NL2021116B1

NL2021116B1 - A method of generating biogas, and a column

Info

Publication number: NL2021116B1
Application number: NL2021116A
Authority: NL
Inventors: Jarich Rijpma Yde
Original assignee: Biobrella Bv
Priority date: 2018-06-13
Filing date: 2018-06-13
Publication date: 2019-12-19
Also published as: WO2019240577A1; BR112020021191A2

Abstract

A method of generating biogas in a pond, said pond comprising — pond water comprising digestible organic material, and — micro—organisms capable of forming biogas by digesting said digestible organic material; wherein at least part of the surface of the pond water in the pond is provided with a cover for collecting the generated biogas, the cover cooperates with a column; wherein the method comprises the steps of — supplying water containing digestible organic material to the pond, and — extracting biogas generated by the micro—organisms; For improved circulation of water in the pond below the cover, the column is a hollow column and pond water from the pond is passed through the hollow column.

Description

(2?) Aanvraagnummer: 2021116

Θ 2021116 ©B1 OCTROOI (22) Aanvraag ingediend: 13 juni 2018 (51) Int. Cl.:

C02F 11/04 (2018.01) C02F 3/28 (2019.01) C12M

1/113 (2019.01) (30) Voorrang:

(4/) Aanvraag ingeschreven: 19 december 2019 (43) Aanvraag gepubliceerd:

(73) Octrooihouder(s):

BIOBRELLA BV te Lage Vuursche (72) Uitvinder(s):

Yde Jarich Rijpma te Silvolde (74) Gemachtigde:

ir. W.J.J.M. Kempes te Hilversum (47) Octrooi verleend:

december 2019 (45) Octrooischrift uitgegeven:

december 2019

54) A method of generating biogas, and a column

57) A method of generating biogas in a pond, said pond comprising

- pond water comprising digestible organic material, and

- micro-organisms capable of forming biogas by digesting said digestible organic material;

wherein at least part of the surface of the pond water in the pond is provided with a cover for collecting the generated biogas, the cover cooperates with a column;

wherein the method comprises the steps of

- supplying water containing digestible organic material to the pond, and

- extracting biogas generated by the micro-organisms;

For improved circulation of water in the pond below the cover, the column is a hollow column and pond water from the pond is passed through the hollow column.

NLB1 2021116

Dit octrooi is verleend ongeacht het bijgevoegde resultaat van het onderzoek naar de stand van de techniek en schriftelijke opinie. Het octrooischrift komt overeen met de oorspronkelijk ingediende stukken.

A method of generating biogas, and a column

The present invention relates to a method of generating biogas in a pond, said pond comprising

- pond water comprising digestible organic material, and

wherein at least part of the surface of the pond water in the pond is provided with a cover for collecting the generated biogas, wherein the cover cooperates with a column, which column is oriented transverse to the horizontal;

wherein the method comprises the steps of

- supplying water containing digestible organic material to the pond, and

- extracting biogas generated by the micro-organisms by digesting the organic material.

Water containing digestible organic material is typically available as waste water of various sources such as palm oil production or processing of tapioca. Not only is discharging this waste water detrimental to the environment as it may lead to a change of the biosystem due to the overabundance of digestible organic material, it is also wasteful. In addition, uncontrolled emissions of biogas from open wastewater lagoons make significant contributions to global warming as methane is a strong greenhouse gas

For this reason, a method according to the preamble is known, wherein the organic material is digested to generate and collect biogas. This biogas, which comprises methane as a combustible component, can be used for various purposes, including put to use in the plant that generated the wastewater.

DE29780436U1 discloses a method according to the preamble wherein a column is used to retain the cover at a desired location. The bioreactor comprises a centrally located mixing device for moving the liquid in the bioreactor. The mixing device is mounted vertically moveable to said column.

The present invention relates to an improvement in the above method.

To this end, a method according to the preamble is characterized in that said column provides a channel in a direction along the longitudinal axis of the said column; and pond water from the pond is passed through said channel and returned to said pond.

Thus the column improves the circulation of pond water in the pond.

Typically, the column will have an overall density of less than 1 kg/liter, allowing it to float. The top half of the column will be relatively light and the bottom half will be relatively heavy, allowing it to remain substantially upright.

Typically, the column will be a hollow column comprising a lumen, the lumen capable of serving as the channel.

Typically pond water is taken in by the column at a first height and discharged at a second height different from the first height. Preferably the water is taken in at a relatively high position and discharged from the channel at a relatively low position, generating an upward flow of pond water in the pond.

In the present application, the term water containing digestible organic material is referred to as waste water for the sake of brevity. In principle, however, the method is also suitable for generating biogas from water prepared for the purpose of generating biogas by adding waste to water.

Sources of waste water other than agriculturally-based process water are dairy, food and beverage production.

