DE102006024081A1 - Biogas production in fermentation tank, comprises agitating fermentable biomass to form a floating layer on biomass, collecting the arising biogas, and supplying floating layer into lateral motion along longitudinal direction of tank - Google Patents

Abstract

The method for biogas production in a fermentation tank, comprises agitating fermentable biomass to form a floating layer (S) on biomass (M), collecting the arising biogas, supplying floating layer into lateral motion along longitudinal direction of tank and sprinkling the floating layer with a liquid percolate. The floating layer is broken apart at the end of the fermentation tank that is downstream to the direction of movement of the floating layer. The biomass to be fermented is supplied to the tank in the region of circular flow profiles. Rupture of the layer takes place periodically. The method for biogas production in a fermentation tank, comprises agitating fermentable biomass to form a floating layer (S) on biomass (M), collecting the arising biogas, supplying floating layer into lateral motion along longitudinal direction of tank and sprinkling the floating layer with a liquid percolate. The floating layer is broken apart at the end of the fermentation tank that is downstream to the direction of movement of the floating layer. The biomass to be fermented is supplied to the tank in the region of circular flow profiles. Rupture of the floating layer takes place periodically and the lateral motion is caused simultaneously around the region of rupture of the floating layer that takes place at the downstream end of the fermentation tank. For the generation of constant or periodic lateral motion of the floating layer, the more-liquid fractions of biomass that lie below the floating layer are dispersed in circular flow patterns. A retention time of the floating layer section in the fermentation tank is adjusted using the path of motion along the surface in the fermentation tank until the downstream end, namely until to the rupture of the floating layer in such a manner that an essentially complete aeration of the biomass bound in the floating layer is achieved. The retention time amounts between 30-120 days and the periodic rupture of the floating layer along with simultaneous motion of the floating layer takes place every 7 days or in day/night-sequence. An independent claim is included for a fermentation tank for the biogas production.

Description

The The invention relates to a method for producing biogas in a fermentation tank, in the fermentable Biomass is moving, getting a floating layer on the biomass forms and biogas is collected. Further concerns the invention a fermentation tank for Biogas production with a bottom, sidewalls and a gas-tight cover, being in the container fermentable Fed biomass will, in the container the fermentable Biomass is moved, forms a floating layer and emerging Biogas is caught.

biogas plants are in more diverse Design known in the art. Basis of every biogas plant is a fermentation tank, in the one to be fermented Substances are introduced and the biogas is generated. These too Biogas fermenter called container have mostly upright cylindrical shape, typically with a diameter of 15 to 25 m and a height of about 5 m or so-called. elevated tanks also up to 15 or 20 m. To pick up the static loads and to guide into the ground is the bottom plate and usually the cylindrical outer wall concrete. Sheet metal containers are also known in the prior art, on its inside an enamelled surface or of rust-protected steel, in particular V4A, are formed.

Of the concrete tanks becomes topside often completed by a supporting air roof, under which a gas-tight PE film aufwölbbar, for example, rests on a wooden ceiling construction to a provide variable gas storage space above the feeds.

In the known fermenters is for homogenization of the biomass for the fermentation process a stir and moving the biomass required. Stirrers are in very different Design known in the art. There are slow-moving ones paddle mixers, the most about a radially arranged to the cylindrical fermentation tank axis of rotation rotate. Furthermore, submersible mixers are known which with a Propeller similar a propeller a stronger one Flow impulse on transmit the biomass. The submersible mixers can be pivoted about their vertically arranged support shaft, to different areas in the fermentation tank too mix thoroughly.

adversely in the known methods for biogas production in the foregoing described fermentation tanks, that for the entire fermentation process and thus the for the trigger Biogas required circulation the biomass is in conflict with the preferred closed and about one longer Period undisturbed Formation of a floating layer on the biomass. In the known Fermenting is usually stirred intermittently and thereby substantially destroyed the entire floating layer. In the consequence leads this indeed to an increased release of biogas, with it but also to a concentrated release of hydrogen sulphide as part of the biogas. The disadvantage here is that the for biological desulfurization effective floating layer on the Biomass only has to re-form, so a reduction hydrogen sulfide content due to oxidation during these periods he follows.

