Classifications

• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
  • C12M21/00—Bioreactors or fermenters specially adapted for specific uses
  • C12M21/04—Bioreactors or fermenters specially adapted for specific uses for producing gas, e.g. biogas
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F9/00—Multistage treatment of water, waste water or sewage
• • C—CHEMISTRY; METALLURGY
  • C05—FERTILISERS; MANUFACTURE THEREOF
  • C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
  • C05F17/00—Preparation of fertilisers characterised by biological or biochemical treatment steps, e.g. composting or fermentation
  • C05F17/60—Heating or cooling during the treatment
• • C—CHEMISTRY; METALLURGY
  • C05—FERTILISERS; MANUFACTURE THEREOF
  • C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
  • C05F17/00—Preparation of fertilisers characterised by biological or biochemical treatment steps, e.g. composting or fermentation
  • C05F17/80—Separation, elimination or disposal of harmful substances during the treatment
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
  • C12P5/00—Preparation of hydrocarbons or halogenated hydrocarbons
  • C12P5/02—Preparation of hydrocarbons or halogenated hydrocarbons acyclic
  • C12P5/023—Methane
• • 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
  • C02F11/00—Treatment of sludge; Devices therefor
  • C02F11/10—Treatment of sludge; Devices therefor by pyrolysis
• • 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
  • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
  • C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
• • 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
  • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
  • C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
  • C02F11/127—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering by centrifugation
• • 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
  • C02F11/18—Treatment of sludge; Devices therefor by thermal conditioning
  • C02F11/185—Treatment of sludge; Devices therefor by thermal conditioning by pasteurisation
• • 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 the field of waste and effluent treatment, and in particular to a method and system for the production of biogas, including the sanitization ("hygienization") of pathogen-containing digestate formed in said production of biogas and originating from the feedstock.
• Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is generally carried out in four stages: hydrolysis; fermentation and acidification; acetogenesis, and methanogenesis. During these four stages, the organic matter in the waste and wastewaters is transformed to biogas, a mix of methane (CH4) and carbon dioxide (CO2) and a nutrient rich sludge (digestate) .
• the raw biogas can be used directly as fuel or upgraded to natural gas-quality biomethane.
• the raw or upgraded biogas can be utilized in combined heat and power gas engines; it has therefore a large potential as a renewable energy source.
• the nutrient-rich digestate can be composted and used as fertilising soil amendment in agriculture. Thus, anaerobic digestion can be used for industrial or domestic purposes to manage waste and to produce fuels .
• Anaerobic digesters can be designed and engineered to operate using a number of different configurations and can be categorized into batch vs. continuous process mode, mesophilic vs. thermophilic temperature conditions, high vs. low portion of solids, and single stage vs. multistage processes.
• Important digester parameters include temperature, pH, f eedstock-to- microorganism ratio, organic loading rate, hydraulic and solids retention time, adequate mixing, and others.
• Temperature is one of the most important parameters influencing the performance of anaerobic digestion processes. Depending on the temperature, the following types of digestion are distinguished: psychrophilic digestion (10-20°C) ; mesophilic digestion (20-45°C) ; and thermophilic digestion (50-70°C) .
• the conventional operational temperature levels for anaerobic digesters are mesophilic and thermophilic.
• thermophilic AD processes have been shown to produce more biogas in a shorter time and to achieve good hygienization of the waste feedstock by reducing several indicator organisms, including Escherichia coii and Salmonella, and by inactivating plant seeds in the resulting digestate.
• the digestate is to be used as a fertilizer, it generally needs to be hygienized, meaning that pathogenic microorganisms are removed from the digestate.
• Temperatures above 50°C for the digestion is one effective way to achieve hygienization.
• thermophilic conditions require significantly higher energy input and thus increase operational costs. Further, at higher temperature, not only methane production can be increased but also the generation of free ammonia, which can have an inhibitory effect on the digestion performance.
• mesophilic systems are preferable in view of reduced energy consumption and operational costs, but they come with the drawbacks of lower biogas production and lack of hygienization (compared to thermophilic systems) .
• hygienization may be achieved by either specific hygienization treatments, e.g. pasteurization, a prolonged residence time within the digester, e.g. 15 days and longer, and/or high pH.
• EP3150569A1 discloses a method for producing a fertilisation product from anaerobic digestate by pasteurization of the digestate in specific tanks, in which the digestate is heat treated at a temperature of from 70°C to 80°C. This temperature is chosen to ensure killing of harmful microorganisms while minimizing the degradation of organic materials in the digestate. Thus, specific equipment and treatment conditions are required exclusively to achieve hygienization.
• the pH within the fermenter can be increased e.g. by the addition of lime, caustic soda, ammonia, or urea.
• the recommendation for high pH treatment of sewage products requires pH 12 for at least 3 months. However, it was found that microbial activity tends to decrease at high pH levels. When ammonia is present, lower pH and shorter treatment times may suffice. At the same time, the use of ammonia creates an environmental issue and constitutes an occupational hazard.
