DESC:A Digester, System and Method thereof for producing biofuel
Field of the Invention
This invention, in general relates to a digester, system and method for producing biofuel. More particularly, the current disclosure provides a cost-effective mass production of biogas employing an innovative digester.
Background of the Invention
The Biogas biological process and its anaerobic methane production using organic substrates is known to mankind for over 2000 years. Due to the rising imbalance between supply and demand of energy for humans, there have been various renewable energy systems developed, but the cost and security of energy, emissions of harmful gases and other pollutants from the existing means of energy production are the major problems that have led to many technological developments in alternative energy sources. One of the alternate energy sources are biomass to produce energy that has become attractive worldwide as a clean and sustainable source of energy.
During the last decades, there have been multiple attempts to setup a biogas plants or systems that produces biogas on a large scale and fulfills the requirement of industries and societies. These systems were usually associated with a high cost, complexities, inefficient mixing, lower yield, and abnormal functioning under diverse climatic condition. It is not yet possible to provide a finished digester in the biofuel system to the user in order to facilitate users with “plug and operate’’ functioning, such systems involved assembly of different components or equipment on-site that is further making the installation labor intensive. Biogas digesters operate by mixing of the substrate with different reactants in the internal biogas container, and by wear and tear on the mixer blades, therefore the digester consumes a high amount of power in the mixing process, further contributing to the operating cost.
As detailed above, there are various solutions that have been provided according to the existing arts, however, still there are challenges existing because of the complex setup and on-site assembly of the systemdue to the manufacturing of unfinished product in the conventional system, thus increasing the local work, and also the installation and operationbecomes not so user friendly. Further, the traditional mixing in the existing digester leads to high consumption of power, therefore increasing the operating cost of the system.

Below are the few prior arts disclosed in relation to the present invention.
CN101760366 discloses an automatic power fermentation tank group used for fermenting grape fermentation broth in the wine-making industry, which can be used for enhancing fermentation quality by improving a soakage effect. The fermentation tank group comprises at least two tank bodies; a communicating pipe is arranged between the tank bodies; the top of each tank body is provided with an exhaust valve; when the broth level of the fermentation broth in one tank body is in the lowest position during fermentation, the broth level is still higher than a port of the communicating pipe; and when the broth level of the fermentation broth in one tank body is in the highest position, the broth level is still lower than the exhaust valve. The automatic power fermentation tank group uses gases produced during the aggregated fermentation of both the tank bodies and controls the exhaust valve to enable a pressure difference to generate between the tank bodies so as to further form power for driving the fermentation broth to flow between different tank bodies and enabling the broth level of the fermentation broth in each tank body to fluctuate up and down, thereby promoting the thorough mixing of pomacecap with the fermentation broth, effectively destroying the consolidation of the pomacecap, achieving the purpose of effectively soaking effective matters in peels and enhancing fermentation quality.

DE000003341027 discloses an apparatus for producing biogas and/or fertiliser from organic waste, which is made up of a prefermentation chamber which can be sealed to be gas-tight and which is provided with an inlet for the organic waste and a gas outlet, and a secondary fermentation chamber which is coupled to a prefermentation chamber via a connection pipe and which can be sealed to be gas-tight and which is provided with a gas outlet and an overflow for the degraded waste usable as fertiliser. In this case, a valve is arranged in the connection pipe between the prefermentation chamber and the secondary fermentation chamber, which valve is closed until a differential pressure of at least 1 bar between the prefermentation chamber and the secondary fermentation chamber is attained, so that when the valve is opened, the fermentation sludge can be forced from the prefermentation chamber into the secondary fermentation chamber and vice versa.

US20200172449 discloses a digester system comprising a primary digester tank containing a primary feed material portion, a secondary digester tank containing a secondary feed material portion, a first conduit connected between the primary digester tank and the secondary digester tank to define a primary tank lower opening within the primary digester tank and a secondary digester tank lower opening within the secondary digester tank, and a flow control valve configured to allow or prevent flow of fluid through the first conduit. When the flow control valve is configured to allow flow of fluid through the first conduit, a portion of the primary feed material portion flows from the primary digester tank to the secondary digester tank to form the secondary feed material portion.

In all the above prior arts, the mixing of feed materials inside the digesters/fermenters is time consuming as it is happening to a lesser extent, hence, inefficient. In the above-mentioned prior arts, the area for mixing of feed materials is the connecting pipe connected between the tanks or fermentation chamber and later in the tanks with help of agitators or naturally, wherein, mixing of feed materials does not take place effectively in the connecting pipe, therefore, mixing rate becomes low, thereby lowering the yield of biogas production. Conventional Digesters have focused on mixing substrates using the pressure difference by controlling their flow through pipes, therefore, continuity in the substrate mixing is not achieved and also not ensuring an effective mixing of substrates.

Conventional Digesters have heating systems placed inside them for maintaining the favorable internal temperature during mixing of substrates and production of biofuel, but after using such heating systems inside the digester continuously for some time, a certain amount of substrate or biomass while mixing sticks to the heating elements of the heating system and forms a thick layer, further acting as an insulating layer causing reduction in the heating rate, thus rendering the heating system ineffective due to the break down caused by the formation of thick layer. At the same time, servicing of the heating system placed inside the digester causes problems in carrying out the servicing of the digesters.

