Note: Descriptions are shown in the official language in which they were submitted.
CA 02755512 2011-10-19
Biogas Plant and Servicing Device for a Biogas Plant
Description
The present invention relates to a biogas plant and a
servicing device for a biogas plant.
Various biogas plants and servicing devices for biogas plants
have become known in the prior art. Biogas plant are as a rule
provided with one or more fermenter tanks for fermenting the
fermenting substrates and as a rule with an agitator provided
for stirring and at least partially homogenising the
fermenting substrates in the fermenter tank.
Most of these agitators have agitator blades with which to mix
and agitate the fermenting substrates. In dependence on the
substrates to be fermented and further ambient conditions and
on the materials employed the agitators require inspection and
if necessary maintenance at specified intervals. Some or all
of the agitator blades may be exchanged for example.
For maintenance on an agitator the agitator which is disposed
on a mounting or holding rod or the like is traversed from the
lower fermentation section in which the fermenting substrates
are located, to the upper gas section. For gaining access to
the agitator, for example a biogas plant equipped with a
flexible top sheeting may be opened and the top sheeting
removed entirely to thus gain easy access to the agitator.
This method, however, involves the drawback of considerable
work for removing the top sheeting. Also, the biogas
1
CA 02755512 2011-10-19
collecting in the gas section above the fermentation section
escapes as the top sheeting is removed.
For biogas plants having a concrete top, DE 199 51 959 Al has
made known a rectangular maintenance shaft inserted in the
concrete top allowing maintenance of the agitator without
significantly compromising the gas production. In the case of
fermenters having a high solids content the maintenance shaft
is bipartite with the top part terminating approximately 10 cm
above the normal liquid level. In the case of maintenance a
lower shaft portion is inserted into the top shaft portion for
immersing in the fermenter mass. For sealing the top shaft
portion is provided with a circumferential sealing channel
with which when assembled a sealing collar of the lower shaft
portion engages. These two-part maintenance shafts involve the
drawback that each case of maintenance requires newly
inserting the lower shaft portion and sealing against the top
shaft portion and removing again after maintenance. Also, the
fermenter filling volume must be kept within narrow limits for
achieving reliable sealing. Therefore this document proposes
for fermenters having a low solids content a one-piece
maintenance shaft reaching at least 10 cm beneath the normal
liquid filling level. For balancing the gas a shut-off pipe
connection to the gas headspace of the fermenter is provided.
In the case of maintenance the work involved is reduced
compared to a two-piece maintenance shaft. The drawback of
this is, however, that these maintenance shafts are suitable
for low solids contents only. Also, deposits may accumulate on
the immersed shaft. Another drawback is a permanent increase
in the agitating resistance and thus in energy consumption.
EP 1 717 305 B1 has made known a biogas plant servicing shaft
for a fermenter of a biogas plant with a top sheeting with the
2
CA 02755512 2011-10-19
servicing shaft being provided as a gas-tight, dome-shaped
cover across a servicing opening in the fermenter tank cover.
The agitating unit held vertically in the fermenter tank can
be moved upwardly from the lower fermentation section into the
servicing shaft interior. After opening a servicing flap at
the servicing shaft the agitator device can be serviced in the
interior of the dome-type servicing shaft and one or all of
the agitator blades may be exchanged as needed.
A biogas plant servicing shaft according to EP 1 717 305 Bl
operates reliably, allowing servicing the agitator device
while involving little work wherein maintenance does not
require removal of the entire top sheeting. However, as the
servicing flap is opened, the biogas which has collected in
the upper gas section of the fermenter tank and which is under
overpressure, escapes while air and thus a considerable amount
of oxygen enters the fermenter tank requiring removal prior to
restarting operation.
In view of the described prior art it is therefore the object
of the present invention to provide a servicing device and a
biogas plant having a servicing device involving ease of
operation and ease of maintenance while minimizing biogas
losses when carrying out maintenance.
