WO2025238599A2 - Appareil et procédé d'utilisation efficace d'une biomasse par fermentation anaérobie - Google Patents

Appareil et procédé d'utilisation efficace d'une biomasse par fermentation anaérobie

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WO2025238599A2
WO2025238599A2 PCT/IB2025/055094 IB2025055094W WO2025238599A2 WO 2025238599 A2 WO2025238599 A2 WO 2025238599A2 IB 2025055094 W IB2025055094 W IB 2025055094W WO 2025238599 A2 WO2025238599 A2 WO 2025238599A2
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aqueous solution
fermentation medium
ion
separation unit
chambers
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WO2025238599A3 (fr
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Leo-Nicolas GRAB
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    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
    • B01D61/428—Membrane capacitive deionization
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
    • B01D61/44—Ion-selective electrodialysis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/005—Combined electrochemical biological processes
    • 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
    • C12M29/00—Means for introduction, extraction or recirculation of materials, e.g. pumps
    • C12M29/04—Filters; Permeable or porous membranes or plates, e.g. dialysis
    • 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
    • C12M29/00—Means for introduction, extraction or recirculation of materials, e.g. pumps
    • C12M29/18—External loop; Means for reintroduction of fermented biomass or liquid percolate
    • 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
    • C12M29/00—Means for introduction, extraction or recirculation of materials, e.g. pumps
    • C12M29/26—Conditioning fluids entering or exiting the reaction vessel
    • 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
    • C12M47/00—Means for after-treatment of the produced biomass or of the fermentation or metabolic products, e.g. storage of biomass
    • C12M47/10—Separation or concentration of fermentation products
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/26—Further operations combined with membrane separation processes
    • B01D2311/2688—Biological processes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
    • C02F1/4693—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
    • C02F1/4693—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis
    • C02F1/4695—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis electrodeionisation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/28—Anaerobic digestion processes

Definitions

  • the invention relates to apparatuses and processes for the efficient utilization of biomass by anaerobic fermentation for the production of gaseous fuel, fertilizer and solid fuel.
  • Plant biomass (called biomass in the context of this description) presents a valuable source for the production of carbon dioxide neutral electricity, heat and fuels.
  • biomass dry weight biomass
  • Utilization of plant biomass can be achieved by anaerobic fermentation of the biomass, thereby producing biogas (methane and other components). Methane as a chemical energy carrier can then subsequently be used as a gaseous fuel for various purposes, including the production of electricity.
  • Biogas can be produced from biodegradable material such as e.g. biodegradable municipal waste, waste plant material, animal waste such as manure, sewage, paper waste, food waste etc. It may, however, also be produced from biomass produced particularly for this purpose. While utilization of biomass is partially restrained by environmental issues like the conservation of humus (the organic matter in the ground) and the protection of natural habitats, there is also a lack of economically viable and efficient technologies, which greatly hinders a mobilization of a major part of this potential.
  • biomass is highly inhomogeneous and comprises a complex mixture of various compounds, such as cellulose, sugars, proteins and fats, which contain a variety of elements in differing amounts.
  • the main constituents of all organic matter are carbon (C), oxygen (O) and hydrogen (H), as well as considerably smaller amounts of nitrogen (N) and sulfur (S), present mainly in amino acids.
  • plants comprise other elements such as potassium (K), calcium (Ca), magnesium (Mg), phosphorus (P) and chlorine (Cl).
  • K potassium
  • Ca calcium
  • Mg magnesium
  • P phosphorus
  • Cl chlorine
  • Their specific concentrations (g per kg dry weight) greatly vary between different species (e.g., wheat straw contains up to 15 g potassium per kg dry mass compared to 35 g/kg dry mass for normal grass vegetation). This high degree of inhomogeneity, both in constituent elements and their concentration, makes it difficult to find a single process applicable to all kinds of biomass.
  • thermal processes convert the nitrogen and sulfur contained within its fuel into nitroxides (NO X ) as well as sulfuric oxides (SO X ), which are major air pollutants.
  • NO X nitroxides
  • SO X sulfuric oxides
  • wood contains very little of these two elements (0.03 - 0.1 %w/w dry mass N and 0.01 - 0.05 %w/w dry mass S, in contrast to 1-5 %w/w dry mass N and 0.2 - 0.5 %w/w dry mass S in grass vegetation).
  • almost all other kinds of biomass contain much more of these two elements, therefore necessitating extensive cleaning of the exhaust gas, which reduces the profitability of the entire process.
  • both potassium and chlorine cause major problems (again wood being an exception).
  • Many potassium compounds possess a melting temperature below 800 °C, which means that ashes with high potassium content start melting during combustion, leading to slag buildup and potential failure of the ash removal system.
  • both potassium and chlorine lead to corrosion on parts which are in contact with the exhaust gas (such as heat exchanger and pipes), increased particle emissions via formation of KCI and KSO4 as well as HCI-emissions [Ref-02],
  • Biogas is produced by anaerobic organisms such as methanogens and sulfur-reducing bacteria, in a multi-step fermentation process called anaerobic digestion or anaerobic fermentation.
  • anaerobic digestion or anaerobic fermentation A short overview of the processes involved is provided in WO 2019/166694 A1 (cf. Figure 1).
  • Biogas primarily consists of methane CH4 and carbon dioxide CO2. It may also comprise further compounds in lower quantities such as hydrogen sulfide H2S, water vapor H2O, hydrogen H2, ammonia NH3, nitrogen N2 and oxygen O2.
  • biogas can be produced in bioreactors called anaerobic digesters or anaerobic fermenters, in which biodegradable material is processed in an anaerobic environment.
  • bioreactors called anaerobic digesters or anaerobic fermenters, in which biodegradable material is processed in an anaerobic environment.
  • Various such installations are known from the state of the art, which are optimized for the characteristics of the type of biomass with which they should operate.
  • wet waste fractions such as wastewater sludge and animal manure
  • processing preferably takes place in completely stirred vertical cylindrical tank reactors at a low dry matter content (most often ⁇ 10 %w/w).
  • the input biomass has to be diluted with a liquid. While it possible to recirculate such liquid back to the reactor; side products of the fermentation process that accumulate in the recirculated liquid that show an inhibiting effect on the fermentation process.
  • Reactors that are optimized for drier biomass compositions often use the so-called plugflow principle, in which biomass is fed into a horizontal tank reactor from one end of the reactor, and the processed material is removed from the other end of the reactor. During the fermentation processing, the biomass material passes through the horizontal reactor based on a plug-type flow.
  • Such reactors operated on the plug-flow principle can be operated at higher dry content (e.g. a dry matter content of 10-30 %w/w).
  • US 5601720 shows an example of a fermentation installation with passive conveying of the biomass through the horizontal reactor.
  • US 2008/0138888 A1 , WO 2015/075298 A1, and WO 2019/115862 A1 disclose examples of fermentation installations using actuators for conveying of the biomass through the horizontal reactor.
  • WO 2019/166694 A1 shows a variant of such a fermentation installation with a vertical reactor with separate compartments through which the biomass is conveyed gravitationally.
  • biogas as a fuel, for example in internal combustion engines, heating or cooking facilities, or fuel cells, methane is the primary carrier of chemical energy, seconded by hydrogen.
  • Inert compounds such as carbon dioxide decrease the calorific value of the biogas and thus may be removed in the production process.
  • Impurities such as hydrogen sulfide or ammonia should be removed to avoid the formation of pollutants such as sulfur oxides (SO X ) and nitrogen oxides (NO X ) in a subsequent combustion process.
  • Anaerobic digestion can be inhibited by certain compounds, by negatively affecting the activity of one or more of the groups of microorganisms responsible for the different steps of organic matter degradation.
  • the degree of inhibition depends on the concentration of the inhibitor compound in the anaerobic digester.
  • Potential inhibitors are e.g. ammonium ions, sulfide ions, and metal ions such as Na, K, Mg, Ca, which form during the degradation of the various organic compounds such as proteins, or a present in the biological material.
  • Anaerobic digestion by microorganisms is not as susceptible to moderate concentrations of ions such as K + , Na + , Ca 2+ , Mg 2+ , since the microorganisms themselves need them in order to grow and function.
  • K + is highly inhibitory to anaerobic bacteria at concentrations > 12 g/L.
  • Methanogens are strongly inhibited during these processes by high levels of ammonia [Ref-03], which renders e.g. the utilization of chicken manure and other substrates high in nitrogen very difficult.
  • the lignin ends up in the fermentation residues, which are often used as compost fertilizer that can be spread on fields. Up to 20% of the lignin becomes part of the humus, and the rest is digested by aerobic microorganisms.
  • fermentation residues provide nutrients and organic matter to the ground, they do so in a very inefficient way.
  • the distribution as fertilizer requires a large amount of logistics and infrastructure, which is expensive and consumes a lot of time and fuel, thus posing a great problem especially to farmers in poorer regions. Due to this, the transportation distances have to be chosen as small as possible, which often leads to these residues simply being disposed of on the next-best field.
