Title of Invention

METHOD FOR ANAEROBICALLY FERMENTING BIODEGRADABLE ORGANIC MATERIAL AND DEVICE FOR THE SAME

Abstract Method for anaerobically fermenting biodegradable organic material, whereby this material is mixed with a quantity of already fermented material as an inoculum for the active anaerobic fermentation and this mixture is introduced at the top into a fermentation chamber (1A) in which a fermenting mass is situated, which, while being fermented, moves from an inlet (6A) situated at the top towards an outlet (8) situated at the bottom. Before the mixture is added to the fermenting mass, it is expanded beforehand until its density approximately coincides with the density of the already present fermenting mass at the beginning of this downward movement.
Full Text Method and device for anaorobically fermenting organic
material.
This invention relates to a method for anaerobically fermenting biodegradable
organic material and device for the same.
This invention relates to a method for anaerctoically
fermenting biologically degradable organic material,
whereby this material is mixed with a quantity of already
fermented material as an inoculum for the active
anaerobic fermentation, and whereby this mixture is
introduced at the top into a fermentation chamber in
which a fermenting mass is situated, which moves from an
inlet situated at the top towards an outlet situated at
the bottom.
By organic material, here in particular the organic
fraction of domestic waste is intended, and of similar
industrial waste and other organic fractions, such as,
for example, slurry from water purification installa-
tions, slurry from the paper industry, or other kinds of
organic slurry.
Methods for anaerobically fermenting organic waste can be
divided into wet and dry manners of fermentation.
With wet fermentation methods, fresh or recycled water is
added to the solid organic waste or slurry in order to
form a highly liquid mash or slurry which can be pumped
easily and which can easily be misted in a fermentation
tank, such mash with 6 to 10% of dry matter, depending on
the viscosity of the starting material to be treated , is
pumped into a fermentation tank and is transformed into
biogas, in mixed fermentation systems, in one or two
phases and with mesophilic or thermophilic temperatures.
Due to the high water content of the material in the
termentation tank, the density in this tank is relatively
uniform, and the produced biogas can easily escape from
the mixed mash.
With a dry fermentation, on the contrary, the quantity of
water which is added is limited, such that a relatively
solid biologically degradable waste is pumped or pushed
into a "dry" fermentation tank by means of special pumps.
For organic fractions originating from domestic waste,
the dry matter content of the material fed into the tank
is between 15 and 45%. For more viscous materials, this
may be up to 10 to 15%.
In most cases, with dry fermentation the material is
pumped at the bottom into the standing tank, whereby gas
is injected in order to obtain a mixing and a horizontal
movement of the material. The tank may also be installed
horizontally and may be provided with a mixing device
which realizes the horizontal movement.
Such method of introducing the material at the bottom of
a standing tank is described in WO 86/0520O. Biogas is
brought into the fermentation tank at different
locations, through the underside, such that thxs
underside is divided into sectors. The biogas provides
for a mixing of the contents of the sectors and a
movement of the fermenting mass from one sector to the
other and finally towards the outlet, also situated at
the bottom.
EP-A-0.476.217 describes a method, whereby a horizontal
fermentation tank with therein a mixing device is used.
After having been mixed with a portion of fermented
material, the biodegradable material is pushed, through a
feeding tube realized as a heat exchanger, into the tank
and in this tank is mixed by a blender, as a result of
which the fermenting mass flows horizontally through the
tank, from one extremity to the other, where it is
discharged at the bottom.
According to EP-A-0.205.721 and EP-A-0.577.209, the
fermentation is performed in a vertical fermentation
tank, without a nixing device therein. The biodegradable
material is mixed with fermented material as an inoculum
and is pumped into the tank at the top.
In the tank, the fermenting mass sinks, as fermenting
material is discharged at the bottom. This latter is
performed by means of a sliding grid moving to and fro
above the flat bottom of the tank, which grid pushes this
fermented material into a screw conveyor device situated
therebelow. This device pushes the fermented material
into another screw functioning as a lock by forming a
stopper of fermented material at its conical outlet.
In the method according to EP-A-0-577.209, moreover, due
to the design of the device, a fraction division into, a
liquid and a solid fraction is obtained, such that the
content of solid matter in the fermentation tank can be
maintained and that the dry matter content of the fed
material, which consists of a mixture of inoculum and
fresh material, is situated between 15 and 40%.
In these fermentation tanks without mixer, it is typical
that the content thereof rises and expands as a result of
the produced biogas. This biogas can not bubble