This object is solved by a servicing device having the
features of claim 1. The biogas plant according to the
invention is the object of claim 10. Preferred specific
embodiments of the invention are the subjects of the
corresponding subclaims. Further advantages and features of
the invention can be taken from the embodiment.
3
CA 02755512 2011-10-19
The servicing device according to the invention comprises a
servicing unit and a servicing section and it is provided to
be used in a biogas plant which biogas plant comprises at
least one fermenter tank wherein an interior space of the
fermenter tank is provided with at least one fermentation
section and at least one gas section. The fermenter tank is
sealed substantially gas-tight by at least one gas closing
wall disposed at the fermenter tank. The servicing unit is
provided with at least one movable sealing device which when
installed as intended can be moved at least between an
inoperative position and a sealing position. The sealing
device comprises at least one retention wall of a flexible
material. The sealing device is suitable to separate the
servicing section from the gas section substantially gas-tight
in the sealing position, at least while the biogas plant is in
use as intended.
The servicing device according to the invention has many
advantages. One considerable advantage of the servicing device
according to the invention is that in the sealing position the
servicing section is sealed gas-tight from the gas section by
the flexible retention wall. The flexible retention wall
allows maintenance on an agitator with a variable fermenter
mass filling level. Ease of maintenance is provided. The
flexible length of the retention wall allows a flexible
adjustment to the currently prevailing conditions.
Concurrently the sealing device is provided at the servicing
device including in the inoperative position and does not
require removal every time after maintenance. In the
inoperative position the sealing device is typically mostly
provided above the liquid level and is at least not
substantially immersed in the liquid. This prevents a greatly
4
, CA 02755512 2011-10-19
increased flow resistance. Also, converting and installing
components is not required for every maintenance.
The invention allows uncomplicated and easy maintenance on an
agitator or an agitator device located in the servicing
section while at the same time prohibiting the biogas located
in the gas section of the fermenter tank from escaping to the
exterior through the servicing section of the servicing unit.
This allows uncomplicated maintenance involving minor losses
of gas. Moreover no - or only minor quantities of - oxygen can
enter from the exterior during maintenance which requires
removal at restarting to ensure the proper methane content.
Moreover the scouring period during which fresh air is fed to
the servicing section to avoid explosive gas mixtures can be
kept very brief. Furthermore, after a performed maintenance
the biogas plant can be restarted immediately without removing
any components which on the whole causes considerably lower
costs and losses.
In a preferred more specific embodiment of the invention the
servicing section is connected with the gas section to be gas-
permeable at least in the inoperative position of the sealing
device. This means that during normal operation of the biogas
plant the servicing section is connected with the gas section
at least in part and in particular entirely so as to allow the
biogas produced by the fermenting substrates to collect in the
servicing section as well. For normal operation the flexible
retention wall is pulled upwardly so as to not form a separate
gas headspace at the servicing unit.
Preferably the sealing device is attached at the servicing
unit. In an advantageous configuration the servicing unit is
5
CA 02755512 2011-10-19
provided with at least one attachment frame with the sealing
device fixed to the attachment frame. The attachment frame is
in particular provided to be sealingly attached to the gas
closing wall or the tank cover of the biogas plant.
In particular is the attachment frame attached to a carrying
console of the servicing unit. The servicing unit may for
example be configured as or comprise a servicing shaft. A
servicing platform may be provided, the servicing platform and
the servicing unit in particular being supported by the
carrying console. The carrying console may be attached to the
tank wall of the fermenter tank. Attachment of the carrying
console is conceivable to the inner tank wall or else to the
outer tank wall. It is likewise possible to support the
carrying console on a separate foundation external of the
fermenter tank.
The sealing device is in particular approximately channel-
shaped when in the sealing state. Particularly preferably does
the retention wall consist at least in part of a gas-tight
web, a film hose or the like.
