DE102011015611A1 - Producing biogas from organic substrates, comprises creating a solid-liquid phase mixture of organic solid and/or liquid substrates, and performing biological treatment of the mixture within fermenters consecutively connected in series - Google Patents

Abstract

The process comprises creating a solid-liquid phase mixture (5) of organic solid and/or liquid substrates (2a, 2b) by adding water, performing biological treatment of the solid-liquid phase mixture within fermenters (3a, 3b) consecutively connected in series until the last fermenter obtains a stabilized digestate with a low residual gas potential, where the biological treatment includes anaerobic fermentation process and aerobic fermentation process using biologically active microorganisms, and separating a partial flow of volume flow discharged from the last fermenter. The process comprises creating a solid-liquid phase mixture (5) of organic solid and/or liquid substrates (2a, 2b) by adding water, performing biological treatment of the solid-liquid phase mixture within fermenters (3a, 3b) consecutively connected in series until the last fermenter obtains a stabilized digestate with a low residual gas potential, where the biological treatment includes anaerobic fermentation process and aerobic fermentation process using biologically active microorganisms, separating a partial flow of volume flow discharged from the last fermenter and separating the partial flow of the stabilized digestate into a liquid and a solid phase (11), transferring a portion of the volume flow of the resulting liquid phase for the biological treatment of other untreated organic substrates directly or indirectly through one of the fermentation tanks of upstream slurry containers in one of the fermenters, intermittently transferring the resulting volume flow of the solid phase to a thermal treatment for thermal disintegration, transferring the thermally treated volume flow of the solid phase for renewed biological treatment through the fermentation tank of the upstream containers in one of the fermenters, and extracting non-heat-treated solid-phase from the system to avoid the accumulation of the thermal treatment-resistant fractions in the system. The step of transferring the thermally treated volume flow of the solid phase is carried out at time intervals, which are determined by a simulation model. An autoclave: is used for the thermal treatment; using residual and/or excess heat "Q" is operated from a cogeneration unit; and is operated at a temperature of 170[deg] C and a pressure of 0.8 MPa. An independent claim is included for a device for producing biogas from organic substrates.

Description

The invention relates to a method for producing biogas from organic substrates and to an apparatus for carrying out the method according to the preamble of patent claims 1 and 7 of the invention.

Methods and devices for generating biogas from organic substrates have been known for quite some time in a variety of configurations. That's how it describes DE 10 2007 037 202 A1 a process in which renewable resources (NawaRo) are introduced into an at least first anaerobic fermenter reactor together with liquid and other necessary for a methanogenesis substrates and subjected there to a fermentation process, subsequently subjected to the digestate a solid-liquid phase separation and the separated solid phase a thermopressure hydrolysis at temperatures of at least 170 ° C and pressures of at least 1.0 MPa is subjected and the thus treated solid phase either recycled to the first anaerobic fermenter reactor or fed to a second anaerobic fermenter reactor and subjected to a further fermentation process. In view of the above process, which is to get along with one or two fermenter reactors, it is assumed that in conventionally connected in series or cascaded reactors only the first reactor should be fully utilized, since the largest proportion of microbiologically available organic materials already implemented in the first 20 to 30 days. It is further stated that 40% of the organic substrates are degraded in the first or single fermenter reactor. If this assumption is continued, a fermentation residue removal after said 20 to 30 days from the first or single fermenter reactor and a downstream treatment, in this case solid-liquid separation, can still be expected to result in significant biogas outgassing and associated methane emissions , Such outgassing requires additional complex measures for gas-tight storage and / or further treatment of said fermentation residues in order to avoid biogas losses or the load on the atmosphere. In addition, in a separation of the solid digestate from the existing first or single fermenter reactor ingredients are disadvantageously thermally treated with, which can potentially be degraded biochemically even without thermal treatment or biological way in one or more further stages.

The object of the invention is to provide a further improved in terms of the prior art process for the production of biogas from organic substrates by biological treatment, which in avoiding the discharge of biogas into the environment or atmosphere, with minimized mechanical and plant engineering effort and with the lowest possible energy input allows maximization of the biogas yield. Furthermore, it is an object of the invention to provide a suitable device for carrying out the method.

The invention is based on the finding that due to disintegration, in particular thermal disintegration of solid stabilized digestate, d. H. of solid digestate with low residual gas potential, a maximum biogas yield is permitted in one or more subsequent biological treatment stages.