It is, therefore, important to work on the alternative solution to develop a modular improved mobile biofuel system which obviates the complexity and challenges of the prior arts and provide an innovative system which is easy to install, user friendly, time and powersaving, entailing low capital and operating expenses and smoothly workable over a wide range of climatic conditions.
Summary of the Invention
It is an objective of the present invention to manufacture components fora biofuel production system on an industrial scale.
It is an objective of the present invention to provide a digester for producing biofuel that involve minimum steps for its assembly thereby enabling an easy shipping directly to consumers for use.
It is an objective of the present invention to provide a digester in the biofuel production system that works principally on ‘’plug and operate’’ method in order to minimize the local work.
It is an objective of the present invention to provide a digester in a biofuel production system which functions on reduced power consumption thereby effectively minimizing the operating expense.
It is an objective of the present invention to provide a digester in biofuel production systemthat requires low maintenance cost and little maintenance time.
It is an objective of the present invention to provide a method for producing biofuel that enhances the extent of mixing of biomass inside the digester, thereby maximizing specially the production of biogas.
It is yet another objective of the present invention to provide a method for producing biofuel which is easy to perform by any common person without any extensive training.
It is another objective of the present invention to provide a digester in a biofuel production system which is easy to install, operate and much more user compliant.
It is an objective of the present invention to provide a system that functions efficiently under a wide range of climatic conditions.
It is yet an objective of the present invention to provide a digester in a biofuel producing system, which is equipped with smart heating system having a long service spanfor effective heat transfer and at the same time, service friendly too.
It is an objective of the present invention to provide a system for production of biofuel, wherein said system comprises of digester unit capable of efficient bio-waste management.
It is an objective of the present invention to provide a biofuel producing system that requires minimum accessories and nearly no electrical devices to operate.
It is another objective of the present invention to provide a biofuel producing system capable of producing wide variety of biofuel related products having diverse industrial applications.
The above and other objectives of the present invention are achieved according to the following embodiments of the present invention.
A term “communicating vessel” is used in this invention, it is referring to the plurality of vessels that are present inside the digester for storing the biomass feed and mixing the feed for producing the biogas, wherein each such vessels are separated by a wall, which is referred to as a communicating wall in this specification.
Termssuch as “inverted U-shaped pipe”,“valve”and“mixing apparatus” have been used in various embodiments of the present invention, wherein “inverted U-shaped pipe and valve” are the parts of the mixing apparatus, which is controlling, regulating and directing the accumulated biofuel, preferably the bio-gases within the communicating vessel for an appropriate mixing of the biomass without involving any electrical source or specific mixing equipment, and further driving the process of mixing of biomass continuouslyin the communicating vessels at the communicating wall of the communicating vessel without requiring any internal or external activation, wherein the “mixing apparatus” is an apparatus helping in mixing of the biomass inside the digester.
Terms such as “digester” and “enclosure” are used in this specification, wherein enclosure refers to the space within which the biofuels are produced, whereas the digester refers to the enclosure along with other integrated equipment helping in the production of biogas other, wherein, the digester excludes the container for source feed and storage container for the produced gas.
In accordance with one exemplary embodiment of the present invention, there is provided a digester for producing biofuel comprising an enclosure provided with atleast one inlet for receiving the biomass and at least one outlet for exiting the produced biofuel, wherein the enclosure comprises of at least two communicating vessels, each configured to transfer and exchange the biomass with its adjacent vessel by way of a mixing mechanism to produce biofuel, at least one mixing apparatus capable of enabling a natural and continuous self-mixing of biomass in the communicating vessels without involving any separate source of power for maintaining the mixing of the biomass for a required period of time, wherein said communicating vessels are partitioned by a communicating wall positioned vertically within the enclosure and designed to be provided with plurality of perforations at its bottom so as to provide a path for natural efficient mixing of the biomass between the adjacent communicating vessels.

In accordance with just above embodiment of the present invention, wherein each said mixing apparatus comprises of an inverted U-shaped pipe for connecting the adjacent communicating vessels from their top and employing it for transferring the produced biofuel from one communicating vessel to the adjacent communicating vessel through the inverted U-shaped pipe vessel corresponding to the mixing of the biomass in the communicating vessels without involving any separate source of power for maintaining the mixing of the biomass for a required period of time, wherein said mixing apparatus further comprises of one or more sensors for detecting a threshold value of at least one specific parameter, wherein said specific parameter is but not just limited to differential pressure between the adjacent communicating vessels, wherein said threshold value of the predetermined differential pressure varies between 5-200 mbar.

In accordance with the above exemplary embodiment of the present invention, wherein said mixing apparatus further comprises of a valve operably and functionally integrated in the inverted U-shaped pipe to allow the produced biofuel to transfer from one communicating vessel to another corresponding to the detected threshold value of the predetermined differential pressure.