immediately upward as in a wet tank and can not easily
escape, due to the high viscosity of the material in
which it is created and through which it must weave its
way upward.
In practice, the material will expand as a consequence
thereof, and its density will be reduced by about 10 to
40%. The average density depends on various parameters,
such as the degree of biogas production, the feeding
frequency, the kind of structure of the added material,
and the height of the feeding tank. Depending on the
feeding, the density may vary from 0.7 to 1.2 kg/l.
It was noted that this feeding matter, being a mixture of
fresh biodegradable waste and fermented material or
residue, has a density which mostly is higher than 1.0
kg/l, on account of the fact that the prevailing biogas
during mixing of the fermented material and the fresh
material can escape from the fermented material.
When this feeding matter with fresh material and
inoculum, which, due to the degassification, has obtained
a higher density, is brought at the top into the
fermentation tank in which the material has a lower
density, then, depending on the difference in density,
the dimensions and the diameter of the fermentation tank
and the extraction system thereof, too fast a sinking of
this feeding matter through the mass in the tank can be
noted, such that this feeding matter arrives faster at
the bottom than the remainder of the fermenting mass and,
thus, is discharged from the tank without having
undergone an optimum fermentation.
The invention aims at a method which does not have these
disadvantages and whereby the mixture of fresh material
and fermented material is brought at the top into a
vertical fermentation chamber in which material moves
downward from the top, however, whereby it is avoided
that said added mixture sinks faster than the remainder
of the fermenting mass.
According to the invention, the mixture, before being
added to the fermenting mass and further moving downward
during fermentation, is expanded beforehand until its
density approximately coincides with the density of the
already fermenting mass at the beginning of this downward
movement.
Preferably, the mixture is beforehand expanded or reduced
in density, while being moved upward.
Preferably, a mixture is made of one quantity of fresh
material, together with one to ten quantities of
fermented material.
Preferably, a mixture is treated, having a dry matter
content of 10 to 45%.
The downward movement of the fermenting mass in the
fermentation chamber can take place in a fermentation
tank which is free of any mixer, whereby the mixture is
supplied at the upper side of the fermentation tank,
after it has been reduced in density in an expansion
vessel.
The mixture can be expanded beforehand by means of a
preceding biological prefermentation, by injecting a gas
into the mixture, by beating this mixture or also by
adding chemicals which lead to the release of gasses in
the mixture, or by a combination of two or more of these
procedures.
If the expansion or density reduction is performed by
means of biological pre-fermentation, this can be
performed in an expansion vessel in which the mixture
remains at least 5 minutes, and preferably between 15
minutes and 3 hours.
The sojourn time in the expansion vessel also may be more
than three hours, for example, 3 to 72 hours.
The invention also relates to a device which is
particularly suitable for applying the method according
to any of the preceding forms of embodiment.
Consequently, the invention relates to a device for
anaerobically fermenting organic waste, which device
comprises a fermentation tank with a fermentation
chamber, an outlet for fermented material at the bottom
of this tank, and a biogas outlet at the top and a
feeding device comprising a mixer and which, at the top,
gives out into the fermentation tank, and which is
characterized in that the feeding device comprises at
least an expansion vessel situated between the mixer and
the fermentation tank.
The feeding device also may comprise a pump to wnich the
mixer gives out, whereby the expansion vessel is situated
between the pump and the fermentation tank.
This expansion vessel may be situated at least partially
in the fermentation tank as well as at the exterior side
thereof.
The expansion vessel may be reduced to a supply conduit.
The device may comprise a device for gas injection or an
inlet for chemicals which lead to the release of gasses,
wnich latter connects to the expansion vessel, the mixer
or a pump connected thereto, or a beating device can be
provided in the feeding device.
With the intention of better showing the characteristics
of the invention, hereafter, as an example without any
limitative character, several preferred forms of
embodiment of a method and device for anaerobically
fermenting orqanic material according to the invention
are described, with reference to the accompanying
drawings, wherein:
figure 1 schematically represents a vertical cross-
section of a device for anaerobic fermentation
according to the invention;
figure 2 represents a cross-section according to line
II-II in figure 1;
figure 3 schematically represents a cross-section
analogous to that of figure 1, however, relating to
another form of embodiment;
figure 4 represents a cross-section according to line
IV-IV in figure 3;
figures 5 to 9 represent schematic cross-sections