In the post-published earlier patent application DE 10 2005 061 039 Therefore, a method for biogas production and a fermentation tank for the same is described in the same applicant, in which the most undisturbed formation of a floating layer is generated by a lateral movement in a direction along an elongated fermentation tank.

there However, it has been found that the degradation activity of biological Mass in the floating layer by sprinkling with percolate considerably can be increased.

For the percolation are biologically active liquids, especially during the fermentation process resulting liquid and / or manure. Of course can this liquid diluted with water to achieve better pumping and spraying ability.

task The invention is a method for substantially continuous Indicate biogas production and a fermentation tank with the defined residence times with most effective implementation of organic matter (biomass) in methane. there aims to provide a broad spectrum of biomass with low processing costs be processable.

Is solved this object with a method for biogas production according to claim 1 and a fermentation container according to claim 7th

The required for the biogas production anaerobic fermentation (fermentation) of biomass is favored by the inventive method or in the fermentation tank according to the invention by a substantially undisturbed floating layer. The introduced into an elongated fermentation tank biomass forms a floating layer on its surface, which is set along the longitudinal extent of the fermentation container in one direction in motion. At the downstream end, the floating layer is dissolved. By sprinkling the floating layer with percolate fluid, the swimming will be carried over the entire duration of the transport layer along the elongated fermentation tank reaches an intensive fermentation. In this case, a very complete implementation of the biomass and thus production of methane gas is achieved.

Thereby, that the resolution the floating layer is periodic and parallel to a lateral Movement around the section of the downstream end of the fermentation tank made Scum resolution is caused, the floating layer transport and the floating layer dissolution becomes periodic carried out in sections, so that both the drive means for the floating layer as well the dissolution agent for the Floating layer not constantly must be operated.

If for generating the steady or periodic lateral movement the floating layer the underlying liquid fractions of the biomass be placed in one or more roller-like flow paths, becomes the energy input required to homogenize the biomass at the same time to advance the floating layer into the intended Direction used. Preferably, the flow path rotates around horizontal and oriented substantially perpendicular to the lateral direction of movement Axes, which is a kind of "drive" of the floating layer through the along the flow path circulating more liquid Fractions of biomass in the manner of a "conveyor belt" results.

Device is a directed backflow to According to the invention required flow movement below the floating layer in the direction of the lateral movement achieved in that on or near the bottom in the longitudinal direction of container at least one flow channel is provided, wherein in or immediately before or behind the flow channel at least a first flow generating means is arranged. With the flow channel is channeled the quasi-flow, so to speak so that in the fermentation tank a Flow path through the flow channel as reflux and otherwise Cross section of the fermentation tank, in particular close the surface the required outgoing current for generating the lateral movement the floating layer is provided. Of course you can too two or more flow channels next to each other at the bottom of the container, for example at channels with a smaller cross-section or fermenters with a large width to be ordered. Then it is necessary for each flow channel also a first flow generating means having. Furthermore, it is conceivable that each flow channel also two or more Flow generation means are provided.

Advantageous is the flow channel a pipe, to erroneous flows and to avoid current short circuits. For the Milieu within the biomass in the fermentation tank are channel concrete segments suitable. These are also especially for cost reasons and for one easy handling, namely preferred for segmental incorporation.

Around a good mixing of the biomass with already existing in the fermentation tank, flowable biomass to achieve vaccination with the required microorganisms, will be fermented Biomass in the field of roller-like flow paths fed to the container. This is in accordance with the device achieved that for feeding biomass to be fermented a feed screw is provided, which the to be fermented Biomass the flow channel, preferably fed vertically from above.

Around a substantially complete one To achieve gasification of the biomass bound in the floating layer, is a residence time of a floating layer section in the fermentation tank on the movement path along the surface in the fermentation tank until to the downstream End, so until the resolution the swimming layer adjusted. Preferably, the residence time is 30 to 120 days. In this case, a periodic resolution of the floating layer with parallel movement of the floating layer, for example every 7 days, following the day / night schedule or other operational requirements accomplished become.