• a) Erstellung eines Fest-Flüssig-Phasengemisches aus besagten Substraten gegebenenfalls unter Hinzufügen von Wasser,
• b) biologische Behandlung des Fest-Flüssig-Phasengemisches innerhalb einer Mehrzahl hintereinander in Reihe geschalteter Gärbehälter bis am letzten Gärbehälter ein stabilisierter Gärrest mit geringem Restgaspotenzial zu verzeichnen ist,
• c) Separieren zumindest eines Teilstroms eines aus dem letzten Gärbehälter ausgetragenen Volumenstroms und Trennung des besagten Teilstroms aus stabilisiertem Gärrest in eine flüssige und eine feste Phase,
• d) Überführung zumindest eines Teils des Volumenstroms der sich ergebenden flüssigen Phase zur biologischen Behandlung weiterer unbehandelter organischer Substrate unmittelbar oder mittelbar über einen der Mehrzahl Gärbehälter vorgelagerten Behälter in zumindest einen der Gärbehälter,
• e) diskontinuierliches Überführen des sich ergebenden Volumenstroms der festen Phase zu einer thermischen Behandlung respektive thermischen Desintegration desselben, und
• f) Überführung des thermisch behandelten Volumenstroms der festen Phase zur neuerlichen biologischen Behandlung unmittelbar oder mittelbar über einen der Mehrzahl Gärbehälter vorgelagerten Behälter in zumindest einen der Gärbehälter, wobei
• g) zur Vermeidung der Akkumulation von gegenüber der thermischen Behandlung resistenten Fraktionen im System der besagten thermischen Behandlung zeitlich eine Entnahme von nicht thermisch behandelter fester Phase aus dem System folgt.

Starting from a process for the production of biogas from organic substrates by biological treatment, said biological treatment of the organic substrates is carried out by a per se known fermentation process with the exclusion of oxygen (anaerobically) and with the aid of biologically active microorganisms, and wherein the organic Substrates are solid and / or liquid type, the task is therefore solved by the following successive steps to be performed:

• a) preparation of a solid-liquid phase mixture of said substrates optionally with the addition of water,
• b) biological treatment of the solid-liquid phase mixture within a plurality of successively connected in series fermenter until the last fermentation tank a stabilized digestate with low residual gas potential is recorded,
• c) separating at least one substream of a volumetric flow discharged from the last fermenter and separating said substream of stabilized digestate into a liquid and a solid phase,
• d) transfer of at least part of the volume flow of the resulting liquid phase for the biological treatment of further untreated organic substrates directly or indirectly via one of the plurality of fermentation tank upstream container in at least one of the fermentation tanks,
• e) discontinuously transferring the resulting volume flow of the solid phase to a thermal treatment or thermal disintegration thereof, and
• f) transfer of the thermally treated volume flow of the solid phase for renewed biological treatment directly or indirectly via one of the plurality of fermentation tank upstream container in at least one of the fermentation tanks, wherein
• g) to prevent the accumulation of resistant to the thermal treatment Fractions in the system of said thermal treatment temporally follows a removal of non-thermally treated solid phase from the system.

The solid-liquid separation of the thermally treated solid, stabilized digestate after the last biological treatment stage, the disintegration of poorly degradable organic substances targeted at minimal flow and maximum proportion of said poorly degradable organic matter. This allows a higher substrate-specific biogas yield and thus a reduction of the biogas plant supplied organic substrates with the same amount of biogas. Furthermore, the removal of the solid, stabilized digestate after the last biological treatment stage significantly prevents the risk of methane emission during solid-liquid separation and further treatment. Furthermore, in the removal of the solid, stabilized digestate after the last biological treatment stage, the disadvantageous effect of the "killing" of adhering biomass residues by thermal treatment, which can be recorded according to the prior art, is largely negligible. An impairment of the biogas yield by adversely affecting any readily degradable ingredients is hardly expected here. The fact that the discontinuous thermal treatment of the volume flow of the solid phase and transfer or return of the same follows in the cycle in the biological treatment process a removal of non-thermally treated digestate in the form of said solid phase from the system is advantageously avoided that respect Thermal treatment resistant fractions of the solid phase in the biogas plant system unnecessarily accumulate and this may have an adverse effect on the biogas production of the system.

Advantageous embodiments and further developments of the method according to the invention can be taken from the subordinate subclaims.

Thus, as organic substrates of a solid type, in particular substrates with a high lignocellulose content, ie. h., Renewable resources (NawaRo) and as organic substrates of liquid type, in particular manure can be used. In relation to this results from the process an increase in the biogas yield with the same use of substrates, which is a conservation of the resources required for this is possible.