  • such fermentation residues fertilizer has a nutrient concentration, typically only 1 %w/w. As a result, such fertilizer is not very profitable, which also reduces the profitability of biomass based energy production.
  • a vibrating, water-cooled grate can be used in order to keep the melting ash from sticking to it and thus clogging the ash removal system. Furthermore, some of the exhaust gas is recirculated into the combustion chamber for the purpose of lowering the temperature within [Ref-04],
  • grate firing technologies in general suffer from low efficiency [Ref-05] compared to the direct combustion of coal dust used in coal burners, which is even further aggravated by the lower combustion temperature.
  • the addition of a vibrating mechanism and water-cooling also significantly increases the capital and operational cost. Considering that, so far, this technology is only viable for burning relatively “high quality” biomass such as wheat straw and miscan- thus, which contain comparatively little nitrogen, potassium and chloride.
  • Mechanical pretreatment consists of milling, extruding and hammering of the raw biomass in order to decrease the average particle size and increase its surface area and thus accessibility by microorganisms. This boosts the biological degradation and biogas production. At the same time, however, these methods consume a lot of energy and only lead to a very small net positive energy generation. Therefore, considering the interest rate, maintenance and write-off, the additional investment in usually not profitable [Ref- 06],
  • the raw biomass is mixed with water and put into a pressure vessel, where it is heated to 140-180 °C for 10-120 minutes. Afterwards, the pressure is suddenly released, thus leading to a “steam explosion”, which further opens up the biomass structure, increasing its biological accessibility. While this process does not require a lot of electricity, it does consume a lot of heat which does get expensive if there is not enough inexpensive waste heat from the biogas electrification. Furthermore, it requires a lot of expensive infrastructure and is difficult to automate [Ref-07],
  • Chemical pretreatment [Ref-08] and biological pretreatment [Ref-09] aims at a depolymerization of the biomass fibers, which increases their anaerobic digestibility. This is achieved by treating the biomass with strong acids and bases such as H2SO4, HCI and NaOH (chemical pretreatment), or with white rot fungi, which are even capable of breaking down the lignin with the help of specialized enzymes (biological pretreatment).
  • chemical pretreatment involves the use of dangerous chemicals and expensive process infrastructure.
  • the white rot fungi used in biological pretreatment consume a part of the energy contained within the biomass, thus again lowering the overall energy efficiency.
  • medium and ‘liquid medium’ are used synonymously, and in particular include aqueous solutions such as the fermentation medium.
  • a first aspect of the invention concerns a device for modifying the liquid fermentation medium in an anaerobic fermentation bioreactor.
  • the device further comprises means for retrieving an aqueous solution in the form of liquid filtered fermentation medium from a liquid fermentation medium in an anaerobic fermentation bioreactor and feeding said aqueous solution as the first input stream to the first ion separation unit; and means for returning the first output stream of the first ion separation unit as a modified liquid fermentation medium to an anaerobic fermentation bioreactor.
  • the anaerobic digestion of the liquid fermentation medium takes place in a fermentation bioreactor.
  • the fermentation substrate to be digested comprises solid components, as well as a liquid fermentation medium, which is essentially an aqueous solution comprising solved organic and inorganic compounds, potentially in combination with amounts of lipophilic compounds such as liquid fatty substances.
  • the resulting liquid modified fermentation medium has a decreased concentration of ions.
  • ions such as K + , Na + , Ca 2+ , Mg 2+ in the liquid aqueous medium below a certain threshold, where the ions do not have a detrimental physiological effect on the various microbes that are involved in anaerobic digestion.
  • gaseous fuel i.e. biogas
  • the amount of K + and Cl- ions in the liquid fermentation medium, and thus also the overall fermentation substrate, can be minimized, which leads to a minimal overall content of potassium and chlorine in the resulting fermentation residue.
  • This increases the melting temperature of ashes resulting from combustion of said fermentation residues and thus simplifies the thermal utilization of the fermentation residues as solid fuel.
  • the corrosive properties of combustion exhaust gases are reduced, as well as the emission of fine particulate matter and HCI.
  • compounds comprising sulfur or nitrogen such as e.g. H2S or NH3, and others, can be continuously removed from the liquid fermentation medium, namely in their ionized form, such as SO 2- , HS _ and NH 4 + . This allows minimizing the emission of nitroxides (NO X ) and sulfuric oxides (SO X ) in the exhaust gases. As a result, the fermentation residue becomes a more valuable solid fuel.
  • the aqueous solution with increased ion content in comparison to the liquid filtered fermentation medium, as it can be produced with a liquid fermentation medium modification device according to the invention, can also be further utilized.
  • this aqueous solution with higher ion concentration can be used e.g. as a source material for producing liquid or solid fertilizer products.
  • means are provided for increasing the temperature of the aqueous solutions in the device.
  • one or more of the input streams of aqueous solution can be heated by a heating element and/or a heat exchanger.
  • the first ion separation unit is realized as a dialysis apparatus.
  • the dialysis apparatus of the first ion separation unit comprises an dialysis stack with alternatingly arranged multiple first chambers and multiple second chambers, which are separated by semipermeable membranes; wherein the first input stream of aqueous solution is fed to the multiple first chambers, and the second input stream of aqueous solution is fed to the multiple second chambers; and wherein a combined outflow of the multiple first chambers forms the first output stream of aqueous solution, and a combined outflow of the multiple second chambers forms the second output stream of aqueous solution.
  • Dialysis is generally believed in the state of the art to be a slow and unselective process. However, surprisingly it has been found that dialysis is nevertheless a very advantageous method for reducing the ion content of a fermentation medium, in particular due to insensitivity to fouling.
  • the semipermeable membranes used in the ion separation unit are hy- drophilically coated polypropylene (PP) membranes, as they are for example used as battery separators for lithium ion batteries.
  • PP polypropylene
  • Such membranes may have a thickness of 15-25 pm.
  • Such membranes can be equipped with a hydrophilic surface treatment and a ceramic coating, such as TiC>2, SiC>2 or AI2O3.
  • Such membranes are inexpensive, robust and easily cleanable.
  • One advantage of such an ion separation unit is its insusceptibility to fouling caused by organic contents of the incoming aqueous solution, which in particular can be the filtered fermentation medium coming from the filtration unit. Because there is no external driving force for the osmosis across the membranes, clogging and deposition of residues on the membranes is almost completely avoided.
  • a polypropylene membrane having a surface coating comprising SiC>2 nanoparticles with a diameter of 10-15 nm and a polyacrylic acid/poly vinyl alcohol binder is particularly advantageous in regard to hydrophilicity, high fouling resistance, robustness even at high temperatures (up to 120 °C), and longevity.
  • the first ion separation unit is realized as an electrodialysis apparatus.
  • Electrodialysis allows the transport of salt ions from one solution through ion-exchange membranes to another solution under the influence of an applied electric potential difference in an electrodialysis cell.
  • An electrodialysis cell consists of a dilute compartment and a concentrate compartment formed by an anion exchange membrane (AEM) and a cation exchange membrane (CEM) placed between two electrodes.
  • AEM anion exchange membrane
  • CEM cation exchange membrane
  • multiple electrodialysis cells are arranged to an electrodialysis stack, in which alternat- ingly arranged anion-exchange membranes and cation-exchange membranes form stacked multiple electrodialysis cells.
  • the electrodialysis process is advantageously run in a continuous manner, in which the first input stream continuously flows into the electrodialysis cell stack, where it acts as the dilute, and leaves as the first output stream, while second input stream continuously flows into the electrodialysis cell stack, where it acts as the concentrate, and leaves as the second output stream.
  • Electrodialysis is particularly efficient for aqueous solutions with moderate ion concentrations.
  • the electrodialysis apparatus of the first ion separation unit comprises an electrodialysis stack with alternatingly arranged multiple first chambers and multiple second chambers, which are alternatingly separated by low-pressure ultra-filtration membranes and cation exchange membranes; and means for applying a voltage across the electrodialysis stack; wherein the first input stream of aqueous solution is fed to the multiple first chambers, and the second input stream of aqueous solution is fed to the multiple second chambers; and wherein a combined outflow of the multiple first chambers forms the first output stream of aqueous solution, and a combined outflow of the multiple second chambers forms the second output stream of aqueous solution.
  • the electrodialysis apparatus of the first ion separation unit comprises an electrodialysis stack with alternatingly arranged multiple first chambers and multiple second chambers, which are alternatingly separated by anion exchange membranes and cation exchange membranes and means for applying a voltage across the electrodialysis stack; wherein the first input stream of aqueous solution is fed to the multiple first chambers, and the second input stream of aqueous solution is fed to the multiple second chambers; and wherein a combined outflow of the multiple first chambers forms the first output stream of aqueous solution, and a combined outflow of the multiple second chambers forms the second output stream of aqueous solution.
  • the first ion separation unit is realized as a capacitive deionization apparatus according to the invention, as discussed further below.
