Claims:We claim:

1. A system (100) for extracting digestate from an energy generating plant, the system comprising:
a bioreactor (10) adapted to receive and digest biomass substrate to produce energy such as biogas and digestate, the bioreactor (10) having a plurality of first set of openings (5) configured thereon for extraction of the digestate therefrom;
at least one jet distributor (20) attached to the bioreactor (10) for passing jets of extraction liquid therein at a controlled rate for dislodging the digestate therefrom, the at least one jet distributor (20) having a plurality of second set of openings (15) configured thereon corresponding to the plurality of first set of openings (5) on the bioreactor (10), the jets of liquid passes through the plurality of second set of openings (15) into the bioreactor (10) at controlled interval of time and rate to flow out through the plurality of first set of openings (5) while carrying the digestate therewith;
at least one pump (30) connected to the at least one jet distributor (20) to supply the extraction liquid therein;
at least one motor (40) connected to the at least one jet distributor (20) to control the jet flow therefrom; and
at least one motorized valve (50) connected to the bioreactor (10) to extract the digestate therefrom at a controlled rate.

2. The system (100) as claimed in claim 1, wherein the bioreactor (10) is a conical shaped bioreactor having slopes at a base (3) thereof to facilitate flow of the digestate towards the at least one motorized valve (50).

3. The system (100) as claimed in claim 1, wherein the bioreactor (10) contains no moving parts.
4. The system (100) as claimed in claim 1, wherein the biomass substrate used for biogas production is selected any one of fibrous high solid material, agro residue, non-fibrous material and combinations thereof.

5. The system (100) as claimed in claim 1, wherein the biomass substrate contains total solids of about 8 to 25 percent.

6. A method for extracting digestate from an energy generating plant, the method comprising the steps of:
passing extraction liquid into at least one jet distributor (20) through at least one pump (30) connected thereto at a rate controlled by at least one motor (40) connected thereto;
passing jets of the extraction liquid through a plurality of second set of openings (15) of the at least one jet distributor (20) into a bioreactor (10) for carrying and dislodging digestate therewith, the digestate being formed by digestion of biomass substrate in the bioreactor (10), wherein the bioreactor (10) contains no moving parts and the biomass substrate used for biogas production is selected any one of fibrous high solid material, agro residue, non-fibrous material and combinations thereof, the biomass substrate contains total solids of about 8 to 25 percent; and
extracting digestate from bioreactor (10) through a plurality of first set of openings (5) configured thereon by actuating opening of at least one motorized valve (50) connected to the bioreactor (10), wherein the bioreactor (10) is a conical shaped bioreactor having slopes at a base (3) thereof to facilitate flow of the digestate towards the at least one motorized valve (50).

, Description:Field of the invention

The present invention relates to a system and a method for extracting digestate from energy generating plant, and more particularly to a water / liquid jet based extraction system designed for optimum energy production and power utilization from high solids fibrous material substrate and / or agro residues / products subjected to a biomethanation process in a bioreactor (digester) containing no moving parts inside the reactor tank.

Background of the invention

The biomethanation process generates biogas as the product and other by products from the biomass substrate. The biomass used for the process plays a crucial role for the entire biomethanation process. When the biomass is high solids fibrous and / or an agro residue, biogas production, and extraction of the solid digestate / feed after the biogas production is a formidable task, thereby resulting in accumulation of the digestate and making / creating problems in the biogas generation process consistency. The fibres tend to form mesh and it then becomes difficult to remove / extract from the digester without compromising the anaerobic nature of the system. Presently, the technology available for feed withdrawal from large vessels or silos is using screws. In case of fibrous substrate inside the digesters, screws tend to create holes / tunnels and not remove further material. Complex mechanisms such as planetary rotation can be designed, however such systems are very difficult to maintain and still end up being unreliable, especially for large volume digesters. Moreover, it requires considerable power and has very high energy consumption with frequent maintenance requirements and high capital cost. It is very difficult to deal with such requirements in an anaerobic system. Also the screw arrangement becomes extremely unwieldy for large-scale biogas production plant.