analogous to those of figures 1 and 3. however,
relating to still other forms of embodiment of the
invention.
The device for anaerobically fermenting organic material,
represented in figures 1 and 2, substantially consists of
a closed fermentation tank 1, which comprises a
fermentation chamber 1A, and a feeding device 2
comprising a transport device 3, a mixer 4, a pump 5 and
an expansion vessel 6, which, at the top, gives out into
the fermentation tank: 1, The outlet of the expansion
vessel 6 at the top forms the inlet 6A of the
fermentation tank 1.
The inlet for material in the fermentation tank 1, thus,
is situated at the top, and the outlet 8, which can be
closed off by a valve 7, is situated below the funnel-
shaped bottom of this fermentation tank 1. This
fermentation tank 1 also may have a flat bottom with an
outlet & in the bottom, possibly by means of screws of
other extraction systems, or an outlet 8 at the underside
of its wall.
In the outlet 8, as represented, transport screws 9 can
be installed. The mixer 4 is connected to this outlet 8
and is situated below an extremity of the transport
device 3, which, in the represented example, is formed by
a transport conveyor- By means of this transport conveyor
or another transport device, such as a screw conveyor,
fresh organic material can be added to the mixer 4.
Downstream of the valve 7, a branch 10, which can be
closed off by a valve 11, connects to the outlet 8,
between two screws 9. In the branch 10, downstream of the
valve 11, a transport screw 12 can also be arranged. The
branch 10 connects to a dewatering device 13.
To the mixer 4, a water conduit 15, which can be closed
off by means of a valve 14, is connected for possibly
supplying water to the mixer 4, as well as a steam
conduit 17, which can be closed off by a valve 16, for
injecting steam in order to heat the material.
The outlet of the mixer 4 connects to the inlet of the
pump 5, whereas the outlet of the pump 5, on one hand,
connects to a conduit 19, which can be closed off by a
valve 18, which conduit 19 serves for transporting off
material, and, on the other hand, connects to the
underside of the expansion vessel 6, by means of a
conduit 20 which possibly can be closed off by a valve
20A.
The expansion vessel 6 penetrates into the fermentation
tank 1 through the funnel-shaped bottom thereof and, with
its opening, gives out into the fermentation tank 1 above
the upper side of the inlet 6A, below or above the level
21 of the fermenting mass in this tank 1.
The expansion vessel 6, for example, is round, as well as
the fermentation tank 1, but has a much smaller diameter.
At the top, an outlet 22 for biogas connects to the
fermentation tank 1.
Fresh material to be treated is introduced into the mixer
4 by means of the transport device 3, together with a
part of the fermented material which is coming through
the opened valve 7 out of the fermentation tank 1 and
further is transported by the screws 9 or another
transport, device to the mixer 4.
In the mixer 4, the fresh material and the fermented
material as an inoculum are mixed in a ratio of one
quantity of fresh material for one to ten quantities of
fermented material.
The dry matter content of the fixture is maintained
between 10 and 45% and preferably between 15 and 45% and,
if necessary or desired, a quantity of water, for
example, waste water, is brougnt into the mixer 4 through
water conduit 15. This water can be supplied hot in order
to bring the final eixture to a temperature of 30 to 42ºC
(mesophilic) or 45 to 60ºC (thermophilic) . If no water
must be added, steam can be injected, by means of the
steam conduit 17, into the mixer 4 in order to tiring the
temperature onto the desired level.
Subsequently, the fixture produced in the mixer 4 is
pumped to the expansion vessel 6 through conduit 20.
Valve 18 is closed and valve 20A is open. In this
expansion vessel 6, the mixture moves upward, as
indicated by arrow p1, whereas, it undergoes a biological
pre-fermentation with the production of biogas.
As a consequence thereof, the mixture will rise in the
expansion vessel 6 and decrease in density. The sojourn
time of the mixture in this expansion vessel 6 is at
least 10 minutes and preferably is situated between 30
minutes and 3 hours.
This sojourn time is chosen such that, when, due to the
pumping in of new mixture, the mixture is pushed out of
the expansion vessel 6 and arrives at the top of the
fermentation tank 1, its density is approximately equal
to the density of the fermenting mass which already has
been present at the top of this fermentation tank 1.
As a result of the formation of biogas, the density of
this pre-fermented supplied mixture, due to rising, is
lower than the density of the fresh supplied mixture
which is pumped by the pump 5 from the mixer 4 into the
expansion vessel 6.
In the fermentation tank 1, the further fermentation
takes place, and the fermenting mass sinks towards the
outlet 8, where it leaves the fermentation tank 1 as
fermented material. The formed biogas is discharged
through outlet 22.
By opening the valve 11, fermented material from outlet 8
gets into branch 10. This material is transported by the
screw 12 to the dewatering device 13, where it is
separated into press water 13A and a press cake 13B,
which are transported off.
