The invention relates to a device for anaerobically fermenting
substances comprising a preacidifier inside of which the substances
are subjected to a preacidification, a fermenter inside of which
the preacidified substances ferment, and transfer means for transferring
the substances out of the preacidifier and into the fermenter. The
device is characterized in that the transfer means are designed
for selectively transferring sufficiently preacidified substances.
The invention also relates to a method for anaerobically fermenting
substances involving a preacidification during which the substances
are preacidified by means of a preacidifier, a fermentation during
which the preacidified substances ferment inside a fermenter, and
a transferring during which substances are transferred out from
the preacidifier and into the fermenter, whereby the sufficiently
preacidified substances are selectively transferred.
14. Apparatus for the anaerobic fermentation of materials with
a preacidifier in which said materials are subject to a preacidification,
a fermenter in which said preacidified materials ferment, and transport
means for transporting said materials from said preacidifier into
said fermenter, wherein said transport means are formed to selectively
transport sufficiently preacidified materials.
15. Apparatus according to claim 15, wherein said transport means
comprise a withdrawal device for the withdrawal from the upper portion
of said preacidifier, which are preferably formed by a spillway
of said preacidifier or by a withdrawal nozzle end arranged in the
upper portion of said preacidifier.
16. Apparatus according to claim 15, wherein said transport means
comprise a control device for said withdrawal device, with which
said withdrawal device and preferably an agitation device such as
a stirrer can be driven.
17. Apparatus according to claim 14, wherein said transport means
comprise a sieve.
18. Apparatus according to claim 14, wherein said transport means
comprise a floatation device and a withdrawal device in the lower
portion of said preacidifier.
19. Apparatus according to claim 18, wherein said transport means
comprise a control device for said withdrawal device with which
said withdrawal device and preferably said floatation device can
20. Apparatus according to claim 14, wherein a mechanical pretreatment,
prehackling device for solubilizing/hackling at least part of said
materials is provided.
21. Method for the anaerobic fermentation of materials with a preacidification
at which said materials are preacidified with a preacidifier, a
fermentation at which said pre-acidified materials ferment in a
fermenter, and a transport at which materials from said preacidifier
are transported into said fermenter, wherein said sufficiently preacidified
materials are selectively transported.
22. Method according to claim 21, wherein the transport comprises
letting said materials deposit themselves in said preacidifier and
a subsequent withdrawal of materials from an upper portion of said
23. Method according to claim 21, wherein said materials are guided
through a sieve during the transport.
24. Method according to claim 21, wherein the transport comprises
a floatation and an at least partially simultaneous transport from
the lower portion of said preacidifier.
25. Method according to claim 21, wherein said materials comprise
fluids and solids.
26. Method according to claim 21, wherein at least part of said
materials, particularly said solids are pretreated preferably mechanically
prehackled before they are put into said preacidifier.
 The invention relates to an apparatus and a method for the
anaerobic fermentation of materials.
 An apparatus and a method according to the preamble of claim
1 and of claim 8 is known from the DE 198 04 007. This document
relates to the treatment of an organically burdened fluid whereat
the gas is generated in the fermentation stage. In practice it has
turned out that the average duration of stay of the burdened fluids
in the pre-acidification stage is approximately 15 hours and a total
process approximately 30 hours. In this time the process water is
sufficiently pre-acidified so that it can be transported into the
fermenter without involving the risk that there would occur yet
another acidification in the fermenter which would be very disadvantageous
for the fermentation process particularly by damaging the methane
producing bacteria due to low pH-values. Usually in the pre-acidification
a pH-value of 6.0 or below must be reached. The pre-acidification
serves to solubilize complex carbon compounds since the fermentation
bacteria can utilize simple carbon compounds only.
 During the fermentation biogas is extracted which represents
a mixture of methane and carbon dioxide and which can be used for
 Further, from practice solid reactors are known in which
pre-acidification and fermentation for the extraction of biogas
take place jointly. In such reactors solid to pasty materials can
be treated, whose time of stay is weeks until a sufficient total
process has taken place.
 At breweries fluid burdened process waters for example from
cleaning processes for example and as more solid organic materials
yeasts and draff, i.e. brewer grain for example arise. At fruit
juice extraction plants also press residues like solid peel particles
arise besides the process water. At such or similar production sites
at which organically burdened fluids as well as organic remains
arise normally both i.e. two independent reactors are therefore
required primarily due to the incompatible pre-acidification periods
in order to utilize the materials for biogas production. This is
however quite costly and complicated.