In accordance with one exemplary embodiment of the present invention, there is provided a digester for producing biofuel comprising an enclosure provided with atleast one inlet for receiving the biomass and at least one outlet for exiting the produced biofuel, wherein the enclosure comprises of at least two communicating vessels, each configured to transfer and exchange the biomass with its adjacent vessel by way of a mixing mechanism to produce biofuel, at least one mixing apparatus capable of enabling a natural and continuous self-mixing of biomass in the communicating vessels without involving any separate source of power for maintaining the mixing of the biomass for a required period of time, wherein said communicating vessels are partitioned by a communicating wall positioned vertically within the enclosure and designed to be provided with plurality of perforations at its bottom so as to provide a path for natural efficient mixing of the biomass between the adjacent communicating vessels, wherein said biofuel mainly includes biogas produced in the communicating vessels, wherein biogas comprises mainly of methane and Carbon dioxide as the two main components but not only limited to the same.
In accordance with one embodiment of the present invention, there is provided a digester for producing biofuel comprising an enclosure provided with atleast one inlet for receiving the biomass and at least one outlet for exiting the produced biofuel, wherein the enclosure comprises of at least two communicating vessels, each configured to transfer and exchange the biomass with its adjacent vessel by way of a mixing mechanism to produce biofuel, at least one mixing apparatus provided with a sensor to detect the threshold value of the predetermined differential pressure which further opens the valve integrated in the inverted U-shaped pipe for transfer of produced biogas, thereby further enabling a natural, efficient and continuous self-mixing of biomass in the communicating vessels through the perforations of the communicating wall without involving any separate source of power for maintaining the mixing of the biomass for a required period of time, wherein the predetermined differential pressure to be set depends on the dimension of the digester, and preferably varies in the range of 5-200 mbar, and the volume of biomass transfer from one communicating vessel to another is proportional to the size of digester and predetermined differential pressure, and the amount of biogas produced is directly proportional to the self-mixing of the biomass through the perforations of the communicating wall, and is more than the volume of biomass being transferred through the perforations of the communicating wall from one communicating vessel to another.
In accordance with one exemplary embodiment of the present invention, wherein said inverted U-shaped pipe enables transfer of biomass in the ratio of 1:2:3 from one communicating vessel to another through the plurality of perforations in the communicating wall corresponding to the detected threshold value of the predetermined differential pressure in the respective ratio of 2:3:10 by the one or more sensors.

In accordance with above exemplary embodiment of the present invention, wherein said inverted U-shaped pipe of mixing apparatus fitted in a 40’ or 20’ enclosure from the top enables a transfer of 2830 or 1400 liters of biomass from one communicating vessel to another through the plurality of perforations in the communicating wall corresponding to the detected threshold value of the predetermined differential pressure of 10 mbar by the sensor to produce more than 2830 liters of biogas corresponding to 40’ enclosure and more than 1400 liters of biogas corresponding to 20’ enclosure.

In accordance with above exemplary embodiment of the present invention, wherein said inverted U-shaped pipe of mixing apparatus fitted in a 40’ or 20’ feet enclosure from the top enables a transfer of 5660 or 2830 liters of biomass from one communicating vessel to another through the plurality of perforations in the communicating wall corresponding to the detected threshold value of the predetermined differential pressure of 15 mbar by the sensor to produce more than 5660 liters of biogas corresponding to 40’ enclosure and more than 2830 liters of biogas corresponding to 20’ enclosure.

In accordance with above exemplary embodiment of the present invention, wherein said inverted U-shaped pipe of mixing apparatus fitted in a 40’ or 20’ feet enclosure from the top enables a transfer of 8490 or 4245 liters of biomass from one communicating vessel to another through the plurality of perforations in the communicating wall corresponding to the detected threshold value of the predetermined differential pressure of 50 mbar by the sensor to produce more than 8490liters of biogas corresponding to 40’ enclosure and more than 4245 liters of biogas corresponding to 20’ enclosure.

In accordance with one exemplary embodiment of the present invention, wherein said digester for producing biofuel is assembled to be directly operated by plugging it to any power source in a biofuel plant or biofuel producing system. In accordance with one exemplary embodiment, there is provided a digester for producing biofuel comprising an enclosure provided with atleast one inlet for receiving the biomass and at least one outlet for exiting the produced biofuel, wherein the enclosure comprises of at least two communicating vessels, each configured to transfer and exchange the biomass with its adjacent vessel by way of a mixing mechanism to produce biofuel, at least one mixing apparatus capable of enabling a natural and continuous self-mixing of biomass in the communicating vessels without involving any separate source of power for maintaining the mixing of the biomass for a required period of time, wherein said communicating vessels are partitioned by a communicating wall positioned vertically within the enclosure and designed to be provided with plurality of perforations at its bottom so as to provide a path for natural efficient mixing of the biomass between the adjacent communicating vessels, wherein said enclosure is provided with an insulation member on the outer surface for maintaining its internal temperature and configured to function efficiently even under extreme temperature conditions, wherein thickness of said insulation member varies between 40-120 mm.

In accordance with one embodiment of the present invention, there is provided a mixing apparatus in a digester having atleast two communicating vessels for producing biofuel comprising an inverted U-shaped pipe for connecting the adjacent communicating vessels from their top and employing it for transferring the produced biofuel, preferably biogas, from one communicating vessel to the adjacent communicating vessel through the inverted U-shaped pipe vessel corresponding to the mixing of the biomass in the communicating vessels without involving any source of power for a required period of time, one or more sensors for detecting a threshold value of atleast one specific parameter and a valve operably and functionally integrated in the inverted U-shaped pipe to allow the produced biofuel to transfer from one communicating vessel to another corresponding to the detected threshold value of the predetermined differential pressure, and wherein said inverted U-shaped pipe with the help of sensors and valve in coordination with the communicating vessel enables a natural and continuous self-mixing of biomass in the communicating vessels without involving any separate source of power for maintaining the mixing of the biomass for a required period of time, wherein said specific parameter is but not just limited to differential pressure between the adjacent communicating vessels.