According to a preferred embodiment, water passed through the column is subjected to stripping with air before being re-introduced into the pond.

This results in a significant reduction of the concentration of dissolved CO₂. As a result the acidity of the water is reduced, thus enhancing the conditions for anaerobic digestion.

According to a favourable embodiment, the channel is a first channel and the column comprises a further channel wherein water is transported in a direction opposite of the direction through the first channel, and water in a riser channel chosen from the first channel and the further channel is discharged from an outlet of the riser channel and exposed to air in the atmosphere to strip CO₂before the water is returned to the pond.

With the riser channel, CO₂ is stripped from the water, which is returned to the pond by gravity, simultaneously effectuating flow of the water in the pond. The water going up may be transported using a pump. The channel other than the riser channel may be a supply channel which allows water to be supplied from relatively high in the pond and delivered to the riser channel at a lower level; or it may be a discharge channel, allowing water that has been subjected to stripping to be returned into the pond relatively low in the pond. It is preferred that the column comprises in addition to the riser channel both a supply channel and a discharge channel.

According to a favourable embodiment, the riser channel is provided with an outlet for air to introduce air in said riser channel at a location below the water level of the pond for stripping pond water in the riser channel;

wherein air is introduced in said riser channel to entrain the water in said riser channel.

The air will not only entrain the pond water in the riser channel and escape at the outlet, but concomitantly CO₂ is stripped from the water, which water is returned to the pond by gravity, simultaneously effectuating flow of the water in the pond.

According to a favourable embodiment, the column comprises a discharge channel with an inlet opening for passing pond water stripped using the riser channel downward before discharging it via an outlet opening of the discharge channel into the pond.

Thus the circulation in the pond is performed more effectively, wherein water comprising a relatively high concentration of methane is moved upward towards the cover.

According to a favourable embodiment, the air is introduced pulse-wise with the inlet of the discharge channel at a vertical distance D of at least 20 cm above the water level of the pond.

This allows for the discharge of water from the column at a relatively high speed, resulting in improved circulation, even at a relatively large distance from the column. D is preferably at least 50 cm, preferably at least 75 cm. This results in a hydrostatic pressure and greater discharge speed of water discharged from the column. Pulse-wise (batch-wise) introduction of air can be achieved using for example an electrical air pump.

According to a favourable embodiment, water containing digestible organic material is introduced in the water passed through the column.

Thus the water comprising organic material is diluted, which is in particular advantageous in case of waste water having a high biological oxygen demand (BOD). The dilution of the waste water before it is introduced in the pond water below the cover reduces the risk of toxic concentrations that may impede the production of biogas.

It also avoids the problem known in the art where feed pipes for waste water are distributed over the bottom of the pond, which feed pipes over time bury themselves in the sediment on the bottom of the pond. This causes uneven distribution of digestible organic material in the pond water below the cover.

According to a favourable embodiment, the inlet for water to a channel of the column is at least 2 meters above the outlet for water from the column, preferably at least 3 meters and more preferably at least 4 meters.

A larger distance improves circulation of pond water over a larger horizontal distance from the column.

The outlet is for example the outlet opening of an injection tube (a pipe).

According to a favourable embodiment, the water is discharged into sludge on the bottom of the pond.

This enhances the generation of biogas.

According to a favourable embodiment, the column is provided with a collar capable of moving in a longitudinal direction of the column, the cover being connected to the collar.

Thus biogas can be generated at different pond water levels and the cover is not damaged by changes in pond water level. The hollow column will be provided with one or more, for example slot-like, inlet openings for pond water and the collar will allow passage of water from the pond to the one or more slot-like inlet openings. Typically the largest diameter of slot-like openings will run in a longitudinal direction of the column. In case of a multitude of openings, they will be at differnt distances from one end of the column to allow water to enter at different pond water levels.

According to a favourable embodiment, at least one of the column and the collar comprises a flotation body.

This helps to maintain the orientation of the column and hence the channel(s). For reasons of simplicity, it is preferred that the collar comprises the flotation body.

Finally, the present invention relates to a column for a cover for a pond for generating biogas, wherein the column comprises

- a supply channel with an inlet opening for pond water,

- a riser channel comprising

- an inlet for pond water from the supply channel,

- an outlet for air for stripping pond water in the riser channel, and

- an outlet for a mixture of air and pond water, and

- a discharge channel with an inlet opening for passing stripped pond water downward before discharge thereof via an outlet opening into the pond.

Such a column is useful for the method according to the invention. Preferably the column comprises a weighted foot, allowing the column to float like a float of a fishing rod. This allows the column to be moved to its final location in the pond even if there is water in the pond. Thus, construction doesn't have to be postponed until the pond is empty.

The outlet opening through which water enters the pond is for example an outlet opening of an injection tube.

The invention also relates to embodiments of the column as specified in the dependent method claims and discussions thereof, in any combination, repetition of which has been forsaken for the sake of brevity only.