It is clear that the device may comprise more than one
expansion vessel 6, whereby the expansion vessels 6, for
example, three expansion vessels 6, are connected to the
pump 5, and whereby preferably, they are equal to each
other and installed in the same manner. In figures 1 and
2, two additional expansion vessels 6 are represented in
dashed line.
The form of embodiment represented in figures 3 and 4
differs from that according to figures 1 and 2 in that
the expansion vessel 6, expansions vessels 6,
respectively, if there are several, is or are provided at
the exterior side on the fermentation tank 1.
In figure 3, moreover in dashed line a conduit 23 is
represented, which forms a bypass of the expansion vessel
6, which bypass, on one hand, connects to the conduit 19
and, on the other hand, branches off in branches 23A
which give out onto the upper side of the fermentation
tank 1 and can be closed off by a valve 24. The outlets
of the branches in the tank 1 form the inlet 6A of this
tank 1.
The functioning is as described above, however, if
desired, through bypass 23, the mixture of inoculum and
fresh material can be brought without expansion into the
fermentation tank 1.
The expansion of the mixture of inoculum and fresh
material does not necessarily have to take place by means
of a pre-fermentation in an expansion vessel 6. This
expansion may also be obtained lay injecting gas, for
example, part of the collected biogas, into the mixture,
whereby/ when being introduced into the fermentation
chamber 1A, the mixture immediately expands, and the
density thereof becomes equal to the density at the
fermenting mass at the top of the fermentation chamber
1A.
This gas can be injected into the expansion vessel 6,
however, this expansion vessel 6 may also be reduced to a
normal conduit, for example, only the bypass 23 with the
valves 24 of the form of embodiment according to figures
3 and 4, whereby the gas is brought under pressure into
the mixture.
In figure 5, such device is represented, whereby thus to
conduit 23, an injection conduit 25 gives out which can
be closed off by a valve 26.
The same effect can be obtained by, instead of injecting
gas, injecting a chemical agent which causes gas
production in the mixture. In figure 5, in dashed line an
inlet 27 of such chemical agent is represented, which
connects to conduit 23 and can be closed off by a valve
28. This chemical agent which causes gas production,
possibly can be added in the mixer 4 or in the pump 5.
Still another possibility for reducing the density of the
mixture of fresh material and inoculum supplied to the
fermentation chamber 1A and for expanding this mixture,
consists in beating this mixture, for example, in the
expansion vessel 6.
In this case, too, the expansion vessel 6 can be reduced
to a conduit 23, whereby the beating can take place by
beating devices 29 in chambers 30 in the branches 23A of
this conduit 23, as represented in figure 6.
The expansion vessel 6 does not necessarily have to
extend over the entire height of the fermentation tank 1.
It may, for example, be a vessel which connects to the
fermentation tank 1 at the exterior, at half the height.
The device does not necessarily have to comprise a pump
5. Instead of a pump, it may comprise another transport
mechanism, such as a screw or the like.
The expansion vessel 6 may also be formed by one or more
compartments 32, bordered by partitions 31, of a vertical
tank 33, whereby then the space outside of the
compartment 32 or the compartments 32 forms, form,
respectively, the fermentation tank 1 with the
fermentation chamber 1A.
It is essential, that the compartment 32 or the compart-
ments 32 gives out, give out, respectively, at the top of
the fermentation chamber 1A, and allow for a certain
upward flow of the mixture to be fermented.
In figure 7, a device with such tank 3 3 is represented. A
partition 31, situated above the conical bottom of the
tank 33, together with a part of the wall of the tank 33
forms a compartment 32 which is closed at the bottom and
open at the top. The mixture of fresh material and
inoculum is introduced into this compartment at the
bottom, where it is expanded by means of biological pre-
fermentation.
In figure 8, a similar device is represented, however, in
this case the partition 31 is directed upwardly inclined,
starting from the inside of the tank. As represented,
this ring can be provided over the entire inner
circumference of the tank 33, such that the compartment
thus forms 3 circle-shaped gutter, or can be provided
locally, such that several trough-shaped compartments 32
are formed at the interior side of the tank 33. which
latter compartments form an expension vessel.
The expansion vessel 6 may not only be situated at an
interior side of the termentation tank 1, as represented
in figures 1 and 2, however, it may also be situated
centrally, around the fermentation tank 1, as represented
in figure 9.
This fermentation tank 1 then is formed by a tubular
element which is open at the top and which protrudes with
one outlet 8 through the funnel-shaped bottom of
expansion vessel 6.
The invention is in no way limited to the forms of
embodiment described in the aforegoing and represented in
the figures; on the contrary, such method and device for
anaerobically fermenting biodegradable material may be
realized in different variants, without leaving the scope
