not shown). Before a fermenter is opened, the biogas contained therein can be displaced by exhaust gas and thus pressed into the gas reservoir 32. As a result, the biogas is not lost in the subsequent opening of the fermenter 16 by the otherwise required direct or indirect (via biofilter) discharge into the ambient air. In particular, damage to the environment is prevented by the greenhouse gas methane, which is 28 times as harmful as carbon dioxide (CO ₂ ). After refreshing the fermentation mass and closing the fermenter 16, engine exhaust may in turn be introduced to displace the oxygen-rich atmosphere in the fermenter 16 so that the anaerobic digestion process starts faster, increasing plant performance.

In conventional biogas plants with fermentation of solids, the four stages of fermentation, hydrolysis, acidogenesis, acetogenesis and methanogenesis all take place in the fermenter. However, there is the problem that the fermentative and acidogenic bacteria of a On the other hand, the acetogenic and methanogenic bacteria on the other hand prefer different living conditions. The hydrolytic and acidogenic bacteria prefer an acidic range with a pH of 5.7 to 6.3. By contrast, the optimum pH of the methanogenic bacteria is between 6.7 and 7.5. If the pH falls well below this range, the methanogenic bacteria are inhibited and methane production drops drastically. A particular problem is that the acidity temporarily drops significantly after a fermentation mixture, which is caused in particular by the auto-hydrolysis that always occurs in fresh material. Shortly after a booster freshening, the living conditions for the methanogenic bacteria are therefore particularly bad.

Moreover, since the methanogenic bacteria have relatively long reproduction times, it would be advantageous, from the viewpoint of the methanogenic bacteria, to relatively rarely regenerate the fermentation mass. However, this means that the throughput of fresh mass is relatively low and thus the performance of the biogas plant is below its optimum potential.

Within the scope of the advantageous developments of the invention, it is possible to spatially separate the hydrolysis and the methanation to a certain degree. In the PUT conditions are created in which the methanogenic bacteria live well, reproduce well and can produce a lot of methane. This means that in the context of the invention, the methane production is at least partially shifted from the garage fermenter into the PUT, ie that a considerable proportion of methane gas is produced by the acedogenic and methanogenic bacteria in the PUT. The structure is designed so that the products of the acid-fast fermentative (hydrolytic) and acidogenic bacteria are washed out by the percolate and passed into the PUT. In the PUT, the acetogenic and methanogenic bacteria can convert these products to methane gas. The acidity of the percolate decreases so that it is introduced into the fermenter after passing through the PUT at an elevated pH. In this cycle, the hydrolytic and acidogenic bacteria in the fermenter and the acetogenic and methanogenic bacteria in the PUT each find their preferred living conditions, and hyperacidity of the fermenter is effectively avoided. In particular, the acid-susceptible methanogenic bacteria can propagate undisturbed in the PUT and produce methane, unlike in the fermenter, where they are exposed to an acid spike at each boil-up refreshment. In particular, this allows a high methane yield even with relatively short fermentation cycles of about nine days. Of course, in the garage fermenter also methanogenesis still takes place, but to a lesser extent than without separation into fermenter and PUT. Clearly, one could say that the garage fermenter tends to become a hydrolysis vessel and the PUT a methane reactor, although of course also in the garage fermenter and in the percolate, which is sprayed into the garage fermenter, methanogenic bacteria are present and therefore also in the garage fermenter considerable amount of methane gas is produced.

In Fig. 11 is a schematic sectional plan view of a PUT 34 is shown according to a development of the invention. The PUT 34 comprises a mixing chamber 98 in which the percolate, which originates from six associated fermenters (F ₁ to F ₆ in FIG. 11), is combined and thereby mixed. This has the consequence that the acidity of the individual percolate contributions compensates. For example, if the percolate from one of the six fermenters is particularly acidic just because a fermentation liquor has just taken place, this acidic peak will be substantially lessened by the less acidic percolate from the other five fermentors.

The fermenter 34 comprises a plurality of partitions 100, which form a channel structure through which the percolate is guided, as indicated in Fig. 11 by the arrows. The channel structure is chosen so that the flow rate within the channel structure is less than 4 cm per second, preferably less than 2.5 cm per second. While the percolate flows through the channel structure, the products of the hydrolytic and acicogenous bacteria are degraded by the methanogenic and acetogenic bacteria, whereby the acidity of the percolate gradually decreases. This means that the acidity of the percolate immediately after entry into the PUT 34 is still relatively high and gradually decreases along the channel structure. Thus, of the variety of acetogenic and methanogenic bacterial strains involved in fermentation, those that tolerate lower pH will preferentially settle near the entrance of the PUT 34, and those that are less acid resistant will tend to be in the range of the exit 102. Overall, the individual bacterial strains thus each settle where the living conditions are most favorable for them, whereby the overall methanogenesis is increased. While the acetogenic bacteria produce hydrogen, the methanogenic bacteria consume hydrogen. The most efficient way to exchange hydrogen is between acetogenic and methanogenic bacteria when they are in intimate cell contact. For this purpose, the bacteria involved form a flake structure in the PUT. So that these flakes are not destroyed by the shear forces in the percolate flow, the flow rate is kept below 4 cm per second, preferably below 2 cm per second, by a suitable choice of the channel structure.

In order to build the largest possible population of acetogenic and methanogenic bacteria in the PUT, artificial settlement structures are preferably provided for them. FIG. 12 schematically shows a PUT 34 according to an embodiment of the invention, in which nets 104 filled with woodchips are provided as artificial settlement structures. For the sake of simplicity, in the illustration of Fig. 12, the channel structure has been omitted. It should be understood, however, that the channel structure and artificial settlement surfaces 104 are preferably combined. The woodchips in the nets 104 provide a very large settlement surface for the acetogenic and methanogenic bacteria.