The present invention will now be illustrated with reference to the drawing where

Fig. 1 shows schematically a perspective view of a pond for generating biogas;

Fig. 2Ά to Fig. 2D shows schematically of a device for generating biogas in respectively a a perspective view, a top view, a side view and a cross-sectional view;

Fig. 3A shows a side view of the column of the device shown in Fig. 2D in more detail;

Fig. 3B to Fig. 3D show cross-sectional views of the column 120 of the device 100 shown in Fig. 2D in more detail; and

Fig. 3E shows a top view of the column of the device shown in Fig. 2D in more detail.

Fig. 1 shows schematically a perspective view of a pond 170 for generating biogas using a device 100 comprising a cover 110 and central column 120. Only two devices 100 are shown here; but typically most of the surface area of a pond 170 will be substantially covered.

The pond 170 comprises a body of water 171.

Raw wastewater containing digestible organic material is supplied from a storage tank 180 via a wastewater supply conduit 181 to the column 120, which will be discussed in more detail below.

The water in the pond 170 is circulated, as will be discussed in more detail with reference to Fig. 3A to Fig. 3D. In the embodiment discussed here, this is done using a air-operated pump, for which reason there is a compressor 190 and air supply conduit 191 to the column 120, which will be discussed in more detail below as well.

Biogas is collected below the cover 110 and extracted via gas conduit 111.

Excess water in the pond 170 can be discharged via discharge conduit 172.

Fig. 2A to Fig. 2D shows schematically of a device for generating biogas in respectively a a perspective view, a top view, a side view and a cross-sectional view.

Fig. 2A shows a perspective view part of the pond 170, with the wastewater supply conduit 181, the air supply conduit 191 and the gas conduit 111 for discharge of the biogas, which will be used for various purposes or burned off in a burner or flare to convert the biogas containing a powerful greenhouse gas such as methane into a less potent greenhouse gas such as carbon dioxide. Fig. 2B shows the same in top view.

Fig. 2C and Fig. 2D show a side view and a corresponding cross-sectional view of the device 100 in the pond 170, with the lower end of the column 120 above pond floor 273 of the pond 170.

In this embodiment, the column 120 floats and is kept upright using ballast 221 at the bottom end of the column 120, and by a collar 230 comprising a flotation body 231, which may be any body having a density lower than water such as foam, or a body defing a chamber filled with a gas such as air or biogas. Covers of adjacent columns can also be connected, thus forming a grid and helping columns to remain upright.

Above the pond floor 273 the column 120 is provided with water exhaust pipes 222, that play a role in the circulation of water in the pond 170, as will be explained below. Typically, this water will be rich in digestible organic material, which will be broken down anaerobically into methane-containing biogas.

To collect the biogas more efficiently, the cover 110 comprises along its circumference a skirt 212. If the cover 110 is lifted by accumulation of biogas under it, the biogas cannot escape to the atmosphere thanks to said skirt 212.

To accommodate for

- varying water levels in the pond 170, e.g. due to varying amounts of nutrient-rich water supplied to the pond, water discharged via the water discharge conduit 172 or rain, and

- varying levels of biogas under the cover 110 the cover 110 is movable along the longitudinal direction of the column 120. To this end, a collar 230 is provided capable of moving up and down using the column 120 as a guide. The cover 110 is connected to said collar 230. The collar 230 does not seal against the column 120; but instead it allows water to pass between the collar 230 and the column 120, as will be explained in more detail below. If desired, the top of the collar 230 can be sealed against the column 120, e.g. with a skirt.

The collar 230 or a separate skirt extending along the periphery of a centrally located opening in cover 110 through which the column 120 protrudes serves to reduce the risk of biogas from passing to the atmosphere .

Fig. 3Ά shows a side view of the column of the device shown in Fig. 2D in more detail and Fig. 3B to Fig. 3D, not showing the collar 230, show cross-sectional views from three different directions of said column 120 in more detail.

The column 120 comprises a bottom compartment 360 that supplies the water exhaust pipes 222 with water circulated through the column 120 .

Pond water is let into the column 120 via an first inlet opening 321. This first inlet opening 321, or plurality thereof, is not blocked by the collar 230, and water from the body of water 171 can pass between the collar 230 and the outer wall of the column 120 and via the first inlet opening 321 into a longitudinally extending first compartment 330 (supply channel 330) of the column 120. In here, the water moves downward to a second inlet opening 341 of a longitudinally extending second compartment 340 of the column 120. In this longitudinally extending second compartment 340 air is introduced as will be discussed below, entraining the water in the second compartment 340 (riser channel 340), causing it to overflow at a second outlet opening 342 of the second compartment 340 higher than the water level of the pond. From there, it spills into a collection trough 310 (Fig. 3B) and flows from there further via a third inlet opening 351 of a longitudinally extending third compartment 350 (discharge channel 350) into the bottom compartment 360 from where it flows into the body of water 171, completing the water recirculation cycle .