• the problem solved by the present invention is thus to provide a method and a system for efficient conversion of biomass into biogas by anaerobic digestion at a reduced input of energy and chemicals and which achieves effective and economical hygienization of the resulting digestate .
• the thermal treatment step includes treatment of the digestate by hydrothermal carbonization for a treatment time of at least 30 minutes, preferably at least one hour, more preferably at least 2 hours, in particular 2-5 hours. While one minute heat treatment has been found to be effective for hygienization purposes, treating the digestate by hydrothermal carbonization for at least 2 hours allows effective conversion of the digestate into valuable products, such as high quality fuel.
• the temperature for hydrothermal carbonization is preferably within the range of 175°C to 350°C, more preferably 175°C to 280°C.
• Hydrothermal carbonization has the benefit that it allows treatment of digestate with various moisture contents without pre-drying, which saves energy and costs for drying before processing. Thus, it is possible to treat digestate directly out of the digester or either or both of liquid and solid digestate fractions.
• the method may additionally include a step of condensing steam and vaporized compounds from the digestate with the aid of a condensing system that may involve passing the vapor through a series of cooled pipes or surfaces. As the vapor cools, the water and some of the organic compounds condense back into the liquid phase. This liquid, known as the condensate, is then collected. It may require further treatment to separate water from other condensed organic compounds, depending on its intended use or disposal requirements.
• the condensing system includes a multistage vacuum system that is designed to efficiently condense and separate various components from the vaporized compounds under reduced pressure, with the goal of producing a clean condensate, e.g. for use in industrial processes or for disposal with minimal environmental impact.
• the thermal treatment step is carried out at ambient pressure. This reduces the construction and operational costs.
• the pH within the digester is kept below 12. While it has been suggested in the prior art to increase the pH within the digester over 12 to achieve hygieni zation, the method of the present invention does not require such measures .
• the present invention provides a system for the hygieni zation of a digestate in the production of a biogas .
• Said system includes
• an anaerobic digester configured to produce methane- containing biogas and a digestate through anaerobic digestion of organic biomass through microorganisms in the absence of oxygen, the anaerobic digester comprising an inlet for receiving organic biomass , a first outlet for discharging a biogas , a second outlet for discharging a digestate , and a temperature controller to keep the temperature within the digester below 50 ° C ;
• the particle si ze of said organic biomass Prior to feeding the organic biomass into the anaerobic digester, the particle si ze of said organic biomass can be reduced by e . g . shredding, grinding or sieving . Reducing the particle si ze of the organic biomass will lead to a decreased viscosity of the digestate . This reduces the energy consumption and the wear on any agitator or mixing device installed within the digester for mixing or transporting the digestate within the digester .
• the digester is a dry or semi-dry digester operated in plug flow mode .
• There are two main types o f anaerobic digestion processes for treatment of biodegradable wastes namely "wet anaerobic digestion systems” , which use organic material with consistency of 10-20% dry matter or less , and “dry ( or semi-dry) anaerobic digestion systems” for organic matter with consistency of 20 to 40% dry matter or more .
• Digestate with a dry matter content of at least 20% is generally preferred as the solid fraction of the digestate can be converted into valuable product , such as fuel or char .
• I f the digestate has a high viscosity ( i . e . reduced water content )
• plug flow digesters have a higher speci fic throughput capacity compared to stirred digesters .
• Heat energy from the thermal treatment unit can be used for drying any of the solid and liquid digestate fractions or for heating the digester .
• the heat treatment reactor is preferably a reactor selected from the group consisting of pyrolysis reactor, a gasi fication reactor, torrefaction reactor, hydrothermal gasification reactor, hydrothermal liquefaction reactor and hydrothermal carbonization reactor.
• the system further includes a sanitizer; heat transfer means for transferring heat energy liberated from the heat treatment reactor to the sanitizer; and means for supplying at least part of the liquid digestate fraction to the sanitizer.
• the sanitizer is intended for heat treatment of the liquid digestate to achieve hygienization of the latter.
• direct process heat integration can be used to directly transfer (waste) heat from the heat treatment reactor to the sanitizer using a heat exchanger or other common means for heat recovery, such as economizers and waste heat boilers.
• the biogas treatment unit is an amine upgrader .
• An amine upgrader typically involves amine gas treating, which removes carbon dioxide , hydrogen sul fide , water, and other contaminants from biogas . It involves the chemical absorption of these gases by aqueous solutions of amines . The gas is passed through a solution where the impurities react with the amine , forming a non-volatile compound that can be separated . The cleaned gas , now with reduced levels of CO2 and H2S , can be used for further applications , and the amine solution can be regenerated for reuse by heating to release the absorbed gases .
• the system employs heat integration between the heat treatment reactor and the biogas treatment unit .