In accordance with just above embodiment of the present invention, wherein said communicating vessels are partitioned by a communicating wall positioned vertically within the digestor, wherein, said communicating wall is provided with plurality of perforations at its bottom so as to provide a path for natural efficient mixing of the biomass between the adjacent communicating vessels.
In accordance with one of the exemplary embodiments of the present invention, wherein said biogas bag is cylindrical in shape and is horizontally mounted on the digester/ communicating vessels to store the produced biogas for further applications.
In accordance with one embodiment of the present invention, wherein there is provided an operably connected Inverted U-shaped pipe and valve with the communicating vessels responsible for performing mixing apparatus.
In accordance with one embodiment of the present invention, wherein said Inverted U-shaped pipe connects two adjacent communicating vessels on the top of the digester, wherein said adjacent vessels are partially separated by the Communicating wall.
In accordance with one embodiment of the present invention, wherein said perforations in communicating wall are subjected to change in dimensions in accordance with substrate viscosity, size of the vessels and desired velocity of biomass corresponding to any change in the mixing apparatus.
According to the present invention, a modular mobile digester is provided for producing biofuel from all biomass substrates, which further undergo a wet fermentation process to release biofuel applicable for several energy related applications.
In accordance with one exemplary embodiment of the present invention, said biogas can be made to flow for various applications, like Combined Heat and Power (CHP) unit or other applications but not limited to electricity generation for on-site direct use or Grid connection, battery charging, charging electric vehicles, compressed biogas, biogas feed in gasgrid, direct burning, or heating purposes.
In accordance with oneexemplary embodiment of the present invention, wherein the side walls of the enclosure are providedwith a corrugated structure, wherein said corrugated structure of the side walls are further jacked by an additional insulation member to prevent heat loss and allow the heat to get distributed uniformly on the digester walls, wherein insulation member is capable offully covering the lateralcorrugated walls, wherein thickness of said insulation member varies between 40-120 mm depending on the geographical conditions of the place, wherein said insulating wall is preferably made up of Polyurethane Foam (PUF) which insulate the container/digester from all sides.
In accordance with one exemplary embodiment of the present invention, wherein said enclosure is provided with a heating unit on its outer surface for maintaining its internal temperature between 25-65 °C, wherein the outer surface of the enclosure is corrugated wall structure, wherein fluids are smartly made to circulate via the corrugated structure wall to maintain the temperature of digester between 25-65 °C, thus helping the digester to work even at surrounding temperature as low as -40°C and as high as 60°C.
Brief Description of the Drawings
Figure 1 shows a digester for producing biofuel.
Detailed Description of the Invention
In accordance with one embodiment of the present invention, there is provided a system for producing biofuel comprising a digester having an enclosure provided with atleast one inlet for receiving the biomass and atleast one outlet for exiting the produced biofuel, wherein each said enclosure comprises of atleast two communicating vessels, each configured to transfer and exchange the biomass with its adjacent vessel by way of a mixing mechanism to produce biofuel; and atleast one mixing apparatus capable of enabling a natural and continuous self-mixing of biomass in the communicating vessels without involving any source of power for a required period of time, a flexible bag adapted to store biofuel, preferably biogas, being produced inside the communicating vessels and create sufficient pressure to enable release of gas without requiring any external means for sucking gas out of the bag, feed source containing biomass and capable of feeding the enclosure, and wherein said communicating vessels are partitioned by a communicating wall positioned vertically within the digester, wherein, said communicating wall is provided with a plurality of perforations at its bottom for providing the path for natural efficient mixing of the biomass between the adjacent communicating vessels, and wherein, said mixing apparatus enables a natural and continuous self-mixing of biomass in the communicating vessels without involving any separate source of power for maintaining the mixing of the biomass for a required period of time.

In accordance with one exemplary embodiment of the present invention for the system for producing biofuel, wherein said mixing apparatus comprises of an inverted U-shaped pipe for connecting the adjacent communicating vessels from their top and employing it for transferring the produced biofuel, preferably biogas from one communicating vessel to the adjacent communicating vessel through the inverted U-shaped pipe vessel corresponding to the mixing of the biomass in the communicating vessels without involving any separate source of power for maintaining the mixing of the biomass for a required period of time, wherein said mixing apparatus further comprises of one or more sensors for detecting a threshold value of atleast one specific parameter, wherein said mixing apparatus comprises a valve operably and functionally integrated in the inverted U-shaped pipe to allow the produced biofuel to transfer from one communicating vessel to another corresponding to the detected threshold value of the predetermined differential pressure, wherein said specific parameter is but not just limited to differential pressure between the adjacent communicating vessels.

In accordance with one exemplary embodiment of the present invention for the system for producing biofuel, wherein said mixing apparatus fitted on the top of the enclosure for connecting the communicating vessels enables transfer of biomass in the ratio of 1:2:3 from one communicating vessel to another through the plurality of perforations in the communicating wall corresponding to the detected threshold value of the predetermined differential pressure in the respective ratio of 2:3:10 by the one or more sensors by transferring the produced biofuel, preferably biogas, from one communicating vessel to another through the inverted U-shaped pipe.