Accordingly, there is a need to provide a system and a method for extracting digestate from energy generating plant that overcomes the above mentioned drawbacks of the prior art, especially the extraction system is designed to work efficiently with less power and can be used for high solids fibrous, biomass and / or for agro residues / products with Total Solid (TS) content ranging from 8 - 25 percent.

Objects of the invention

An object of the present invention is to extract spent substrate/digestate during biogas production from a biomethanation process using high solids fibrous, material and / or agro residues as biomass substrate

Another object of the present invention is to extract spent substrate/digestate from inside the bioreactor using a specifically designed jet distributor.

Yet another object of the present invention is to extract the solid digestate from the bioreactor which contains no moving part inside the bioreactor.

Still another object of the present invention is to extract the non-flowing solid digestate with total solids ranging from 8 to 25 per cent from inside the bioreactor.

Further object of the present invention is to achieve less energy consumption for the biomethanation reactor using the said system.

Still further object of the present invention is optimum utilization of power and energy generated through the biomethanation process using the said system.

Summary of the invention

Accordingly, the present invention, in one aspect, provides a system for extracting digestate from an energy generating plant. The system comprises a bioreactor, at least one jet distributor, at least one pump, at least one motor and at least one motorized valve.

The bioreactor is adapted to receive and digest biomass substrate to produce energy such as biogas and digestate. The biomass substrate used for biogas production is selected any one of fibrous high solid material, agro residue, non-fibrous material and combinations thereof. The biomass substrate contains total solids of about 8 to 25 percent. The digester is a conical shaped bioreactor having slopes at a base thereof to facilitate flow of the digestate towards at least one motorized valve. The bioreactor contains no moving parts inside the tank. The bioreactor includes a plurality of first set of openings configured thereon for extraction of the digestate therefrom.

The at least one jet distributor is attached to the bioreactor for passing jets of extraction liquid therein for dislodging the digestate therefrom. The at least one jet distributor includes a plurality of second set of openings configured thereon corresponding to the plurality of first set of openings on the bioreactor. The jets of extraction liquid passes through the plurality of second set of openings into the bioreactor at controlled interval of time and rate to flow out through the plurality of first set of openings while carrying the digestate therewith.

The at least one pump is connected to the at least one jet distributor to supply the extraction liquid therein. The at least one motor is connected to the at least one jet distributor to control the jet flow therefrom. The at least one motorized valve is connected to the bioreactor to control the extraction of the digestate therefrom.

In another aspect, the present invention provides a method for extracting digestate from an energy generating plant.

Brief description of the drawing

The objectives and advantages of the present invention will become apparent from the following description read in accordance with the accompanying drawings wherein,
Figure 1 shows a system for extracting digestate from energy generating plant, in accordance with the present invention.

Detailed description of the invention

The foregoing objects of the invention are accomplished and the problems and shortcomings associated with the prior art techniques and approaches are overcome by the present invention as described below in the preferred embodiment.

The present invention provides a system and a method for extracting digestate from energy generating plant. The extraction system is water / liquid jet based extraction system designed for high solids fibrous, material substrate and / or agro residues / products for producing optimum energy and power utilization during a biomethanation process.

The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.

Referring now to Figure 1, in an aspect, there is shown a system (100) for extracting digestate from an energy generating plant (not shown) in accordance with the present invention. Specifically, the energy generating plant is a biogas production plant. However, it is understood that the system (100) can be adaptively used with any other energy generating plant. The energy generating plant (herein after ‘the biogas production plant’) comprises a feed preparation system, a blending system, a digester feeding system, the (digester) extraction system (100), a fertilizer unit, a biogas storage unit, and a biogas scrubbing and power generation with waste heat recovery system. The system (100) comprises a bioreactor (10), at least one jet distributor (20), at least one pump (30), at least one motor (40), at least one motorized valve (50) and the necessary piping / plumbing (not shown).