 The DE 199 37 876 A1 discloses a method for the biological
conversion of organic materials to methane gas, which method is
to achieve a power enhancement by shifting the stable operating
point of the system. For that purpose the residence time of organic
components in the reactors is to be uncoupled from the hydraulic
residence time by the retention of organic components by means of
a semipermeable membrane in order to achieve a better adaptation
of the bacteria growth.
 The object of the present invention is therefore to create
an apparatus and a method with which a more cost effective simpler
alternative for the production of biogas from fluid and solid materials
can be realized.
 This objective is achieved by an apparatus with the characteristics
of claim 1 and a method with the characteristics of claim 8.
 Preferred embodiments are disclosed in the respective sub
 With the apparatus according to the present invention means
for transporting materials into the fermenter are provided with
which it is possible by selective process control to transport all
materials in a sufficiently pre-acidified condition. Here, still
insufficiently pre-acidified normally more solid sparsely solubilized
materials are left in the pre-acidifier for sufficient pre-acidification.
 Accordingly the method according to the present invention
relates to such one at which only sufficiently pre-acidified materials
 In this way it is possible to put fluid respectively largely
solubilized materials as well as solid or pasty less solubilized
ones into a pre-acidifier and subsequently feed them sufficiently
pre-acidified to a common fermenter.
 For the selective transport a variety of material characteristics
can be utilized which distinguish the sufficiently pre-acidified
materials from the still insufficiently pre-acidified materials.
 While for example sufficiently pre-acidified solid or pasty
materials are soaked by the pre-acidification solubilization and
dissolve in the fluid the insufficiently pre-acidified solids are
normally coarse grained and sedimenting, respectively. Thus, a selection
can be done by sieving and treating for example whereat the sieve
for example has to be designed so that the still insufficiently
pre-acidified solids get caught in the sieve and the fluid and soaked
materials can pass through the sieve.
 Furthermore, it has turned out that the still insufficiently
pre-acidified solids in the pre-acidifier deposit themselves on
the bottom of the same if no agitation or stirring takes place in
the pre-acidifier. This means that upon switch-off of the agitation
or of the stirring normally taking place in the pre-acidifier the
insufficiently pre-acidified materials gather in the lower portion,
whereas the sufficiently pre-acidified materials gather in the upper
portion whereby a selection of sufficiently pre-acidified materials
by a withdrawal of materials in the upper portion of the pre-acidifier
is rendered possible by carrying out the forwarding into the fermenter
only during the "rest phases".
 It has furthermore turned out that by a flotation for example
by blowing air or gas into the pre-acidifier from the bottom the
solids preferably bloat on the surface so that also here a separation
of still insufficiently pre-acidified materials from the sufficiently
pre-acidified materials results so that a selection during transport
by a withdrawal of materials from the lower portion of the pre-acidifier
 A preferred embodiment with very coarse feedstock materials
such as peels, grains or the like includes a pre-treatment preferably
a mechanical pre-comminution of the solids with a chopper or a mill
or the like. A pre-treatment particularly a mechanical pre-comminution
facilitates the solubilization of the solid materials in the pre-acidifier.
 Preferred embodiments of the apparatus according to the
present invention and the method according to the present invention
are explained on the basis of the accompanying figures, in which:
 FIG. 1 shows a three-dimensional perspective view of an
apparatus according to the invention,
 FIG. 2 shows a schematic sectional view of the apparatus
according to the invention,
 FIG. 3 shows a schematic sectional view of another embodiment
according to the invention, and
 FIG. 4 shows a sectional view of a further embodiment of
 In FIG. 1 an apparatus for the pre-acidification and anaerobic
fermentation of materials is shown in a schematic three-dimensional
illustration. The apparatus comprises a pre-acidifier 2, a fermenter
with a main load stage 3a and a light load stage 3b and a final
sedimentation stage 4. For the performance of the anaerobic fermentation
main load stage 3a and light load stage 3b are covered by a tarpaulin
for example for collecting and storing the arising gases, which
is not illustrated in FIG. 1 for the sake of clarity. This tarpaulin
can additionally cover pre-acidification 2 for example when the
flotation occurs by means of gas or gas circulation (not illustrated).
 Between pre-acidifier 2 and main load stage 3a a divider
17, between main load stage 3a and light load stage 3b a double
divider 18 as well as between light load stage 3b and final sedimentation
stage 4 a divider 19 are put in which can be adjustable or fixed.