Around the floating layer at the downstream Is to dissolve end of the fermentation tank is at the downstream End of the fermentation tank mechanical means of dissolving provided the floating layer. The mechanical agent is preferred to the resolution the floating layer rotates as needed about its cylinder axis, horizontally and substantially perpendicular to the direction of movement of the floating layer arranged snail.

In Further embodiment, the screw on both sides of a middle position in opposite directions arranged screw sections, preferably with the resolution of Floating layer supporting, essentially arranged radially to the worm axis tines. At this middle position is the intake of a dip-cutting pump arranged to feed a press screw separator. The pump serves to remove the dissolved, floating layer components supplied from the screw to the center, the screw extruder being a solid phase for dumping from a liquid Phase, which is reused as percolate, separated.

For the elongated fermentation tank is provided in comparison to the width of 2 to 10 times, preferably 3 to 5 times the length. For example, can the fermentation tank has a width of 12 m and a length of 40 m with a height of 6 m. The surface layer that forms on the surface can reach a thickness of 3 m. When transporting from the upstream to the downstream end of the elongated fermentation tank, the layer thickness of the floating layer should be approximately halved, so in the example mentioned here only about 1.5 m.

If the irrigation system has ripples, the inside and along the side walls arranged on the fermentation tank are, with the irrigation of the floating layer simultaneously the boundary layer between the laterally moving floating layer and the sidewall of the fermentation tank with Wetted percolate, so that the friction between floating layer and Sidewall by the percolate, as a kind of "lubricant" is reduced. As a result, the drive power to be inputted is to cause the lateral movement of the floating layer is reduced.

Around to be able to stockpile the percolate liquid required for irrigation is a separate temporary storage container is provided. On the long sides of the fermentation tank becomes each a variable, separate storage volume with a flexible partition, in particular of PVC-coated fabric with a float clamped. These flexibly separated storage volumes are stored in the Change with liquid fermentation substrate, preferably from the sinking layers forming on the bottom of the fermentation tank filled and emptied in the meantime. The variable, separated storage volumes serve as a post-fermenter with a defined residence time for the fermentation substrate.

If the flexible storage volumes on the upstream side of the laterally movable floating layer wider and on the downstream side on the solvent are formed narrower, which has a Hauptgärraum forming residual volume of the Fermentation tank one trapezoidal Floor plan, which widens to the removal side. This will be the lateral transport of the floating layer to the solvent (discharge side) easier. By pumping the liquid Biomass between the two flexible storage volume or in a Gärsubstratendlager can support the mobility of the floating layer in the main fermentation room or be improved. In the fermentation substrate dump can excess liquid biomass be stored until landed on agricultural land becomes.

The in the fermentation tank in the flexible storage volume cached liquid biomass or percolate is thus also under the cover of the entire Fermentation container stored, so that from the percolate escaping methane gas also collected becomes. In contrast to an external percolate intermediate container thus elaborate arrangements, such as gas manifolds and the like.

Thereby, that a means of dissolution is provided by sinking layers, which one on guide rails bound flushing device has, can Any collecting at the bottom of the fermentation tank Sink layers dissolved become.

following is an embodiment of Invention described with reference to the accompanying drawings.

In this shows:

1 a longitudinal section through a fermentation tank according to the invention and

2 a plan view of the fermentation tank according to 1 ,

The in 1 shown fermenter 1 has an elongated rectangular base. The fermentation tank 1 has a floor 10 and sidewalls 11 to 14 on, which are made of concrete. The side walls 11 and 12 form the rectilinear side walls in the longitudinal extension of the elongated fermentation tank 1 , The side walls 11 and 12 are arranged parallel to each other. The side or end walls 13 . 14 in width are in cross section in 1 shown. The upstream end of the elongated fermentation tank in the context of this invention 1 is on the front wall 13 defined and the downstream end on the end wall 14 ,

Over the top of the fermentation tank 1 is a cover 15 For example, designed as a supporting air roof, under which a gas-tight PE film is ausbölbbar, for example, this is based on a wooden support structure to provide a variable gas storage space G above the fermentation tank. Within the gas space G is above the fermentation tank 1 a sprinkler system 5 in the form of a trickle line 51 arranged.