The bioreactor (10) is adapted to receive biomass substrate for digestion thereof to produce energy and digestate. Specifically, the biomass substrate is subjected to an anaerobic digestion or a biomethanation process for production of biogas as energy. The biomass substrate used for biogas production is selected from but not limited to fibrous high solid material, agro residue / produce and combinations thereof. In an embodiment, the biomass substrate may also be mixed with non-fibrous substrate material. The biomass substrate contains total solids of about 8 to 25 percent. The bioreactor (10) contains no moving parts and thus the system (100) does not exert any additional pressure on the material, which can cause change of state or solid liquid separation.

The bioreactor (10) has a specific shape and geometry. The shape of the bioreactor (10) is an essential feature of the system (100). The bioreactor (10) is a conical shaped bioreactor having slopes at a base (3) thereof. The base (3) of the bioreactor (10) can be given particular slope from inside by various means allowing the dislodged solids from within the bioreactor (10) to flow towards the point of extraction. The bioreactor (10) is designed in conical shape such that it is part of an inverted V that prevents the fibrous material inside from bridging in the bioreactor (10) and thereby ensuring removal of digestate on First in First out (FIFO) basis. Thus, the inverted ‘V’ does not allow the fibrous biomass digestate / substrate to form interlocking mesh and bridge. When the material from underneath is removed, the one above has tendency to fall due to increasing diameter of the vessel as the material goes down. The digestate extraction operation requires minimal power and maintenance.

The bioreactor (10) includes a plurality of first set of openings/nozzles (5) configured thereon for extraction of the digestate therefrom. Specifically, the plurality of first set of openings (5) is configured at a bottom and / or side wall towards the bottom of the bioreactor (10).

The at least one jet distributor (20) is attached to the bioreactor (10) for passing jets of extraction liquid therein for dislodging the digestate therefrom. In an embodiment, the at least one jet distributor (20) is attached at a bottom (not numbered) of the bioreactor (10). In another embodiment, the at least one jet distributor (20) is placed at a convenient location near the bioreactor (10). The extraction liquid is selected from any one of hot water, cold fresh water and liquid from the digestate after separating the major solids therefrom by any suitable conventional means of solid-liquid separation known in the art.

The at least one jet distributor (20) includes a plurality of second set of openings (15) configured thereon corresponding to the plurality of first set of openings (5) on the bioreactor (10). Specifically, the plurality of second set of openings/nozzles (15)/ jet inlets (15) is configured on a periphery (not numbered) of the at least one jet distributor (20) towards the (3) of the bioreactor (10). The number and locations of the jet inlets (15) are designed according to the size of the bioreactor (10) and the biomass substrate used for biogas generation.

The jets of the extraction liquid are of high velocity and are specifically oriented in a non-radial direction. The jets of extraction liquid passes through the plurality of second set of openings (15) on the at least one jet distributor (20) into the bioreactor (10) at controlled interval of time and rate to flow out therefrom through the plurality of first set of openings (5) on the bioreactor (10) at the periphery towards the base (3) thereof while carrying the digestate therewith. Since liquid and overall mass balance inside the bioreactor (10) is critical, measured quantity and flow rate of extraction liquid is important. Hence, the jets of the extraction liquid are forced into the bioreactor (10) through the plurality of first set of openings (5) at a time such that the material balance is maintained. The connections to the jets work in a sequential manner with the help of rotary seals (not shown) in the at least one jet distributor (20) to ensure enough amount of extraction liquid is sent inside the bioreactor (10) at desired location with designed velocity to ensure that the solids to be extracted are dislodged from original location and are incorporated in a flowing slurry which can be extracted. This in turn ensures smooth and easy removal of digestate from the bottom of the bioreactor (10).

The at least one pump (30) is connected to the at least one jet distributor (20) to supply the extraction liquid therein.

