EP4676892A1 - Digesteur anaérobie sec pour biomasse lignocellulosique à hydrodynamique unique (dad pour biomasse lignocellulosique) - Google Patents

Digesteur anaérobie sec pour biomasse lignocellulosique à hydrodynamique unique (dad pour biomasse lignocellulosique)

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Publication number
EP4676892A1
EP4676892A1 EP24766634.0A EP24766634A EP4676892A1 EP 4676892 A1 EP4676892 A1 EP 4676892A1 EP 24766634 A EP24766634 A EP 24766634A EP 4676892 A1 EP4676892 A1 EP 4676892A1
Authority
EP
European Patent Office
Prior art keywords
reactor
slurry
feed
solids
biogas
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP24766634.0A
Other languages
German (de)
English (en)
Inventor
Anupoju Gangagni Rao
Sameena Begum
Vijayalakshmi Arelli
Sudharshan JUNTUPALLY
Naveen Kumar Mamindlapelli
Parmeshwar Patil
Vivek Rathore
Jaya Rawat
Anurag Singh
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Council of Scientific and Industrial Research CSIR
Bharat Petroleum Corp Ltd
Original Assignee
Council of Scientific and Industrial Research CSIR
Bharat Petroleum Corp Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Council of Scientific and Industrial Research CSIR, Bharat Petroleum Corp Ltd filed Critical Council of Scientific and Industrial Research CSIR
Publication of EP4676892A1 publication Critical patent/EP4676892A1/fr
Pending legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/02—Biological treatment
    • C02F11/04—Anaerobic treatment; Production of methane by such processes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2203/00—Apparatus and plants for the biological treatment of water, waste water or sewage
    • C02F2203/006—Apparatus and plants for the biological treatment of water, waste water or sewage details of construction, e.g. specially adapted seals, modules, connections
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel

Definitions

  • the present invention relates to a reactor for the dry anaerobic digestion of lignocellulosic biomass for biogas and biomanure (digestate) generation.
  • the present invention provides a reactor that can be operated at high solids in the range of 20 - 40 % and which can handle low density feedstocks such as lignocelluloses.
  • the reactor of the instant invention in its configuration consists of truncated cones and a central duct that creates unique hydrodynamic flow of the material from top to bottom of the reactor. The arrangement of the cones is provided in such a way that the formation of scum layer on the surface of the material is completely prevented.
  • the developed reactor is enormous useful in the sectors of solid waste management, especially renewable energy generation and lignocellulosic waste management.
  • the invention shall help attain the 7 th sustainable development goal of affordable and clean energy.
  • the objectives of the solid-state anaerobic digestion process are to operate the digester with slurry consisting of more than 20 % total solids (TS) for the generation of biogas and biomanure.
  • TS total solids
  • Anaerobic digestion of high solids biomass helps in the usage of lower volume of water required for dilution of feedstock to obtain desired consistency.
  • the quantity of digestate or stabilized solids generation in solid-state anaerobic digestion is low.
  • anaerobic digestion dates back to long years, beginning as early as the 10 th Century.
  • the first application of anaerobic biological process to the treatment of organic wastes was the septic tank, invented in 1895.
  • a variety of applications of the anaerobic concept have evolved over the past nearly 100 years.
  • Early applications, beginning in 1918, were for the treatment of sludge from domestic sewage.
  • anaerobic contact and "anaerobic activated sludge” was applied to livestock slaughtering wastewaters. This process made use of a clarifier unit to separate solids from the liquid.
  • anaerobic treatment applications included various attached growth (up flow, down flow, and expanded bed) treatment approaches.
  • AD is basically classified into two types namely, slurry AD ( ⁇ 15 % TS) and dry AD (> 20 % TS) based on solids consistency of the feed material.
  • the performance of an anaerobic digester depends on the number of internal and external factors such as substrate type, organic loading rate temperature, pH, HRT, mixing of slurry and C/N ratio.
  • Majority of the indigenous biogas technologies in India are suitable slurry digestion of organic wastes.
  • One of the major disadvantages in slurry type digestion is the generation of huge volumes of digestate, that makes its handling difficult on a daily basis.
  • the separation of solids and liquids from the digestate using mechanical equipment adds on to the operational and capital costs.