In accordance with above exemplary embodiment of the present invention for the system for producing biofuel, wherein said inverted U-shaped pipe of mixing apparatus fitted in a 40’ or 20’ enclosure from the top enables a transfer of 2830 or 1400 liters of biomass from one communicating vessel to another through the plurality of perforations in the communicating wall corresponding to the detected threshold value of the predetermined differential pressure of 10 mbar by the sensor to produce more than 2830 liters of biogas corresponding to 40’ enclosure and more than 1400 liters of biogas corresponding to 20’ enclosure.

In accordance with above exemplary embodiment of the present invention for the system for producing biofuel, wherein said inverted U-shaped pipe of mixing apparatus fitted in a 40’ or 20’ feet enclosure from the top enables a transfer of 5660 or 2830 liters of biomass from one communicating vessel to another through the plurality of perforations in the communicating wall corresponding to the detected threshold value of the predetermined differential pressure of 15 mbar by the sensor to produce more than 5660 liters of biogas corresponding to 40’ enclosure and more than 2830 liters of biogas corresponding to 20’ enclosure.

In accordance with above exemplary embodiment of the present invention for the system for producing biofuel, wherein said inverted U-shaped pipe of mixing apparatus fitted in a 40’ or 20’ feet enclosure from the top enables a transfer of 8490 or 4245 liters of biomass from one communicating vessel to another through the plurality of perforations in the communicating wall corresponding to the detected threshold value of the predetermined differential pressure of 50 mbar by the sensor to produce more than 8490 liters of biogas corresponding to 40’ enclosure and more than 4245 liters of biogas corresponding to 20’ enclosure.

In accordance with the above exemplary embodiment of the present invention, there is provided a method for producing biofuel in a digester having atleast two communicating vessel comprising feeding the biomass into the digester and leaving it for a definite period of time, producing sufficient biofuel to create an optimum condition in terms of atleast one specific parameter for enabling mixing of the biomass between two adjacent communicating vessels, sensing a threshold value of the specific parameter and opening a passage for allowing the produced biofuel, preferably biogas, to transfer from one communicating vessel to another, further causing transfer of biomass from one communicating vessel to another, wherein, said sensing of the threshold value followed by opening of the passage is enabling a natural and continuous self-mixing of biomass in the communicating vessels without involving any separate source of power for maintaining the mixing of the biomass for a required period of time, while maintaining the internal temperature of the digester from outside.

In accordance with the above exemplary embodiment for the method to produce biofuel in a digester having atleast two communicating vessel, wherein said communicating vessels are partitioned by a communicating wall positioned vertically within the digester, wherein said communicating wall is provided with plurality of perforations at its bottom for providing the path for natural efficient mixing of the biomass between the adjacent communicating vessels.

In accordance with the above exemplary embodiment for the method to produce biofuel in a digester having atleast two communicating vessel, wherein said digester is provided with a mixing apparatus on the top, wherein said mixing apparatus further comprising an inverted U-shaped pipe for connecting the adjacent communicating vessels from their top and employing it for transferring the produced biofuel from one communicating vessel to the adjacent communicating vessel through the inverted U-shaped pipe vessel corresponding to the mixing of the biomass in the communicating vessels without involving any separate source of power for maintaining the mixing of the biomass for a required period of time, wherein said mixing apparatus further comprising of one or more sensors for detecting a threshold value of atleast one specific parameter, and a valve as the passage operably and functionally integrated in the inverted U-shaped pipe to allow the produced biofuel to naturally transfer from one communicating vessel to another corresponding to the detected threshold value of the predetermined differential pressure.

Referring to Figure 1 that shows a digester (1) for producing biofuel, wherein the digester comprises of an enclosure (4), wherein the enclosure is provided with atleast one inlet (10) for receiving the biomass and at least one outlet (11) for exiting the produced biofuel, wherein the enclosure (4) comprises of communicating vessels (2), each configured to transfer and exchange the biomass with its adjacent vessel by way of a mixing mechanism occurring at the perforations (12) of the communicating wall (3) at its bottom to produce biofuel. A mixing apparatus (5) is provided at the top of the enclosure (4) for connecting the adjacent communicating vessels (2), which enables a natural and continuous self-mixing of biomass in the communicating vessels (2) at the bottom of bottom of the communicating wall (3) without involving any separate source of power for maintaining the mixing of the biomass for a required period of time, there is no provision of any external electrical equipment for the functioning of the mixing apparatus to enable mixing of the biomass inside the digester (1). Also, said communicating vessels (2) are partitioned by a communicating wall (3) positioned vertically within the enclosure and designed to be provided with plurality of perforations (12) at its bottom so as to provide a path for natural efficient mixing of the biomass between the adjacent communicating vessels (2). An agitator (6) is provided on the top of one side of the enclosure (4), which can also be used in mixing of the biomass. There is provided a flexible bag (8) adapted to store biofuel, preferably biogas, being produced inside the communicating vessels (2) and create sufficient pressure to enable release of gas without requiring any external means for sucking gas out of the bag; The digester is provided with a heating unit situated on the outer surface of the enclosure, wherein the heating unit is provided with an inlet (13) for hot water which further circulates around the enclosure to maintain the internal temperature of the digester between 25-65 °C and exits through an outlet (14) for the water, wherein said mixing apparatus (5) comprises of an inverted U-Shaped pipe (5c) connecting the adjacent communicating vessels (2) for transferring the produced biogas inside the enclosure (4) from one communicating vessel (2) to another. The mixing apparatus (5) is provided with a sensor (5a) for detecting the threshold value of predetermined differential pressure between the adjacent communicating vessels (2), which further enables the opening of the valve (5b) integrated in the inverted U-Shaped pipe (5c) for the transfer of the produced biogas from one communicating vessel (2) to another, wherein the produced biogas transferred to the other communicating vessel (2) pushes the biomass to transfer from one communicating vessel (2) to another for mixing.