  • a liquid fermentation medium modification device comprises a second ion separation unit that is configured to receive a first input stream of aqueous solution and a second input stream of aqueous solution, and to transfer ions from said first input stream to said second input stream, thereby forming a first output stream of aqueous solution with decreased ion content in comparison to the first input stream and a second output stream with increased ion content in comparison to the second input stream; wherein the first ion separation unit and the second ion separation unit are fluidly connected in such a way that the second output stream of aqueous solution of the first ion separation unit and the first output stream of aqueous solution of the second ion separation unit are mixed and are used as the second input stream of the first ion separation unit and as both the first input stream and the second input stream of the second ion separation unit.
  • Such a liquid fermentation medium modification device with two stages of ion separation allows to achieve higher concentration of ions in the resulting concentrated aqueous solution.
  • ion separation devices that are most suitable can be used.
  • a dialysis-stack based ion separation unit can be used as a first ion separation unit, because it is particularly insensitive to membrane fouling, and a capacitive-deionization based ion separation unit can be used as the second ion separation unit for efficient concentration of the ion load in the resulting aqueous solution.
  • such a liquid fermentation medium modification device comprises an intermediate concentration solution tank, wherein the mixing of the second output stream of the first ion separation unit and the first output stream of the second ion separation unit takes place in said intermediate concentration solution tank.
  • the second ion separation unit is advantageously realized as an electrodialysis apparatus.
  • the electrodialysis apparatus of the second ion separation unit comprises an electrodialysis stack with alternatingly arranged multiple first chambers and multiple second chambers, which are alternatingly separated by low-pressure ultra-filtration membranes and cation exchange membranes; and means for applying a voltage across the electrodialysis stack; wherein the first input stream of aqueous solution is fed to the multiple first chambers, and the second input stream of aqueous solution is fed to the multiple second chambers; and wherein a combined outflow of the multiple first chambers forms the first output stream of aqueous solution, and a combined outflow of the multiple second chambers forms the second output stream of aqueous solution.
  • the electrodialysis apparatus of the second ion separation unit comprises an electrodialysis stack with alternatingly arranged multiple first chambers and multiple second chambers, which are alternatingly separated by anion exchange membranes and cation exchange membranes and means for applying a voltage across the electrodialysis stack; wherein the first input stream of aqueous solution is fed to the multiple first chambers, and the second input stream of aqueous solution is fed to the multiple second chambers; and wherein a combined outflow of the multiple first chambers forms the first output stream of aqueous solution, and a combined outflow of the multiple second chambers forms the second output stream of aqueous solution.
  • the second ion separation unit is advantageously realized as a capacitive deionization apparatus according to the invention, as discussed further below.
  • a modification device comprises a filtration unit that is configured to be fluidly coupled to an anaerobic fermentation bioreactor for receiving liquid fermentation medium from said anaerobic fermentation bioreactor, and for returning liquid modified fermentation medium to said anaerobic fermentation bioreactor; wherein the filtration unit comprises one or more filter stages that are configured to remove particles from the retrieved liquid fermentation medium to form a liquid filtered fermentation medium; and wherein the filtration unit and the first ion separation unit are fluidly connected in such a way that liquid filtered fermentation medium can be conveyed from the filtration unit to the first ion separation unit and can be fed as the first input stream to the first ion separation unit; that the first output stream of the first ion separation unit can be conveyed as liquid modified fermentation medium to the filtration unit.
  • a first filter stage of the filtration unit is realized as a cross-flow filter.
  • cross-flow filter allows for an efficient continuous filtration process, in contrast to a dead-end filtration process, since any particulate matter remaining at the filter surface is continuously removed.
  • the filtration unit advantageously comprises a first filter line and a second filter line that are arranged parallel to each other, and the filtration unit is advantageously configured such that said first filter line and said second filter line can be alternatingly switched to a filtrate outlet of the filtration unit and to a backwash inlet of said filtration unit, such that one of the two filter lines is in a filtering mode, in which liquid fermentation medium flows in one direction and is filtered to a liquid filtered fermentation medium, while the other of the two filter lines is in a backwash mode, in which liquid modified fermentation medium flows in a reversed flow direction and cleans the filter line by backwashing.
  • Backwashing allows for an efficient cleaning of filter stages for which crossflow filtration is not possible, in particular any filter stage serially arranged downstream of a first filter stage. Since two filter lines are available, the two lines can be regularly switched, as needed, between filtering and backwashing. This allows for a continuous operation of the filtering unit.
  • the liquid modified filtering medium in addition to being efficiently returned to the bioreactor by flowing backward through the filter stages, and exiting through the first filter stage, also acts as the backwashing agent, conveying all accumulated particulate matter back into the liquid fermentation medium.
  • the filtration unit and the first ion separation unit are fluidly connected in such a way that liquid filtered fermentation medium from the filtration unit can be fed as the second input stream to the first ion separation unit.
  • the device comprises an ammonia stripping apparatus for retrieving ammonia from a second output stream of the first ion separation unit, or from a second output stream of the second ion separation unit.
  • ammonia allows for an efficient retrieval of valuable ammonia from the aqueous solution with increased ion concentration in comparison to the liquid filtered fermentation medium.
  • the ammonia can then be used otherwise, for example for producing high nitrogen fertilizers such as ammonium nitrate.
  • a second aspect of the invention concerns an installation for producing gaseous fuel from biomass by anaerobic digestion.
  • Such an installation according to the invention comprises an anaerobic fermentation bioreactor and a liquid fermentation medium modification device according to the invention, as discussed above.
  • a first filter stage of the filtration unit has a filter inlet surface, wherein said filter inlet surface is in contact with the interior of the anaerobic fermentation bioreactor.
  • the anaerobic fermentation bioreactor comprises an agitator that is configured to generate a flow of the fermentation substrate essentially parallel to the filter inlet surface of the first filter stage of the filtration unit.
  • Such an embodiment allows implementing cross-flow filtration at the first filter stage, enabling an efficient continuous filtration process, in contrast to a dead-end filtration process, since any particulate matter remaining at the filter surface is continuously removed by the flow generated by the agitator.
  • the anaerobic fermentation bioreactor comprises a perforated floor, through which liquid fermentation medium that is part of fermentation substrate in the interior of the anaerobic fermentation bioreactor can be retrieved.
  • a bioreactor is particularly useful for fermentation substrates with low water content, such as for example in a plug-flow fermenter. Since the content of liquid fermentation medium in the fermentation substrate is low, filtering liquid fermentation medium directly from the fermentation substrate would not be effective. The liquid fermentation medium continuously flowing or dripping through the perforated floor, driven by gravitation, can be collected and used for a subsequent filtration step.
  • the filtration unit of the device is configured to receive liquid fermentation medium retrieved through the perforated floor.
  • such an installation according to the invention is advantageously configured to convey liquid fermentation medium retrieved through the perforated floor and liquid modified by the fermentation medium modification unit back into the anaerobic fermentation bioreactor.
  • the liquid modified fermentation medium with its decreased ion content, can be conveyed to the top of the bioreactor, where it can for example be dripped or sprayed onto the fermentation substrate in the bioreactor.
  • the top of the bioreactor can for example be dripped or sprayed onto the fermentation substrate in the bioreactor.
  • This recirculation levels the composition of the liquid fermentation medium within the bioreactor.
  • it also results in a continuous redistribution of the microbe population within the fermentation substrate.
  • the first filter stage of the filtration unit has a filter inlet surface, wherein said filter inlet surface is in contact with liquid fermentation medium retrieved through the perforated floor.
  • the installation comprises a filtrate tank for the temporary storage of liquid fermentation medium retrieved through the perforated floor.
  • a first filter stage of the filtration unit has a filter inlet surface, wherein said filter inlet surface is in contact with the interior of the filtrate tank.
  • an installation according to the invention comprises an agitator that is configured to generate a flow of the liquid fermentation medium essentially parallel to the filter inlet surface of the first filter stage of the filtration unit.
  • an installation according to the invention comprises a storage for compounds removed from the liquid fermentation medium, for example a storage tank.
  • a third aspect of the invention concerns a method for producing gaseous fuel from biomass by anaerobic digestion.
  • Such a method according to the invention comprises the steps of: providing an anaerobic fermentation bioreactor; providing a liquid fermentation medium modification device according to the invention, as discussed above; providing biomass as fermentation substrate to be anaerobically digested; anaerobically digesting said fermentation substrate in said anaerobic fermentation bioreactor, whereby biogas and fermentation residue are produced; and retrieving the produced biogas as gaseous fuel; wherein the ion content in the fermentation substrate is continuously reduced by removing ions from a liquid fermentation medium with said liquid fermentation medium modification device.
  • liquid fermentation medium is retrieved from the fermentation substrate; the retrieved stream of liquid fermentation medium is filtered, resulting in a stream of liquid filtered filtration medium, ions are removed from at least a part of the stream of liquid filtered fermentation medium, resulting in a stream of liquid modified fermentation medium that has a decreased ion content in comparison to the liquid filtered fermentation medium, and a stream of aqueous solution that has an increased ion content in comparison to the liquid filtered fermentation medium; and the stream of liquid modified fermentation medium is returned into the fermentation substrate.
  • a fourth aspect of the invention concerns a capacitive deionization apparatus for reducing the ion concentration of an aqueous solution.