  • Low density substrates like lignocellulosic biomass requires huge volumes of water if they have to be treated in slurry digester.
  • bio methanation of low density materials in slurry digesters results in the formation of a scum layer on the top of the surface due to solid liquid phase separation leading to chocking of the entire system.
  • the main disadvantage of the present anaerobic digesters is the long residence time typically required to digest the organic wastes.
  • the anaerobic digesters are suitable for the treatment of organic solid waste are "batch" or one-stage digesters.
  • the batch digester is a closed or domed vessel within which very large quantities of organic waste is fermented.
  • Anaerobic batch digesters take 40 to 50 days to adequately digest the organic solids (U.S. Pat. No. 5,637,219).
  • Higher solid content feed to digester has a potential to increase the efficiency of conversion of organic matter in the biomass to biogas, but the higher solid content in the range of 20 - 40 % in the digester can cause reduction in mass and heat transfer between bacteria, enzymes, and substrate in the digester due to poor hydrodynamics (mixing of reactor contents). Hydrodynamics is a major factor that contributes in the mass transfer, structure and metabolism of microbial community in the AD process. It was mentioned that the close contact between acetogens and methanogens can lead to effective methanogenesis which can achieved by smooth and adequate mixing. Negative impacts of inadequate mixing are observed as lower methane yield, loss of digester volume (dead zones), increase in operational expenses, clogging and chocking of lines of the entire system.
  • the tank geometry, placement of inlets and outlets provides a means of efficient mixing in the digester. Therefore, it is of utmost importance that the anaerobic digesters require adequate mixing that enhances the homogeneous distribution of nutrients and micro-organisms and can avoid formation of surface crust and sedimentation. Mixing in the anaerobic digester can be attained by various methods such as slurry recirculation, biogas recirculation and provision of impellers.
  • anaerobic digestion apparatus which comprises: an anaerobic digestion reactor comprising an outer vessel and an inner vessel, wherein the outer vessel is a container sealed from the outside, and the inner vessel is vertically installed inside the outer vessel to thereby partition the outer vessel into an inner anaerobic reaction unit and an outer anaerobic reaction unit; a liquid reverse-flow pipe and a liquid reverse-flow valve, wherein the liquid reverse-flow pipe is vertically installed below the height of the inner vessel inside the inner anaerobic reaction unit and guides liquid in the inner anaerobic reaction unit to the outer anaerobic reaction unit, and the liquid reverse-flow valve controls opening and closing of the liquid reverse-flow pipe; and an impulse mixer for transferring liquid to the inner anaerobic reaction unit from the outer anaerobic reaction unit.
  • the anaerobic digestion apparatus thusly configured prolongs the retention time of the organic solid matter and the anaerobes and enables uniform mixing thereof, and thus can improve digestion efficiency of the organic solid
  • Batch processes are easy to handle as it requires low operational and capital cost with less control systems (Liu et al., 2018).
  • the biogas generation in batch process is very less in the initial days and it continuously increases reaching a peak point followed by gradual decrease and seize of biogas due to the depletion of the organic material.
  • a solid state anaerobic batch system can handle the organic waste with a total solid concentration in the range of 20 to 40%.
  • the reactor is loaded with fresh substrate and it is discharged then loaded with fresh substrate. Batch systems have higher reaction rates with higher methane yield (Li et al., 2011).
  • a company called Bekon in Germany has a largest batch anaerobic system called “BEKON DIGESTER”. It is also called as garage type percolating reactor which is mainly used for anaerobic digestion of agricultural waste, source separated waste, OFMSW and yard waste for the generation of biogas.
  • a recirculation system is arranged for the recirculation of the leachate generated from the feedstock. The leachate is pumped to the surface of the substrate to maintain suitable the moisture in the system.
  • BEKON digesters can be operated at mesophilic and thermophilic temperature.
  • BIOFerm digesters are batch systems suitable for solid-state anaerobic digestion of high solids containing wastes at mesophilic temperature. BIOFerm digesters were used for feed stocks with total solid concentrations in the range of 25-30%. Feedstock is loaded in to the chambers and remained for 28 days (Andre, et al., 2018). Heat is supplied in to the system by in-wall radiant process at the same time, the percolate is also sparged on the surface of the feedstock through the sprinklers. In this process, the percolate which is sprayed on the entire biomass acts as the inoculum for the AD process. BIOFerm solid state digesters were suitable for substrates such as OFMSW and yard waste.