The air for entraining the water upward in the second compartment 340 is provided via the air supply conduit 191.

In the embodiment here, this is done using an airlift principle by introducing air intermittently via the air supply conduit 191 and inverted pipe end 381 into the second compartment 340 near the second inlet opening 341 thereof. This causes the water in the second compartment 340 to rise, which is collected by the collection trough 310 and passed into the third inlet opening 351. As a result, the water moving downward through the third compartment 350 will be discharged from the pipes 222, improving circulation on the body of water.

The second compartment 340 is filled with water from the first compartment 330, thus extracting water from the pond at a relatively high location (i.e. away from the exhaust pipes 222) further improving circulation of water in the pond 170.

Wastewater containing digestible organic material is preferably introduced into the column 120 via the wastewater supply conduit 181. This allows the wastewater to be diluted before they are discharged into the pond 170, thus avoiding local high concentrations which can be detrimental to the micro-organisms necessary to digest the organic material. In Fig. 2D it can be seen that the wastewater containing digestible organic material is supplied to the second compartment 340.

Fig. 3E shows a top view of the column of the device shown in Fig. 2D in more detail, with trough 310 in which water elevated by the pump is received from the outlet opening 342 and from where it flows into the third inlet opening 351 to the bottom compartment and is discharged through the exhaust pipes 222.

The invention can be varied within the scope of the appended claims. For example, the pipes 222 can be abstained from, at the cost of less optimal circulation of water in the pond; and the wall of the column will comprise water outlet openings.

Claims

CONCLUSIONS

A method for generating biogas in a pond (170), wherein said pond (170) comprises the following. pond water (171) comprising biodegradable organic material, and

micro-organisms capable of forming biogas by breaking down said biodegradable organic material; wherein at least a portion of the surface of the pond water (171) in the pond (170) is provided with a cover (110) for collecting the generated biogas, the cover (110) cooperating with a column (120) which column (120) is perpendicular to the horizontal; wherein the method comprises the steps of

supplying water (171) containing biodegradable organic material to the pond (170), and

- extracting biogas generated by the microorganisms by digesting the organic material;

characterized in that the column (120) provides a channel in a direction of the longitudinal axis of said column (120); and pond water (171) from the pond (170) is passed through said channel and is returned to the pond (170).

The method of claim 1, wherein water passed through the column (120) is subjected to air stripping before being returned to the pond (170).

The method of claim 2, wherein the channel is a first channel and the column comprises a further channel wherein water is transported through the first channel in a direction opposite to the direction, and water in a riser channel selected from the first channel and the second channel channel is drained via an outlet from the riser channel and exposed to air in the CO ₂ stripping atmosphere before the water is returned to the pond.

The method of claim 3, wherein the riser (340) is provided with an outlet (381) for introducing air into said riser (340) at a location below the water level of the pond (170) for stripping pond water (171) in the ascending channel (340);

wherein air is introduced into said riser channel (340) for entraining water in said riser channel (340).

The method of any one of claims 3 or 4, wherein the column (120) has a drain (350) with an inlet opening for downputting pond water (171) that has been stripped using the riser (340) before passing through a discharge outlet (342) from the drain (350) into the pond (170).

The method of claim 5, wherein the inlet of the drain (350) is at a vertical distance D of at least 20 cm above the water (171) mirror of the pond (170).

The method of any one of the preceding claims, wherein water containing digestible organic material is introduced into the water (171) passed through the column (120).

A method according to any preceding claim, wherein the water inlet to a channel of the column (120) is at least 2 meters above the water outlet from the column (120), preferably at least 3 meters and more preferably at least 4 meters.

The method of any one of the preceding claims, wherein the water (171) is drained into sludge at the bottom of the pond (170).

A method according to any one of the preceding claims, wherein the column (120) is provided with a collar capable of moving in a longitudinal direction of the column (120), the cover (110) being connected to the collar.

The method of claim 10, wherein at least one of the column (120) and the collar (230) comprises a floating body (231).

A column (120) for a cover (110) for a pond (170) for generating biogas, characterized in that the column (120) comprises - a supply channel (330) with a supply opening for pond water (171) )

- a riser channel (340) that

- an inlet for pond water (171) from the supply channel (330),

- an air outlet for stripping pond water (171) in the riser (340), and

5 - an outlet (342) for a mixture of air and pond water (171), and

- a discharge channel (350) with a supply opening (381) for allowing the stripped pond water (171) to pass downwards before it is discharged through a discharge opening to the pond (170).

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2/8

3/8

4/8

100

5/8

110 231 340

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FIG. 3B

FIG. 3A

7/8

FIG. 3D

FIG. 3C

8/8

FIG. 3E