Apparatus for producing biomethane and method for producing biomethane from waste using same

Abstract

The present invention relates to an apparatus for producing biomethane and a method for producing biomethane from waste using same. The apparatus for producing biomethane, which corresponds to one aspect of the present invention, is directed to a technique for producing biomethane from wastewater to be discarded and is environmentally friendly and economical. In addition, the apparatus for producing biomethane of the present invention utilizes carbon materials, such as carbon dioxide, present in the atmosphere and thus can contribute to carbon neutrality. In addition, the apparatus for producing biomethane of the present invention separately performs a liquid fermentation process, thereby exhibiting excellent biomethane production efficiency.

Description

Device for producing biomethane and method for producing biomethane from waste using the same

[0001] The present invention relates to a device for producing biomethane and a method for producing biomethane from waste using the same.

[0002] Fossil fuels are a widely used resource for energy production. However, fossil fuel reserves are limited, and combustion produces particulate matter, carbon monoxide, carbon dioxide, sulfur oxides, and nitrogen oxides, making them a major source of environmental pollution. Therefore, research into alternative energy sources to fossil fuels is actively underway, with biogas, in particular, gaining recognition as a clean energy source.

[0003] Biogas is a gas produced by digesting organic waste with a high biomass content, such as livestock manure, food waste, and sewage treatment plant sludge, under anaerobic conditions with little oxygen. The main components of biogas are methane, which accounts for approximately 60-70%, and carbon dioxide, which accounts for approximately 30-40%. It also contains trace amounts of hydrogen sulfide and ammonia. While methane is a highly useful alternative to coal and oil and can be easily converted into hydrogen, it poses a problem of contributing to global warming when released directly into the atmosphere. Therefore, the industry has long been developing technologies to separate methane from biogas, and recently, research into technologies for highly efficient biomethane production has been attracting attention.

[0004] Known technologies for separating biomethane include water scrubbing, which utilizes differences in gas solubility to separate methane and carbon dioxide; pressure swing adsorption (PSA), which exploits differences in the adsorption properties of gaseous substances; and membrane separation, which utilizes differences in gas molecule polarity. However, these technologies have recently shown clear limitations, such as difficult maintenance and low economic feasibility, leading to a decline in their development. Consequently, technologies for producing high-purity biomethane have recently attracted more attention.

[0005] Biomethane production methods can be broadly categorized into physicochemical and biological methods. The former, however, has the disadvantage of requiring large amounts of energy to maintain high-temperature and high-pressure conditions during production. Biological methods, on the other hand, utilize only light energy, water, organic matter, and microorganisms, making them environmentally friendly and therefore preferred over physicochemical methods. However, biological methods face technical limitations, including high initial facility investment costs and low biogas production efficiency.

[0006] [Prior Art Literature]

[0007] (Patent Document 1) Korean Patent Publication No. 10-1544097

[0008] In one aspect, an object of the present invention is to produce biomethane from waste.

[0009] In one aspect, an object of the present invention is to produce high purity biomethane from waste.

[0010] In one aspect, the object of the present invention is to produce high purity biomethane with high efficiency.

[0011] In order to achieve the above object, the present invention provides, in one aspect, a device for producing biomethane, comprising: a first reactor (10) for producing a fermentation product containing an organic acid from a liquid phase containing wastewater; a second reactor (20) for producing a fermentation product containing an organic acid from a gas phase; and a third reactor (30) for producing methane from fermentation products derived from the first reactor and the second reactor.

[0012] In addition, in order to achieve the above-mentioned purpose, the present invention provides, in one aspect, a device for producing biomethane, in which a gaseous fermentation product among the fermentation products produced in the first reactor is introduced into a second reactor.

[0013] In addition, in order to achieve the above-mentioned purpose, the present invention provides, in one aspect, a biomethane production device further comprising a fourth reactor (40); and a hydrogen supply tank (50), wherein a gas phase of a fermentation product produced in the third reactor flows into the fourth reactor, and the hydrogen supply tank supplies hydrogen to the fourth reactor.