  • the fresh feedstock is continuously fed in to the digester and the same amount of the digested material is removed from the reactor on a daily basis.
  • the main difference between batch and continuous system is the stages involving in batch system are well defined whereas in continuous process there is consistency in feed stock and the reactors resulting in a constant generation of biogas.
  • the inlet and outlet valve mechanism is used to feed and withdraw the slurry.
  • the design of the continuous reactor decides the operation of the entire process (Kothari et al., 2014).
  • the main advantages of continuous process compared to batch process are inoculum requirement is less in continuous process compared to batch and the continuous reactors can handle high OER with small land usage and the biogas yield is very high.
  • DRANCO process which is known as solid state anaerobic digester.
  • First DRANCO plant was started in 1992 in the city of Brecht, Belgium (12,000 t/y).
  • Dranco process There are several plants in operation currently working based on Dranco process, such as Bassum, Germany with the capacity of 13,500 t/y one more in Kaiserslautern, Germany with the capacity of 20,000 t/y and in the city of Salzburg, Austria with the capacity of 20,000 t/y (Rapport et al., 2008).
  • Dranco process is a complete SSAD process of organic fraction of MSW in a continuous plug flow reactor system.
  • Hydrolysis, acidogenesis, acetogenesis and methanogenesis occurs in a single reactor with the total solids concentration of substrate ranging between 15 to 40% (Van et al., 2019).
  • the entire process is operated at thermophilic temperature with a retention time of 20 days.
  • the feedstock enters the reactor from top and the digestate is collected from the bottom of the reactor. No internal mixing is provided in the process. Internal mixing in the system through agitators is avoided by providing recirculation of the leachate.
  • the KOMPOGAS technology was established by W. Schmid of Glattbrugg, Switzerland in 1980s.
  • the Kompogas technology is based on the use of thermophilic fermentation process where the operational temperature of the process is between 50-60°C and the hydraulic residence time for KOMPOGAS process is 15 to 20 days.
  • the kompogas reactor is a horizontal tank which is made up of steel. Axial mixers were arranged in the reactors with slow rotating speed which is meant for the transfer the feedstock from inlet to outlet of the reactor.
  • Kompogas process is able to treat the organic waste with TS concentration of 23 to 28% and it is a single stage system (Hartmann et al., 2006). Recyclable digestate and process water may be added to the feed stream in order to reduce the solid content.
  • Valorga reactor is a vertical cylinder type reactor with horizontal plug-flow behaviour. Two openings are introduced on either side of the wall for inlet and outlet of the organic matter. The walls of the reactor intensifies the organic matter and moves in a circular way in order to transport round and it continuously covers the entire surface of the reactor. There is a pneumatic system for mixing the high solid organic matter.
  • the biogas generated from the reactor is injected with high pressure from the bottom of the reactor in a periodic manner and it allows the efficient vertical mixing (Fu et al., 2018). Due to this process mechanical processes can be avoided for transfer or circulation of the organic matter and also suitable interactions happen between fresh feed stock and digestate.
  • the advantages of the Valorga process include optimal degradation of organic matter due to the recirculation of pressurized biogas and it is a reliable process, it eliminates the pathogens due to the perfect degradation of organic matter (Li, et al., 2011).
  • the main objective of the present invention is therefore to provide a dry anaerobic digester for lignocellulosic biomass with unique hydrodynamics, which obviates the drawbacks of the hitherto reported prior art.
  • Another objective of the present invention is to provide a dry anaerobic digestor with unique hydrodynamics for the generation of biogas and biomanure from lignocellulosic biomass with a solids consistency in the range of 20 - 40 % in the slurry.
  • Still another objective of the present invention is to provide a reactor that delinks the residence time of the feed hydrolysis duct from the residence time of the main reactor for efficient digestion of the low-density material without any phase separation.
  • Yet another objective of the present invention is to provide a reactor wherein the perforated truncated cone above the bottom truncated cone ensures the movement of slurry towards upward flow regime through the perforations (20 mm) while the solid material is retained in the bottom part of the reactor.