The method to produce biofuel, preferably biogas, starts with loading the biomass into one of the communicating vessel (2) of the digester (1), and leaving the same for a required period of time, wherein a significant amount of pressure difference is created between the adjacent communicating vessels (2) due the biogas being produced naturally or with the help of the agitator (6), when the pressure difference becomes equal to the predetermined differential pressure set for the mixing apparatus (6), the sensor (5a) of the mixing apparatus (5) senses the predetermined differential pressure and opens the valve (5b) integrated in the inverted U-shaped pipe (5c) of the mixing apparatus (5) enabling the produced biogas to transfer from one communicating vessel (2) to another, wherein the transferred biogas into another communicating vessel (2) or escaped biogas via the inverted U-shaped pipe (5c) pushes the biomass through the plurality of perforations (12) at the bottom of the communicating wall (3) and enables the transfer and self-mixing of the entire biomass loaded corresponding to the predetermined differential pressure for a particular batch, wherein, once the predetermined differential pressure between the communicating vessel (2) is attained and produced biogas starts to move from one communicating vessel (2) to another via the inverted U-shaped pipe (5c) of mixing apparatus (5), then the loaded biomass continues to mix from one communicating vessel (2) to another through the perforations (12) of the communicating wall (3) to produce more and more biogas for a particular batch and then it requires no additional force to continue the process of mixing, which further highly contributes to reduced power consumption, efficient biogas production and a notable saving of operating cost. In this invention, “Mixing mechanism” is referred to as continuous and natural mixing of the biomass through the perforations of the communicating wall as explained above.
The biogas produced from the mixing of the biomass can be used for various applications. Usually, for optimal biogas production, temperature of the digester is maintained between 25 and 65°C by circulating fluids preferably, hot water to maintain the above-mentioned temperature with the help of but not limited to heat generated from the CHP (Combined Heat and Power system) or just from a boiler which is burning biogas.
The biofuel production using biomass is an incredibly old process, however optimization to the process is constantly researched. Today it is a standard procedure to heat and mix the substrates for better and quicker biogas yield. There are many kinds of mixing systems which all require additional energy, while the mixing apparatus disclosed in the present invention uses the pressure created by biogas within the communicating vessel to activate the valve and works basically according to the principal of communicating vessels for mixing of the biomass through the perforations provided in the communicating wall.
In accordance with one embodiment of the present invention, while the produced biofuel, preferably biogas escapes via the inverted U-shaped pipe of the mixing apparatus and communicating vessels to the flexible gas bag, the biomass inside the communicating vessel naturally and effectivelymixes with each otherunder the law of communicating vessels.
In one of the exemplary embodiments of the present invention, when the fermentation process is just started within the digester or while the feed is being loaded into the digester,since there is not enough biogas present inside the vessel initially to activate the valve of the mixing apparatus, the agitator providedfor the digester is automatically brought into use to mix the biomass for some time, wherein said agitator is used unless the predetermined differential pressure is not achieved, once the predetermined differential pressure is attained, the agitator is switched off, and the mixing apparatus becomes operational for mixing of the biomass, and the agitator is no more used for mixing of the biomass inside the digester to produce biogas thus saving the power consumption to a great extent.
In one of the exemplary embodiments of the present invention, wherein saiddigester is capable of producing biofuel by taking almost a negligible help from the agitator, but at the same time, said agitator may also serve as an emergency mixer.
In one of the exemplary embodiments of the present invention, wherein said enclosure or communicating vessels are usually made from but not only limited to custom made mild steel corrugated plates. The angle of the corrugation is built in such a way that the container can hold minimum of 2 bar pressure. All inside walls of the enclosure, are protected by Polyurethane or similar coating and/or FRP (Fiber-reinforced plastic) or both but not strictly limited to them.
In one of the exemplary embodiments of the present invention, wherein the sizes of the digester/ containers are slightly smaller than the standard or HQ sea containers, thus allowing them to be pushed into such standard or HQ sea container for increasing its cost effectiveness and easy transportation.
In the present invention, the digester is configured for minimal daily attention and service time and minimal operating costs. The disclosed mixing apparatus and the communicating wall partitioning communicating vessel are reinforcing the above features in the digester. With the help of just one pump, the whole system can be operated and nearly no other electrical devices or power consuming equipment are needed, wherein mixing apparatusfavorably operates between 5 mbar to 200 mbar pressures for the disclosed digesters and does not require any maintenance thus reduces the operating expense significantly.
According to the present invention, the disclosed digester just needs to be delivered to customers, installed on-site, plug and can be made ready to operate as there are no additional steps involved to bring the digester in operating condition, the usual need for heavy civil construction is not necessary.Such digesters can be installed for many kind of biomass substrates and modular with any kind of biofuel system.
Apart from the biogas production, the digester of present invention is capable of producing bio-fertilizer which can be used as a substitute for chemical fertilizers.
According to the present invention, the produced biogas is stored in biogas bag and from there it is aligned to be used for various application.
In accordance with the preferred embodiment of the present invention, biomass is wet as mixing apparatus works well with liquid biomass, wherein are biomass are selected from but not limited to animal slurries, food waste, slaughter-house waste, sewage sludge, or vegetable-waste or the combination of allkinds of biomass isused.
In the present invention, there is also provided a service hole for a person to go inside the digester and service the internal components.If required, it may be constructedon both sides of the communicating vessels.
The parameter such as temperature, pressure, digester dimensions and materials used in the construction of bio-digesterare discussed based on the exemplary embodiments and can be varied depending on the uses of raw materials, user requirement and can be further worked upon within the scope the disclosure and can be submitted in the future by way of amendments.
Referring the accompanying drawings are provided herein illustrating the further understanding of the present disclosure and are incorporated in and constitute a part of this complete specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, however, the same will be further expanded within the scope of the disclosure and serve to explain the principles of the present invention.
,CLAIMS:We claim:
1. A digester (1) for producing biofuelcomprises:
an enclosure (4) provided with atleast one inlet (10) for receiving the biomass and atleast one outlet (11) for exiting the produced biofuel, wherein the enclosure (4) comprises of:
atleast twocommunicating vessels (2), each configured to transfer and exchange the biomass with its adjacent vessel by way of a mixing mechanismto produce biofuel; and
atleast onemixing apparatus (5)capable ofenabling a natural andcontinuousself-mixing of biomass in the communicating vessels (2) without involving any separate source of power for maintaining the mixing of the biomass for a required period of time,
wherein said communicating vessels (2) are partitioned by a communicating wall (3) positioned vertically within the enclosure and designed to be provided with plurality of perforations (12) at its bottom so as to provide a path for natural efficient mixing of the biomass between the adjacent communicating vessels (2).