 In the portion of pre-acidifier 2 stirrers 6, 7 can be arranged
with which an agitation can be carried out in the portion of pre-acidifier
2. Stirrers 6, 7 can be driven by a control device 14 via signal
or power supply lines 15. Via a signal or power line 16 control
device 14 can also be connected to a pump 5c with which a transport
from pre-acidifier 2 into main load stage 3a via pipelines 5a and
5b can take place. At this the end of a nozzle and of a pipeline
5b are arranged in the portion of pre-acidifier 2 in the upper portion
of pre-acidifier 2 i.e. for example above the middle along the height
of pre-acidifier 2. Main load stage 3a as well as light load stage
3b can comprise partition walls not further illustrated. Double
divider 18 between main load stage 3a and light load stage 3b as
well as divider 19 between light load stage 3b and final sedimentation
stage 4 may comprise transfer ports 20 or overflow spillways with
which materials from the respective stage can pass over into the
 The basin illustrated in FIG. 1 can be embedded into the
ground which however is not illustrated in figure 1 for reasons
 While in FIG. 1 pre-acidifier 2, fermenter 3a, 3b as well
as final sedimentation stage 4 are accommodated in a basin they
can also be arranged individually in a basin or tank.
 In FIG. 2 there is a schematic sectional view of the apparatus
of FIG. 1, in which tarpaulin 13 is illustrated which covers the
main load stage and the light load stage. Under tarpaulin 13 the
biogas produced can gather so that the tarpaulin bulges as illustrated
in FIG. 2.
 Furthermore in FIG. 2 the induction of the materials A and
B via feed mechanisms 8 and 9 and for B alternatively via a pre-treatment
25, respectively, is schematically illustrated. While the fluid
material A is normally fed through a pipeline the solid material
B can be fed via a conveyor belt or via containers or the like.
If the solid material B is available in a pasty or bloated form
it can also be fed via a pipeline 9. In FIG. 2 a possible pre-treatment
25 of the solid materials B is also specified.
 In FIG. 3 another embodiment of apparatus 1 is schematically
illustrated. Here a sieve 12 is arranged at the entry of a pipeline
5b which serves for transporting from pre-acidifier 2 into main
load stage 3a. While sieve 12 is arranged here in an approximately
middle position with respect to the vertical height of pre-acidifier
2, it can also be arranged further up or further down. Sieve 12
is required to have a mesh aperture or transfer port opening size
such that solids B which are fed into the pre-acidifier cannot pass
through as long as they are insufficiently pre-acidified.
 Instead of a pipeline 5b and a sieve 12 as transport means
a sieve or a rack in a spillway or just a spillway with an automatically
lockable valve can also be arranged through which materials from
pre-acidifier 2 flow over into main load stage 3a. Such a spillway
can be arranged at the upper end of divider 17 for example and can
probably be lockable. The described spillways can also be arranged
in the middle or lower part of divider 17.
 Instead of a sieve 12 any other suitable device for separating
coarse structured materials from soft or fluid materials as for
example an intermediate sedimentation stage can also be provided.
From such an intermediate sedimentation stage the solid materials
would be transported back into pre-acidifier 2 so that they undergo
a further pre-acidification.
 FIG. 4 shows a further embodiment of the invention. At this
a pipe 5e is provided as transport means, whose entry nozzle end
is located in the lower portion of pre-acidifier 2. Furthermore
a flotation device 10, 11 is provided with which air or gas which
is fed through a pipeline 10 can be induced in the bottom portion
of preacidifier 2.
 A pump 5d is connected via a signal, a compressed-air, a
hydraulic or a power line to a control device 14 which can drive
pump 5d or an automatic valve (not illustrated). Furthermore, control
device 14 is connected to an optional stirrer 6, 7 and/or to flotation
device 10, 11, 21 via one or more signal, compressed-air, hydraulic
or power lines and can drive these.
 A first embodiment of a method according to the invention
shall be explained on the basis of FIGS. 1 and 2.
 Via pipelines 8 a brewery waste water (process water) for
example is fed into the portion of pre-acidifier 2. The draff, yeasts
and filtered out remains furthermore arising at the brewery can
be fed into the portion of pre-acidifier 2 unprocessed, completely
or partially pretreated via suitable transport means such as pipelines
or conveyor belts or the like as solids B.