  • a capacitive deionization apparatus according to the invention for reducing the ion concentration of an aqueous solution comprises a working chamber; a first inlet line opening toward the working chamber in multiple first inlet openings arranged on a first wall at a first longitudinal end of the working chamber; a first out line exiting the working chamber at multiple first outlet openings arranged on a second wall at a second longitudinal end of the working chamber; a second inlet line opening toward the working chamber in a second inlet opening; a second outlet line exiting the working chamber at a second outlet opening; multiple first electrodes in the form of flat porous carbon electrodes, each protruding from the first wall of the working chamber between a pair of the first inlet openings; and multiple second electrodes in the form of flat porous carbon electrodes, each protruding from the second wall of the working chamber between a pair of the first outlet openings
  • An advantageous embodiment of such a capacitive deionization apparatus comprises means for applying an adjustable voltage differential between the multiple first electrodes and the multiple second electrodes.
  • the multiple first electrodes and/or the multiple second electrodes are electrically connected to controllers that provide them with an adjustable voltage in regard to ground.
  • a fifth aspect of the invention concerns a method for reducing the ion concentration of an aqueous solution.
  • a capacitive deionization apparatus according to the invention as discussed above is provided; in an ion accumulation step a first input stream of an aqueous solution with a certain ion concentration is provided via the first inlet line; a certain voltage is applied between the group of multiple first electrodes and the group of multiple second electrodes; the first stream of aqueous solution is conveyed though the working chamber of the device, from the multiple first inlet openings along the electrode stack to the multiple first outlet openings, wherein anions are electrostatically adsorbed in the porous carbon matrix of the positively charged group of electrodes and cations are electrostatically adsorbed in the porous carbon matrix of the negatively charged group of electrodes, thereby reducing the ion concentration of the passing aqueous solution; a first output stream of aqueous solution with an i
  • the aqueous solution of the second input stream is the same as the aqueous solution of the first input stream.
  • the voltages applied between pairs of neighboring first electrodes and second electrodes are sequentially reduced to zero, synchronized with the flow of the aqueous solution along the meandering flow path through the work chamber, so that the aqueous solution containing the ions from the previously discharged pair of electrodes also receives the released ions from the next pair of electrodes, thereby effectively increasing the ion concentration of the aqueous solution.
  • a sixth aspect of the invention concerns a device for modifying the liquid fermentation medium in an anaerobic fermentation bioreactor.
  • Such a device comprises a filtration unit configured to be fluidly coupled to an anaerobic fermentation bioreactor, to receive liquid fermentation medium from the anaerobic fermentation bioreactor, and to return liquid modified fermentation medium to said anaerobic fermentation bioreactor.
  • the device comprises one or more filter stages that are configured to remove particles from the retrieved liquid fermentation medium to form a liquid filtered fermentation medium; and a first ion separation unit configured to receive a first input stream of liquid filtered fermentation medium and to produce a first output stream of aqueous solution with ion content in comparison to the liquid filtered fermentation medium and a second output stream with increased ion content in comparison to the liquid filtered fermentation medium.
  • the filtration unit and the first ion separation unit are fluidly connected in such a way that liquid filtered fermentation medium can be conveyed from the filtration unit to the first ion separation unit and can be fed as the first input stream to the first ion separation unit; that the first output stream of the first ion separation unit can be conveyed as liquid modified fermentation medium to the filtration unit; and that the second output stream of the first ion separation unit forms an aqueous solution that has an increased ion content in comparison to the liquid filtered fermentation medium.
  • the first filter stage of the filtration unit is realized as a cross-flow filter.
  • the filtration unit comprises a first filter line and a second filter line that are arranged parallel to each other.
  • the filtration unit is configured such that said two filter lines can be alternatingly switched to a filtrate outlet of the filtration unit and to a backwash inlet of said filtration unit, such that one of the two filter lines is in a filtering mode, in which liquid fermentation medium flows in one direction and is filtered to a liquid filtered fermentation medium, while the other of the two filter lines is in a backwash mode, in which liquid modified fermentation medium flows in a reversed flow direction and cleans the filter line by backwashing.
  • the first ion separation unit is configured to receive a first input stream of aqueous solution and a second input stream of aqueous solution and to transfer ions from said first input stream to said second input stream, thereby forming a first output stream of aqueous solution with decreased ion content in comparison to the first input stream and a second output stream with increased ion content in comparison to the second input stream.
  • the filtration unit and the first ion separation unit are operatively connected in such a way that liquid filtered fermentation medium can be conveyed from the filtration unit to the first ion separation unit and forms the first input stream of the first ion separation unit, and optionally the second input stream of the first ion separation unit.
  • the first ion separation unit is realized as an electrodialysis apparatus.
  • a particularly advantageous embodiment of such a liquid fermentation medium modification device comprises a second ion separation unit configured to receive a first input stream of aqueous solution and a second input stream of aqueous solution and to transfer ions from said first input stream to said second input stream, thereby forming a first output stream of aqueous solution with decreased ion content in comparison to the first input stream and a second output stream with increased ion content in comparison to the second input stream.
  • the first ion separation unit and the second ion separation unit are operatively connected in such a way that the second output stream of aqueous solution of the first ion separation unit and the first output stream of aqueous solution of the second ion separation unit are mixed and are used as the second input stream of the first ion separation unit and as both the first input stream and the second input stream of the second ion separation unit; and that the second output stream of the second ion separation unit forms an aqueous solution that has an increased ion content in comparison to the liquid filtered fermentation medium.
  • the second ion separation unit is realized as an electrodialysis apparatus, similar as discussed above for the first ion separation unit.
  • An even more advantageous embodiment of such a liquid fermentation medium modification device comprises an intermediate concentration solution tank, wherein the mixing of the second output stream of the first ion separation unit and the first output stream of the second ion separation unit takes place in said intermediate concentration solution tank.
  • the first ion separation unit and/or the second ion separation unit are realized as an electrodialysis apparatus.
  • a further advantageous embodiment of a liquid fermentation medium modification device comprises an ammonia stripping apparatus for retrieving ammonia from the second output stream of the first ion separation unit or the second ion separation unit.
  • a seventh aspect of the invention concerns an installation for producing gaseous fuel from biomass by anaerobic digestion.
  • Such an installation according to the invention comprises an anaerobic fermentation bioreactor and a liquid fermentation medium modification device according to the invention.
  • a first filter stage of the filtration unit has a filter inlet surface, wherein said filter inlet surface is in contact with the interior of the anaerobic fermentation bioreactor.
  • the anaerobic fermentation bioreactor comprises an agitator that is configured to generate a flow of the fermentation substrate essentially parallel to the filter inlet surface of the first filter stage of the filtration unit.
  • the anaerobic fermentation bioreactor comprises a perforated floor through which liquid fermentation medium that is part of fermentation substrate in the interior of the anaerobic fermentation bioreactor can be retrieved.
  • the filtration unit of the liquid fermentation medium modification device is advantageously configured to receive liquid fermentation medium retrieved through the perforated floor.
  • an installation according to the invention is configured to convey liquid fermentation medium retrieved through the perforated floor and liquid modified by the fermentation medium modification unit back into the anaerobic fermentation bioreactor.
  • a first filter stage of the filtration unit has a filter inlet surface, wherein said filter inlet surface is in contact with liquid fermentation medium retrieved through the perforated floor.
  • Another particular advantageous embodiment of such an installation according to the invention comprises a filtrate tank for the temporary storage of liquid fermentation medium retrieved through the perforated floor.
  • a first filter stage of the filtration unit has a filter inlet surface, wherein said filter inlet surface is in contact with the interior of the filtrate tank.
  • the installation according to the invention comprises an agitator that is configured to generate a flow of the liquid fermentation medium essentially parallel to the filter inlet surface of the first filter stage of the filtration unit.
  • An installation according to the invention advantageously comprises a storage for compounds removed from the liquid fermentation medium, for example a storage tank.
  • An eighth aspect of the invention concerns a method for producing gaseous fuel from biomass by anaerobic digestion.
  • Such method according to the invention comprises the steps of: providing an anaerobic fermentation bioreactor; providing biomass as fermentation substrate to be anaerobically digested; anaerobically digesting said fermentation substrate in said anaerobic fermentation bioreactor, whereby biogas and fermentation residue are produced; and retrieving the produced biogas as gaseous fuel; wherein the ion content in the fermentation substrate is continuously reduced by removing ions from the liquid fermentation medium.
  • liquid fermentation medium is retrieved from the fermentation substrate; the retrieved stream of liquid fermentation medium is filtered, resulting in a stream of liquid filtered filtration medium, ions are removed from at least a part of the stream of liquid filtered fermentation medium, resulting in a stream of liquid modified fermentation medium that has a decreased ion content in comparison to the liquid filtered fermentation medium, and a stream of aqueous solution that has an increased ion content in comparison to the liquid filtered fermentation medium; and the stream of liquid modified fermentation medium is returned into the fermentation substrate.