  • Still another objective of the present invention is to provide a reactor wherein the bottom truncated cone elongated through the central duct is provided to ensure the retainment of solids and divert the flow from bottom to towards the middle perforated truncated cone.
  • Yet another objective of the present invention is to provide a reactor wherein the top truncated cone is provided for the easy movement of the thinner slurry towards the perforated plate.
  • Still another objective of the present invention is to provide a reactor wherein the conical bottom of the reactor is a place where maximum solids are retained and the mixing of solids in the cone is ensured through pressurized biogas purging.
  • Yet another objective of the present invention is to provide a reactor having the capability of intermittent mixing of digester slurry by using the autogenerated biogas pressure and slurry recirculation from bottom to top.
  • the present invention provides a reactor for dry anaerobic digestion of lignocellulosic biomass (20 - 40 % solids) comprising a vertical cylindrical digestion tank with elongated conical bottom and a domed top, a central duct, a perforated plate and three truncated cones (two closed truncated cones fixed to the central duct and one open truncated perforated cone fixed to the wall of the cylinder).
  • a perforated plate is placed on top of the truncated cones.
  • a truncated cone is a cone with the tip straight cut off with a larger base circle and the top surface with the smaller circle.
  • Two sample ports are provided to the digester just below the perforated truncated cone and bottom truncated cone to withdraw samples for characterization and also for mixing the feed to ensure appropriate buffering.
  • the feed inlet mechanism and the gas collection point are both located at the top of the reactor.
  • the feed prepared from lignocellulosic biomass consisting of 20 - 40 % solids is transported to the bottom of the reactor through the central hydrolysis duct using pumping mechanism.
  • the reactor is provided with gas purging line for pressurized biogas purging in the main reactor as well as the elongated cone area where maximum solids are retained to ensure effective mixing of material inside the digester.
  • the reactor is provided with digestate recirculation mechanism so that the digested liquid can be withdraw from the top and recirculated back to the reactor.
  • the present invention provides a dry anaerobic digester for lignocellulosic biomass with unique hydrodynamics comprising a reactor (1) for anaerobic digestion of a lignocellulosic biomass slurry, wherein the said reactor comprises of:
  • (x) means for pre and post processing mechanisms/elements such as the feed preparation tank (FPT); digestate collection tank (DCT);
  • the present invention provides a dry anaerobic digester, wherein the lignocellulosic biomass (rice husk/rice straw/wheat straw etc) slurry consisting of 20 to 40 % solids is pumped into the reactor from top through the central duct (4) that flows towards bottom of the reactor (1) in a distributed manner.
  • the lignocellulosic biomass rice husk/rice straw/wheat straw etc
  • the present invention provides a dry anaerobic digester, wherein the slurry inlet mechanism (2) is provided with valve mechanism for feeding the slurry to the tank under atmospheric conditions and the gas inlet is provided with a gas distribution system.
  • the present invention provides a dry anaerobic digester, wherein the working of the reactor starts with the preparation of feed slurry of required solids consistency in the FPT, followed by its pumping to the main reactor through the feeding line with an inverted cone that is mounted to the feed hydrolysis duct (4), wherein the feed slurry is initially allowed to flow through the central duct towards the bottom of the reactor which then expands creating an upward flow regime from the bottom due to the presence of a truncated cone.
  • the present invention provides a dry anaerobic digester, wherein the central duct in the reactor acts as a feed hydrolysis duct where the feed slurry gets hydrolysed, and the residence time of the feed hydrolysis duct is delinked with the residence time of the main reactor.
  • the present invention provides a dry anaerobic digester, wherein the perforated truncated cone above the bottom truncated cone ensures the movement of slurry towards upward flow regime through the perforations, while the solid material is retained in the bottom part of the reactor, wherein the bottom truncated cone (7) elongated through the central duct (4) is provided to ensure the retainment of solids and divert the flow from bottom towards the middle perforated truncated cone, wherein the perforated cone (6) consists of perforations with a diameter of 20 mm to ensure the flow of high solids material upwards.