of the invention.
We Claim:
1. Method for anaerobically fermenting biodegradable organic
material, whereby this material is mixed with a quantity of already
fermented material such as herein described as an inoculum for the
active anaerobic fermentation and this mixture is introduced at the
top into a fermentation chamber (1A) in which a fermenting mass
such as herein described is situated, which, while being fermented,
moves from an inlet (6A) situated at the top towards an outlet (8)
situated at the bottom, characterized in that the mixture, before
being added to the fermenting mass and further moving downward
during fermentation, is expanded beforehand until its density
coincides with the density of the already present fermenting mass
at the beginning of this downward movement.
2. Method as claimed in claim 1, wherein the mixture beforehand is
expanded or is reduced in density, while being moved upward.
3. Method as claimed in claim 1 or 2, wherein a mixture is made of
one quantity of fresh material, together with one to ten quantities
of fermented material.
4. Method as claimed in any of the preceding claims, wherein a
mixture of biologically fresh material and fermented material is
fermented, having a dry matter content of 10 to 45%.
5. Method as claimed in any of the preceding claims, wherein the
downward movement of the fermenting mass in the fermentation
chamber (lA) can take place in a fermentation tank (1) which is
free of any mixer, whereby the mixture is introduced at the upper
side of the fermentation tank (1) after it has been reduced in
density in an expansion vessel (6).
6. Method as claimed in any of the preceding claims, wherein the
mixture is expanded beforehand by means of one or more of the
following techniques: a preceding biological pre-fennentation, the
injection of a gas into the mixture, the beating of the mixture, the
addition of chemicals which cause the formation of gas in the
mixture.
7. Method as claimed in claim 6, wherein the expansion or density
reduction is performed by a biological pre-fermentation, and that
they are performed in an expansion vessel (6) in which the mixture
remains at least 5 minutes and preferably between 15 minutes and
3 hours.
8. Method as claimed in claim 6, wherein the mixture"s sojourn time
in the expansion vessel (6) during expansion is 3 to 72 hours.
9. Device for anaerobically fermenting biodegradable organic
material waste, which comprises a vertical fermentation tank (1),
an outlet (8) for fermented material at the bottom of this tank (1),
and an outlet (22) for biogas at the top, and a supply device (2)
which comprises a mixer (4) and which gives out into the
fermentation tank (1) at the top thereof, characterized in that the
supply device (2) comprises at least one vertical expansion vessel
(6) which is situated between the mixer (4) and the fermentation
tank (1).
10. Device as claimed in claim 9, wherein the supply device (2)
comprises a pump (5) to which the mixer (4) gives out, whereby
the expansion vessel (6) is situated between the pump (5) and the
fermentation tank (1).
11. Device as claimed in claim 9 or 10, wherein the expansion vessel
(6) is situated at least partially in the fermentation tank (1)
12. Device as claimed in claim 9 or 10, wherein the expansion vessel
(6) is installed at the exterior side of the fermentation tank (1).
13. Device as claimed in claim 9 or 10, wherein the expansion vessel
(6) is a compartment (32) formed by at least one partition (31) and
the interior wall of a tank (33), whereby the chamber of the tank
(33) next to the compartment forms the fermentation tank (1).
14. Device as claimed in claim 9 or 10, wherein the expansion vessel
(6) completely surrounds the fermentation tank (1).
15. Device as claimed in claim 9 or 10, wherein the expansion vessel
(6) is reduced to a conduit (23).
16. Device as claimed in any of the claims 9 to 15, wherein it
comprises an injection device (25-26) for gas, or an inlet (27) for at
least a chemical agent which causes gas production, which
connects to the expansion vessel (6), to the mixer (4) or to a pump
(5) connected to the mixer (4).
17. Device as claimed in any of the claims 9 to 16, wherein a beating
device (29) is provided in the expansion vessel (6).
18. Device as claimed in claims 15 and 17, wherein the conduit (23),
by means of branches (23A), gives out onto the upper side of the
fermentation tank (1) and that in the branches (23A), chambers
(30) are formed in which a beating device (29) is provided.
19. Device as claimed in any of the claims 9 to 19, wherein the
fermentation tank (1) has a flat bottom.
Method for anaerobically fermenting biodegradable organic material,
whereby this material is mixed with a quantity of already fermented
material as an inoculum for the active anaerobic fermentation and this
mixture is introduced at the top into a fermentation chamber (1A) in
which a fermenting mass such as herein described is situated, which,
while being fermented, moves from an inlet (6A) situated at the top
towards an outlet (8) situated at the bottom, characterized in that the
mixture, before being added to the fermenting mass and further moving
downward during fermentation, is expanded beforehand until its density
coincides with the density of the already present fermenting mass at the
beginning of this downward movement.