2. The digester (1) as claimed in claim 1, whereineach said mixing apparatus (5) comprises of an inverted U-shaped pipe (5c) for connecting the adjacent communicating vessels (2) from their top and employing it for transferring the produced biofuel from one communicating vessel (2) to the adjacent communicating vessel (2) through the inverted U-shaped pipe vessel (5c) corresponding to the mixing of the biomass in the communicating vessels (2) without involving any separate source of power for maintaining the mixing of the biomass for a required period of time.

3. The digester (1) as claimed in claim 1, wherein said mixing apparatus (5) further comprises of one or more sensors (5a) for detecting a threshold value of atleast one specific parameter.

4. The digester (1) as claimed in claim 4, wherein said specific parameter is but not just limited to differential pressure between the adjacent communicating vessels (2).

5. The digester (1) as claimed in claim 3 and 4, wherein said threshold value of the predetermined differential pressure varies between 5-200 mbar.

6. The digester (1) as claimed in claim 1, wherein said mixing apparatus (5) further comprises of a valve (5b) operably and functionally integrated in the inverted U-shaped pipe (5c) to allow the produced biofuel to transfer from one communicating vessel (5) to another corresponding to the detected threshold value of the predetermined differential pressure.

7. The digester (1) as claimed in claim 1, wherein said biofuel mainly includes biogas produced in the communicating vessels (2).

8. The digester (1) as claimed in claim 2, wherein said inverted U-shaped pipe (5c)enables transfer of biomass in the ratio of 1:2:3 from one communicating vessel (2) to another through the plurality of perforations (12) in the communicating wall (3) corresponding to the detected threshold value of the predetermined differential pressurein the respective ratio of 2:3:10 by the one or more sensors (5a).

9. The digester (1) as claimed in claim 1, wherein said digester for producing biofuel is assembled to be directly operated by plugging it to any power sourcein a biogas plant or biogas producing system. 10. The digester (1) as claimed in claim 1, wherein said enclosure (4) is provided with an insulation member on the outer surface for maintaining its internal temperature, wherein thickness of said insulation member varies between 40-120 mm.

11. The digester (1) as claimed in claim 1, wherein said enclosure (4) is provided with a heating unit on its outer surface for maintaining the internal temperature between 35-65 °C.

12. A mixingapparatus (5) in a digester (1) having atleast two communicating vessels (2) for producing biofuel comprises:
an inverted U-shaped pipe (5c) for connecting the adjacent communicating vessels (2) from their top and employing it for transferring the produced biofuel, preferably biogas, from one communicating vessel (2) to the adjacent communicating vessel (2) through the inverted U-shaped pipe (5c) corresponding to the mixing of the biomass in the communicating vessels (2) without involving any source of power for a required period of time;
one or more sensors (5a) for detecting a threshold value of atleast one specific parameter; and
a valve (5b) operably and functionally integrated in the inverted U-shaped pipe (5c) to allow the produced biofuel to transfer from one communicating vessel (2) to another corresponding to the detected threshold value of the predetermined differential pressure,
wherein said inverted U-shaped pipe (5c) with the help of sensors (5a) and valve (5b) in coordination with the communicating vessel (2)enablesa natural and continuous self-mixing of biomass in the communicating vessels (2) without involving any separate source of power for maintaining the mixing of the biomass for a required period of time.