  • the present invention provides a dry anaerobic digester, wherein the pressure build-up inside the feed hydrolysis duct stimulates the downward movement of the acidified slurry towards the bottom and the presence of truncated cone directs the flow behaviour regime upwards for further digestion of the organic material.
  • the present invention provides a dry anaerobic digester, wherein the top truncated cone (5) is provided for the easy movement of the thinner slurry towards the perforated plate and the perforated plate (3) with 10 mm perforations ensures further retainment of solids and allows the liquid to flow towards up which is then withdrawn as the final digestate.
  • the present invention provides a dry anaerobic digester, wherein the middle perforated truncated cone (6) fixed to the wall of the cylindrical reactor and the top and bottom truncated cones are meant to create turbulence in the reactor disturbing the flow behaviour of the slurry.
  • the present invention provides a dry anaerobic digester, wherein formation of scum layer on the top surface of the slurry with the fibrous material leading to choking of pipelines is avoided with the presence of truncated cones.
  • the present invention provides a dry anaerobic digester, wherein the arrangement of truncated cones (5, 6, and 7) creates unique hydrodynamics inside the reactor with materials such as lignocellulosic biomass.
  • the present invention provides a dry anaerobic digester, wherein in addition to the truncated cone (5, 6, and 7), the recirculation of the slurry from the bottom to top ensures the creation of flow regime upwards.
  • the present invention provides a dry anaerobic digester, wherein the pressurized biogas purging further improves the hydrodynamic behaviour of the thick slurry inside the digester and ensures appropriate mixing without any mechanical equipment for efficient heat transfer, nutrients exchange between the microorganisms and organic material.
  • the present invention provides a dry anaerobic digester, wherein the water sprinklers (10) mounted on the wall of the vertical cylinder ensure the periodic sprinkling of water to arrest any foaming that forms on the top of the digested slurry.
  • the present invention provides a dry anaerobic digester, wherein the biogas generated from the reactor is stored in biogas balloon which is then compressed and sent back to the reactor partially through the gas purging line.
  • the present invention provides a dry anaerobic digester, wherein the digestated liquid accumulated above the perforated plate is collected in the digestate collection tank which is partially utilized as a buffering agent and a diluent in the feed slurry, wherein samples from the sample points (8) can be collected for analysis periodically to check the health of the reactor.
  • the present invention provides a dry anaerobic digester, wherein the elongated conical bottom (9) of the reactor is a place where the maximum solids are retained and the mixing of solids in the cone is ensured through biogas purging, wherein the solids can be drained out using the drain valve (11) as per the need.
  • FIGURE 1 illustrates a sectional view of the reactor in accordance with an embodiment of the present invention.
  • the reactor in accordance with one embodiment of the present invention comprises:
  • the innovation also contains pre and post processing mechanisms/elements such as the feed preparation tank (FPT); Digestate collection tank (DCT); the biogas collection lines connected to the biogas balloon; digestate recirculation ports at the bottom of the reaction and on top of the elongated cone; a compressor, feeding pumps (slurry pumping and recirculation); and a biogas purging line.
  • FPT feed preparation tank
  • DCT Digestate collection tank
  • biogas collection lines connected to the biogas balloon
  • digestate recirculation ports at the bottom of the reaction and on top of the elongated cone
  • a compressor feeding pumps (slurry pumping and recirculation); and a biogas purging line.
  • the innovation is designed primarily for the treatment of lignocellulosic biomass such as rice straw/rice husk with a total solids consistency in the slurry between 20 - 40 %.
  • lignocellulosic biomass such as rice straw/rice husk
  • One of the major obstacles in the AD of lignocellulosic biomass is the formation of scum layer on the top surface of the slurry with the fibrous material leading to choking of pipelines. Scum layer formation occurs due to the phase separation of the material into solid and liquid. Phase separation of solid and liquid occurs particularly in low density materials such as lignocellulosic biomass. Therefore, the reactor is designed in a way that the maximum solids including the fibrous material is retained inside the reactor for efficient digestion.
  • the working of the reactor starts with the preparation of feed slurry of required solids consistency in the FPT, followed by its pumping to the main reactor (1) through the feeding line with an inverted cone that is mounted to the feed hydrolysis duct (2).