All of the configurations particularly preferably provide for
the sealing device to extend longer in the sealing position
than in the inoperative position. In the sealing position the
sealing device is preferably at least 50 % longer and in
particular more than twice as long as in the inoperative
position. This means that the servicing section which is
preferably provided inside the sealing device at least in
part, extends considerably longer in the sealing position than
in the inoperative position.
It is preferred for the sealing device to comprise bellows.
6
CA 02755512 2011-10-19
The sealing device may be telescopically extendable and may
for example comprise slightly conical and flexible or gas-
tight, flexibly interconnected cylinder segments which are
telescoped. This does not require for the sealing body to be
shaped cylindrically but its cross-section may be rectangular
or polygonal or otherwise. What is significant is that the
retention wall is configured substantially gas-tight at the
sealing device when the sealing device is in the sealing
position.
Preferably at least one displaceable guide member is provided
which may for example be configured as a guide rope or a guide
chain. The sealing device is preferably displaceable by means
of the guide member where the retention wall of the sealing
device can be lowered by the guide member at least from the
inoperative position to the sealing position.
A flexible guide member and a flexible retention wall offer
considerable advantages since retracting the guide member
causes the guide wall to contract such that it requires little
space in the inoperative position.
Preferably the sealing device is provided with at least one
mounting frame or mounting unit to spread the retention wall.
Such a mounting unit or such a mounting frame allows to
maintain the cross-section of the sealing device substantially
unchanged whether the servicing device with the sealing device
is in the inoperative position or in the sealing position.
At this point reference is made to the fact that the term
"inoperative position" of the sealing device is understood to
mean a position in which the sealing device is inactive while
the biogas plant itself may certainly be in operation which it
7
, CA 02755512 2011-10-19
usually is. The sealing device is, however, displaced into the
sealing position when maintenance is intended to be performed
on the servicing device or for example on an agitator in the
servicing section of the servicing device.
Preferably a number of mounting units or mounting frames are
provided which spread the retention wall of the sealing device
at predefined intervals or in spaced-apart positions. The
particular mounting units or mounting frames may be
interconnected although they may be separately provided at the
retention wall. It is as well conceivable for a mounting unit
to comprise a coiled mounting wire or the like with which to
spread the sealing device wherein the mounting unit retains
the cross-section approximately constant while the retention
wall is longitudinally displaceable. The cross-section is in
particular dimensioned for the agitator device to pass
through.
In advantageous more specific embodiments at least one
weighting device is connected with the lower end of the
sealing device. This allows that as the guide member is
relieved the sealing device is transferred from the
inoperative position to the sealing position.
For example when the flexible guide member is configured as a
rope or the like and is at least partially wound up in the
inoperative position, then unwinding the guide member may
cause the lower end of the sealing device to automatically
move downwardly when a weight is provided at the lower end of
the sealing device. In this way the sealing device is
automatically transferred from the inoperative position to the
sealing position as the flexible guide member is allowed to
descend. Transferring the sealing device from the sealing
8
CA 02755512 2011-10-19
position to the inoperative position can be done by retracting
or winding up the flexible guide member.
A crank mechanism is preferably connected with the guide
member for descending or retracting the flexible guide member.
Preferably the sealing device is disposed at the servicing
device in the inoperative position.
Preferably the flexible guide member is guided at the sealing
device in eyelets or the like. As the flexible guide member is
retracted, it contracts the retention wall of the sealing
device.
The biogas plant according to the invention is equipped with
at least one fermenter tank and comprises a fermentation
section provided in an interior space of the fermenter tank
and a gas section. The fermenter tank is sealed substantially
gas-tight by a gas closing wall or a tank cover. At least one
agitator device and at least one servicing device with a
servicing section are provided which agitator device can be
transferred at least from an operating position in the
fermentation section to a maintenance position in the
servicing section of the servicing device. At least one
movable sealing device with at least one retention wall of a
flexible material is provided which is displaceable between an
inoperative position and a sealing position wherein when in
the sealing position the sealing device separates the
servicing section from the gas section substantially gas-
tight.