FIG. 13 shows a cross section through another PUT 34 or a channel section thereof according to a development of the invention. In the PUT 34 of FIG. 13, notches 106 are formed in the PUT channel walls, into which rods or battens 108 mounted transversely to the passageway are inserted. These rods or battens 108 are made of a corrosion-resistant material, such as wood. These bars or battens 108, possibly in combination with underneath longitudinally extending slats or slats (not shown), serve to hold down the wood chip-filled nets 104 or other settlement bodies so that they do not float above the percolate level.

In the illustration of FIG. 13, further filling bodies, for example nets 110, in turn filled with wood chips, are provided which form settling areas for sulfur bacteria. The sulfur bacteria serve to biologically bind to the resulting in the anaerobic bacterial fermentation harmful sulfur compounds, in particular H ₂ S, COS and CS ₂ . As a result, the biogas is desulfurized in a simple and cost-effective manner, which is advantageous for several reasons. For example, the hydrogen sulfide in the biogas can lead to significant problems in the use of gas, such as corrosion in the equipment and the engines. Even concrete components can be affected by corrosion if hydrogen sulfide oxidizes in the air and sulfuric acid is formed. Another problem is that the combustion of hydrogen sulfide produces sulfur dioxide, which causes problems on the exhaust side. Therefore, it is extremely advantageous if the biogas is at least partially desulfurized in this way.

For the sulfur bacteria it is advantageous if the atmosphere in the PUT contains 0.5 to 1% oxygen (corresponding to 2.5% to 5.5% air). To this end, in the PUT 34 of Fig. 13, an inlet 112 is provided with a controllable valve 114 through which the appropriate amount of air is introduced into the PUT. Since the acetogenic and methanogenic bacteria in the percolate settle below the percolate level, the oxygen-containing atmosphere does not harm them.

For their function, the sulfur bacteria firstly need contact with the biogas they are supposed to clean, secondly, the already mentioned oxygen for the oxidation of sulfur, thirdly water for the microbiological process and, fourthly, nutrients for their own growth. Water and nutrients are contained in percolate. In the illustration of FIG. 13, the packing 110 intended for the settlement of sulfur bacteria is placed on the bars or battens 108. The level is chosen such that the fillers 110 are wetted by the percolate at a high percolate level, and are exposed to the biogas at a low percolation level. These fluctuations in the percolate level are correlated with the fermentation liquor, in which large quantities of percolate are squeezed out of the fermentation mass, which leads to an increase in the level in the PUT.

Furthermore, an outlet 116 for biogas is shown in FIG. 13, which is generated in the PUT 34 and is supplied to the associated gas storage or to the gas engines. In Fig. 14, an alternative embodiment is shown, in which a device 118 for spraying the filler body 110 with percolate is installed. The device 118 includes a conduit 120 and a pump 122 through which percolate can be withdrawn from a lower portion of the PUT 34 of FIG. 14 and sprayed onto the settlement surfaces 110 through nozzles 124 on the ceiling of the PUT 34. In this way, the packing 110 forming settlement areas for sulfur bacteria can be supplied with sufficient percolate, ie, water and nutrients, and moreover are exposed to the biogas atmosphere having the above-mentioned low oxygen content.

Fig. 15 is a schematic diagram in which six fermenters 16 and a PUT 34 are not shown to scale. As shown in FIG. 15, the percolate outlets of the fermenters 16 are connected to a percolate manifold 126. The percolate passed through this percolate manifold 126 is directed to a sump 128 which functionally corresponds to the mixing chamber 98 of FIG. In this collecting container 128, the percolate from the six fermenters 16 shown is mixed, with acid peaks are leveled from individual fermenters. The percolate is then introduced from the collection container 128 into the PUT 34, in which, for the sake of clarity, the channel structure and the packing are not shown as artificial settlement areas for bacteria.

The output 102 of the PUT 34 is connected to another line 130, which in turn has a branch 132 for each of the six fermenters 16. These branches 132 serve to spray percolate from the PUT 34 into the fermenters 16 through nozzles 84 (see FIG. 10) on the fermenter cover.

By the construction of FIG. 15, a percolate cycle is created from the six fermenters 16 via the collection container 128 into the PUT 34, and from the PUT 34 via the conduit 130 and the branches 132 again into the fermenters 26. As explained above, this design results in reducing the acid load contained in the percolate between leaving the fermenters 16 and re-entering the fermenters 16. This is done by forming a population of methanogenic bacteria in the PUT that produces high methane yields. Along with the population of methanogenic bacteria, acid digestion capacity increases so that higher acid peaks in fermenters 16 can be more often "digested". This allows the fermenter 16 more often and more Fresh mass to be loaded, whereby the system performance, ie the room capacity in kg oTS / m ³ fermenter room / day increases. Overall, therefore, fewer fermenters need to be built for the same amount of substrate, or in other words, less investment in investment must be made for the same amount of electricity produced, thereby increasing the productivity and economy of the plant.

Despite an increased acid concentration in the fermenter, the biochemical processes are very stable. The higher acid concentration in the fermenter, which is made possible by the construction shown, leads to a higher degradation of the organic substances, as a result of which the substrate performance also continues to rise and also the raw material procurement costs decrease.

As further shown in FIG. 15, all six fermenters 16 are connected to a biogas manifold 134, through which biogas is passed from the fermenters 16 to the gas reservoir or gas engine. The PUT 34 also has an outlet 136 for biogas connected to the biogas manifold 134. Further, the PUT 34 is connected to a balance gas storage 138.

Finally, the PUT 34 includes a drain 140 through which percolate can be drained from the PUT 34 and discarded. The percolate does not become infinitely old in the cycle shown. The ability to dispose of percolate from the circulation is important so that it does not lead to undesirable concentrations of inhibitors in the percolating percolate. The drain 140 is chosen to be so large that the pull created during its opening is sufficient to wash away deposits on the bottom of the PUT 34 so that it does not need to be cleaned or only rarely.

The PUT 34 shown in Fig. 15 is also connected via a loop 141 to other PUTs of the biogas plant 10, which in turn are connected to another group of fermentors in a similar manner, as shown in Fig. 15. Through the ring line 141, a balance in the percolate amount can be created between the individual PUTs 34. Also, other PUTs may temporarily replace one of the PUTs, for example, if it can not be operated for maintenance. The fermentation and Power generation operation can then be maintained undisturbed, so there is no production losses for gas and electricity.