  • a liquid fermentation medium modification device according to the invention is provided, and the filtering of the liquid fermentation medium and the removal of ions from the liquid filtered fermentation medium is carried out with said liquid fermentation medium modification device.
  • a ninth aspect of the invention concerns a method for producing fertilizer.
  • one of the methods for producing gaseous fuel from biomass by anaerobic digestion according to the invention is carried out, and the aqueous solution with increased ion content resulting from said method is utilized to produce liquid fertilizer and/or solid fertilizer.
  • a tenth aspect of the invention concerns a method for producing solid fuel.
  • one of the methods for producing gaseous fuel from biomass by anaerobic digestion according to the invention is carried out, and the fermentation residue of the anaerobic digestion process is utilized to produce solid fuel.
  • gaseous fuel produced with a method for producing gaseous fuel from biomass by anaerobic digestion according to the invention fertilizer produced with a method for producing fertilizer according to the invention, and solid fuel produced with a method for producing solid fuel according to the invention.
  • Figure 1 schematically shows an embodiment of an anaerobic digester installation according to the invention with a fermentation medium modification device according to the invention.
  • Figure 2 schematically shows a wet fermentation bioreactor with an embodiment of a fermentation medium modification device according to the invention.
  • Figure 3 schematically shows an embodiment of an ion separation unit of a fermentation medium modification device according to the invention, with an electrodialysis stack.
  • Figure 4 schematically shows another embodiment of a fermentation medium modification unit according to the invention, with a second ion separation unit.
  • Figure 4A schematically shows another embodiment of an ion separation unit of a fermentation medium modification device according to the invention, with a modified electrodialysis stack.
  • Figure 4B schematically shows a further embodiment of an ion separation unit of a fermentation medium modification device according to the invention, with a dialysis stack.
  • Figure 4C schematically shows a further embodiment of a fermentation medium modification unit according to the invention, with a second ion separation unit and heating elements.
  • Figure 4D schematically shows part of a fermentation medium modification unit similar to Figures 4 and 4C, with two separate buffer tanks.
  • Figure 4E schematically shows part of an ion separation unit similar to Figure 4C, with an alternative arrangement of heat exchangers.
  • Figure 5 schematically shows another embodiment of a wet fermentation bioreactor with a fermentation medium modification unit according to the invention.
  • Figure 6 schematically shows an embodiment of a dry fermentation bioreactor with a fermentation medium modification unit according to the invention.
  • Figure 7 schematically shows an embodiment of a fermentation medium modification unit according to the invention with an ammonium stripping unit.
  • Figure 8 schematically shows another embodiment of a fermentation medium modification unit according to the invention with a second ion separation unit and an ammonium stripping unit.
  • Figure 9 schematically shows a capacitive deionization apparatus according to the invention.
  • Figure 10 schematically shows the capacitive deionization apparatus of Figure 9 in an ion accumulation mode.
  • FIG 11 schematically shows the capacitive deionization apparatus of Figure 9 in an ion discharge mode.
  • pumps or other means to convey liquids from one point to another are generally not shown. A skilled person knows how the described conveying paths of the liquids can be achieved.
  • the anaerobic digester installation 1 comprises a fermentation bioreactor 10, in which the anaerobic digestion processes with the biomass take place.
  • the fermentation bioreactor 10 is supplied with biomass material 31 to be processed by the biomass supply 30.
  • Said biomass supply 30 can for example be realized with a conveyor that obtains suitably prepared biomass material 31 from a reservoir and conveys it into the fermentation bioreactor 10.
  • the fermentation bioreactor 10 can be realized as a completely stirred bioreactor, in which the fermentation medium 11 has only a small dry mass content of biomass.
  • the fermentation bioreactor 10 can be realized as a plug-flow fermenter. Fermentation residues 41 are retrieved from the fermentation bioreactor 10 and stored in a fermentation residue storage 40 for later use or disposal.
  • the fermentation process can be carried out batchwise or continuously, the latter being advantageous in regard to process stability.
  • the fermentation bioreactor 10 is operatively connected to a fermentation medium modification device 500 according to the invention, which modifies the composition of the fermentation medium 11 in such a way that the conditions for the biogas generating microbe population are in a certain, optimal range and the concentration of certain compounds in the fermentation residue is reduced.
  • the fermentation medium modification device 500 comprises a filtration unit 100 and an ion separation unit 200.
  • the filtration unit 100 operatively connects the fermentation bioreactor 10 and the ion separation unit 200.
  • Compounds 81 removed from the fermentation medium are stored in a storage 80 for later use or disposal.
  • the general process, which runs continuously alongside anaerobic digestion, can be roughly separated into two steps.
  • the fermentation medium 91 namely the aqueous part of the fermentation substrate 11 , comprising of water and the soluble compounds of the substrate (such as potassium, ammonium and chloride ions, as well as proteins, sugars and other organic compounds) is separated from the rest of the substrate in the filtration unit 100.
  • the ions are removed from the resulting filtrated substrate medium 93 and are collected in a concentrate 81 , while the rest of the solution forms a modified fermentation module 92 that is recirculated into the fermenter 10.
  • the details of the implementation, in particular the configuration of the filtration unit 100, depend on the concrete setup of the fermentation bioreactor 10.
  • a fermentation medium modification device can be implemented both with a “wet” fermenter, and with a “dry” fermenter.
  • FIG. 2 A more detailed embodiment of a fermentation medium modification unit 500 according to the invention, being operatively connected to a fermentation bioreactor 10 with “wet” fermentation substrate is shown in Figure 2, while Figure 3 shows a possible advantageous embodiment of an ion separation unit 200 as it can be used in said fermentation medium modification unit 500.
  • a wet fermentation bioreactor 10 comprises an agitator 15 for agitating the fermentation substrate 11 slurry. While present in any type of wet fermenter, the agitator 15 can vary in form, size and arrangement.
  • liquid fermentation substrate 11 is sucked through a first filter stage 101 , 10T.
  • the first filter stage 101 , 10T is located inside the fermentation bioreactor 10 and is suitably mounted 110 to the bioreactor wall 12.
  • the mesh size of the first filter stage 101 , 10T can be in the range of approx, a 0.1-1.0 mm, depending on the average particle size and dry matter content in the fermentation substrate 11 .
  • the first filter stage within the fermenter 10 comprises two separate chambers 101 and 10T. Each chamber is connected to a pipe 108, 109 leading out of the fermenter.
  • the geometry and position of the filter 101 , 101 is chosen in such a way that the agitator 15 creates a flow across the surface 111 of the filter 101 , 10T, which mitigates the unwanted formation of a filtration cake.
  • This method is known as “crossflow filtration”, in contrast to the usual “dead end filtration”, and allows for a continuous and stable filtration process.
  • Two pairs of second 102, 102' and third 103, 103' filter stages are provided.
  • a first filtration conduit 108 connects a first chamber of the first filter stage 101 a second filter stage 102 with pore size 30-70 pm and a third filter stage 103 with pore size 0.1-2.0 pm.
  • a second filtration conduit 109 connects a second chamber of the first filter stage 101 with another second filter stage 102' and another third filter stage 103'. Similar for the first filter stage, the pore size of the second and third filter stages is advantageously chosen depending on the fermentation substrate’s properties.
  • the resulting filtrate solution is conveyed along the first filtration conduit 108 (indicated by a black arrow) through the second filter stage 102 and the third filter stage 103 and valve 104 toward a filtrate outlet conduit 106 of the filtration unit 100.
  • aqueous solution with reduced ion concentration is flowing back from a backwash inlet conduit 107 of the filtration unit 100 via valve 104 through the other third filter stage 103' and second filter stage 102' and the second filtration conduit 109 to the second chamber of the first filtration stage 101 , thereby flushing the filtration stages.
  • a 4/2 valve 104 is used to periodically switching the two filter lines 108, 109 to the filtrate outlet conduit and the backwash inlet conduit 107, so that alternatingly one of the two filter lines 108, 109 provides filtered solution that is fed through outlet 106 to the ion separation unit 200, and the other line 109, 108 receives aqueous solution from the ion separation unit 200 through inlet 107 that is then used for backwashing the inactive three filter stages.
  • the necessary pressure differential is produced by a self-priming circulation pump 501 that also conveys the aqueous solution through the ion separation unit 200.
  • the stream of filtrate incoming through the filtrate outlet conduit 106 of the filtration unit 100 is split into two parts, which are fed to a first feed line 221 and a second feed line 22 of the ion separation unit 200.
  • a first effluent line 223 of the ion separation unit 200 carrying an output stream of aqueous solution with reduced ion concentration, is connected to the backwash inlet conduit 107 of the filtration unit 100 and is ultimately fed back into the fermentation bioreactor 10.
  • a second effluent line 224 of the ion separation unit 200, carrying an output stream of aqueous solution 81 with increased ion concentration, is connected to a high concentration solution tank 80.
  • electrodialysis is not only the most mature technology, but also offers some other key advantages such as high selectivity towards inorganic ions (Cl-, K + , NH 4 + etc.) and comparatively high organic fouling resistance.