Im in 1 illustrated embodiment is at the downstream end, namely on the end wall 14 a feed screw 16 vertically arranged to be fermented biomass M in the sealed area of the fermentation tank 1 into it promotes.

In the fermentation tank 1 is added to be fermented biomass, with a pumpable liquid phase of the biomass B and a floating on the surface floating layer S in the fermentation tank 1 form. For intensive mixing the via the feed screw 16 introduced, to be fermented biomass M in the already existing biomass B in the fermentation tank 1 is a flow channel 2 on the ground 10 of the fermentation tank in the form of a pipe 20 , consisting of individual channel concrete segments 21 provided, in or on which a flow-generating means 24 is arranged in the form of a submersible mixer.

In the illustrated embodiment, the submersible mixer 24 at the inlet opening 22 of the flow channel 2 arranged. Immediately before that is biomass B with feed screw 16 fed vertically from above. When operating the submersible mixer 24 is the in the fermentation tank 1 biomass B stirred for homogenization for the fermentation process and added according to arrow Y in a backflow. Accordingly forms outside the flow channel 2 an outflow characterized by arrow X, which the forming on the surface of the liquid phase of the biomass B floating layer S in the desired lateral movement from the upstream end (end wall 13 ) to the downstream end (end wall 14 ) drives.

At the same time as the circulation in the fermentation tank 1 located biomass B and thus for the lateral movement of the resting on the liquid phase of the biomass B floating layer S, this floating layer S on the irrigation system 5 watered with percolate.

At the downstream end (end wall 14 ) is a means 3 for dissolution of the floating layer S in the form of a screw or screw conveyor 30 arranged. The snail 30 has radially projecting from its peripheral surface tines 31 to better absorb and dissolve the floating layer. In a preferred embodiment, the screw 30 two counter-rotating screw conveyors, the dissolved floating layer fragments to the center of the screw 30 promote and there supply a dip-cutting pump, the floating layer components to a press screw separator 32 promotes.

In the press screw separator 32 In principle, a solid phase is separated from a liquid phase. In this case, the solid phase of the floating layer fragments is transported on pressing its liquid phase to an output, so that fermented dry matter T for further use, for example, for application to agricultural land, falls out. The liquid phase is temporarily stored as percolate.

In 2 are in the top view in the fermentation tank 1 two variable storage volumes 4 . 4 ' , shown, each along the side wall 11 or side wall 12 extend. The respective variable storage volume 4 . 4 ' is from the remaining area of the fermentation tank 1 through a flexible partition 41 For example, separated from PVC-coated fabric. One on the flexible partition 41 floating bodies arranged in the area of its upper edge 42 Ensures that the flexible partition 41 not below the filling level of the fermentation tank 1 can fall. Now be in this variable storage volume 4 or 4 ' promoted liquid components of the biomass, the storage volume expands by flexible expansion of the partition wall or unfolding the partition wall 41 out. Accordingly, variable amounts of substrate liquid may be in the variable storage volume 4 or 4 ' be cached. These flexibly separated rooms (storage volume 4 . 4 ' ) are alternately filled or emptied in alternation with liquid fermentation substrate from the sink layers forming on the bottom of the fermentation tank and serve as secondary fermenters with a defined residence time.

When the flexible side tanks (storage volume 4 . 4 ' ) on the entry side (front side 13 ) wider and on the downstream side to the sampling device 3 get narrower, get the main grog room 17 a trapezoidal plan, which widened to the removal side. By pumping the liquid biomass between the flexible storage volume 4 and 4 ' or in a fermentation substrate, the mobility of the floating layer S can be improved. The fermentation substrate final storage serves as an intermediate storage for substantially outgrown material until it is applied to agricultural land.