The biogas plant according to the invention also has many
advantages. By way of the servicing device with the movable
9
, CA 02755512 2011-10-19
sealing device a biogas plant is provided in which the sealing
device is readily displaceable between an inoperative position
and a sealing position. Maintenance can be carried out without
requiring extensive installing and removing of components.
Transfer between the inoperative position and the sealing
position can be done independently of the filling level in the
fermenter. This allows a gas-tight separation of the servicing
section of the servicing device from the gas section of the
biogas plant so as to dispense with releasing the entirety of
the biogas accumulated in the gas section of the fermenter
tank for carrying out maintenance or repairs for example on an
agitator present in the servicing section.
The biogas plant is in particular equipped with a servicing
device as it has been described above.
In a simple configuration the biogas plant virtually consists
of the fermenter tank and the tank cover provided thereat, and
of the servicing device and an agitator device. The biogas
produced by the fermenting substrates is collected and may be
discharged if required through a dedicated gas pipe.
Particularly preferably the agitator device is held vertically
adjustable at a mounting rod or holding rod or the like. This
enables transfer of the agitator device from the operating
position to a maintenance position. The operating position
will typically be located within the fermentation section of
the fermenter tank and the maintenance position, above the
fermentation section. The maintenance position may be provided
within the gas section or even above the tank cover. The
maintenance position is for example provided above the tank
cover when a servicing shaft or the like extending above the
tank cover is provided, wherein for maintenance the agitator
10
CA 02755512 2011-10-19
device is transferred from the lower fermentation section to
the upper servicing section to carry out maintenance.
Then the holding rod will as a rule extend within the
servicing section from the fermentation section into the gas
section and optionally from there into the interior of the
servicing shaft and even beyond.
In a particularly simple configuration the servicing device is
equipped with a servicing opening which servicing opening may
be located on the surface of the tank cover or the gas closing
wall or it may be provided therein. This structure does not
necessarily require a dome-shaped servicing shaft
configuration. Then the section in which maintenance is
carried out may be provided above the gas closing wall or the
tank cover in the open air. To this end the agitator device is
transferred on the mounting rod or holding rod from the
fermentation section upwardly as far as above the tank cover
while the sealing device reliably seals the servicing section
inside the tank from the gas section.
The gas closing wall may be formed by the single- or double-
walled tank cover. It is also conceivable for the gas closing
wall to be provided as a gas holder sheeting beneath the
actual tank cover. It is conceivable to configure the tank
cover as a top sheeting which may be provided for or
prohibited from being walked on. It is also conceivable for
the tank cover to be configured at least in part as a rigid
cover, e.g. as a concrete roof or concrete ceiling. In the
case of a concrete roof or concrete ceiling the gas closing
wall is as a rule formed by the concrete roof or concrete
ceiling itself.
11
CA 02755512 2011-10-19
In all of the configurations the servicing device preferably
comprises a carrying console for supporting the servicing
device in particular on the inner or outer tank wall. A
servicing shaft, if provided, is preferably also supported by
the carrying console.
Preferably the sealing device is disposed and retained at the
servicing device in the inoperative position. In the sealing
position the sealing device preferably extends from the
servicing device downwardly at least as far as the
fermentation section. The sealing device may as well extend as
far as beneath the fermentation section surface. It is also
conceivable for the sealing device to lie on the fermentation
section, its edges being slightly immersed in the fermentation
section to allow the tightest possible connection of the
sealing device with the fermentation section. The edge may for
example be immersed in the fermenter mass approximately 2 cm
to 5 cm.
In all of the configurations it is preferred for the sealing
device to surround at least part of the holding rod or the
mounting rod at least in the sealing position. This ensures
that in the case of height displacement the agitator device
moves up and down inside the sealing device and does not need
to penetrate the retention wall such that an additional
sealing at the mounting or holding rod can be omitted.
As was described above, a mounting unit or a mounting frame or
a number of these mounting units or mounting frames may be
provided for spreading the sealing device in the sealing
position.