The at least one motor (40) is connected to the at least one jet distributor (20) to control the jet flow therefrom.

The at least one motorized valve (50) is connected to the bioreactor (10) to control the extraction of the digestate therefrom. The final extraction from the bioreactor (10) is effected through the at least one motorized valve (50) that ensures controlled output of the digestate. The at least one motorized valve (50) allows for controlling the opening of the system (100) with a view to maintain the rate of extraction to a desired level such the overall mass balance and the levels of the material inside the bioreactor (10) is maintained. If the levels are not maintained, and / or the rates of inflow and outflow are not matched, the bioreactor (10) can be subjected to pressure or vacuum, leading to some mechanical damage or failure. The slopes at the base (3) of the conical shaped bioreactor facilitated flow of the digestate towards the at least one motorized valve (50).

The extracted digestate being considerably high in liquid content is passed through a solid-liquid separation system (not shown). The separated liquid/slurry is recycled and may be mixed with hot water for being used as the extraction liquid for continuing the extraction method for speedy extraction while the solid are capable of being used as a culture or sent out as manure depending on the process design.

Referring again to figure 1, in another aspect, there is shown a method for extracting digestate from the energy generating plant in accordance with the present invention. Specifically, the method will now be described in conjunction with the system (100) of the present invention. The method comprises the steps which are described as herein below:

In a first step, the method involves passing extraction liquid into at least one jet distributor (20) through the at least one pump (30) connected thereto. The jet flow in the at least one jet distributor (20) is controlled by the at least one motor (40) connected thereto.

In a further step, the method involves passing jets of the extraction liquid through the plurality of second set of openings (15) of the at least one jet distributor (20) into the bioreactor (10) for carrying digestate therewith. The digestate is formed by digestion of biomass substrate in the bioreactor. The bioreactor (10) contains no moving parts and the biomass substrate used for biogas production is selected any one of fibrous high solid material, agro residue, non-fibrous material and combinations thereof. The biomass substrate contains total solids of about 8 to 25 percent.

In the final step, the method involves extracting the digestate from the bioreactor (10) through the plurality of first set of openings (5) configured thereon by actuating opening of the at least one motorized valve (50) connected to the bioreactor (10). The slopes at a base (3) of the conical shaped bioreactor facilitates the flow of the digestate towards the at least one motorized valve (50).

Advantages of the invention

1. The system (100) and the method help in generating optimum biogas using solids fibrous, material and / or agro residues / product as biomass substrate with total solids ranging from 8 to 25 per cent and beyond.
2. The system (100) and the method ensure uniform withdrawal of digestate from high solids, fibrous, biomass substrate inside the bioreactor (10) thereby overcoming the problem of bridging of the digestate inside the bioreactor (10) and in turn affecting biogas plant operation.
3. The system (100) and the method require considerably less power. The system (100) is capable of working with single pump (30) or multiple pumps for dislodging and extracting fibrous material from the bottom portion of the large bioreactor (10). The total optimum energy consumed by all the peripherals of the biogas generation plant is less than 20 percent of the total energy available in the biogas produced.
4. The system (100) and the method control the rate of extraction by controlling the opening of the at least one motorized valve (50) actuated by any suitable means known in the art to control the opening thereby controls and maintains the mass balance of solids and liquids as well as the levels of digestate inside the bioreactor (10).
5. The system (100) and the method allow for extraction of fibrous material without breaking the anaerobic condition of the bioreactor (10).
6. The system (100) is easy to clean and maintain, reduces complexity since it contains no moving parts inside the bioreactor (10).
7. The system (100) has at least one jet distributor (20) that allows extraction liquid to be sent into the bioreactor (10) to dislodge the high solid material for extraction.
8. The bioreactor (10) of the system (100) is shaped as section of an inverted ‘V’, further, the specific slopes inside of the base (3) of the bioreactor (10) facilitates flow of the dislodged material towards the at least one motorized valve (50).

The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention.