Single-chamber microbial electrolysis cell system without ion exchange membrane and method for producing clean gas, such as hydrogen and biogas, by using same

Abstract

One embodiment of the present invention provides a system and method for producing hydrogen and biogas, capable of shortening the hydrogen production start time of a microbial electrolysis cell through techniques of determining the voltage application time at each step, monitoring electrochemically active microbial populations, and inhibiting methane conversion bacteria for hydrogen production, in order to shorten the stabilized culture period of the microbial populations through a single-chamber microbial electrolysis cell system.

Description

Single-chamber microbial electrolysis cell system without ion exchange membrane and method for producing clean gases such as hydrogen and biogas using the same

[0001] The present invention relates to a single-chamber microbial electrolysis cell system without an ion exchange membrane and a method for producing clean gases including hydrogen and biogas using the same, and more particularly, to a single-chamber microbial electrolysis cell system utilizing a technology for determining step-by-step voltage application times, monitoring an electrochemically active microbial community, and inhibiting methane-converting bacteria for hydrogen production in order to shorten the stabilization culture period of a single-chamber microbial electrolysis cell microbial community, and a method for producing clean gases including hydrogen and biogas using the same. In addition, the present invention provides a technology that can be applied to a post-treatment process of an anaerobic digestion process to increase biogas production efficiency and applicability, and to achieve wastewater treatment and energy recovery simultaneously.

[0002]

[0003] Microbial electrolysis cells have been actively researched recently due to their advantage in producing hydrogen by applying them to the treatment of high-concentration wastewater containing organic acids such as acetate, which are difficult to produce hydrogen through conventional fermentation processes.

[0004] In general, a two-chamber microbial electrolysis cell equipped with an ion exchange membrane between a reduction chamber and an oxidation chamber is widely used, but due to contamination and electrical resistance of the ion exchange membrane and the increase in the price of the reactor, a single-chamber microbial electrolysis cell without an ion exchange membrane is attracting attention.

[0005] In order to rapidly produce hydrogen through the operation of a single-chamber microbial electrolysis cell without an ion exchange membrane, the organic matter decomposition performance of a specific electroactive microbial community distributed within the reactor is important simultaneously with the externally applied voltage, and in addition to hydrogen production, it is important to appropriately inhibit a specific microbial community that produces methane among the biogas produced through the decomposition of organic matter.

[0006] However, most existing single-chamber microbial electrolysis cells require time ranging from as little as one month to as long as over a year to operate and stabilize a specific electrochemically active microbial community for hydrogen production. Consequently, technological development to shorten the time it takes for single-chamber microbial electrolysis cells to initiate hydrogen production within this short timeframe remains limited.

[0007] Many previous studies have the disadvantage of requiring a long time for the entire process (pre-process) for hydrogen production, such as culturing specific electrochemically active microbial communities that decompose organic matter for a long time in microbial fuel cells (MFCs) and then release electrons, or applying low voltage (<0.6 V, based on total cell voltage) for a long time to induce stabilization of microbial electrolysis cells.

[0008] [Prior Art Literature]

[0009] (Republic of Korea Registered Patent Document 0001) 10-1714431

[0010]

[0011] The technical problem to be achieved by the present invention is to provide a technology capable of shortening the time required for hydrogen production through operation of a single chamber microbial electrolysis cell and stabilizing the culture of a specific electrochemically active microbial community.

[0012] The goal is to provide a carbon-neutral and environmentally friendly technology that can produce hydrogen and biogas containing large amounts of hydrogen while treating high-concentration organic wastewater.

[0013] By not using an ion exchange membrane, the disadvantages of ohmic loss due to the membrane, difficulty in scale-up due to the complexity of the reactor structure, biofouling of the membrane, and increased reactor price due to the high cost of the membrane are resolved.

[0014] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0015]

[0016] In order to achieve the above technical problem, one embodiment of the present invention provides a single chamber microbial electrolysis cell system without an ion exchange membrane, including: a power supply unit; a microbial electrolysis chamber connected to the power supply unit; an electrode unit positioned within the chamber; and a water bath connected to the chamber and used to maintain a temperature, wherein the chamber includes: a gas collection unit for confirming biogas production within the chamber; an organic matter supply unit for supplying organic matter into the chamber; a gas supply unit for supplying an inert gas into the chamber; a sampling unit for confirming consumption of organic matter within the chamber; a solution replacement unit for replacing organic matter within the chamber; and a stirring unit for stirring within the chamber; wherein the electrode unit includes an oxidation electrode and a reduction electrode installed opposite to each other within the chamber; and a reference electrode positioned next to the oxidation electrode or the reduction electrode.

[0017] In an embodiment of the present invention, the chamber may be cylindrical or cassette-shaped, and when the chamber is cassette-shaped, the cassette-shaped chamber may be characterized in that only the reduction electrode is exposed to the air to inhibit methanogenic bacteria formed on the reduction electrode, or the oxidation electrode and reduction electrode can be separated and detached for electrode maintenance.

[0018] In an embodiment of the present invention, the method may be characterized by monitoring biogas generated inside the chamber through the gas collection unit and performing a method of exposing the reduction electrode to the air to inhibit methanogens formed on the reduction electrode, a method of replacing the organic medium when operating in batch mode, a method of removing a solution-phase methanogen colony by operating the HRT for less than 24 hours when operating continuously, or a method of supplying a chemical inhibitor or antibiotic into the chamber.

[0019] In an embodiment of the present invention, a gas-liquid separator may be coupled to one side of the chamber.

[0020] In an embodiment of the present invention, the gas-liquid separator can reduce the residence time of hydrogen produced within the chamber, thereby reducing the activity of microorganisms that consume the produced hydrogen.

[0021] In order to achieve the above technical task, another embodiment of the present invention provides a method for producing hydrogen using a single-chamber microbial electrolysis cell system without an ion exchange membrane, the method comprising the steps of: supplying organic matter to a chamber through an organic matter medium without applying an external voltage; forming an electrochemically active microbial community by applying an external voltage to the chamber; inhibiting methane-producing bacteria formed on a reduction electrode within the chamber; and producing hydrogen and biogas.

[0022] In an embodiment of the present invention, the step of supplying organic matter to the chamber through the organic matter medium without applying the external voltage may be characterized in that anaerobic digestion conditions are formed inside the chamber to form hydrogen and biogas, and the anaerobic digestion conditions are characterized in that an inert gas is supplied into the chamber at a rate of 50 ml / min or less for 15 to 20 minutes.

[0023] In an embodiment of the present invention, the step of supplying organic matter to the chamber through the organic matter medium without applying an external voltage may be characterized by maintaining the temperature of the chamber at 20 to 35°C.

[0024] In an embodiment of the present invention, the external voltage may be characterized by being applied at 0.6 to 1.2 V using a two-electrode voltage application method.

[0025] In an embodiment of the present invention, the step of inhibiting methanogenic bacteria located on the reduction electrode in the chamber may be characterized by being performed through a method of exposing the reduction electrode to air, a method of replacing the organic medium when operating in a batch mode, a method of removing a community of methanogenic bacteria in a solution phase by operating the HRT for less than 24 hours when operating continuously, a method of exposing the hydrogen-producing reduction electrode to air for 10 minutes to 1 hour, or a method of supplying a chemical inhibitor or antibiotic.

[0026] In an embodiment of the present invention, the chemical inhibitor may be selected from the group including Sodium 2-bromoethanesulfonate, 2-bromoethanesulfonate, Iodopropane, and lumazine, and the antibiotic may be selected from the group including Neomycin sulfate, 2-chloroethane sulfonate, and 8-aza-hypoxanthine.

[0027] In an embodiment of the present invention, the step of producing hydrogen may be characterized by being performed by monitoring the potential of the oxidation electrode within the chamber based on the reference electrode within the chamber, checking the concentration of the organic substance, and replacing the organic substance medium.

[0028] In an embodiment of the present invention, the step of producing hydrogen and biogas may be characterized in that the carbon dioxide, methane, and hydrogen contents of the biogas produced are controlled according to the voltage applied to the single chamber microbial electrolysis cell system without the ion exchange membrane, the temperature of the chamber, the HRT (the time the reactants remain in the chamber), or the application of a method for inhibiting the activity of methanogens and homoacetogens, thereby producing biogas suitable for the intended use.

[0029] In an embodiment of the present invention, in the step of supplying organic matter to the chamber through an organic medium without applying an external voltage, when the organic matter is a liquid containing an organic acid and a gas containing carbon dioxide and methane, organic contaminants contained in the liquid containing the organic acid are removed within the chamber, and at the same time, carbon dioxide in the gas is converted into methane by combining with hydrogen produced in a single-chamber microbial electrolysis cell system, and highly soluble impurities including sulfur compounds, silicic acid, and malodorous substances contained in the gas are removed while passing through the liquid within the chamber, so that the content ratio of hydrogen and methane of biogas produced in the single-chamber microbial electrolysis cell system increases, thereby improving its quality.

[0030]

[0031] According to an embodiment of the present invention, the time required for hydrogen production and stabilization of a specific electrochemically active microbial community culture through operation of a single chamber microbial electrolysis cell can be shortened.

[0032] It can provide a carbon-neutral and environmentally friendly technology that can produce hydrogen and high-hydrogen biogas while treating high-concentration organic wastewater such as sewage and food waste sludge.

[0033] It overcomes thermodynamic limitations, can produce hydrogen from various organic substances at room temperature and pressure, and consumes less electric energy (0.6~1.2V) compared to the water electrolysis process (theoretical value > 1.23V). Furthermore, since it does not use an ion exchange membrane, it can solve the disadvantages of Ohmic loss due to the membrane, difficulty in scale-up due to the complexity of the reactor structure, biofouling of the membrane, and increased reactor price due to the high-cost membrane.

[0034] Currently, high-concentration organic wastewater, such as sewage and food waste sludge, is converted into biogas, such as methane, through an anaerobic digestion process. However, the methane content of biogas from the anaerobic digestion process is only 40-60% at most, so it has a low calorific value, making it difficult to directly replace city gas or use it for combined heat and power generation. The technology proposed in the present invention can further convert organic acids, which are difficult to convert into methane, into hydrogen during the anaerobic digestion process itself, and thus can be utilized to improve the gas composition of biogas, increase the calorific value during combustion, and serve as a pretreatment process for the subsequent hydrogen separation process. In addition, biogas from the anaerobic digestion process, which contains sulfur compounds, siloxanes, and odorous substances, can be passed through the liquid phase of a microbial electrolytic cell to remove highly soluble contaminants, thereby contributing to improving the quality of biogas.

[0035] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the detailed description of the present invention or the composition of the invention described in the claims.

[0036]

[0037] Figure 1 is (a) a schematic diagram of a single-chamber microbial electrolysis cell system without an ion exchange membrane according to an embodiment of the present invention, and (b) an actual appearance of a lab-scale single-chamber electrolysis cell system.

[0038] Figure 2 is a schematic diagram of (a) a single-chamber microbial electrolysis cell system without a cylindrical ion exchange membrane according to an embodiment of the present invention, and (b) an actual appearance of a bench-scale single-chamber electrolysis cell system.

[0039] Figure 3 is a schematic diagram of (a) a single-chamber microbial electrolysis cell system without a cassette-type ion exchange membrane, in which the oxidation electrode and reduction electrode can be detached and attached as needed according to an embodiment of the present invention, and (b) a schematic diagram of a bench-scale single-chamber electrolysis cell system.

[0040] Figure 4 is a schematic diagram of a method for producing clean gas including hydrogen and biogas using a single chamber microbial electrolysis cell system without an ion exchange membrane according to an embodiment of the present invention.

[0041] Figure 5 shows the results (based on NGS analysis) of (a) a microbial community attached to an oxidation electrode at the phylum level, (b) a microbial community attached to a reduction electrode, and (c) a microbial community attached to the oxidation electrode and reduction electrode at the genus level after operation of a single-chamber type microbial electrolysis cell system without an ion exchange membrane according to an embodiment of the present invention.

[0042] Figure 6 shows the results of hydrogen production in biogas production in a single-chamber type microbial electrolysis cell system without an ion exchange membrane according to an embodiment of the present invention (a) without application and (b) after application of the technology proposed in the present invention.

[0043] FIG. 7 is a schematic diagram of a single chamber microbial electrolysis cell system without an ion exchange membrane coupled with a gas-liquid separator according to one embodiment of the present invention.

[0044] Figure 8 is a schematic diagram of an anaerobic digestion tank connected to a single chamber microbial electrolysis cell system according to one embodiment of the present invention, in which anaerobic digestion conditions are created.

[0045]

[0046] Hereinafter, the present invention will be described with reference to the attached drawings. However, the present invention can be implemented in various different forms and is therefore not limited to the embodiments described herein. In the drawings, irrelevant parts have been omitted for clarity of description, and similar parts have been designated with similar reference numerals throughout the specification.

[0047] Throughout the specification, when a part is said to be "connected (connected, contacted, or coupled)" to another part, this includes not only cases where it is "directly connected," but also cases where it is "indirectly connected" with another part in between. Furthermore, when a part is said to "include" a component, this does not exclude other components, but rather implies that it may include other components, unless otherwise specifically stated.

[0048] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, it should be understood that the terms "comprises" or "has" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0049] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0050]

[0051] A single chamber microbial electrolysis cell system without an ion exchange membrane according to one embodiment of the present invention is described.

[0052] Figure 1 is (a) a schematic diagram of a single-chamber microbial electrolysis cell system without an ion exchange membrane according to an embodiment of the present invention, and (b) an actual appearance of a lab-scale single-chamber electrolysis cell system.

[0053] Figure 2 is a schematic diagram of (a) a single-chamber microbial electrolysis cell system without a cylindrical ion exchange membrane according to an embodiment of the present invention, and (b) an actual appearance of a bench-scale single-chamber electrolysis cell system.

[0054] Figure 3 is a schematic diagram of (a) a single-chamber microbial electrolysis cell system without a cassette-type ion exchange membrane according to an embodiment of the present invention, and (b) a schematic diagram of a bench-scale single-chamber electrolysis cell system.

[0055] Referring to FIGS. 1 to 3, a single-chamber microbial electrolysis cell system without an ion exchange membrane according to an embodiment of the present invention comprises: a power supply unit (100); a microbial electrolysis chamber (200) connected to the power supply unit (100); an electrode unit positioned within the chamber (200); and a water bath (300) connected to the chamber (200) and used to maintain a temperature; wherein the chamber (200) comprises: a gas collection unit (210) for confirming biogas production within the chamber (200); an organic matter supply unit (220) for supplying organic matter into the chamber (200); a gas supply unit (230) for supplying an inert gas into the chamber (200); a sampling unit (240) for confirming consumption of organic matter within the chamber (200); a solution replacement unit (250) for replacing organic matter within the chamber (200); And a stirring unit (400) for stirring inside the chamber; and the electrode unit may include an oxidation electrode (201) and a reduction electrode (202) installed opposite each other inside the chamber (200); and a reference electrode (203) located next to the oxidation electrode (201) or the reduction electrode (202).

[0056] The above chamber may be cylindrical or cassette-shaped, and when the chamber is cassette-shaped, the cassette-shaped chamber may expose only the reduction electrode to the air to inhibit methanogenic bacteria formed on the reduction electrode, or the oxidation electrode and reduction electrode may be separated and detached for electrode maintenance.

[0057] Meanwhile, the present invention monitors biogas generated inside the chamber through the gas collection unit and, in order to inhibit methanogens formed on the reduction electrode, performs a method of exposing the reduction electrode to the air, a method of replacing the organic medium when operating in batch mode, a method of removing a solution-phase methanogen colony by operating the HRT for less than 24 hours when operating continuously, or a method of supplying a chemical inhibitor or antibiotic into the chamber.

[0058] In order to monitor the biogas produced at this time, the gas composition can be checked in real time by connecting the gas chromatography (GC) equipment to the gas collection unit in the reactor, and the amount of gas produced can be checked in real time by connecting it to a respirometer.

[0059] At this time, the amount of methanogenic bacteria formed on the reduction electrode can be inferred by confirming the amount of biogas produced through the method described above, and the methods described above can be performed to inhibit the formed methanogenic bacteria.

[0060] Accordingly, a monitoring unit including a gas chromatography device is further connected to the gas collection unit of the single chamber microbial electrolysis cell system without an ion exchange membrane of the present invention, so that a user can check the amount of biogas produced through the monitoring unit and infer the amount of methane-producing bacteria through this, and then, in order to inhibit the formed methane-producing bacteria, the user can immediately proceed with a method of exposing the reduction electrode to the air.

[0061] Alternatively, the user may use a method of replacing the organic medium when operating the reactor in batch mode or a method of removing the solution-phase methanogenic bacteria community by operating the reactor in continuous mode with an HRT of less than 24 hours.

[0062] Alternatively, the user may perform a method of supplying a chemical inhibitor or antibiotic into the chamber.

[0063] At this time, it does not matter whether one or more of the above-mentioned methods is used.

[0064] Meanwhile, microbial electrolysis cells are being actively researched recently due to their advantage in producing hydrogen and biogas containing large amounts of hydrogen by applying them to the treatment of high-concentration wastewater containing organic acids such as acetate, which are difficult to produce hydrogen from using existing fermentation processes.

[0065] At this time, the microorganism electrolysis cell is largely divided into a two-chamber reaction system and a single-chamber reaction system. In the case of the two-chamber reaction system, the reaction system is divided into an oxidation chamber and a reduction chamber by an ion exchange membrane, and the organic matter supplied by electroactive microorganisms to the oxidation chamber is decomposed into electrons and hydrogen ions (H + ) is generated, and the electrons and hydrogen ions (H ) generated in this way + ) These electrons move to the reduction electrode through the external circuit and form hydrogen ions (H + ) passes through the ion exchange membrane and moves to the reduction chamber, where a hydrogen generation reaction occurs at the reduction electrode.

[0066] Although a two-chamber microbial electrolysis cell equipped with an ion exchange membrane between a reduction chamber and an oxidation chamber is widely applied, the present invention discloses a single-chamber microbial electrolysis cell without an ion exchange membrane due to contamination and electrical resistance of the ion exchange membrane, complexity of the reactor structure, and increase in reactor price.

[0067] Specifically, the present invention discloses a technique for determining the stepwise application time of voltage, monitoring the electrochemically active microbial community, and inhibiting methane conversion bacteria for hydrogen production in order to shorten the stabilization culture period of a single-chamber microbial electrolysis cell microbial community.

[0068]

[0069] In the case of the two-stage process, microorganisms are inoculated and cultured only in the oxidation chamber. This method has the advantage of allowing for chamber differentiation, allowing microorganisms to be grown only in the oxidation chamber. However, the disadvantage is that the membrane or ion exchange membrane performance deteriorates over time. Furthermore, the use of the membrane or ion exchange membrane complicates the reactor structure, making modifications difficult and increasing manufacturing costs.

[0070] Accordingly, the present invention initiates a reactor by introducing microorganisms into a single chamber without an ion exchange membrane.

[0071] It is important to selectively cultivate specific electrochemically active microbial communities on both the oxidation and reduction electrodes.

[0072] And since microorganisms cannot be formed only at the oxidation electrode, measures must be taken to enable electrochemically active microorganisms to be selectively cultured at the oxidation electrode and reduction electrode, and among the microorganisms cultured at the reduction electrode, methanogens must be inhibited using the method presented above to enable a large amount of hydrogen to be produced.

[0073] Meanwhile, a single-chamber microbial electrolysis cell system without an ion exchange membrane may produce biogas containing CH4 and CO2 in addition to hydrogen production because it does not have an ion exchange membrane to separate the oxidation and reduction reactions of organic substances in the reactor.

[0074] In this process, specific microbial communities that consume hydrogen, such as Methanogen (CO2+ 4H2--> CH4+ 2H2O) and Homoacetogen (2CO2+ 4H2--> CH3COOH + 2H2O), may be involved, and if the two communities are properly controlled, more stable production of biogas containing hydrogen may be possible.

[0075] By controlling the content of carbon dioxide, methane, and hydrogen, which are the main components of biogas, using the technology proposed in the present invention, biogas with a high hydrogen content that can be used for combustion or gas power generation can be produced, or it can be used as a pretreatment process to reduce the burden of the pressure sweep adsorption (PSA) process that produces high-purity hydrogen.

[0076] For this purpose, a gas-liquid separator (500) may be further combined on one side of a single chamber of the single chamber microbial electrolysis cell system without an ion exchange membrane of the present invention.

[0077] FIG. 7 is a schematic diagram of a system in which a gas-liquid separator (500) is further combined with a single chamber microbial electrolysis cell system without an ion exchange membrane according to one embodiment of the present invention.

[0078] Referring to FIG. 7, it can be seen that a gas-liquid separator (500) is coupled to one side of a chamber of a single chamber microbial electrolysis cell system without an ion exchange membrane according to one embodiment of the present invention.

[0079] As previously explained, certain hydrogen-consuming microbial communities, such as Methanogen (CO2+ 4H2--> CH4+ 2H2O) and Homoacetogen (2CO2+ 4H2--> CH3COOH + 2H2O), can interfere with stable hydrogen production within the reactor.

[0080] Accordingly, various methods for inhibiting Methanogen and Homoacetogen have been studied, and in particular, papers have been reported on methods for inhibiting by injecting chemicals that inhibit related enzymes, such as 2-bromoethanesulfonate and chloroform. However, this does not only affect specific enzymes, but also affects the activity of all microorganisms, which can reduce the performance of the entire reactor. In particular, it is difficult to apply to large-scale reactors due to cost and environmental issues.

[0081] By physically suppressing methanogen and homoacetogen through the reactor structure and operation, it is possible to minimize the residence time of hydrogen produced through the microbial electrolysis cell reaction in the reactor and to suppress the reaction of methanogen and homoacetogen consuming hydrogen as much as possible. For this purpose, a gas-liquid separator (500) can be used.

[0082] Specifically, the gas headspace of the microbial electrolysis cell is minimized (i.e., the liquid phase is filled to the top of the reactor), and the gas (biogas containing hydrogen) generated from the top of the reactor and the liquid flowing out are transferred to a gas / liquid separator to be separated into gas and liquid, and the gas is collected at the top and the liquid is collected at the bottom and returned to the microbial electrolysis cell. In this way, effective separation of electrolyte and gas is possible, and in particular, it becomes possible to quickly separate the generated hydrogen from the microbial electrolysis cell chamber (reactor) to suppress methanogenic bacteria or acetic acid-producing bacteria.

[0083] At this time, if the generated hydrogen is not separated quickly, the hydrogen produced by Methanogen or Homoacetogen is recycled as mentioned above, which causes a problem in that the production speed and yield of hydrogen decrease.

[0084] The design considerations for incorporating a gas-liquid separator (500) into the single chamber microbial electrolysis cell system without an ion exchange membrane according to the present invention are as follows.

[0085] First, a gas pocket where the gas generated in the microbial electrolysis cell reactor is collected must be located at the top of the MEC reactor, and a gas pump must be connected so that the gas passed to the gas-liquid separator can be collected in the gas storage at the top of the reactor.

[0086] In addition, a liquid pump (510) can be installed at the bottom of the gas-liquid separator (500) to recirculate the electrolyte (microbial medium) to minimize the loss of the electrolyte and maintain the continuity of the process.

[0087] The gas produced through this configuration is captured at the upper part of the gas-liquid separator (500), the captured gas is stored in a gas storage, and the liquid is introduced into the reactor from the lower part of the gas-liquid separator (500) by a liquid pump so that the reaction can continue.

[0088] In addition, a monitoring system is further incorporated outside the reactor to track the potential of the oxidation electrode, which changes according to the concentration of the substrate being introduced, and at the same time, measure the pH range, temperature, and partial pressure maintained within the reactor.

[0089] Therefore, in a single chamber microbial electrolysis cell system without an ion exchange membrane combined with the gas-liquid separator (500) of the present invention, a certain space can be formed at the top of the chamber so that a gas pocket can be formed.

[0090] Additionally, a gas storage tank may be located at the top of the gas-liquid separator (500).

[0091] In addition, a liquid pump (510) is positioned at the bottom of the gas-liquid separator (500), and the liquid pump (510) can connect the gas-liquid separator (500) and the chamber.

[0092] Through the above-described configuration, the gas-liquid separator (500) of the present invention can reduce the residence time of hydrogen produced within the chamber, thereby reducing the activity of microorganisms that consume hydrogen produced within the chamber.

[0093]

[0094] Hereinafter, a specific method for producing hydrogen using a single-chamber microbial electrolysis cell system without an ion exchange membrane having the aforementioned characteristics will be described.

[0095]

[0096] A method for producing hydrogen and biogas using a single chamber microbial electrolysis cell system without an ion exchange membrane according to one embodiment of the present invention is described.

[0097] The method for producing clean gas including hydrogen and biogas using a single chamber microbial electrolysis cell system without an ion exchange membrane according to one embodiment of the present invention can apply all of the contents described for the single chamber microbial electrolysis cell system without an ion exchange membrane described above, and although detailed descriptions of overlapping parts are omitted, the same can be applied even if the descriptions are omitted.

[0098]

[0099] Figure 4 is a schematic diagram of a method for producing clean gas including hydrogen and biogas using a single chamber microbial electrolysis cell system without an ion exchange membrane according to an embodiment of the present invention.

[0100] Referring to FIG. 4, a method for producing hydrogen and biogas using a single-chamber microbial electrolysis cell system without an ion exchange membrane according to one embodiment of the present invention may include a step of supplying organic matter to a chamber through an organic matter medium without applying an external voltage; a step of forming an electrochemically active microbial community by applying an external voltage to the chamber; a step of inhibiting methane-producing bacteria formed on a reduction electrode within the chamber; and a step of producing hydrogen.