  • An electrodialysis stack 210 comprises multiple, alternatingly arranged first chambers 213 and second chambers 214, which are alternatingly separated by anion exchange membranes 215 and cation exchange membranes 216. Said anion exchange membranes 215 and cation exchange membranes 216 are only permeable by negative ions or positive ions, respectively.
  • the number of layers as well as the dimensions of the stack depend on the amount of ions that need to be separated as well as the tradeoff between energy consumption and membrane cost.
  • a higher membrane area means less electrical resistance and thus a reduced voltage differential that must be provided by the energy-consuming electrodes 226 and 227 but also increases building costs.
  • the outermost chambers 211 , 212 are filled with an electrolyte, usually sodium sulphate, which is circulated by a pump 225.
  • An anode 226 is arranged in the anode chamber 211
  • a cathode 227 is arranged in the cathode chamber 212.
  • Anode 226 and cathode 227 are connected to a voltage source 217, which drives a direct current through the electrodialysis stack 210.
  • ions from the solution in the first chambers 213 are transported across the membranes 215, 216 into the second chambers 214.
  • electrolysis of water may take place, wherein molecular hydrogen is produced at the cathode 227 in the cathode chamber 212 and molecular oxygen is produced at the anode 226 in the anode chamber 211 .
  • the hydrogen gas can be collected and fed into the fermentation bioreactor 10.
  • the resulting increased partial pressure of hydrogen in the fermentation bioreactor 10 inhibits acetogens, i.e. bacteria that break down volatile fatty acids such as valeric acid, butyric acid and propionic acid into acetic acid.
  • a decreased activity of acetogens means that the chain-length of the recoverable volatile fatty acids increases.
  • An increased partial pressure of hydrogen also increases homoacetogenesis, the production of acetic acid from carbon dioxide and molecular hydrogen.
  • the first feed line 221 feeds aqueous solution 315a received from the filtration unit 100 to the multiple first chambers 213. While the aqueous solution 315b passes said parallel first chambers 213, the aqueous solution is largely depleted of negative and positive ions. The anions cross the anion exchange membranes 215 toward the positive electrode 226, and the cations cross the cation exchange membranes 216 toward the negative electrode 227. The resulting aqueous solution 315c with decreased ion concentration is collected in the first effluent line 223.
  • the second feed line 222 feeds aqueous solution 316a received from the filtration unit 100 to the multiple second chambers 214. While the aqueous solution 316b passes said parallel second chambers 214, the ion concentration in the aqueous solution is largely increased. This concentrated aqueous solution 316c is collected in the second effluent line 224.
  • Parallel flow directions of the two aqueous solutions 315b, 316b within the chambers 213, 214, as shown in Figure 3, are particular advantageous when both input streams 315a, 315b have the same origin, and therefore could take advantage of a simpler configuration, with one single input feed line 3212, 322.
  • the flow directions of the two aqueous solutions 315b, 316b can be opposite to each other, which in the setup as discussed above can be achieved for example by switching the connections of the first feed line 221 and the first effluent line 223.
  • the setup shown in Figures 1 and 2 is particularly advantageous for fermentation substrates that contain a lot of water, since the water within the increased ion concentration stream 81 is not returned to the fermenter 10 but directed from second effluent line 224 into a storage tank 80. This lowers the water content in the fermenter 10, which in turn increases organic loading and biogas production.
  • FIG. 4 Another advantageous embodiment of a fermentation medium modification device 500 is shown in Figure 4.
  • the depicted fermentation medium modification device 500 comprises a second ion separation unit 250, similar to the first ion separation unit 200.
  • Filtrate from the filtration unit 100 is fed only to the first feed line 221 of the first ion separation unit 200.
  • the corresponding first effluent line 223 with the low ion concentration stream leads back to the filtration unit 100, as in the previous examples.
  • the second effluent line 224 with high ion concentration solution is connected to an intermediate storage tank 520, whose content serves both as the feed aqueous solution 82 for the second feed line 222 for the first ion separation unit 200, and as the feed for both feed lines 251 , 252 of the second ion separation unit 250.
  • the tank 520 effectively decouples the fluid systems of the first ion separation unit 200 and the second ion separation unit 250 and acts as a buffer.
  • the first effluent line 253 with the low ion concentration stream is returned back to the intermediate storage tank 520.
  • the other, second effluent line 254 of the second ion separation unit 250, carrying an output stream of aqueous solution 81 with highly increased ion concentration, is connected to a high concentration solution tank 80.
  • the working voltage of the second ion separation unit 250 is higher than for the first ion separation unit 200, thus achieving a much higher concentration in the secondary concentrate stream in second effluent line 254 than in the primary concentrate stream in second effluent line 224.
  • intermediate storage tank 520 Since water is continuously removed from intermediate storage tank 520 toward the storage tank 80, it is connected to a fresh water supply 260 via a 2/2 valve (not shown), in order to control the fluid level of the intermediate tank 520.
  • This advantageous embodiment of a fermentation medium modification unit 500 offers several advantages. For one, it not only allows the independent control of the final concentration, but it can also achieve higher concentrations, since the input feed to the secondary ion separation unit 250 is already more concentrated than the filtrate feed 221 to the first ion separation unit 200. Thus, more ions end up in the final concentrate 81. Additionally, the second ion separation unit 250 can be run with optimal parameters to mitigate the fouling of the ion exchange membranes by the organic matter in the filtrate [Ref-15, Ref-16], For example, it could run at lower voltage, higher flow rates, or with a pulsed electric field (PEF) electrodialysis [Ref-17], This leads to increased performance and longer lifetime of the membranes.
  • PEF pulsed electric field
  • a potential problem with utilizing electrodialysis stacks for separating ions from solutions similar to the filtered fermentation medium 93 is membrane fouling, i.e. the deposition and accumulation of undesirable matter such organic compounds and/or inorganic compounds on membrane surfaces, thereby degrading the performance of the membranes and decreasing their lifetime.
  • the filtered fermentation medium 93 carries a considerable amount of organic matter, which can in particular foul the anion exchange membranes due to their mainly negative charge (e.g. deprotonated fatty acids).
  • VFA volatile fatty acids
  • FIG 4A shows a modified electrodialysis stack 230, similar to the electrodialysis stack 210 in Figure 3, in which the anion exchange membranes have been replaced by low- pressure ultra-filtration membranes 232.
  • modified electrodialysis stack 230 The general function of such a modified electrodialysis stack 230 is similar to the electrodialysis stack 210 of Figure 3, and reference is given to the corresponding discussion above. Ions from the solution in the first chambers 213 are transported across the membranes 232, 216 into the second chambers 214.
  • Such a modified electrodialysis stack 230 provides several advantages.
  • low-pressure ultra-filtration membranes 232 have a slightly negative surface charge, they are more resistant to fouling by organic matter. This increases the lifetime of such membranes, which in addition are considerably less expensive than anion exchange membranes. Furthermore, low-pressure ultra-filtration membranes have a lower electrical resistance due to their smaller thickness ( ⁇ 50 pm compared to 400 pm for anion exchange membranes) and a considerably higher diffusion coefficient, which increases the efficiency of the separation process and decreases the electric power consumption.
  • modified electrodialysis stack 232 is particularly advantageous for the first ion separation unit 200, which treats the filtered fermentation medium 93 carrying the main load of organic material.
  • the modified electrodialysis stacks 232 can also be applied for the second ion separation unit 250, in which the ion concentration is further increased.
  • Dialysis is generally believed in the state of the art to be a slow and unselective process. However, surprisingly it has been found that dialysis is nevertheless a very advantageous method for reducing the ion content of a fermentation medium, in particular due to insensitivity to fouling.
  • a dialysis stack 240 (only partially shown) comprises a multitude of alternatingly arranged first chambers 213 and second chambers 214, which are separated by semiper- meable membranes 242.
  • An aqueous solution 315a with an ion concentration to be decreased is fed through first feed line 221 to the first chambers 213.
  • Another aqueous solution 316a with lower ion concentration, in a simple case clear water, is fed a through second feed line 222 to the second chambers 214, with an opposite flow direction.
  • the aqueous solution 315c flowing out of the first chambers 213 is collected by first effluent line 223, and the aqueous solution 316c flowing out of the second chambers 214 is collected by second effluent line 224.
  • Ions in the aqueous solution 315b in the first chambers 213 are transported by osmosis through the semipermeable membranes 242 into the aqueous solution 316b in the second chambers 214.
  • Opposite flow directions are particularly advantageous in this setup. Because the diffusion from the aqueous solution 315b in the first chamber 213 across the membrane 242 to the aqueous solution 316b in the second chamber 214 is driven only by the concentration differential across the membrane, and not by an applied static voltage as in the electrodialysis setups discussed further above, the constant concentration differential resulting from the opposite flow direction along the axis of the chambers 213, 214 achieves the best dialysis efficiency.
  • Stacking the first and second chambers 213, 214 chiefly optimizes the available membrane surface for a given flow cross-section.
  • the semipermeable membranes 242 used in the ion separation unit 200 of Figure 4B are hydrophilically coated polypropylene (PP) membranes, as they are for example used as battery separators for lithium ion batteries.