 In this portion a fermentation by acidogeneous bacteria
into mainly organic acids, hydrogen carbon dioxide as well as low
alcohols occurs. At this a pH-value of approximately 6 and below
or 5.5 and below is achieved.
 To support the thorough mixing one or more stirrers 6, 7
for example are employed in the portion of pre-acidification 2.
 The materials A and B are put into the portion of pre-acidifier
2 continuously or intermittently.
 From pre-acidifier 2 a transport of materials into main
load stage 3a must occur continuously or in intervals. For this,
stirrers 6 and 7 or other agitation devices for example are switched
off by means of control device 14. After a while (some minutes up
to several ten minutes) the solids which are normally still insufficiently
pre-acidified deposit themselves in the lower portion of pre-acidifier
2. In the upper portion of the reactor the sufficiently pre-acidified
fluid materials as well as the soaked and therefore sufficiently
preacidified solids gather. After the deposition in the portion
of pre-acidifier 2 which is caused by a switch-off for example of
stirrers 6, 7 a pump 5c is switched on via control device 14 which
transports materials via pipelines 5a and 5b from the upper portion
of pre-acidifier 2 into main load stage 3a or control device 14
opens the alternatively installed valve.
 In main load stage 3a and in light load stage 3b the pre-acidified
materials ferment and methanate, respectively, under the formation
of biogas and the materials leaving light load stage 3b are final-treated
in final sedimentation stage 4. The final-treated materials can
be re-transported to the process, for example into the light load
stage 3b, by means of pump 22 and pipeline 23 or taken out in a
controlled way as surplus sludge by means of valve 24.
 The draff and the filtered-out remains can be mechanically
pre-hackled or purified otherwise so that for example a preset grain
size of solid material results. This is advantageous to the controlled
process control as well as to the accelerated pre-acidification
of the solids.
 On the basis of FIG. 3 a further embodiment of the method
shall be explained. The addition of materials A, B to pre-acidifier
2 as well as the fermentation and final sedimentation is the same
as the procedure described with reference to FIGS. 1 and 2.
 In this method materials are transported continuously or
in intervals from pre-acidifier 2 into main load stage 3a with a
pipeline 5b and a pump, not illustrated, through a sieve 12. Sieve
12 retains the still insufficiently pre-acidified solids and lets
the sufficiently pre-acidified fluid and soaked materials pass through.
 At this the withdrawal from pre-acidifier 2 can be carried
out in a middle position, as illustrated in figure 3, or further
up or further down.
 Furtheron, means for keeping sieve 12 free such as slides
can be provided which remove in suitable intervals material accumulating
on sieve 12. For that purpose a device can also be provided which
creates a cross current in sieve 12 in order to remove accumulating
material from sieve 12 in this way.
 The agitation device, here stirrers 6, 7 may be switched
on or switched off during the transport.
 Using FIG. 4 a further embodiment of a method shall be explained.
 Here the feed of the materials A, B and the fermentation
and final sedimentation, respectively, are the same as described
with reference to FIGS. 1 and 2.
 For the transport of materials from pre-acidifier 2 into
main load stage 3a a pump 21 for example with which air or gas is
pumped through a pipeline 10 into the lower portion of the pre-acidifier
is driven by control device 14. There the air or the gas exits through
outlets 11 so that a flotation in pre-acidifier 2 occurs. At this
juncture the insufficiently pre-acidified solids are bloated upwards.
Meanwhile with control device 14 a pump 5d is put in operation which
transports materials via pipelines 5e from pre-acidifier 2 into
main load stage 3a. Here the entry of the nozzle to pump 5d lies
in the lower portion of pre-acidifier 2, because here no insufficiently
preacidified solids are present during the flotation. The nozzle
can however also lie in the middle or upper portion when floating
is not performed but sedimenting.
 An optionally provided stirrer 6, 7 is preferably switched
off during transporting.
 With the method described above it is possible for example
to set the mean duration of stay of fluid materials A in the pre-acidification
2 to approximately 5 to 15, advantageously approximately 10 hours,
and to set the mean duration of stay of solids to between 30 and
150, preferably approximately 100 hours. Thereby it is possible
to transport only sufficiently pre-acidified materials into main
load stage 3a and simultaneously however jointly or individually
process fluid as well as solid materials A, B.
 It has turned out that with the above method a utilization
of the solids for the production of biogas of up to 80% and more
 The advantages in economical respects and in procedural/operational
respects by reduction to one reactor line in the handling of inherently
diverse organic materials are great.