[0101] The first step is to supply organic matter to the chamber through an organic medium without applying external voltage.

[0102] The step of supplying organic matter to the chamber through the organic medium without applying the above external voltage causes dark fermentation to proceed, and as this dark fermentation progresses, the organic matter is decomposed by microorganisms and used. Biogas is produced through this dark fermentation of the carbon source. The biogas may be formed by forming anaerobic digestion conditions inside the chamber. The biogas produced at this time is mainly composed of methane and CO₂, and may contain impurities such as hydrogen sulfide (H₂S), moisture (H₂O), ammonia (NH₃), nitrogen (N₂), and oxygen (O₂).

[0103] The above anaerobic digestion conditions can be formed by supplying an inert gas into the chamber. Nitrogen or argon gas may be used as the inert gas, but is not limited thereto.

[0104] The supply of inert gas may be supplied at a rate of 50 ml / min or less for 15 to 20 minutes.

[0105] The temperature of the chamber may be maintained at 20 to 35°C.

[0106] Chemicals contained in organic matter include sodium acetate, NH4Cl, NaCl, MgSO47H2O, KCl, or yeast extract, which are used as carbon sources and can be used as a medium for microbial growth.

[0107] Secondary sedimentation sludge, food wastewater generated from food wastewater treatment plants, and mixed wastewater containing domestic wastewater and sewage can be used as mixed strain inoculum sources.

[0108] To monitor the biogas produced, gas chromatography (GC) equipment is connected to the gas collection unit within the reactor to monitor the gas composition in real time. The amount of gas produced can be monitored in real time by connecting it to a respirometer.

[0109]

[0110] The next step is to apply an external voltage to the chamber to form an electrochemically active microbial community.

[0111] The external voltage may be a low voltage of 0.6 to 1.2 V applied using a two-electrode voltage application method. Simultaneously, the biogas produced can be monitored. Under the conditions of external voltage application, growth and formation of a specific electrochemically active microbial community that decomposes organic matter occur.

[0112] It may be a process of confirming the growth of a microbial community that can grow under electron supply conditions while simultaneously applying an electric potential while forming a specific electrochemically active microbial community that releases electrons using organic matter.

[0113] At this time, the electrochemically active microbial community that grows and forms can be formed on the surfaces of the oxidation electrode and reduction electrode, and can also be formed inside the medium.

[0114]

[0115] The following is a step for inhibiting methane-producing bacteria formed on the reduction electrode in the chamber.

[0116] To produce hydrogen at the cathode, methanogenic bacteria that produce methane gas must be inhibited. This is because, instead of producing hydrogen by reducing protons and electrons, methanogenic bacteria formed at the cathode compete with each other to produce methane gas by reducing carbon dioxide contained in the biogas to electrons and hydrogen ions.

[0117] The step of inhibiting methanogenic bacteria located on the reduction electrode in the chamber may be performed by a method of exposing the reduction electrode to air, a method of replacing the organic medium, a method of removing a community of methanogenic bacteria in the solution phase by operating the HRT for less than 24 hours in the case of continuous operation, a method of exposing the hydrogen-producing reduction electrode to air for 10 minutes to 1 hour, or a method of supplying a chemical inhibitor or antibiotic.

[0118] The method for replacing the organic medium is to prevent the growth of methanogens within the reactor by replacing the medium quickly, as the growth rate of methanogens is slow. It is desirable to replace the medium as quickly as possible.

[0119] The chemical inhibitor or antibiotic may be supplied into the chamber, wherein the chemical inhibitor may be at least one inhibitor selected from the group including Sodium 2-bromoethanesulfonate, 2-bromoethanesulfonate, Iodopropane, and lumazine, and the antibiotic may be at least one antibiotic selected from the group including Neomycin sulfate, 2-chloroethane sulfonate, and 8-aza-hypoxanthine.

[0120] The operating method of this system can be divided into continuous and batch mode, and the batch mode can be used to change the medium to enable rapid hydrogen production.

[0121]

[0122] The following are the steps in which hydrogen and biogas are produced.

[0123] The step of producing the above hydrogen and biogas may be performed by monitoring the potential of the oxidation electrode in the chamber based on the reference electrode in the chamber, checking the concentration of organic matter, and replacing the organic matter medium.

[0124] As organic matter depletes, the potential of the oxidation electrode also decreases. To monitor this trend, conduct experiments using a voltammeter or LabView software. The potential of the oxidation electrode can be monitored in real time. Experiments can be conducted with the understanding that the potential of the oxidation electrode varies depending on the conductivity of the medium used and the materials of the oxidation and reduction electrodes.

[0125] Biogas monitoring can shorten the time to start hydrogen production by adding methanogen inhibitors.

[0126] Meanwhile, by synthesizing the conditions described above, in the step of producing the hydrogen and biogas, the carbon dioxide, methane and hydrogen contents of the produced biogas can be controlled by adjusting the voltage applied to the single chamber microbial electrolysis cell system without an ion exchange membrane, the temperature of the chamber, the HRT (the time the reactants remain in the chamber), or the application of a method for inhibiting the activity of methanogens and homoacetogens, so that biogas suitable for the intended use can be produced.

[0127] Meanwhile, in the present invention, in a step of supplying organic matter to a chamber through an organic medium without applying an external voltage, when the organic matter is a liquid containing an organic acid and a gas containing carbon dioxide and methane, organic contaminants contained in the liquid containing an organic acid are removed within the chamber, and at the same time, carbon dioxide in the gas is converted into methane by combining with hydrogen produced in a single-chamber microbial electrolysis cell system, and highly soluble impurities including sulfur compounds, silicic acid, and malodorous substances contained in the gas are removed while passing through the liquid within the chamber, so that the content ratio of hydrogen and methane of biogas produced in the single-chamber microbial electrolysis cell system increases, thereby improving its quality.

[0128] In this case, improving the quality of biogas means improving the content of methane and hydrogen contained in the biogas.

[0129] Figure 8 is a schematic diagram of an anaerobic digestion tank connected to a single chamber microbial electrolysis cell system according to one embodiment of the present invention, in which anaerobic digestion conditions are created.

[0130] Referring to Fig. 8, an anaerobic digester is connected to the front end, and at this time, a liquid phase containing organic acid of the anaerobic digester and an exhaust gas containing carbon dioxide and methane are introduced into a single-chamber microbial electrolysis cell system without an ion exchange membrane to purify liquid organic pollutants, while converting gaseous CO2 into methane by combining it with hydrogen produced in the microbial electrolysis cell, and removing highly soluble impurities including sulfur compounds, siloxanes, and odorous substances present in the exhaust gas of the anaerobic digester by passing them through the liquid phase, thereby improving the quality of biogas.

[0131]

[0132] Hereinafter, an experimental example of the present invention will be described in detail.

[0133]

[0134] <Experimental Example>

[0135]

[0136] [Table 1]

[0137]

[0138] Referring to Table 1, it can be seen that when low voltage is applied, the hydrogen production start time is basically one month or one year.

[0139]

[0140] Figure 5 shows the results (based on NGS analysis) of (a) a microbial community attached to an oxidation electrode at the phylum level, (b) a microbial community attached to a reduction electrode, and (c) a microbial community attached to the oxidation electrode and reduction electrode at the genus level after operation of a single-chamber type microbial electrolysis cell system without an ion exchange membrane according to an embodiment of the present invention.

[0141] Referring to Figure 5, it can be confirmed that the microbial community exists in the order of Proteobacteria, Firmicutes, and Bacteroidetes at the oxidation electrode, and in the order of Firmicutes, Euryarchaeota, and Bacteroidetes at the reduction electrode.

[0142] Proteobacteria attached to the anode are known to be bacteria that participate in the process of generating electricity by oxidizing representative organic substances, and include Geobacter. These species can contribute to electron transfer by secreting oxidized substances on the electrode surface. Euryarchaeota attached to the cathode decompose organic substances to produce methane, or they are active in anaerobic environments and produce methane using carbon dioxide and hydrogen. One of the major subgroups is known to be Methanobacterium. Microbial communities formed after methane inhibition can contribute to hydrogen production.

[0143] Figure 6 shows the results of hydrogen production in biogas production in a single-chamber type microbial electrolysis cell system without an ion exchange membrane according to an embodiment of the present invention (a) without application and (b) after application of the technology proposed in the present invention.

[0144] In the case of non-application (a), the technology of the present invention is not applied, and the reactor is operated by applying an applied voltage from the beginning of the reaction using a method reported so far.

[0145] Application (b) was initially operated under anaerobic conditions without applying a potential according to the method suggested in the present invention, and then a potential was applied at the yellow arrow, and the red arrow indicates the point of inhibition of methane-converting bacteria.

[0146] Referring to Figure 6, when the present invention was not applied, methane and carbon dioxide increased over time and hydrogen production was almost non-existent, but when the present invention was applied to inhibit potential application and methane conversion bacteria, it was confirmed that methane and carbon dioxide in the biogas decreased and hydrogen production increased rapidly.

[0147]

[0148] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single entity may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0149] The scope of the present invention is indicated by the claims described below, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

[0150] [Explanation of symbols]

[0151] 100: Power supply unit

[0152] 200: Electrolysis chamber

[0153] 201: Oxidation electrode

[0154] 202: Reduction electrode

[0155] 203: Reference electrode

[0156] 210: Gas collection unit

[0157] 220: Organic matter supply unit

[0158] 230: Gas supply section

[0159] 240: Sampling unit

[0160] 250: Solution replacement part

[0161] 300: Water Bath

[0162] 400: Stirring section

[0163] 500: Gas-liquid separator

[0164] 510: Pump

Claims

1. Power supply unit; A microbial electrolysis chamber connected to the power supply unit; An electrode portion located within the chamber; and A water bath connected to the above chamber and for maintaining temperature; The above chamber, A gas collection unit for confirming biogas production inside the chamber; An organic material supply unit for supplying organic material into the chamber; A gas supply unit for supplying an inert gas into the chamber; A sampling unit for checking the consumption of organic matter inside the chamber; A solution replacement unit for replacing organic matter inside the chamber; and Includes a stirring unit for stirring inside the chamber; The above electrode part, An oxidation electrode and a reduction electrode installed opposite each other in the chamber; and A single chamber microbial electrolysis cell system without an ion exchange membrane, comprising a reference electrode positioned next to the oxidation electrode or the reduction electrode.