  • PP polypropylene
  • Such membranes may have a thickness of 15-25 pm.
  • Such membranes can be equipped with a hydrophilic surface treatment and a ceramic coating, such as TiC>2, SiC>2 or AI2O3.
  • Such membranes are inexpensive, robust and easily cleanable.
  • ion separation unit 200 has insusceptibility to fouling caused by organic contents of the incoming aqueous solution 315a, which in particular can be the filtered fermentation medium coming from the filtration unit 100. Because there is no external driving force for the osmosis across the membranes 24, clogging and deposition of residues on the membranes is almost completely avoided.
  • a polypropylene membrane having a surface coating comprising SiC>2 nanoparticles with a diameter of 10-15 nm and a polyacrylic acid/poly vinyl alcohol binder is particularly advantageous in regard to hydrophilicity, high fouling resistance, robustness even at high temperatures (up to 120 °C), and longevity.
  • the diffusion coefficient D of a particle is inversely proportional to its hydrodynamic radius (Stokes radius) Ro, which grows with molecule size and charge.
  • SA hydrodynamic radius
  • Such an ion separation is particularly well suited for rejecting humic substances, which are a main cause of irreversible fouling in most other membrane processes, in particular electrodialysis. Since the diffusion coefficient of humic substances is at least one order of magnitude lower than for monovalent ions, the latter can pass the membrane 242 driven by the concentration differential, while the former is retained in the first chamber 213 and is eventually returned in the aqueous solution into the fermenter.
  • the diffusion coefficient D of a particle is also proportional to the absolute temperature T, and since higher diffusion coefficients D increase the effective diffusion rates across the semipermeable membranes 242 and thus the efficiency of the diffusion stack, it is advantageous to carry out the process at increased temperatures.
  • the aqueous solutions 315a, 316a are heated before being fed into the chambers 213, 214 of the dialysis stack 240,
  • heating elements 245, 247 provided in the feed lines 221 , 222.
  • Such heating elements can comprise heat exchangers that allow the utilization of waste heat from other processes, for example from exhaust gases from the thermal utilization of biogas to produce electricity.
  • Increased temperatures can also be advantageous for the efficiency of the electrodialysis stacks 210 and modified electrodialysis stacks 230 as shown in Figures 3 and 4A, since the increased mobility of the ions at higher temperatures increase the conductivity of the aqueous solutions 315b, 316b withing the chambers 213, 214, by approx. 2-3% per additional °C.
  • heating elements 245, 247 can also be applied in said setup.
  • a particular advantageous application of such a dialysis-based ion separation unit is its use in a two-stage setup discussed Figures 4 and 8. Since the dialysis process with ion separation unit 200 produces a stream of aqueous solution in increased content of monovalent ions, but virtually no organic molecules, a second stage ion separation unit 250 can be realized e.g. as a electrodialysis-based ion separation unit as shown in Figures 3 or 4A, which is more prone to fouling and clogging. Also a capacitive-deionization- based ion separation unit as discussed further below in Figures 9-11 can be used as a second stage ion separation unit.
  • FIG. 4C A further embodiment of a fermentation medium modification device 500 according to the invention is given in Figure 4C.
  • the corresponding discussion also applies to this further embodiment.
  • a heating element 245 is provided, which can increase the temperature of the aqueous solution 315a, namely the filtered fermentation medium 93 received from the filtration unit 100, prior to feeding 221 to the first ion separation unit 200.
  • a heat exchanger 244 arranged upstream of the heating element 245 in the first feed line 221 allows to recover heat energy from the aqueous solution 315c in the first effluent line 223. This allows minimizing the energy needed in the heating element 245 and thus improves overall energy efficiency.
  • the aqueous solution 315c with decreased ion concentration is then returned as modified fermentation medium 92 to the filtration unit 100.
  • the first ion separation unit 200 is based on a dialysis stack, as discussed above for Figure 4B.
  • Fresh water obtained from fresh water supply line 260 is used as the aqueous solution 82, 316a provided in the second feed line 222 of the dialysis stack 240.
  • a heating element 247 is provided to increase the temperature of the fresh water 316a prior to feeding 222 it to the first ion separation unit 200.
  • the aqueous solution 316c, 8T with the retrieved ions is led from the second effluent line 224 directly into an intermediate concentration solution tank 520.
  • a heat exchanger may be provided to recover heat energy from the aqueous solution 8T leaving the second ion separation unit 250 through the second effluent line 254.
  • the level in the tank 520 is controlled by adjusting the amount fresh water added from the fresh water supply line 260, by increasing or decreasing the flow rate in the second feed line 222. Alternatively or additionally, fresh water may also be directly added to the tank 520 (not shown).
  • the second stage with the second ion separation unit 250 is the same as in Figure 4.
  • FIG. 4D A further variant of a fermentation medium modification device 500 according to the invention is shown in Figure 4D.
  • a heat exchanger 246 is provided that allows the transfer of heat energy from the aqueous solution 8T, 316c leaving the first ion separation unit 200 through second effluent line 224 to the aqueous solution 316a prior to heating 247 it and feeding 222 it into the first ion separation unit 200.
  • the cooled aqueous solution 8T is then collected in an intermediate concentration solution tank 520, which acts as a buffer tank.
  • the aqueous solution provided to the first feed line 251 and the second feed line 252 of the second ion separation unit 250 (not shown) is retrieved from the buffer tank 520.
  • the aqueous solution 95 retrieved from the first effluent line 253 of the second ion separation unit 250 is collected in another buffer tank 525.
  • T o replace the volume of aqueous solution 81 leaving the second ion separation 250 and to control the fluid levels in the buffer tank 525, water retrieved from fresh water supply line 260 is added to the tank 525.
  • Aqueous solution 82 retrieved from buffer tank 520 is heated 246, 247 and is fed to the second feed line 222 of the first ion separation unit 200.
  • FIG. 4E Another variant of a fermentation medium modification device 500 according to the invention is shown in Figure 4E.
  • a first heat exchanger 244' transfers heat energy from the aqueous solution 316c, 8T of the second effluent line 224 to the aqueous solution 315a, 93 that is then heated 245 and fed to the first feed line 221 of the first ion separation unit 200.
  • a second heat exchanger 246' transfers heat energy from the aqueous solution 315c, 9 of the first effluent line 223 to the aqueous solution 316a, 92 that is subsequently heated 247 and fed to the second feed line 222 of the first ion separation unit 200.
  • a fermentation medium modification device as part of an anaerobic digester installation with a fermentation medium with high water content has been shown in Figure 2.
  • Figure 5 Another such embodiment is shown in Figure 5, where the fermentation bioreactor 10 and the part of the filtration unit 100 within the fermentation bioreactor 10 is shown, with the first filtration stage 101 mounted to the bioreactor wall connected to the first filtration conduit 108 and the second filtration conduit 109.
  • the position of the first filter stage 101 in the wet fermenter has been chosen in such a way that the agitator 15, in this case a paddle agitator with approx. 6-30 rpm, creates a crossflow across the surface of the filter 101 , with the flow direction being normal to the drawing plane.
  • the rest of the filtration unit 100 and the fermentation medium modification device 500 can be realized similarly to the filtration unit and the fermentation medium modification device as they have been already discussed for Figures 2, 4, 4C, 4D, 4E, and will be discussed for Figures 7 or 8, and thus are not shown.
  • FIG. 6 shows an embodiment of an anaerobic digester installation 1 that can also be used in the context of a fermentation medium with low water content (“dry” fermentation”), for example in a typical plug-flow fermenter.
  • an agitator (not shown) would be designed to move the highly viscous or even semi-solid fermentation substrate 11 horizontally along a longitudinal axis perpendicular to the drawing plane.
  • the fermentation process takes place in a continuous manner, fresh fermentation substrate being added at one end and fermentation residue removed at the other end of the bioreactor. Since the water content of the fermentation medium 11 is low, a first filter stage within the bioreactor is less efficient, and a cross-flow along the surface of the first filter stage cannot be achieved.
  • a perforated floor 23 is arranged at a lower end of the bioreactor 10, having a mesh size that is sufficiently small to allow the liquid part of the fermentation substrate 11 , namely the fermentation medium 9T, to pass while withholding the solid components of the fermentation substrate.
  • This filtrate I fermentation medium 9T which has a much higher water content, is then conveyed through filtrate effluent line 27 into a filtrate tank 21.
  • the filtrate /fermentation medium 9T is conveyed through filtrate feed line 25 to a permeate nozzle 22 arranged at an upper end of the bioreactor 10, from which it is spayed or dripped onto the fermentation substrate 11.
  • pumps 24, 26 are used to convey the fermentation medium 9T.
  • the filtrate tank 21 can also be arranged above or below the bioreactor 10, such that the fermentation medium 91'can be conveyed along one of the lines 25, 27 by gravitational force only.
  • the fermentation medium modification device 500 is shown only partially, and can be realized similar to Figures 2, 4, 4C, 4D, 4E, 7 or 8.