12
CA 02755512 2011-10-19
On the whole the sealing device forms a gas curtain separating
the biogas section in the fermentation tank from the servicing
section. Although the actual maintenance of the agitator or an
agitator device may be done inside the tank, it may as well be
carried out on the roof or above the roof of the fermenter
tank cover.
In all of the cases normal operation of the biogas plant
provides for the sealing device to be pulled up with the
retention wall. For performing maintenance on the agitator the
agitator may be pivoted towards the outer wall and rotated
upwardly by way of the height displacement for example as far
as the stopper. Subsequently or concurrently the sealing
device retention wall which serves as a gas curtain may be
lowered by means of the guide members of the provided or
additional weights at the retention wall until it reaches and
is perhaps slightly or even deeper immersed in the fermenting
substrate.
Subsequently the maintenance cover or the servicing opening of
the servicing device may be opened and the gas still remaining
in the servicing section, allowed to escape. Then the agitator
can be rotated upwardly until it is for example located above
the tank cover where maintenance is performed. At the same
time the biogas present in the gas section of the fermenter
tank is retained by the retention wall serving as a gas film
so as to cause virtually no loss of gas while concurrently
allowing more comfortable maintenance work. After maintenance
the agitator device can be lowered, the servicing opening
closed, and the sealing film or gas sheeting, pulled back up
and secured. Subsequently the plant can continue normal
operation.
13
CA 02755512 2011-10-19
To reinforce the retention wall of the sealing device a tube
or a carrier or mounting unit may be provided at the lower
edge or in specific intervals to reinforce and spread the
retention wall. For automatically or manually pulling up the
retention wall, closable tubes or the like are mounted to the
corners of the servicing opening of the servicing device
through which the flexible guide member may be threaded.
Other advantages and features of the present invention can be
taken from the exemplary embodiment which will be described
below with reference to the accompanying figures:
These show in:
Fig. 1 a schematic side view of a biogas plant according to
the invention with a sectional detail view of a
fermenter tank;
Fig. 2 an enlarged illustration of the servicing device of the
biogas plant in Fig. 1;
Fig. 3 a schematic illustration of the sealing device of the
servicing device in Fig. 2;
Fig. 4 a schematic, enlarged view of the servicing device in
the inoperative position; and
Fig. 5 an illustration of the servicing device in the sealing
position.
With reference to the Figures 1 to 5 an embodiment of the
biogas plant 1 with a servicing device 2 will be explained
below.
14
CA 02755512 2011-10-19
The biogas plant 1 illustrated in a side view in Fig. 1
comprises a fermenter tank 4 in which a fermentable substrate
for manufacturing biogas is located in the lower fermentation
section 5 wherein the biogas manufactured collects in the gas
section 6 above the fermentation section 5.
The fermenter tank 4 comprises a tank wall 29 and a tank cover
8 which in the present case is configured as a flexible top
sheeting 28. The present top sheeting 28 forms the gas closing
wall 8.
For agitating the fermenting substrate in the interior space 7
of the fermenter tank 4 in the fermentation section 5 and for
promoting the fermentation process, at least one agitator is
provided as an agitator device 23 which is or are disposed at
a holding rod 26 extending from the bottom 27 of the fermenter
tank 4 as far as above the tank cover 28.
The fermenter tank 4 is provided with at least one servicing
device 2 configured as a servicing unit or a servicing shaft
3.
The servicing shaft 3 illustrated in the present embodiment is
supported on a carrying console 14 on the inside of the tank
wall 29.
The servicing shaft 3 comprises a platform 34 for a person to
stay on to perform maintenance. The servicing unit 2 is
connected with the top sheeting 28 or the gas closing wall 8
so as to be gas-tight.