2. In paragraph 1, The chamber may be cylindrical or cassette-shaped, A single chamber microbial electrolysis cell system without an ion exchange membrane, characterized in that when the chamber is a cassette type, the cassette type chamber exposes only the reduction electrode to the air to inhibit methanogenic bacteria formed on the reduction electrode, or the oxidation electrode and reduction electrode can be separated and detached for electrode maintenance.

3. In paragraph 1, In order to monitor the biogas generated inside the chamber through the gas collection unit and to inhibit the methane-producing bacteria formed on the reduction electrode, A single chamber microbial electrolysis cell system without an ion exchange membrane, characterized in that it performs a method of exposing the above reduction electrode to the air, a method of replacing the organic medium when operating in a batch mode, a method of removing a community of solution-phase methanogenic bacteria by operating the HRT for less than 24 hours when operating continuously, or a method of supplying a chemical inhibitor or antibiotic into the chamber.

4. In paragraph 1, A single chamber microbial electrolysis cell system without an ion exchange membrane, characterized in that a gas-liquid separator is further combined on one side of the chamber.

5. In paragraph 4, A single chamber microbial electrolysis cell system without an ion exchange membrane, characterized in that the gas-liquid separator reduces the residence time of hydrogen produced within the chamber, thereby reducing the activity of microorganisms that consume the produced hydrogen.

6. A step of supplying organic matter to the chamber through an organic medium without applying external voltage; A step of forming an electrochemically active microbial community by applying an external voltage to the chamber; A step of inhibiting methane-producing bacteria formed on the reduction electrode in the chamber; and A method for producing hydrogen and biogas using a single chamber microbial electrolysis cell system without an ion exchange membrane, comprising a step of producing hydrogen and biogas.

7. In paragraph 6, The step of supplying organic matter to the chamber through the organic matter medium without applying the above external voltage is as follows: Anaerobic digestion conditions are formed inside the chamber, and hydrogen and biogas are formed. A method for producing hydrogen and biogas using a single-chamber microbial electrolysis cell system without an ion exchange membrane, characterized in that the above anaerobic digestion conditions supply an inert gas into the chamber at a rate of 50 ml / min or less for 15 to 20 minutes.

8. In paragraph 6, The step of supplying organic matter to the chamber through the organic matter medium without applying the above external voltage is as follows: A method for producing hydrogen and biogas using a single chamber microbial electrolysis cell system without an ion exchange membrane, characterized in that the temperature of the chamber is maintained at 20 to 35°C.

9. In paragraph 6, A method for producing hydrogen and biogas using a single-chamber microbial electrolysis cell system without an ion exchange membrane, characterized in that the external voltage is applied at 0.6 to 1.2 V using a two-electrode voltage application method.

10. In paragraph 6, The step of inhibiting the methanogenic bacteria located on the reduction electrode in the above chamber is: A method for producing hydrogen and biogas using a single-chamber microbial electrolysis cell system without an ion exchange membrane, characterized in that the method is performed by exposing a reduction electrode to air, replacing an organic medium, operating an HRT of less than 24 hours in case of continuous operation to remove a community of solution-phase methanogenic bacteria, exposing a hydrogen-producing reduction electrode to air for 10 minutes to 1 hour, or supplying a chemical inhibitor or antibiotic.

11. In paragraph 10, The above chemical inhibitor is selected from the group including Sodium 2-bromoethanesulfonate, 2-bromoethanesulfonate, Iodopropane, and lumazine, A method for producing hydrogen and biogas using a single chamber microbial electrolysis cell system without an ion exchange membrane, characterized in that the antibiotic is selected from the group including neomycin sulfate, 2-chloroethane sulfonate, and 8-aza-hypoxanthine.

12. In paragraph 6, The steps in which the above hydrogen and biogas are produced are: A method for producing hydrogen and biogas using a single-chamber microbial electrolysis cell system without an ion exchange membrane, characterized in that the method comprises monitoring the potential of an oxidation electrode within a chamber based on a reference electrode within the chamber, checking the concentration of organic matter, and replacing the organic matter medium.

13. In paragraph 6, The steps in which the above hydrogen and biogas are produced are: A method for producing hydrogen and biogas using a single-chamber microbial electrolysis cell system without an ion exchange membrane, characterized in that the carbon dioxide, methane and hydrogen contents of the produced biogas are controlled according to the voltage applied to the single-chamber microbial electrolysis cell system without an ion exchange membrane, the temperature of the chamber, the HRT (the time that the reactants remain in the chamber), or the application of a method for inhibiting the activity of methanogens and homoacetogens, thereby producing biogas suitable for the intended use.

14. In paragraph 7, In the step of supplying organic matter to the chamber through the organic matter medium without applying external voltage, If the above organic matter is a liquid containing organic acid and a gas containing carbon dioxide and methane, In the chamber, organic contaminants contained in the liquid phase containing organic acids are removed, while carbon dioxide in the gas is converted into methane by combining with hydrogen produced in the single chamber microbial electrolysis cell system. A method for producing hydrogen and biogas using a single-chamber microbial electrolysis cell system without an ion exchange membrane, characterized in that highly soluble impurities including sulfur compounds, silicic acid, and odorous substances contained in the gas are removed as the liquid phase inside the chamber passes therethrough, thereby increasing the content ratio of hydrogen and methane in the biogas produced in the single-chamber microbial electrolysis cell system and improving its quality.

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