  • the feed slurry is initially allowed to flow through the central duct (4) towards the bottom of the reactor which then expands creating an upward flow regime from the bottom due to the presence of a truncated cone (5).
  • the central duct in the reactor acts as a feed hydrolysis duct where the feed slurry gets hydrolysed.
  • the residence time of the feed hydrolysis duct is delinked with the residence time of the main reactor.
  • the perforated truncated cone (6) above the bottom truncated cone ensures the movement of slurry towards up through the perforations while the solid material is retained in the bottom part of the reactor.
  • the bottom truncated cone (7) elongated through the central duct is provided to ensure the retainment of solids and divert the flow from bottom to towards the middle perforated truncated cone (6).
  • the perforated cone consists of perforations with a diameter of 20 mm to ensure the flow of even denser material (15 - 30 % solids) towards up.
  • the pressure build up inside the feed hydrolysis duct stimulates the downward movement of the acidified slurry towards the bottom and the presence of truncated cone directs the flow behaviour regime towards up for further digestion of the organic material.
  • the top truncated cone is provided for the easy movement of the thinner slurry towards the perforated plate.
  • the perforated plate (3) ensures further retainment of solids and allows the liquid to flow towards up which is then withdrawn as the final digestate.
  • a middle perforated truncated cone fixed to the wall of the cylindrical reactor and the top and bottom truncated cones are meant to create turbulence in the reactor disturbing the flow behaviour of the slurry.
  • truncated cones alleviates the issue of scum formation or floating of the fibrous material on the top surface of the slurry.
  • This arrangement of truncated cones creates unique hydrodynamics (flow behaviour from top to bottom and bottom to top) without any mechanical equipment inside the reactor even with materials such as lignocellulosic biomass.
  • the recirculation of the slurry from the bottom ensures the creation of flow regime towards upwards.
  • the pressurized biogas purging further improves the mixing for efficient heat and mass transfer to take place between the substrate and the microorganisms ensuring suitable hydrodynamic behaviour of the thick slurry inside the digester and ensures appropriate mixing.
  • the water sprinklers mounted on the wall of the vertical cylinder is to ensure the periodic sprinkling of water to arrest any foaming that forms on the top of the digested slurry.
  • the presence of truncated cones in the reactor is provided to ensure proper mixing without the provision of any mechanical equipment and to retain maximum solids in the digester to prevent biomass washout.
  • the biogas that is generated from the reactor is stored in biogas balloon which is then compressed and sent back to the reactor partially through the gas purging line.
  • the digestate that gets accumulated on the top of the perforated plate is collected in the digestate collection tank which is partially utilized as a buffering agent and a diluent in the feed slurry.
  • the conical bottom of the innovation is a place where maximum solids are retained and the mixing of solids in the cone is ensured through pressurized biogas purging. Therefore, the innovation is provided with suitable arrangements for the expansion of slurry at the bottom and its flow towards up creating upward flow regime, retention of solids through perforated cone and plate, delinking of residence time of the reactor as well as the feed hydrolysis duct, provision of slurry recirculation and biogas purging mechanism.
  • the reactor constructed in accordance with the teachings of the present invention also includes a feed preparation system with provision to add lignocellulosic biomass to the reactor vessel and arrangement for feeding a calculated quantity of homogenized slurry to the feed tank of dry anaerobic digester (DADUH for LCB).
  • the feed preparation system may be integrated with the reactor or the lignocellulosic biomass with 20 - 40 % solids may be transported from the feed preparation system to the reactor using pumps.
  • the feed preparation system may be of a rectangular/ circular PPFRP / HDPE / RCC construction with suitable capacity depending on feed rate of lignocellulosic biomass and fitted with an air compressor to homogenize the slurry.
  • the feed preparation system in a preferred embodiment has a slanting bottom with bottom discharge to remove the grits.
  • the digested slurry from digester (tank) is collected in gravity settler tank (digestate collection tank).
  • This unit is suitably designed to receive calculated quantity of digested slurry from the digester (tank).
  • the gravity settler can be in the form of a rectangular/ circular tank having suitable volume depending upon feeding rate to the reactor.
  • the gravity settler has supporting structure with top mounted with mesh so that solids are retained on the top whereas liquid is settled to the bottom. The liquid is pumped back (recycled) to feeding system for the preparation of feed slurry along with fresh water.