As mentioned above, the biogas plant described here is particularly suitable for the fermentation of solid manure and straw. With a relatively high proportion of straw in the fermenter, the ability of the digestate to accept percolate exceeds a capacity of 0.75 m percolate per 1 m fermenter base area and day. In fact, around 1 m ^{3 of} percolate per square meter of fermenter base area and day can be absorbed. With a fermenter base area of 245 m ² , this means that around 250 m ³ are sprayed into a fermenter per day. In preferred operation, the percolate remains in the PUT for about five hours, so the percolate is handled about five times a day. For the ongoing operation of a fermenter, the PUT 34 should thus have a liquid volume of 50 to 60 m ³ ready. Since a PUT 34 supplies six fermenters 16, the PUT 34 should have 360 m ^{3 available} solely for taking up the percolate. However, this volume is still the volume that take the filling for the colonization of bacteria in the PUT. Preferably, the packing takes two thirds of the volume of the PUT. In addition, the PUT 34 is preferably capable of receiving percolate which is squeezed out of the fermentation mass during the fermentation. These are around 420 m ³ . Overall, therefore, the PUT 34 preferably has a volume of 1,500 m ³ . When woodchips are used as packing, the volume of the PUT is ideally 17% to 23% of the volume of the fermenter for which it is intended.

4. Hospital refresher

16 shows schematically a plan view of the fermenter forecourt 18 with the adjacent fermenters. In the representation of FIG. 16 it is schematically shown how the fermentation of the fermentation is carried out on the example of the fermenter F ₁₁ . For this purpose the angegorene fermentation mass is completely removed from the fermenter F ₁₁ and unloaded onto the fermenter forecourt 18th Of the extracted anaerobic digestate about 20% are introduced as digestate in the fermentation bunker 60, where it is subjected to secondary fermentation. The remaining approximately 80% of the fermented fermented mass is pressed out using a screw press so that a liquid phase is formed. This liquid phase is introduced into one or more PUTs. The pressed out fermented fermentation mass serves as so-called inoculation mass for the added fresh mass. After mixing of inoculum and fresh mass, the refreshed fermented mass is returned to the fermenter Fn.

As mentioned at the beginning, the biogas plant in the base section 12 (see FIG. 6) comprises 18 fermenters. Of these 18 fermenters, the fermentation mass is preferably refreshed twice daily, resulting in a fermentation cycle of nine days. This is considerably shorter than the usual fermentation cycles of about 28 days in known solidification processes. In fact, however, with such a shortened fermentation cycle, plant performance can be significantly increased, as the inventor found in computer simulations. As a result of the fact that the particularly acid-sensitive methanogenic bacteria can settle in the PUT, the now more frequently occurring acid peaks can be absorbed during the regeneration of the digestate, without the gas yield being significantly impaired.

By squeezing the fermented nutrients are removed, which are kept in the percolate and in particular for the growth and nutrition of methanogenic and acetogenic bacteria in the PUT are conducive.

5. Electricity and heat generation plant

The power and heat generation plant 22 is shown enlarged in FIG. It comprises four engine compartments 88a to 88d, which are each intended to set up a gas engine with a generator connected. The gas engines use the dried and biologically desulphurised, but otherwise unchanged biogas as fuel. As mentioned above, each motor is supplied via a separate gas compressor which draws the biogas from the central gas reservoir 86 via overpressure and low-pressure switches, gas filters and flashback arresters (not shown) and presses them into the gas control path of the engine at a pressure of 80 to 200 mbar ,

The biogas is burned in the engines, converting chemical energy into mechanical energy and heat. The required combustion air passes through a separate ventilation system 90a to 9Od in the respective engine room 88a to 88d. In addition, for each engine room 90a to 90d a separate vent system 92a to 92d intended. The amount of fresh air supplied is about six times as high as the need for combustion air.

The mechanical energy of the motor is converted in the connected medium voltage generators (not shown) into electrical power, which can be fed directly into a medium voltage grid. The resulting heat of combustion is discharged via cooling circuits of the engines (cooling gas-air mixture, oil cooling, water cooling) (not shown) in three heat exchangers, which are connected in series with each engine. By the engine heat directly fermenters 16, the Perkolatumlauftanks 34, the Frischmassebunker 46, and the digestate bunker 60 are heated. In addition, additional heat may be used to heat a government building (not shown). However, this only accounts for around 5% of the available heat. The majority of the waste heat is used to dry fermentation residues in the dehydrogenation and pelletizer 68, which will be described in more detail below. Further heat can be fed into a BMKW's own local heating network via which, for example, neighboring commercial enterprises can be supplied.

Furthermore, the power and heat generation system 22 includes a docking station 94. The docking station is equipped with the entire periphery of a generator set, in particular the gas compressor, the gas control system, the ventilation system, exhaust gas heat exchangers, exhaust mufflers, supply fresh oil, waste oil and connections the heating system. This periphery can be connected via flexible connections to a mobile generator set, which can be brought in if required.

If a gas engine fails, the gas utilization side of the shown BMKW drops to a maximum of 75% of the power, and this only for a short time, namely until the mobile replacement generator set has been procured. Such a replacement generator set can for example be kept at a central point in Germany on a low loader for a variety of BMKWs and brought in case of need and connected.

However, the docking station 94 serves not only for unplanned failures of a generator set, but in particular for planned maintenance on one of the generator sets, so that the power of the BMKW does not have to be shut down during the maintenance measures, because the substitute generator set, which is connected to the docking station 94, takes over the work of the generator set to be maintained.

Finally, the power and heat generation plant 22 includes an oil storage 96.

6. Device for dehydrating and pelleting fermentation residues

Fig. 17 is a block diagram schematically illustrating the components of the digestate dehydrogenation and pelletizer 68. The device 68 comprises the screw press 70 already mentioned above in connection with FIG. 8. The screw press 70 is capable of dehydrating the fermentation residues that come very wet from the digestate bunker 60 to a moisture content of 45 to 55% by weight. The achievable moisture content is adjusted so that the residual moisture remaining from the waste heat of the gas engines can be dried sufficiently. The resulting during pressing liquid phase is fed as process water back into the fermentation residue bunker 60. If necessary, it is cleaned or chemically worked up. The solid phase is applied to the conveyor belt 66, which is shown in Fig. 8 and is symbolized by an arrow in Fig. 15. Instead of the screw press 70, a decanter can also be used.

As further shown in FIG. 15, a low temperature belt dryer 142 (see also FIG. 8) operatively connects to the screw press 70, during which no dioxins and furans are formed during the drying process due to the low temperature of around 120 ° C. The belt dryer 142 is heated exclusively with the waste heat of the generator sets, which makes the overall process very efficient. The fermentation residues fed from the conveyor belt 66 fall into a discharge hopper (not shown) from which a distributor applies it to an underlying drying belt (not shown). The fermentation residues form a "carpet" on the drying belt which is driven through a drying tunnel (not shown). A warm air stream ventilates the digestate carpet and dries the wet material. The drying process takes place continuously. During the drying process, the moisture content of the fermentation residue is measured and the heat input is controlled so that the water content of the digestate is reduced to 7 to 13% by weight. The aim of the regulation is inter alia that the Belt dryer always ensures the desired low moisture level of the dried fermentation residues with fluctuating parameters such as heat output, moisture of the digestate, dehydration conditions and quality of the fermentation residues. Alternatively, instead of the belt dryer, a drum dryer (not shown) with contact drying may be used which also operates at sufficiently low temperatures.

The belt dryer 142 is designed so that the accumulated residual heat can be used as completely as possible, with particular consideration of summer heat spikes, which are not caused by the sale of e.g. can be leveled for heating purposes.

The belt dryer 142 is followed by a pneumatic conveying system, which is represented by the arrow 144 in the schematic representation of FIG. 15. Since the fermentation residues after drying in the belt dryer 142 are very light, a pneumatic conveyor system is preferable to a conveyor belt because less material is lost during transport and less dust is generated.

From the pneumatic conveying system 144, the dried fermentation residues are introduced into a hammer mill 146, in which the dried fermentation residues are comminuted. The Harnnermühle 146 is a conventional large capacity hammer mill known per se on rigid base frames with vibration dampers, electric door lock, storage temperature monitoring and Mahlkammertemperaturüberwachung, as currently for the milling of natural substrates such as straw, corncob, alfalfa, hay, paper, wood , Hemp or jute is already in use. The hammer mill 146 may alternatively be arranged between the screw press and the belt dryer. In this case, the crushing of the material takes place at an even higher moisture content of the digestate, so that less dust is formed and the associated risk of explosion is prevented. Instead of the hammer mill 146 and a straw mill can be used.

The dried and comminuted fermentation residues are introduced from the hammer mill 146 via a further pneumatic or mechanical conveyor 148 into a conditioner 150. In the conditioner 150, the fermentation residues are mixed with suitable additives. which increases the quality of the pellets finally produced. For example, cereal flour and / or molasses and / or starch may be added to the conditioner 150, thereby increasing the strength of the fermentation residue pellets, which in turn improves combustion. In addition, the fermentation residues in the conditioner 150 can be exposed to water vapor, which makes the mass smoother and easier to pelletize. Additionally or alternatively, the fermentation residues in conditioner 150 may be added with quicklime in small amounts (eg 1 to 2% by weight) to positively influence the ash softening behavior of the pellets upon burning due to the altered ratio of calcium to potassium in the ash. Finally, the fermentation residues in the conditioner 150 sawdust or wood chips can be added, by the quality of the obtained fermentation residual pellets is further increased as a fuel. Further, in the conditioner 150, oil press cakes may be added which are obtained in the recovery of oil from rapeseed or pumpkin seeds and which may increase the calorific value of the fermentation residue pellets. In order to increase the burning behavior of the fermentation residue pellets, magnesium, calcium and / or aluminum can also be added. The aim of the admixture is that the fuel pellets reach standard fuel quality and / or are suitable for use as fuel in accordance with the conditions specified in the first and / or the fourth Federal Immission Control Ordinance (BImSchV).

In the preferred embodiment, the conditioner 150 is placed directly on the pelletizer 152 so that the fermentation residues processed in the conditioner 150 are introduced directly from the conditioner into the pelletizer 152 without a buffer.

The pelletizer 152 is formed by a pelletizing press known per se. In the pelleting press 152, the processed fermentation mass is pressed in a pug mill at high pressure through dies, wherein the lignin contained in the digestate melts, whereby the molding compound is caked together. Behind the die, a knife cuts the pellets off, for example, 15 mm long pieces. Alternatively, however, fuel briquettes can be produced. The pellets are introduced via a further, possibly mechanical conveyor 154 into a cooling device 156, in which the pellets, which have been heated during the conditioning and pelleting, can cool.

Another, possibly mechanical conveyor 158, the pellets are transported in a storage silo 68, which is also shown in Fig. 8, in which they are stored until their removal. The fermentation residue pellets are hydroscopic due to their low water content, that is, they tend to absorb water from the ambient air. Therefore, they are stored in the storage silo 68 in a very dry atmosphere and transported for example in a tank truck from the storage silo 68 to the consumer.

With the dehydration and pelletizer 64 shown, valuable fuel pellets are recovered from the digestate. If the substrate mixture for the fermentation process mainly consists of straw and solid manure, fermentation residue pellets are obtained whose calorific value is between 5000 and 5400 kWh per tonne of dry matter. As a result, an energetically and economically valuable fuel is created, for its generation only waste heat is used, which is obtained anyway, and a small fraction of the power generated anyway in the biomass power plant. Since the fermentation residues are washed out in the fermenter 16 and in the digestate bunker 60, the resulting fuel has a good quality with respect to immission. The efficiency of the biomass power plant as a whole is extremely high due to the inventive combination of biogas production by fermentation of straw and Gärrestepelletie- tion.

Although a preferred embodiment has been shown and described in detail in the drawings and foregoing description, this should be considered as illustrative and not restrictive of the invention. It should be understood that only the preferred embodiment is shown and described and all changes and modifications that are presently and to the future scope of the invention should be protected. Michael Feldmann F30376PCT (Y) List of Reference Signs

10 Biomass power plant as an example of a biogas plant

12 basic section

14 expansion section

16 fermenters

18 fermenter forecourt

20 fermenter gate

22 Electricity and heat generation plant

24 delivery and loading area

26 fermenter forecourt hall section

28 Delivery and loading area hall section

30 technology bridge

31 exhaust gas cooling room

32 foil gas storage

34 percolate circulation tank

36 Southern Technical Room

38 Northern Technical Room

40 light bands

42 delivery bunker for fresh mass

44 conveyor belt

46 fresh bunker

48 staging area

50 bales delivery room

52 digestion area

54 interim storage

56 roller conveyors

58 straw channel

60 digestate bunker

62 Schütttrog for fermentation residues

64 Device for dehydration and pelleting

66 conveyor belt for fermentation residues

68 storage silo for fermentation residue pellets

70 screw press 72 digestive mass

74 gutters

76 collecting troughs

78 shaft

80 lifting pump

82 percolate pump

84 percolate nozzles

86 central gas storage

88a - 88d engine room

90a - 9Od Ventilation systems for engine compartments 88a - 88d

92a - 92d Ventilation systems for engine compartments 88a - 88c

94 docking station

96 oil storage

98 mixing chamber

100 dividing wall

102 output

104 packing as settlement area for methanogenic bacteria

106 notch in channel wall

108 wooden staff

110 packings as settlement area for sulfur bacteria

112 air intake

114 valve

116 outlet for biogas

118 spraying direction

120 pipeline

122 pump

124 percolate nozzles

126 percolate collector

128 collection containers

130 percolate line

132 branch in the percolate line 130th

134 Biogas collecting line

136 outlet for biogas

138 equalization memory 140 Drain from PUT 34

141 PUT loop

142 belt dryer

144 pneumatic conveyor

146 Hammer mill

148 pneumatic conveyor system

150 conditioners

152 pelletizer

154 pneumatic conveyor system

156 cooling device

158 pneumatic conveyor

Claims

FeldmannF30376PCT (Y) 12.12.2007Patentansprüche

A biogas plant (10) for producing biogas by the anaerobic, bacterial solidification process comprising: a plurality of fermentors (16) of the garage type, at least one percolate circulation tank (34) (PUT) connected to at least one associated fermenter for receiving percolate, characterized in that the PUT (34) is connected to the biogas system and has a volume which is at least 5%, preferably at least 7%, particularly preferably at least 10% and in particular at least 12% of the volume of that fermenter (16) or of that fermenter (16). 16) with which it is connected to take up percolate

2. biogas plant (10) according to claim 1, wherein a plurality of PUTs (34) are provided, which are interconnected by a Perkolatleitung, in particular a Perkolatringleitung (141).

3. biogas plant (10) according to claim 1 or 2, wherein the PUTs (34) are arranged above the or the associated fermenter (16).

4. biogas plant (10) according to any one of the preceding claims, wherein the ratio of fermenters (16) to PUTs (34) is at least 3: 1, preferably at least 5: 1.

5. biogas plant (10) according to any one of the preceding claims, wherein the from different fermenters (16) derived Perkolatzuflüsse are mixed together before they are introduced into a PUT.

6. biogas plant (10) according to any one of the preceding claims, wherein the PUT is arranged in a PUT circuit, in the percolate, which by a run out a fermenter (16), must pass through at least one PUT (34) before it is reintroduced into a fermenter (16).

7. Biogas plant (10) according to one of the preceding claims, wherein the at least one PUT (34) is heatable.

8. biogas plant (10) according to any one of the preceding claims, in which in the at least one PUT artificial settlement areas (104) are installed for methanogenic bacteria.

9. biogas plant (10) according to claim 8, wherein the settlement areas are formed by one or more of the following items:

^■ racks in which towel, carpet or curtain-like fabrics can be hung,

■ basket-like structures or hollow balls of acid-resistant plastic, in particular those filled with smaller objects,

^■ lamellar structures made of plastic,

^■ heaps of objects with large surfaces, in particular woodchips or straw,

■ nets (164) filled with woodchips, straw or similar material.

10. biogas plant (10) according to claim 8 or 9, are provided in the means which prevent floating of objects (104), which form artificial settlement structures for methanogenic bacteria.

11. biogas plant (10) according to any one of the preceding claims, wherein in the PUT (34) a channel structure is formed such that percolate, which at an entrance into the PUT (34) enters, is guided to its exit along a flow path whose length is at least three times, preferably at least six times, the largest dimension of the PUT (34).

12. biogas plant (10) according to claim 11, wherein the channel structure is formed such that the biogas which is formed in the PUT (34) is guided until its exit into the biogas system in this channel structure above the flow path of the percolate.

13. biogas plant (10) according to any one of the preceding claims, wherein the at least one PUT (34) access, in particular gas-tight closable hatches, through which it is accessible to operating personnel.

14. Biogas plant (10) according to one of the preceding claims, wherein the at least one PUT (34) has a foil roof.

15. biogas plant (10) according to one of claims 1 to 13, wherein the PUT (34) has a fixed roof and is connected to a compensation gas storage (138).

16. biogas plant (10) according to any one of the preceding claims, in which a device (112) is provided which is suitable in the gas atmosphere of the PUT (34) an oxygen content of 0.2% to 2.5%, preferably from 0 To make 5% to 1%.

17. biogas plant (10) according to any one of the preceding claims, wherein in the PUT (34) artificial settlement areas (110) are arranged for sulfur bacteria.

18. biogas plant (10) according to claim 17, wherein the settlement surfaces (110) are arranged for sulfur bacteria in such a way that they temporarily within the expected fluctuation of the level of the percolate in the PUT (34) wetted by percolate in the PUT (34) be temporarily exposed to biogas.

19. biogas plant (10) according to claim 17 or 18, wherein in the at least one PUT (34) means (124) for spraying the settlement surfaces (110) is provided for sulfur bacteria with percolate.

20. biogas plant (10) according to any one of the preceding claims, in which in the garage fermenters, preferably between the percolation nozzles (84) and the digestate (72), artificial settlement areas for sulfur bacteria are arranged.

21. biogas plant (10) according to any one of the preceding claims, with a press that is suitable, already angegorene fermented mass, which is retrieved in the course of a Gärmassenauffrischung from the fermenter (16) and used as an inoculant for the fresh mass, so that the liquid phase in at least one PUT (34) passed and the solid phase can be mixed with the fresh mass.

22. biogas plant (10) according to any one of the preceding claims, in which a circumferential pipeline is provided with nozzle-like outputs percolate, and in the bottom of the PUTs (34) at least one drain is provided, swirled by the Perkolatschlick and from the PUT (34) can be discharged, wherein the slope of the soil PUT and the diameter of the discharge are so large that the dry matter, which has settled at the bottom of the PUT as Perkolatschlick, is flushed off when drained through the at least one drain.

23. Biogas plant (10) according to one of the preceding claims, with a device for chemical, mechanical and / or thermal digestion of lignin- and / or fibrous renewable raw materials, in particular of straw.

24. Biogas plant (10) according to claim 23, in which the device for mechanical digestion comprises a device for cutting, shredding and / or grinding ligninous and / or fibrous raw materials, in particular a hammer mill or straw mill.

25. biogas plant (10) according to claim 23 or 24, wherein the means for the digestion of lignin- and / or fibrous renewable resources comprises a device for saturated steam treatment.

26. biogas plant (10) according to claim 25, wherein the means for saturated steam treatment comprises a pressure vessel and means which are adapted to produce a water vapor in the pressure vessel, with a pressure which is between 20 and 30 bar and a temperature between 180 ⁰ C and 250 ° C.

27. biogas plant (10) according to any one of claims 23 to 26, wherein the means for digesting lignocellulosic renewable resources comprises a container for soaking them in water, a water-alkali solution, a water-acid solution, percolate or manure ,

A biogas plant (10) according to any one of the preceding claims comprising: means (64) for dehydrating and pelleting digestate suitable for processing digestate into fuel pellets and / or fuel briquettes.

29. Biogas plant (10) according to claim 28, with a device (60) for washing out or eluting the fermentation residues.

30. biogas plant (10) according to any one of the preceding claims, with at least one gas engine and at least one power generator which is operable by the gas engine.

31. Biogas plant (10) according to any one of claims 28 to 30, wherein the means (64) for dehydrating and pelleting comprises means for mechanically dehydrating digestate, in particular a screw press (70) or a decanter.

32. Biogas plant (10) according to any one of claims 28 to 31, wherein the means (64) for dehydrating and pelleting of digestate comprises a drying device, in particular a belt dryer (142) or a drum dryer with contact drying.

33. Biogas plant (10) according to claim 32, wherein the drying device (142) is operated with waste heat from at least one gas engine of the biogas plant (10).

34. Biogas plant (10) according to claim 32 or 33, wherein the temperature of the drying device 180 ° C, preferably does not exceed 140 ° C.

35. Biogas plant (10) according to any one of claims 28 to 34, wherein the means (64) for dehydrating and pelleting of digestate a means for crushing the at least partially dehydrated and optionally dried fermentation residues, in particular a hammer mill (146) or a straw mill comprises.

36. Biogas plant (10) according to any one of claims 28 to 35, wherein the means (64) for dehydrating and pelleting fermentation residues comprises a conditioning device (150) which is suitable, the crushed and at least partially dehydrated and / or dried fermentation residues or to combine several of the following: cereal flour, molasses, starch, quicklime, steam, wood shavings, sawdust, oil press cake, calcium, magnesium, aluminum, nitrogen-binding agents, in particular nitrogen-reducing reducing agents, hydrated lime.

37. Biogas plant (10) according to any one of claims 28 to 36, wherein the means (64) for dehydrating and pelleting fermentation residues comprises a pelleting press (152) which is suitable for pressing the comminuted and dehydrated fermentation residues into pellets or briquettes.

38. Biogas plant (10) according to any one of claims 28 to 37, wherein at least some of the components of the device (64) for dehydrating and pelleting of digestate by a pneumatic and / or mechanical conveyor (144, 148, 154, 158) are connected ,

39. Biogas plant according to one of the preceding claims, with a delivery and loading area (24).

40. Biogas plant (10) according to claim 23 and 39, wherein the means for chemical, mechanical and / or thermal digestion of straw in the delivery and loading area (24) is housed.

41. Biogas plant (10) according to claim 39 or 40, wherein the delivery and loading area (24) stationary conveyor technology (44, 46, 56), which is suitable biomass from the delivery and loading area (24) to a digester forecourt (28) from which a plurality of fermenters (16) of the garage type are accessible.

42. Biogas plant (10) according to claim 39, 40 or 41, in which the delivery and loading area (24) comprises at least one housed delivery bunker (42) for fresh mass.

43. Biogas plant (10) according to claim 42, with first conveying means (44) which are suitable for conveying fresh material from the at least one delivery bunker (42) for fresh mass to a fresh mass bunker (46).

44. Biogas plant (10) according to claim 43, in which the first conveying means comprise a conveyor belt (44) on which fresh material from various delivery bunkers (42) can be conveyed to the fresh material bunker (46).

45. Biogas plant (10) according to claim 43 or 44, with second conveying means, in particular a thrust plate, which are suitable to convey the fresh material through the Frischmassebunker (46) in the direction of the Fermentervorplatz (18).

46. Biogas plant (10) according to one of the preceding claims, which within the delivery and loading area (24) comprises a discharge point (50) with crane and an intermediate storage for bale material, in particular for straw.

47. Biogas plant (10) according to claim 46, which comprises third conveying means, in particular roller conveyors or push conveyors, which are suitable for conveying individual bales or packages of bales along a bale duct (58) to the fermenter forecourt (18).

48. Biogas plant (10) according to one of the preceding claims, with a digestate bunker (60), which is accessible from the fermenter forecourt (18) for introducing fermentation residues.

49. Biogas plant (10) according to claim 48, wherein the digestate bunker (60) comprises stationary conveying means, in particular screw conveyors, which are particularly suitable by their arrangement at the inlet and outlet to transport digestate through the digestate bin (60).

50. Biogas plant (10) according to claim 48 or 49, wherein the digestate bunker (60) is connected to the biogas system.

51. A process for producing biogas after the anaerobic, bacterial solidification process in a biogas plant (10) having a plurality of fermenters (16) of the garage type, in which percolate from the fermenters (16) into at least one percolate flow tank (PUT) (34) is introduced and percolate is recycled from the at least one PUT (34) into at least one associated fermenter (16), characterized in that the PUT (34) is connected to the biogas system and has a volume which is at least 5%, preferably at least 7%, particularly preferably at least 10%, and in particular at least 12%, of the volume of that fermenter or of the fermenter with which it is connected to receive percolate

52. The method of claim 51, wherein the ratio of fermenters (16) to PUTs (34) in the biogas plant at least 3: 1, preferably at least 5: 1.

The process of claim 51 or 52, wherein the percolate circulation from the fermenter (16) to the PUT (34), through the PUT (34) and out of the PUT (34) back into the fermenter (16) is made such that reduces the acid load contained in the percolate between leaving the fermenter (16) and re-entering the fermenter (16).

54. The method of claim 53, wherein the reduction of the acid load by an increased settlement of acetogenic and methanogenic bacteria in the PUT (34).

A method according to any one of claims 51 to 54, wherein the percolate feeds from different fermentors (16) are mixed together before being introduced into a PUT (34).

56. The method according to any one of claims 51 to 55, wherein the percolate, which runs out of a fermenter (16) passes through at least one PUT (34) before it is reintroduced into a fermenter (16).

57. The method according to any one of claims 51 to 56, wherein in the at least one PUT (34) artificial settlement areas (104) are provided for acedogenic and methanogenic bacteria.

58. The method of claim 57, wherein the settlement areas are formed by one or more of the following items:

^■ racks in which towel, carpet or curtain-like fabrics can be hung,

^■ basket-like structures or hollow balls of acid-resistant plastic, in particular those filled with smaller objects,

^■ lamellar structures made of plastic,

^■ heaps of objects with large surfaces, in particular woodchips or straw,

^■ nets (104) filled with woodchips, straw or similar material.

59. The method according to any one of claims 51 to 58, wherein the percolate is guided in the PUT (34) along a Flußweges whose length is at least three times, preferably at least six times the largest dimension of the PUT (34).

60. The method of claim 59, wherein the flow rate of the percolate along the flow path in the PUT (34) is less than 4 cm / s, preferably less than 2.5 cm / s.

61. The method according to any one of claims 51 to 60, wherein the percolate is on average 4 to 12 hours, preferably an average of 5 to 7 hours in the PUT (34).

62. The method according to any one of claims 51 to 61, in which the fermentation mass in the fermenter (16) is so far enriched with loose material, preferably straw, that increase the ability of the digestate to absorb percolate to a capacity of at least 0.75 m percolate per 1 m fermenter surface area per day.

63. The method according to any one of claims 51 to 62, wherein the percolate is maintained at 30 ⁰ C to 40 ⁰ C, preferably 33 ⁰ C to 37 ⁰ C.

64. A method according to any one of claims 51 to 63, wherein the dry substance deposited on the bottom of the at least one PUT (34) as percolate silt is purged by draining at least a portion of the percolate through drains in the bottom of the PUT (34) becomes.

65. The method according to any one of claims 51 to 64, wherein the accumulated at the bottom of the at least one PUT (34) Perkolatschlick before deflation by means of percolate, which exits from nozzles of a circulating pipe, is fluidized.

66. The method according to any one of claims 51 to 65, wherein the fermentation mass per fermenter (16) is refreshed every 6 to 12 days, preferably every 8 to 10 days.

67. The method of claim 66, wherein the number of fermenters (16) is between 12 and 24, preferably between 16 and 20, and two daily fermentation refurbishes are performed.

68. The method according to any one of claims 51 to 67, wherein the fresh mass, in particular a lignin and fibrous substrates existing fresh mass is heated prior to introduction into the fermenter (16).

69. The method according to any one of claims 51 to 68, wherein the fresh mass, in particular a lignin and fibrous substrates existing fresh mass before introduction into the fermenter (16) is subjected to a weakly aerobic prehydrolysis.

70. The method according to any one of claims 51 to 69, wherein the refreshment of the digestate comprises the following steps:

^■ removing the digestate from the fermenter (16),

^■ replacing a part of the digestate with fresh mass, and ^■ introduction of the supplemented by fresh mass fermentation mass in the fermenter, wherein the introducing back into the fermenter, already angegorene in the preceding Gärzylus fermentation mass is extruded so with fresh material in front of a mixing that a liquid phase is formed, which can be passed in at least one PUT, and a solid phase is formed, which can be mixed with the fresh mass.

71. The method of claim 70, wherein in a Gärmassenauffrischung between 13% and 60% of the fermented mass are discharged into a secondary fermenter and the fresh mass fraction is 22% to 69% of the newly entered into the fermenter fermentation.

72. The method according to any one of claims 51 to 71, wherein in the gas atmosphere of the PUT (34), an oxygen content of 0.2% to 2.5%, preferably from 0.5% to 1% is produced.

73. The method according to any one of claims 51 to 72, wherein artificial settlement areas (110) for sulfur bacteria are arranged in PUT.

74. The method of claim 73, wherein the settling surfaces (110) for sulfur bacteria are arranged such that they are temporarily wetted by percolate in the PUT within the fluctuation of the level of percolate in the PUT (34) and are temporarily exposed to the biogas.