  • the filtration unit 100 is connected to the filtrate tank 21 by a first filtration conduit 108 and a second filtration conduit 109, and comprises a second filter stage 102, 102' and a third filter stage 103, 103', similar to the other embodiments of filtration units in this description.
  • the first filtration stage is omitted, because its function of first filtration stage is functionally replaced by the perforated floor 23.
  • the fermentation medium 9T is directly retrieved from the filtrate tank 21.
  • An additional advantage of such a setup is that the microbes present in the fermentation medium 9T are evenly distributed within the fermentation substrate, since there is a constant flow of liquid withing the fermentation substrate from the top to the bottom of the bioreactor, independent from the conveying agitator.
  • the filtration unit 100 can also comprise a first filtration stage, arranged in the filtrate tank 21 , advantageously in combination with a suitable agitator arranged in the filtrate tank 21 for generating a cross-flow along the surface of the first filter stage.
  • a suitable agitator arranged in the filtrate tank 21 for generating a cross-flow along the surface of the first filter stage.
  • FIG. 7 A further embodiment of a fermentation medium modification device 500 according to the invention is shown in Figure 7.
  • the fermentation medium modification device 500 is based on the fermentation medium modification device already discussed for Figure 4. For identical parts, reference is therefore made to said discussion.
  • the output stream of the second effluent line 224 of ion separation unit 200 with an increased ion concentration solution is directed to an intermediate tank 530. From this tank 530, solution is conveyed by pump 551 through line 555 to an ammonia stripping tower 550. The output stream of the ammonia stripping tower is then conveyed by pump 552 through line 556 to the high concentration solution tank 80.
  • Air stripping is a well-known method for removing volatile compounds from aqueous solutions, such as for example waste water streams [Ref-18, Ref-19, Ref-20],
  • aqueous solutions such as for example waste water streams [Ref-18, Ref-19, Ref-20]
  • ammonium ions NH 4 + present in the aqueous solution are reacted into volatile ammonia NH3. This is achieved by increasing the pH to a range near or above the pK a value of ammonium of 9.2, e.g. to a pH value of 10.8-11.5, by adding a suitable basic compound such as lime, slaked lime, sodium hydroxide etc. to the intermediate storage tank 530.
  • a suitable basic compound such as lime, slaked lime, sodium hydroxide etc.
  • the necessary amount of lime water is added to the tank 530 via lime solution supply line 540, in order to adjust the pH of the solution to the required range.
  • the ammonium ions are deprotonated, and ammonia is formed.
  • Gaseous ammonia is then selectively extracted from the aqueous solution by air stripping, while the other ions remain in solution.
  • the gaseous ammonia can then be reclaimed from the air stream as ammonium ions for example by reacting it with a suitable strong acid, e.g. sulfuric acid.
  • the resulting pure ammonia in the ammonia output 558 of the ammonia stripping tower 550 can then be used for the production of nitrogenous fertilizer.
  • FIG 8. A further advantageous variant of a fermentation medium modification device 500 according to the invention is shown in Figure 8.
  • the fermentation medium modification device 50 comprises two ion separation units 200, 250 in series, similar to Figures 4, 4C, 4D, 4E.
  • the highly concentrated output stream of the second ion separation unit 250 is then directed to intermediate storage tank 530.
  • the ammonia stripping is then carried out similar to the embodiment discussed for Figure 7.
  • a capacitive deionization apparatus 300 instead of utilizing an electrolysis stack 210 or a modified electrolysis stack 230, a capacitive deionization apparatus 300 according to the invention can be utilized.
  • Such a capacitive deionization apparatus 300 according to the invention is shown in Figure 9. It is based on electro-sorption of ions on activated carbon electrodes.
  • the capacitive deionization apparatus 300 comprises a stack of flat porous carbon electrodes 307, 308 (shown in cross-section) as they are known from capacitive deionization.
  • the flat electrodes 307, 308 are arranged such that they form a single meandering chamber 305.
  • a group of first electrodes 307 is electrically connected 310 to controllers 312a-312f that provide them with an adjustable positive voltage, while a group of second electrodes 308 is electrically connected 311 to ground.
  • a first inlet line 301 opens toward a first longitudinal end 313 of the chamber 305 of the capacitive deionization apparatus 300, and a first outlet line 302 leaves the chamber on the other, second longitudinal end 314 of the chamber 305 of the capacitive deionization apparatus 300.
  • a second inlet line 303 is connected to an upstream end 317 of the meandering chamber 305 of the capacitive deionization apparatus 300, and a second outlet line 304 leaves the chamber 305 at a downstream end 318.
  • the capacitive deionization apparatus 300 alternatingly switches between ion accumulation mode (as shown in Figure 10) and an ion discharge mode (as shown in Figure 11).
  • the second inlet line 303 and the second outlet line 304 are disconnected from the chamber 305 by valves (not shown).
  • the solution 315a to be concentrated is pumped into the chamber 305 through first inlet line 301 , flows through the chamber along the electrode stack 307, 308, where anions are electrostatically adsorbed in the porous carbon matrix of the positively charged electrodes 307 and cations are electrostatically adsorbed in the porous carbon matrix of the negatively charged electrodes 308, thereby reducing the concentration of the solution 315b, which then leaves the capacitive deionization apparatus 300 through first outlet line 302 as a solution 315c with reduced ion concentration.
  • the first inlet line 301 and the first outlet line 302 are disconnected from the chamber 305 by valves (not shown).
  • a solution 316a with a certain ion concentration e.g. the same solution as the input solution 315a in the ion accumulation mode, is pumped into chamber 305 through second inlet line 303 at the upstream end 317 end, flows along the meandering chamber 305, and leaves the chamber 305 at the downstream end 318.
  • the voltage applied to electrodes 307 are then sequentially reduced to zero, so that the adsorbed ions are released from the porous electrode matrix.
  • This process is synchronized with the flow of the solution 316b through chamber 305, so that the solution containing the ions from the previously discharged electrode pair also receives the released ions from the next electrode pair, thereby effectively increasing the ion concentration of the solution 316b.
  • diffusion along the flow direction of the stream of solution reduces the efficiency, said diffusion is a slow enough process to achieve an efficiency of around 70% - 80% per discharge step.
  • the concentration can be increased from 10 g/l up to 250 g/l.
  • the capacitive deionization apparatus 300 as discussed above has to switch regularly between the ion accumulation mode and the ion discharge mode, and thus is essentially working in a pulsed manner, it is advantageous to decouple the fluid streams of a continuously working first ion separation unit 200 and the following second ion separation unit with a capacitive deionization apparatus 300. This can be achieved for example by buffer tanks 520, 525 as provided in previously discussed embodiments.
  • two or more capacitive deionization apparatuses 300 are connected in parallel, wherein said capacitive deionization apparatuses 300 are operated such that at all times at least one of the capacitive deionization apparatuses 300 is in ion accumulation mode, and at least one of the capacitive deionization apparatuses 300 is in ion discharge mode.
  • the incoming aqueous solution 315a can then be continuously fed to the capacitive deionization apparatuses 300 that are currently in ion accumulation mode.
  • Ref-11 F. Rivera et al. “Enhancement of swine manure anaerobic digestion using membrane-based NH3 extraction”. Bioresource Technology (2022), 362, 127829. Ref-12 S. S. Gupta et al., “Capacitive Deionization (GDI): An Alternative Cost-Efficient Desalination Technique”, in: Advances in Water Purification Techniques, Elsevier, 2019, pp. 165-202.
  • GDI Capacitive Deionization

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Abstract

L'invention concerne un dispositif (500) destiné à modifier le milieu de fermentation liquide (91) dans un bioréacteur de fermentation anaérobie (10), comprenant une première unité de séparation d'ions (200) conçue pour recevoir un premier flux d'entrée (201) de solution aqueuse sous la forme d'un milieu de fermentation filtré liquide (93) à partir d'un bioréacteur de fermentation anaérobie (10) et un deuxième flux d'entrée (202) de solution aqueuse, et conçue pour transférer des ions dudit premier flux d'entrée audit deuxième flux d'entrée, formant ainsi un premier flux de sortie (203) de solution aqueuse ayant une teneur en ions réduite par rapport au premier flux d'entrée (201) et un deuxième flux de sortie (204) ayant une teneur en ions accrue par rapport au deuxième flux d'entrée (202). Le dispositif comprend en outre des moyens (100, 106) destinés à récupérer une solution aqueuse sous la forme d'un milieu de fermentation filtré liquide (93) à partir d'un milieu de fermentation liquide (91) dans un bioréacteur de fermentation anaérobie (10) et introduire ladite solution aqueuse (93) en tant que premier flux d'entrée (201) dans la première unité de séparation d'ions (200) ; et des moyens (100, 107) destinés à renvoyer le premier flux de sortie (203) de la première unité de séparation d'ions (200) en tant que milieu de fermentation liquide modifié (92) à un bioréacteur de fermentation anaérobie (10).
PCT/IB2025/055094 2024-05-15 2025-05-15 Appareil et procédé d'utilisation efficace d'une biomasse par fermentation anaérobie Pending WO2025238599A2 (fr)

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