Alternatively or additionally, this storage volume 4 . 4 ' via non-illustrated delivery lines with pumps liquid biomass as percolate P for irrigation system 5 be encouraged. Alternatively, the filling of the variable storage volume 4 . 4 ' also from external tributaries, for example by catching the liquid phase in the press screw separator 32 respectively.

For the resolution of sinking layers are on the tank bottom 10 in the longitudinal direction and at a preferred distance of about 2 m guide rails 18 from V4A, for example, in connection with heating tubes for heating the biomass attached, which is a lying on a carriage head of a flushing device 6 take up. The guide rails are at the upstream end wall 13 led upwards and end in a closable feed tube 19 above the gas space G and a membrane closing the gas space. The closable tube 19 extends through the gas space G and through the floating layer S and is at periodic intervals, preferably before filling the Nachgärer (storage volume 4 . 4 ' ) or within the post-fermenter before their emptying for recording and start-up of the flushing device 6 open.

The withdrawal of the liquid phase and its transport into the secondary fermenter 4 . 4 ' , if necessary, into the percolate buffer at the separator 32 or also the transport of the Nachgärern 4 . 4 ' into the Gärsubstratendlager takes place over several in the bottom of Hauptgärraums 17 or the post-fermenter 4 . 4 ' arranged withdrawal lines. This preferably occurs during or immediately after the dissolution of the sinking layers.

With the fermentation tank according to the invention or with the method according to the invention for producing biogas, it is also possible to process biomasses which have relatively poor degradation rates, for example grass silage or straw. In this case, the method can also with relatively small drive power in terms of only necessary circulation of the liquid phase of the biomass B in the lower part of the fermentation tank 1 be performed. The floating layer is transported in this circulation and simultaneous homogenization quasi as a side effect, which temporally simultaneously should be the mechanical resolution of the floating layer at the downstream end. Thus, space is created for the further transport of the floating layer at the downstream end.

By The sprinkling of the floating layer with percolate becomes the biological Degradation of the floating layer and thus increased methanogenesis. By Matching the residence time of the biomass to be fermented in the fermentation tank and in particular the residence time of a floating layer section over his Transport route from the upstream until the downstream End of the fermentation tank, can in the context of the percolate irrigation, a substantially complete mining the biomass can be achieved. As the swimming layer is essentially undisturbed until the dissolution promoted Thus, it can also be avoided that only freshly supplied fragments from biomass to the discharge. With the mechanical solvent in connection with a separation of the solid from the liquid components Then the no longer active fermented dry matter T can be targeted removed from the fermentation tank become.

1

fermenter

10

ground

11

Side wall, long side

12

Side wall, longitudinal extension

13

bulkhead

14

bulkhead

15

cover

16

feed screw

17

Hauptgärraum

18

guide rail

19

feed

2

flow channel

20

pipe

21

Channel concrete segment

22

inlet opening

23

outlet

24

Flow generating means, submersible mixer

3

disintegrator

30

Slug, screw conveyor

31

prong

32

screw extractor

33

Reverse slope

4, 4 '

variable storage volume

41

flexible partition wall

42

float

5

sprinkler

51

Rieselleitung

6

flushing

B

biomass, smoother phase

G

headspace

M

to fermented biomass

P

percolate

S

scum

T

fermented dry matter

X

forward flow

Y

backwash

Claims (18)