  • the reactor of the present invention functions as a continuous reactor and everyday known amount of slurry can be fed to the reactor from top controlling the valves of the tank and equal quantity of the digested slurry can be discharged from the top zone of the tank (above perforated plate) to a digestate collection tank.
  • the production of methane can be estimated by methods known in the art. See Ch. 8, Metcalf & Eddy, Inc. (1991).
  • the reactor was operated with lignocellulosic biomass namely rice husk and rice straw for a period of 100 days.
  • the rice husk and rice straw were initially pre-treated for size reduction in a pulveriser machine with a particle size of ⁇ 1mm.
  • the pulverized powder of rice husk and rice straw was used as substrate in the digester for the generation of biogas under dry anaerobic digestion conditions.
  • the total solids in the slurry was varied from 12 % to 20 % followed by 30 and 40 %.
  • the reactor (present innovation) of 70 L volume with an active volume of 50 L was used in the experimental studies. Comparative experimental studies with a conventional slurry digester was also performed.
  • the experiments in the present innovation were performed in batch as well as continuous mode. The examples for continuous mode of operation is given below as reference.
  • the digester was operated in continuous mode (equal amount of feed and digested slurry are fed and withdraw to and from the reactor respectively) and fed with lignocellulosic biomass (rice husk) at (12 % TS concentration) initially at a feed rate of 0.35 L/day at an HRT of 90 days which was gradually reduced to 30 days reaching a feed rate of feed rate of 1 L/day, 2.4 kg TS/m 3 /day, 1.68 kg VS/m 3 /day, and HRT of 30 days.
  • steady VS destruction rate and biogas production was measured.
  • the biogas generation was measured and yields were calculated resulting in 0.3 m 3 /kg VS destroyed at a corresponding CH4 content of 55 % in biogas. Phase separation, choking of pipelines, reactor clogging were the noticeable issues observed when the slurry digester was operated with slurry TS consistency > 12 %.
  • the effective volume of the reactor was 50 L of which the digester was inoculated with anaerobic sludge (40 % of reactors effective volume i.e., 20 L) obtained from a digester treating market vegetable waste.
  • the digester was operated in continuous mode (equal amount of feed and digested slurry are fed and withdraw to and from the reactor respectively) and fed with lignocellulosic biomass (rice husk) at (12 %, 20 %, 30 % and 40 % TS concentration) initially at a feed rate of 0.35 L/day at an HRT of 90 days which was gradually reduced to 30 days reaching a feed rate of feed rate of 1 L/day, 2.4 kg TS/m 3 /day, 1.68 kg VS/m 3 /day, and HRT of 30 days with a slurry of 12 % TS, while the values for 20 %, 30 % and 40 % TS slurry is given in the table below.
  • the effective volume of the reactor was 50 L of which the digester was inoculated with anaerobic sludge (40 % of reactors effective volume i.e., 20 L) obtained from a digester treating market vegetable waste.
  • the digester was operated in continuous mode (equal amount of feed and digested slurry are fed and withdraw to and from the reactor respectively) and fed with lignocellulosic biomass (rice straw) at (12 %, 20 %, 30 % and 40 % TS concentration) initially at a feed rate of 0.35 L/day at an HRT of 90 days which was gradually reduced to 30 days reaching a feed rate of feed rate of 1 L/day, 2.4 kg TS/m 3 /day, 1.68 kg VS/m 3 /day, and HRT of 30 days with a slurry of 12 % TS, while the values for 20 %, 30 % and 40 % TS slurry is given in the table below.
  • anaerobic digester is with unique hydrodynamics for superior biogas generation suitable for lignocellulosic biomass treatment with total solids concentration in the range of 20 - 40 % in the slurry.
  • Middle perforated truncated cones fixed to the wall of the cylindrical reactor and the top and bottom truncated cones are meant to create turbulence in the reactor disturbing the flow behaviour of the slurry, ensure proper mixing of the material inside the digester without any mechanical equipment.
  • the perforated truncated cone above the bottom truncated cone ensures the movement of slurry towards upward flow regime through the perforations (20 mm) while the solid material is retained in the bottom part of the reactor.