• waste heat from the heat treatment reactor can be directly trans ferred to the biogas treatment unit or it may be converted into electrical power through e . g . the Rankine cycle or a micro gas turbine .
• heat energy liberated from the heat treatment reactor can be used for the regeneration of the amine solution by directly trans ferring it to the amine upgrader .
• FIG. 1 is a flow diagram showing the steps of a preferred embodiment of the inventive system .
• Fig . 1 shows the components of a system for the hygieni zation of a digestate in the production of a biogas in accordance with the present invention .
• Said system includes an anaerobic digester 10 configured to produce methane-containing biogas 12 and a digestate 14 through anaerobic digestion of organic biomass 16 through microorganisms in the absence of oxygen .
• the organic biomass 16 can be a variety of usually carbon-rich materials , such as urban wood waste , paper waste , cow manure , food waste , agricultural waste , etc .
• the anaerobic digester 10 comprises an inlet for receiving the organic biomass , an outlet for discharging digestate , and a temperature controller to keep the temperature within the digester 10 below 50 ° C, speci fically in the range of 40 ° C to 48 ° C .
• the residence time of the organic biomass 16 within the anaerobic digester 10 is preferably 10 to 12 days .
• the digester is a plug- flow digester and may include agitators to aid mixing of the digestate within .
• the system further includes trans fer or transportation means for supplying at least part of the digestate 14 that is discharged from the digester 10 to a dewatering device 20 .
• the dewatering device 20 is in this case a screw press that separates the digestate 14 from the digester 10 into a solid digestate fraction 22 and a liquid digestate fraction 24 .
• the solid digestate fraction 22 is supplied to a heat treatment reactor 30, e.g. through transfer pipes connecting the dewatering device 20 and the heat treatment reactor 30.
• the heat treatment reactor 30 is configured to heat the solid digestate fraction 22 to a temperature of at least 175°C.
• the heat treatment reactor can be a pyrolysis reactor, a gasification reactor, torrefaction reactor, hydrothermal gasification reactor, hydrothermal liquefaction reactor or hydrothermal carbonization reactor.
• it is a pyrolysis reactor 30 (also called gasifier) .
• the solid digestate fraction 22 is heated to at least 450°C for a few minutes, during which the solid digestate fraction is converted into a synthesis gas (syngas 32) and biochar 34.
• the syngas 32 can be burned directly in gas engines, cooled to extract pyrolysis oil, used to produce methanol and hydrogen, or converted via the Fischer-Tropsch process into synthetic fuel.
• the pyrolysis reactor 30 is a directly heated pyrolysis reactor, specifically one that applies heat directly to the material, rather than being conducted through a surface such as a reactor wall.
• Heat liberated during the heat treatment of the solid digestate fraction 22 and also heat from syngas 32 is recovered with the aid of heat exchangers.
• the recovered heat 35 is transferred to a sanitizer 36.
• the liquid digestate fraction 24 is collected and some of it is used for humidification of the digester feedstock, meaning that some of the liquid digestate fraction is returned to the digester 10 for increasing the moisture content of the organic biomass 16 within the digester 10. This adjustment of the moisture content and thus the viscosity of the digestate within the digester avoids excessive energy consumption for mixing or agitating the digestate and also reduces the wear on the mixing/agitation means.
• the remaining part of the liquid digestate fraction 24 is transferred to the sanitizer 36 and is heat-treated therein for a duration of at least 1 hour at at least 70°C.
• the two digestate fractions 22, 24 are thus both heat-treated, but independently from one another, in different units and for different durations.
• the treatment of the liquid digestate fraction 24 can thus occur simultaneously to the treatment of the solid digestate fraction 22. Thanks to the heat treatment in the sanitizer 36, the liquid digestate 24 is hygienized, meaning that any pathogens other harmful organisms are effectively killed or at least deactivated.
• the treated liquid digestate 24 is released from the sanitizer 36 and can be used, for example, as fertilizer.
• the system may further include an evaporator (not shown) for condensing the liquid digestate.
• an evaporator is preferably also provided with heat energy recovered from the thermal treatment of the solid digestate fraction and/or the syngas.

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• Chemical & Material Sciences (AREA)
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• Molecular Biology (AREA)
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• Microbiology (AREA)
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• Bioinformatics & Cheminformatics (AREA)
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• Environmental & Geological Engineering (AREA)
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• Oil, Petroleum & Natural Gas (AREA)
• Biomedical Technology (AREA)
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• Processing Of Solid Wastes (AREA)
• Treatment Of Sludge (AREA)

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• 2024
  • 2024-05-30 WO PCT/EP2024/064961 patent/WO2024246243A1/en not_active Ceased
  • 2024-05-30 AU AU2024283142A patent/AU2024283142A1/en active Pending
  • 2024-05-30 EP EP24730945.3A patent/EP4720249A1/de active Pending

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