It can further be provided that, with regard to method step e), the discontinuous transfer of the volume flow of the solid phase for thermal treatment is carried out at time intervals which were determined with the aid of a simulation model.

Furthermore, with regard to method step e), at least one autoclave can be used for the thermal treatment, as a result of which additional pump systems, which disadvantageously influence the energy efficiency of the overall system, are dispensable. Particularly advantageously, the at least one autoclave can be operated by means of residual and / or excess heat "Q" from a combined heat and power plant (CHP), which in turn can advantageously be operated by means of the biogas produced.

Advantageously, the at least one autoclave may be operated at a temperature of about 70 ° C to about 270 ° C and a pressure of up to about 5.5 MPa, preferably at a temperature of about 170 ° C and a pressure of about 0.8 MPa, resulting in the greatest possible digestion of the thermally treated solid phase for further biological treatment.

Finally, it can be provided that, with regard to the method step f), a mash tank is used as one of the plurality of fermentation tank upstream, which in turn allows thorough mixing of the fractions provided for biological treatment or further treatment.

• – zwei oder mehr hintereinander in Reihe geschaltete Gärbehälter zur biologischen Behandlung von organischen Substraten nach einem an sich bekannten Fermentationsverfahren unter Ausschluss von Sauerstoff (anaerob) und unter Zuhilfenahme von biologisch aktiven Mikroorganismen,
• – zumindest eine Separationseinheit zum Separieren zumindest eines Teilstroms eines aus dem letzten Gärbehälter ausgetragenen Volumenstroms stabilisierten Gärrestes und zum Trennen des besagten Teilstroms in eine flüssige und eine feste Phase, und
• – zumindest eine Einrichtung zur thermischen Behandlung respektive thermischen Desintegration des sich aus der vorgelagerten Separationseinheit ergebenden und diskontinuierlich der besagten Einrichtung zugeführten Volumenstroms der festen Phase.

The device for carrying out the method is characterized in that the following units are arranged one after the other in the process direction:

• Two or more fermenters connected in series for the biological treatment of organic substrates by a per se known fermentation process with the exclusion of oxygen (anaerobic) and with the aid of biologically active microorganisms,
• - At least one separation unit for separating at least a partial flow of a discharged from the last fermenter volume flow stabilized digestate and for separating said partial flow into a liquid and a solid phase, and
• - At least one means for thermal treatment or thermal disintegration of the resulting from the upstream separation unit and discontinuously supplied said device volume flow of the solid phase.

As an apparatus for thermal treatment is advantageous to an autoclave.

The method according to the invention and the device according to the invention are explained in more detail below with reference to an exemplary embodiment shown schematically in the drawing. The single FIGURE shows a flow chart for the process according to the invention.

As can be seen from the drawing, according to this embodiment, the device for generating biogas 1 from organic substrates 2a . 2 B solid, and / or liquid type by biological treatment initially two directly behind the other in series fermenter 3a . 3b on which a container 4 is arranged in the form of a so-called Anmaischbehälters. The container 4 or Anmaischbehälter is optionally mechanically comminuted organic substrates 2a solid type, such as renewable resources (NawaRo), and / or with organic substrates 2 B liquid type, such as manure, fed. If the liquid content is insufficient for proper biological treatment, water will still be added. Inside the container 4 Anmaischbehälters is accordingly a solid-liquid phase mixture 5 created, which then in the first, the Anmaischbehälter immediately downstream fermentation tank 3a is transferred.

The biological treatment of the produced solid-liquid-phase mixture 5 will be within the first fermentation tank 3a according to a fermentation process known per se with the exclusion of oxygen (anaerobic) and carried out with the aid of biologically active microorganisms. Said fermentation process includes the self-adjusting over a certain period of time steps hydrolysis, acidification, acetic acid formation and methane formation. The resulting biogas 1 , which consists predominantly of said methane and carbon dioxide, is from the first fermentation tank 3a dissipated.

The residence time of the solid-liquid phase mixture 5 in the first fermentation tank 3a is determined by the current boundary conditions of the process, in particular by the nature of the organic substrates used 2a . 2 B , according to the reaction temperature within the first fermentation tank 3a and the type and amount of microorganisms involved in the reaction. In essence, the method is carried out as a function of said boundary conditions with the aid of empirically and / or computationally determined data.