13. The mixing apparatus (5) as claimed in claim 12, wherein said communicating vessels (2) are partitioned by a communicating wall (3) positioned vertically within the digestor (1), wherein, said communicating wall (3) is provided with a plurality of perforations (12) at its bottomso as to provide a pathfor natural efficient mixing of the biomass between the adjacent communicating vessels (2).
14.The mixing apparatus (5) as claimed in claim 12, wherein said specific parameter is but not just limited to differential pressure between the adjacent communicating vessels (2).
15. A system for producing biofuel comprises:
a digester (1) having an enclosure (4) provided with atleast one inlet (10) for receiving the biomass and atleast one outlet (11) for exiting the produced biofuel, wherein each said enclosure (4) comprisesof:
atleast two communicating vessels (2), each configured to transfer and exchange the biomass with its adjacent vessel (2) by way of a mixing mechanism to produce biofuel; and
atleast one mixing apparatus (5) capable of enabling a natural and continuous self-mixing of biomass in the communicating vessels (2) without involving any source of power for a required period of time,
a flexible bag (8) adapted to store biofuel, preferably biogas, being produced inside the communicating vessels (2) and create sufficient pressure to enable release of gas without requiring any external means for sucking gas out of the bag;
a feed source (7) containing biomass and capable of feeding the enclosure (4), and

wherein, said communicating vessels (2) are partitioned by a communicating wall (3) positioned vertically within the digester (1), wherein, said communicating wall (3) is provided with a plurality of perforations (12) at its bottom for providing the path for natural efficient mixing of the biomass between the adjacent communicating vessels (2), and

wherein, said mixing apparatus (5) enables a natural and continuous self-mixing of biomass in the communicating vessels (2) without involving any separate source of power for maintaining the mixing of the biomass for a required period of time.

16. The system as claimed in claim 15, wherein said mixing apparatus (5) comprises of an inverted U-shaped pipe (5c) for connecting the adjacent communicating vessels (2) from their top and employing it for transferring the produced biofuel, preferably biogas from one communicating vessel (2) to the adjacent communicating vessel (2) through the inverted U-shaped pipe (5c) corresponding to the mixing of the biomass in the communicating vessels (2) without involving any separate source of power for maintaining the mixing of the biomass for a required period of time.

17. The system as claimed in claim 15, wherein said mixing apparatus(5) further comprises of one or more sensors (5a) for detecting a threshold value of atleast one specific parameter.

18. The system as claimed in claim 15, wherein said mixing apparatus (5) comprises a valve (5b) operably and functionally integrated in the inverted U-shaped pipe (5c) to allow the produced biofuel to transfer from one communicating vessel (2) to another corresponding to the detected threshold value of the predetermined differential pressure.

19. The system as claimed in claim 17, wherein said specific parameter is but not just limited to differential pressure between the adjacent communicating vessels (2).

20. The system as claimed in claim 15, wherein said mixing apparatus (5)enables transfer of biomass in the ratio of 1:2:3 from one communicating vessel (2) to another through the plurality of perforations (12) in the communicating wall (3) corresponding to the detected threshold value of the predetermined differential pressure in the respective ratio of 2:3:10 by the one or more sensors (5b)by transferring the produced biofuel, preferably biogas, from one communicating vessel (2) to another through the inverted U-shaped pipe (5c).
21. The system as claimed in claim 15, wherein said enclosure (4) is provided with an insulation member and a heating unit on the outer surface for maintaining its internal temperature between 35-65°C, wherein thickness of said insulation member varies between 40-120 mm.

22. A method for producing biofuel in a digester (1) having atleast two communicating vessel(2) comprising:
feeding the biomass into the digester (1) and leaving it for a definite period of time;
producing sufficient biofuel to create an optimum condition in terms of atleast one specific parameter for enabling mixing of the biomassbetween two adjacent communicating vessels (2);
sensing a threshold value of the specific parameter; and
opening a passage for allowing the produced biofuel, preferably biogas, to transfer from one communicating vessel (2) to another, further causing naturaltransfer of biomass from one communicating vessel (2) to another,
wherein, said sensing of the threshold value followed by opening of the passage is enabling a natural and continuous self-mixing of biomass in the communicating vessels (2) without involving any separate source of power for maintaining the mixing of the biomass for a required period of time, while maintaining the internal temperature of the digester (1)by circulating fluids at a particular temperature on the outer surface of the digester (1).

23. The method as claimed in claim 22, wherein said communicating vessels (2) are partitioned by a communicating wall (3) positioned vertically within the digester (1), wherein said communicating wall (3) is provided with plurality of perforations (12) at its bottom for providing the path for natural efficient mixing of the biomass between the adjacent communicating vessels (2).

24. The method as claimed in claim 22, wherein said digester (1) is provided with a mixing apparatus (5) further comprising an inverted U-shaped pipe (5c) for connecting the adjacent communicating vessels (2) from their top and employing it for transferring the produced biofuel from one communicating vessel (2) to the adjacent communicating vessel (2) through the inverted U-shaped pipe (5c) corresponding to the mixing of the biomass in the communicating vessels without involving any separate source of power for maintaining the mixing of the biomass for a required period of time.

25. The method as claimed in claim 24, wherein said mixing apparatus (5) further comprising of one or more sensors (5a) for detecting a threshold value of atleast one specific parameter, and a valve (5b) as the passage operably and functionally integrated in the inverted U-shaped pipe (5c) to allow the produced biofuel to naturally transfer from one communicating vessel (2) to another corresponding to the detected threshold value of the predetermined differential pressure.
26. The method as claimed in claim 22, wherein said specific parameter is but not just limited to differential pressure between the adjacent communicating vessels.