A process for the production of biogas in a fermentation tank, in which fermentable biomass is moved, forms a floating layer on the biomass and biogas is collected, characterized in that the floating layer brought in a lateral movement in a direction along the fermentation tank and irrigation the floating layer with percolation liquid is, wherein at the downstream in the direction of movement of the floating layer end of the fermentation tank, the floating layer is dissolved. Method according to claim 1, characterized in that that the resolution the floating layer is periodic and parallel to a lateral Movement around the section of the downstream end of the fermentation tank made Scum resolution is caused. Method according to claim 1 or 2, characterized that for generating the steady or periodic lateral movement the floating layer the underlying liquid fractions of the biomass be placed in one or more roller-like flow paths. A method according to claim 3, characterized in that to be fermented biomass in the region of the roller-like flow paths the container is supplied. Method according to claim 1, 2, 3 or 4, characterized that a residence time of a floating layer section in the fermentation tank on the movement path along the surface in the fermentation tank until to the downstream End, so until the resolution the floating layer is adjusted so that a substantially full Gasification of biomass bound in the floating layer achieved becomes. Method according to claim 5, characterized in that that the residence time is 30 to 120 days and the periodic resolution of the Floating layer with parallel movement of the floating layer every 7 Days or in the day / night rhythm. Fermenting tank for biogas production with a bottom ( 10 ), Side walls ( 11 . 12 . 13 . 14 ) and a gas-tight cover ( 15 ), whereby in the container ( 1 ) fermentable biomass (M) is supplied in the container, the fermentable biomass (M) is moved to form a floating layer (S) and resulting biogas (G) is collected, characterized in that the fermentation tank ( 1 ) has an elongated shape, wherein the two side walls ( 11 . 12 ) in the longitudinal direction in the region of the floating layer (S), ie the surface of the biomass (M) parallel to each other or in the direction of movement of the floating layer (S) are arranged slightly diverging to each other, with a sprinkling system ( 5 ) above the floating layer (S) for spraying the floating layer (S) with percolate (P) is provided. Fermenting tank according to claim 7, characterized in that at the downstream end of the fermentation tank ( 1 ) a mechanical means ( 3 ) is provided for dissolving the floating layer (S). Fermenting tank according to claim 8, characterized in that the mechanical means ( 3 ) for the dissolution of the floating layer (S), if necessary, about its cylinder axis rotatable, horizontally and substantially perpendicular to the direction of movement of the floating layer (S) arranged snail ( 30 ). Fermenting tank according to claim 9, characterized in that the screw ( 30 ) on both sides of a middle position mutually oppositely arranged screw sections, preferably with the resolution of the floating layer (S) supporting, arranged substantially radially to the screw axis tines ( 31 ), and at this middle position a submerged cutting pump for feeding a press screw separator ( 32 ), wherein the press screw separator ( 32 ) separates a solid phase (T) to deposit a liquid phase (P), which is reused as percolate. Fermentation tank after Claim 7, 8, 9 or 10, characterized by a comparison to the width 2 to 10 times, preferably 3 to 5 times the length. Fermenting vessel according to claims 7, 8, 9, 10 or 11, characterized in that variable, separated storage volumes ( 4 . 4 ' ) for secondary fermentation of fermentation substrate in the fermentation tank ( 1 ) are formed. Fermenting tank according to claim 12, characterized in that the variable storage volume ( 4 . 4 ' ) with a flexible partition ( 41 ), in particular of PVC-coated fabric, with a floating body ( 42 ) in the fermentation tank ( 1 ) is stretched. Fermenting tank according to claim 13, characterized in that two variable storage volumes ( 4 . 4 ' ) on both longitudinal sides of the fermentation container ( 1 ) are arranged so that the remaining space (Hauptgärraum) of the fermentation tank ( 1 ) has a trapezoidal ground plan extending to the downstream end of the solvent ( 3 ) widened. Fermenting tank according to one of claims 7 to 14, characterized in that the sprinkling system ( 5 ) Pipelines ( 51 ), the inside and along the side walls ( 11 . 12 ) on the fermentation tank ( 1 ) are arranged. Fermenting container according to one of the preceding claims 7 to 15, characterized in that on or near the bottom ( 10 ) in the longitudinal direction of the container ( 1 ) at least one flow channel ( 2 ) is provided, wherein in or immediately before or behind the flow channel ( 2 ) at least one flow-generating means ( 24 ) is arranged. Fermenting vessel according to claim 16, characterized in that for feeding to be fermented biomass (M) a feed screw ( 16 ) is provided, the biomass to be fermented (M) the flow channel ( 2 ) feeds. Fermentation tank after one of the preceding claims 7 to 17, characterized in that a means for the resolution of Sink layers is provided, which is bound to guide rails flushing device having.