After a certain residence time with a corresponding Biogasaustrag from the first fermentation tank 3a becomes the at least partially fermented solid-liquid phase mixture 5 in the first fermentation tank 3a downstream second fermentation tank 3b (In the exemplary embodiment Nachgärer) transferred to further fermentation, wherein in this fermentation tank 3b resulting biogas 1 is also removed. The solid-liquid phase mixture 5 remains in the second fermentation tank 3b until, in this a stabilized digestate 6 is formed, which in turn is characterized by the fact that no more or only one of the prior art, negligible biogas outgassing is recorded. In the present example are two directly behind each other in series fermenter 3a . 3b intended. However, the invention is not limited to said two fermentation tanks 3a . 3b but can also be more than two fermenters directly connected in series 3a - 3n include (not shown).

As can be seen further from the single FIGURE, it is possible to obtain from the second fermentation tank 3b discharged volume flow stabilized digestate 6 already a liquid phase 7 are separated, which then in turn as a liquid fertilizer ready for immediate use.

To the second fermentation tank 3b at least one separation unit closes 8th on, by means of which the entire from the second fermentation tank 3b discharged volume flow or according to the present embodiment, a partial flow 9 the same in a liquid phase 10 and a solid phase 11 is disconnected. The at least one separation unit 8th For example, it can be designed as a screw separator known per se and accordingly not shown here.

The microorganism-enriched liquid phase 10 is advantageously in the biological cycle of the system (biogas plant), especially in the container 4 or Anmaischbehälter same transferred. This measure is particularly suitable when additional liquid is needed due to the dry matter to be processed. Certainly, it may also be indicated and is accordingly also covered by the invention, said liquid phase 10 or parts thereof directly into one of the fermentation tanks 3a . 3b or in both fermentation tanks 3a . 3b in order to control or speed up or improve the fermentation behavior in the same.

The solid phase resulting from the separation 11 stabilized digestate 6 is after a certain time management, for example with the aid of a biogas plant associated computing unit 13 , a facility 12 for thermal treatment, also referred to in the art as thermal disintegration supplied. In the context of such a thermal treatment is at temperatures of about 70 ° C to about 270 ° C and a pressure to 5.5 MPa, preferably at a temperature of about 170 ° C and a pressure of about 0.8 MPa, the structure of the solid phase 11 stabilized digestate 6 further open-minded and is then in the cycle of a further biological treatment within the existing fermentation tank 3a . 3b to disposal.

In that regard, the solid phase 11 stabilized digestate 6 then preferably in the container 4 or mash tank transferred. Based on the recirculated liquid phase 10 it can also be displayed here, said solid phase 11 or parts thereof directly into one of the fermentation tanks 3a . 3b or both fermenters 3a . 3b to convict.

The feed of the solid phase 11 stabilized digestate 6 for thermal treatment and transfer into the mash tank and / or the fermentation tanks 3a . 3b However, it does not take place continuously but discontinuously or at intervals according to empirically and / or computationally determined data, which in the manner of a simulation model within said arithmetic unit 13 are stored. Here, too, the procedural boundary conditions, such as the organic substrates used, play a role 2a . 2 B , the reaction temperature within the fermentation tank 3a . 3b as well as the quality of the solid phase used 11 of the digestate 6 a weighty role. In view of this, it is provided, in particular, that removal of non-thermally treated solid phase takes place in time for a thermal treatment 11 ' out of the system. As a result, it is advantageously avoided that fractions resistant to the thermal treatment accumulate unnecessarily in the system (biogas plant). The non-thermally treated solid phase 11 ' can then be used for composting and / or spent directly on the field for the treatment of the soil. The conditions for the duration of the thermal treatment are the available material flows and residence times and the possible or necessary degree of digestion in the solid phase 11 of the digestate 6 contained organic matter.

In order to achieve the best possible energy efficiency of the biogas plant and to remain as far as possible energetically neutral, is as a device 12 for thermal treatment, a per se known autoclave provided, which in turn is formed by a gas-tight sealable pressure vessel. The required heat energy "Q" can be exemplified by a combined heat and power plant (CHP) 14 be provided and advantageously results from residual and / or excess heat "Q" of the same, such as from the resulting waste heat from a cooling water circuit of the same and exhaust heat. In the present case, a heat input from the outside over the wall of the autoclave is shown. Certainly it is also permitted and accordingly covered by the invention, the solid phase 11 of the digestate 6 by means of hot water or by means of steam within the autoclave.