  • the bottom truncated cone elongated through the central duct is provided to ensure the retainment of solids and divert the flow from bottom to towards the middle perforated truncated cone.
  • the top truncated cone is provided for the easy movement of the thinner slurry towards the perforated plate.
  • the conical bottom of the reactor is a place where maximum solids are retained and the mixing of solids in the cone is ensured through pressurized biogas purging.
  • the perforated plate ensures further retainment of solids and allows the liquid to flow towards up which is then withdrawn as the final digestate.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Molecular Biology (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Chemistry (AREA)
  • Processing Of Solid Wastes (AREA)

Abstract

La présente invention propose un réacteur pour la digestion anaérobie de la biomasse lignocellulosique en vue de la production de biogaz et de biofumier (digestat). Cette innovation est conçue principalement pour le traitement de biomasse lignocellulosique telle que de la paille ou des balles de riz, avec une teneur totale en solides dans la suspension fibreuse comprise entre 20 et 40 %. L'un des principaux obstacles à la digestion anaérobie de la biomasse lignocellulosique est la formation d'une couche d'écume sur la surface supérieure de la suspension fibreuse constituée de matières fibreuses, ce qui entraîne le colmatage des canalisations. La formation d'une couche d'écume est due à la séparation des phases solide et liquide de la matière, à un mauvais contact entre la matière organique et les micro-organismes, ainsi qu'à un faible transfert de chaleur et de masse. La séparation des phases solide et liquide se produit en particulier dans les matériaux de faible densité tels que la biomasse lignocellulosique. Par conséquent, le réacteur est conçu de manière à ce que le maximum de solides, y compris la matière fibreuse, soit retenu à l'intérieur du réacteur pour une digestion efficace. Le réacteur comprend une conduite d'hydrolyse d'alimentation situé à l'intérieur du réacteur. Le temps de séjour hydraulique dans la conduite d'hydrolyse d'alimentation est dissocié de celui du réacteur principal. En outre, le réacteur est doté de cônes perforés ouverts et fermés afin d'assurer un mouvement efficace de la suspension fibreuse du haut vers le bas. La purge du biogaz sous pression dans la zone du cône allongé au bas du réacteur garantit l'absence de sédimentation des solides dans le cône, tandis que la recirculation de la suspension fibreuse et la purge du biogaz sous pression à l'intérieur du digesteur favorisent un mélange efficace du contenu du réacteur dans le digesteur, empêchant la formation d'une séparation de phase, d'une couche d'écume, d'un colmatage, etc. La suspension fibreuse d'alimentation est d'abord autorisée à s'écouler à travers le conduit central vers le bas du réacteur, qui se dilate ensuite en créant un régime d'écoulement ascendant à partir du bas en raison de la présence d'un cône tronqué. Des cônes tronqués perforés assurent la rétention d'un maximum de solides dans le réacteur, empêchant ainsi tout lessivage de la biomasse. Le réacteur est également équipé d'un système de préparation d'alimentation, d'un réservoir de collecte de digestat, d'un ballon de biogaz, d'un mécanisme de vanne d'entrée d'alimentation et de sortie du digestat pour réguler l'alimentation et la sortie du digestat.
EP24766634.0A 2023-03-07 2024-02-09 Digesteur anaérobie sec pour biomasse lignocellulosique à hydrodynamique unique (dad pour biomasse lignocellulosique) Pending EP4676892A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IN202311015544 2023-03-07
PCT/IN2024/050133 WO2024184908A1 (fr) 2023-03-07 2024-02-09 Digesteur anaérobie sec pour biomasse lignocellulosique à hydrodynamique unique (daduh pour biomasse lignocellulosique)

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EP4676892A1 true EP4676892A1 (fr) 2026-01-14

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EP24766634.0A Pending EP4676892A1 (fr) 2023-03-07 2024-02-09 Digesteur anaérobie sec pour biomasse lignocellulosique à hydrodynamique unique (dad pour biomasse lignocellulosique)

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EP (1) EP4676892A1 (fr)
WO (1) WO2024184908A1 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6730223B1 (en) * 2002-11-01 2004-05-04 Comprehensive Resources, Recovery & Reuse, Inc. Apparatus, system and method for treating waste material

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