Documents:

1444-kolnp-2003-granted-abstract.pdf

1444-kolnp-2003-granted-claims.pdf

1444-kolnp-2003-granted-correspondence.pdf

1444-kolnp-2003-granted-description (complete).pdf

1444-kolnp-2003-granted-drawings.pdf

1444-kolnp-2003-granted-examination report.pdf

1444-kolnp-2003-granted-form 1.pdf

1444-kolnp-2003-granted-form 18.pdf

1444-kolnp-2003-granted-form 2.pdf

1444-kolnp-2003-granted-form 3.pdf

1444-kolnp-2003-granted-form 5.pdf

1444-kolnp-2003-granted-letter patent.pdf

1444-kolnp-2003-granted-pa.pdf

1444-kolnp-2003-granted-reply to examination report.pdf

1444-kolnp-2003-granted-specification.pdf

1444-kolnp-2003-granted-translated copy of priority document.pdf


Patent Number 213803
Indian Patent Application Number 01444/KOLNP/2003
PG Journal Number 03/2008
Publication Date 18-Jan-2008
Grant Date 16-Jan-2008
Date of Filing 06-Nov-2003
Name of Patentee ORGANIC WASTE SYSTEMS , NAAMLOZE VENNOOTSCHAP.
Applicant Address DOK NOORD 4, B-9000 GENT
Inventors:
# Inventor's Name Inventor's Address
1 DE BAERE, LUC, ALBERT, OMER, MEDARD SPECHTENPARK 10, B-9840 DE PINTE
2 SMIS, PIET, LODEWIJK, MAGDALENA KOUTERSTRAAT 15, B-9890 GAVERE
PCT International Classification Number C 12 M 1/07
PCT International Application Number PCT/BE02/00101
PCT International Filing date 2002-06-19
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2001/0426 2001-06-20 Belgium