To the digestion of the solid phase 11 of the digestate 6 To make even more effective, said thermal treatment or disintegration can be combined with a known mechanical, chemical and / or biological disintegration / be, where as a mechanical method, the crushing and / or pinching, as a chemical process, the use of acids or alkalis and as a biological process, an enzymatic digestion in question (not shown).

LIST OF REFERENCE NUMBERS

1

biogas

2a

organic substrates

2 B

organic substrates

3a

fermenter

3b

fermenter

4

Container / slurry container

5

Solid-liquid phase mixture

6

Digestate (stabilized)

7

liquid phase

8th

separation unit

9

partial flow

10

liquid phase

11

solid phase

11 '

solid phase

12

Device for thermal treatment

13

computer unit

14

CHP

Q

Thermal energy

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 102007037202 A1 [0002]

Claims (8)

Process for the production of biogas ( 1 ) from organic substrates ( 2a . 2 B ) by biological treatment, said biological treatment of the organic substrates ( 2a . 2 B ) is carried out according to a per se known fermentation process with the exclusion of oxygen (anaerobic) and with the aid of biologically active microorganisms, and wherein the organic substrates ( 2a . 2 B ) are solid and / or liquid type, characterized by the following process steps to be carried out successively: a) Preparation of a solid-liquid phase mixture ( 5 ) from said substrates ( 2a . 2 B ) optionally with addition of water, b) biological treatment of the solid-liquid phase mixture ( 5 ) within a plurality of successively connected in series fermenters ( 3a . 3b ) to the last fermentation tank ( 3b ) a stabilized digestate ( 6 ) with low residual gas potential, c) separating at least one partial flow ( 9 ) one from the last fermentation tank ( 3b ) discharged volume flow and separation of said partial flow ( 9 ) from stabilized digestate ( 6 ) into a liquid phase and a solid phase ( 10 . 11 d) transfer of at least part of the volume flow of the resulting liquid phase ( 10 ) for the biological treatment of further untreated organic substrates ( 2a . 2 B ) directly or indirectly via one of the plurality of fermentation tanks ( 3a . 3b ) upstream containers ( 4 ) in at least one of the fermentation tanks ( 3a . 3b e) discontinuous conversion of the resulting volume flow of the solid phase ( 11 ) to a thermal treatment or thermal disintegration of the same, and f) transfer of the thermally treated volume flow of the solid phase ( 11 ) for renewed biological treatment directly or indirectly via one of the plurality of fermentation vessels ( 3a . 3b ) upstream containers ( 4 ) in at least one of the fermentation tanks ( 3a . 3b g), in order to avoid the accumulation of fractions resistant to thermal treatment in the system of said thermal treatment, time-wise removal of non-thermally treated solid phase ( 11 ' ) follows from the system. A method according to claim 1, characterized in that with regard to the method step e) the discontinuous transfer and thermal treatment of the volume flow of the solid phase ( 11 ) is performed at time intervals determined by means of a simulation model. A method according to claim 1 or 2, characterized in that with regard to the process step e) for thermal treatment, at least one autoclave is used. A method according to claim 3, characterized in that the at least one autoclave by means of residual and / or excess heat "Q" from a combined heat and power plant ( 14 ) is operated. A method according to claim 3 or 4, characterized in that the at least one autoclave at a temperature of about 70 ° C to about 270 ° C and a pressure to about 5.5 MPa, preferably at a temperature of about 170 ° C and a pressure is operated by about 0.8 MPa. A method according to claim 1, characterized in that with regard to the method step f) as one of the plurality of fermentation tanks ( 3a . 3b ) upstream container ( 4 ) a mash tank is used. Device for carrying out the method according to one of claims 1 to 6, characterized in that the following units are arranged one after the other in the process direction: - two or more fermenters connected in series one behind the other ( 3a . 3b ) for the biological treatment of organic substrates ( 2a . 2 B ) according to a fermentation process known per se with the exclusion of oxygen (anaerobic) and with the aid of biologically active microorganisms, - at least one separation unit ( 8th ) for separating at least one partial flow ( 9 ) one from the last fermentation tank ( 3b ) discharged volume flow stabilized digestate ( 6 ) and for separating said partial flow ( 9 ) into a liquid phase and a solid phase ( 10 . 11 ), and - at least one institution ( 12 ) for thermal treatment or thermal disintegration of the upstream separation unit ( 8th ) and discontinuous of said device ( 12 ) supplied volume flow of the solid phase ( 11 ). Apparatus according to claim 7, characterized in that the at least one device ( 12 ) is formed for thermal treatment by at least one autoclave.

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