75. The method of claim 73 or 74, wherein the settling surfaces (110) for sulfur bacteria are sprayed with percolate.

76. The method according to any one of claims 51 to 75, wherein the artificial settlement areas for sulfur bacteria in the garage fermenters, preferably between en Perkolatdüsen (84) and the digestate (72) are installed.

77. The method according to any one of claims 51 to 76, wherein in the fermenter (16) a lowermost layer of bales of lignin and / or fibrous renewable raw material, in particular straw is introduced.

78. The method according to any one of claims 51 to 77, wherein the lignin and / or fiber-containing renewable raw material, in particular straw, before the introduction into the fermenter (16) is pretreated to a chemical, thermal and / or mechanical disruption of the same to effect.

79. The method of claim 78, wherein the pretreatment for thermal digestion comprises saturated steam treatment.

80. The method of claim 79, wherein the saturated steam treatment is carried out so that it softens lignin structures of the lignocellulosic renewable raw material, the external structure of the raw material but overall remains substantially.

81. The method of claim 79 or 80, wherein the saturated steam treatment is carried out at a temperature between 160 ⁰ C and 240 ° C and a pressure between 20 and 30 bar for less than 20 minutes.

82. The method according to any one of claims 79 to 81, wherein the treatment pressure at the end of the saturated steam treatment is lowered by at least 80% within five seconds.

83. The method according to any one of claims 78 to 82, wherein the lignin and / or fibrous renewable raw material, in particular straw, is soaked before further use.

84. The method according to any one of claims 78 to 83, wherein the ligninous and / or fibrous renewable raw material, in particular straw, after the saturated steam treatment in an acidic solution, in particular percolate, in an alkaline solution or in manure is soaked.

85. The method according to any one of claims 78 to 84, wherein the pretreatment of the lignin and / or fiber-containing renewable raw material for mechanical pulping comprises chopping and / or cutting at least a portion thereof.

86. The method of claim 85, wherein the lignin and / or fiber-containing renewable raw material is cut to a particle length of less than 5 cm, preferably less than 2 cm and / or chopped.

87. The method of claim 85 or 86, wherein between 10% and 70% of the lignin or fibrous renewable raw material is cut and / or chopped.

88. The method according to any one of claims 78 to 87, wherein the pretreatment of the lignin and / or fiber-containing renewable raw material for mechanical pulping comprises the grinding of at least a portion thereof.

89. The method of claim 88, wherein between 5% and 100%, preferably between 20% and 65% of the lignin- and / or fibrous raw material are ground.

90. The method of claim 88 or 89, wherein the degree of grinding of the lignin and / or fiber-containing raw material corresponds to a Sieblochdurchmesser of at most 8mm, preferably a Sieblochdurchmesser of at most lmm.

91. The method according to any one of claims 78 to 90, wherein the lignin and / or fiber-containing renewable raw material between the pretreatment and the introduction into the fermenter (16) for anaerobic, bacterial fermentation no additional acids, enzymes, fungi or yeasts from the outside be supplied.

92. The method according to any one of claims 78 to 91, wherein the lignin and / or fiber-containing renewable raw material, in particular straw, is provided in bale form, wherein the bales have a density of at least 200 kg / m ³ , preferably at least 208 kg / m have.

93. The method according to any one of claims 78 to 92, wherein the chemical pretreatment comprises a mixing of the lignin and / or fiber-containing renewable raw material, in particular straw, with solid manure, liquid manure, percolate and / or percolate-containing fermentation mass.

94. The method according to any one of claims 78 to 93, wherein the chemical pretreatment comprises soaking the lignin and / or fiber-containing renewable raw material, in particular straw, in a water-acid solution, a water-alkali solution, percolate or manure ,

95. Method according to one of claims 78 to 94, in which the fermentation residues consisting of lignin and fiber-containing material, in particular from the digestate of straw, are dried to a water content of less than 25%, preferably less than 15%, and to wood content. or lean gas to be gasified.

96. The method of any one of claims 51 to 94, further comprising a step of dehydrating and pelleting digestate to produce fuel pellets or fuel briquettes.

97. The method of claim 96, wherein the substances harmful to combustion, in particular chlorine, nitrogen, sulfur, potassium chloride and / or silicates are washed or eluted from the fermentation residues after their removal from the fermenter.

98. The method of claim 97, wherein the leaching of the fermentation residues in the digestate bunker (60) is made.

99. The method of claim 97 or 98, wherein the fermentation residues are mechanically dehydrated after washing, in particular using a screw press (70) or a decanter.

100. The method according to any one of claims 96 to 99, wherein the fermentation residues are dried in a drying device, in particular a belt dryer (142) or a drum dryer with contact drying.

101. The method of claim 100, wherein the drying device is operated with waste heat from at least one gas engine of the biogas plant (10).

102. The method according to any one of claims 96 to 101, wherein the at least partially dehydrated and optionally dried fermentation residues are mechanically comminuted, in particular in a hammer mill (146) or straw mill.

103. The method according to any one of claims 96 to 102, wherein the comminuted and at least partially dehydrated and / or dried fermentation residues one or more of the following admixtures are added: cereal flour, molasses, starch, quicklime, steam, wood chips, sawdust, oil press cake, calcium , Magnesium, aluminum, nitrogen binding agents, especially nitrogen reducing reducing agents, hydrated lime.

104. The method according to any one of claims 96 to 103, wherein the comminuted and dehydrated fermentation residues are pressed into pellets or briquettes.

105. The method according to any one of claims 51 to 104, wherein a concentration of pollutants in the percolate is prevented by a part of the circulating percolate from the Perkolatkreislauf, preferably regularly, is drained.

106. The method of claim 105, wherein the draining of a portion of the percolate over the percolate loop (141), wherein the part of the percolate is discharged into the Gärrestbunker and / or in a tank from which the percolate is then disposed of.

107. The method according to any one of claims 97 to 99, wherein the purification of the liquid phase, in particular of the pollutants potassium, nitrogen, sulfur and chlorine, is carried out by an ultrafiltration associated with a reverse osmosis.