In the position illustrated in Figs. 1 and 2 the sealing
device 9 is in the inoperative position 10 in which the
CA 02755512 2011-10-19
retention wall 15 of the sealing device 9 is disposed
contracted at the attachment frame 13 of the servicing device
2. In the inoperative position 10 the sealing device 9
requires little space. This position is provided for normal
operation of the biogas plant 1 wherein the agitator device 23
agitates the fermenting substrate in the fermentation section
while the biogas produced collects above the fermentation
section 5 in the gas section 6.
The present sealing device 9 comprises a retention wall 15
which on the whole is configured as bellows 16 and which can
be transferred from the position illustrated in Fig. 2 to the
telescoped position illustrated in Fig. 3. Figure 3
illustrates the sealing device 9 in the sealing position 11.
Presently this is achieved in that the flexible guide members
17 configured as ropes are lowered via the crank mechanism 33
wherein the dead weight of the sealing device 9 or else
additional weights 21 cause the retention wall 15 to descend.
The retention wall 15 may be spread via additional mounting
units 18 located on the retention wall at specified intervals.
The retention wall 15 is connected with the guide member 17
configured as a rope via attachment eyelets 32.
When the guide member 17 is descended then the dead weight or
the additional weights 21 cause the retention wall 15 to lower
until the retention wall 15 reaches the surface of the
fermentation section 5 and may be immersed somewhat. This
achieves a tight closing of the servicing section 12 located
inside the sealing device against the gas section 6.
In this sealing position 11 maintenance can be performed. To
this end the agitator device 23 is traversed outwardly towards
the tank wall where it is pivoted and then raised until it is
16
CA 02755512 2011-10-19
located above the fermentation section in the servicing
section 12 which by way of the lowered retention wall 15 is
separated from the gas section 6 so as to be gas-tight.
In the illustrated embodiment the agitator device 23 is
transferred as far as above the tank cover 28 until it is
located within that portion of the servicing section 12
provided inside of the servicing shaft 3. There the servicing
opening may be opened subsequently and after allowing any
biogas still present in the servicing section to escape the
agitator device is comfortably accessible for maintenance.
The sealing device may be articulated on one side while the
other side is pivotal for transferring the retention wall
between the inoperative position 10 and the sealing position
11. It is possible for the pivot point to be slightly disposed
at the level of the maximum filling level or slightly below
wherein the larger part and in particular at least half, three
quarters or more of the sealing device 9 is located above the
fermenter mass in the inoperative position 10.
In an alternative configuration the servicing shaft for
example does not extend dome-like above the tank cover but in
a simple case a servicing opening is provided in the tank
cover which after opening allows raising the agitator device
as far as above the tank cover whereupon maintenance can be
done on the agitator device the open air above the tank cover
28.
Figure 4 again shows the operating position where the sealing
device is in the inoperative position 10 and the biogas plant
may be in normal operation. To allow a better view the top
17
CA 02755512 2011-10-19
sheeting is illustrated transparent to offer a view into the
interior of the fermenter tank 4.
Figure 5 similarly illustrates the sealing position 11 in
which maintenance 25 may be performed. The retention wall 15
of the sealing device 9 which serves as a gas curtain has been
lowered as far as the level of the fermentation section 5.
On the whole the invention allows particular ease of
maintenance on an agitator device and other components.
Performing maintenance involves very minor loss of gas while
also a minimum of oxygen enters the plant. Employing the
invention is also efficient in terms of economics.
18
CA 02755512 2011-10-19
List of reference numerals:
1 biogas plant
2 servicing device
3 servicing unit, servicing shaft
4 fermenter tank
fermentation section
6 gas section
7 interior space
8 gas closing wall, tank cover
9 sealing device
inoperative position
11 sealing position
12 servicing section
13 attachment frame
14 carrying console
retention wall
16 bellows
17 guide member
18 mounting frame
19 position
position
21 weighting device
22 end
23 agitator device
24 operating position
maintenance position
26 holding rod
27 bottom
28 top sheeting
29 tank wall
displacement device
31 agitator blade
19
CA 02755512 2011-10-19
32 attachment eyelet
33 crank mechanism
34 platform