[0014] In addition, in order to achieve the above-mentioned purpose, the present invention provides, in one aspect, a biomethane production device further including a mixing tank (60) for mixing a fermentation product produced from the first reactor and a fermentation product produced from the second reactor.

[0015] In addition, in order to achieve the above-mentioned purpose, the present invention provides, in one aspect, a device for producing biomethane, wherein the organic acid includes acetic acid.

[0016] In addition, in order to achieve the above-mentioned purpose, the present invention provides, in one aspect, a device for producing biomethane, wherein the gas phase includes at least one of hydrogen and carbon dioxide.

[0017] In addition, in order to achieve the above-mentioned purpose, the present invention provides, in one aspect, a device for producing biomethane, wherein the internal temperature of the third fermentation tank is 30 to 55°C.

[0018] In addition, in order to achieve the above-mentioned purpose, the present invention provides, in one aspect, a device for producing biomethane, wherein the internal temperature of the fourth fermentation tank is 55 to 80°C.

[0019] In addition, in order to achieve the above-mentioned purpose, the present invention provides, in one aspect, a device for producing biomethane, in which the hydrogen supply tank supplies hydrogen so that the mole fraction (hydrogen:carbon dioxide) of hydrogen and carbon dioxide present in the fourth reaction tank is 3 to 5:1.

[0020] In addition, in order to achieve the above-mentioned purpose, the present invention provides, in one aspect, a method for producing biomethane from waste by utilizing the above-mentioned device.

[0021] One aspect of the present invention, a biomethane production device, is an environmentally friendly and economical technology that produces biomethane from wastewater. Furthermore, the biomethane production device of the present invention utilizes carbon dioxide and other carbonaceous substances present in the atmosphere, thereby contributing to carbon neutrality. Furthermore, the biomethane production device of the present invention performs the liquid-phase fermentation process separately, thereby achieving excellent biomethane production efficiency.

[0022] Figures 1 to 9 are implementation examples of a device for producing biomethane, which is one aspect of the present invention.

[0023] Figure 10 shows an example of an anaerobic metabolic pathway for organic matter decomposition.

[0024] This invention is a research result (Project No.: ARQ202201657001, Project Name: Development of Demonstration Technology for Energy Conversion Using Unused Composite Biomass, Research Period: 2022.04.01.~2022.12.31.) supported by the Waste Resource Utilization Energy Conversion Demonstration Technology Development Project of the Korea Environmental Industry & Technology Institute under the Ministry of Strategy and Finance.

[0025] Below, with reference to the attached drawings, embodiments of the present invention are described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, irrelevant parts have been omitted for clarity of description, and similar reference numerals have been used throughout the specification to indicate similar elements.

[0026] Terms or words used in the specification and claims of the present invention are not to be construed as limited to their usual or dictionary meanings, and should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0027] Throughout the specification of the present invention, when a part is said to "include" a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless specifically stated otherwise.

[0028] Throughout the specification of the present invention, “A and / or B” means A or B, or A and B.

[0029] Additionally, in this specification, the temperature unit is Celsius (℃) unless otherwise specified.

[0030] Hereinafter, the present invention will be described in detail with reference to the attached drawings, but the present invention is not limited thereto.

[0031] In one aspect, the present invention is a device for producing biomethane, comprising: a first reactor (10) for producing a fermentation product containing an organic acid from a liquid phase containing wastewater; a second reactor (20) for producing a fermentation product containing an organic acid from a gas phase; and a third reactor (30) for producing methane from fermentation products derived from the first reactor and the second reactor.

[0032] In this specification, “fermentation product” refers to all substances produced during and after fermentation, including fermentation intermediate products and fermentation final products.

[0033] In one aspect, the wastewater may include organic wastewater. The organic wastewater may refer to wastewater with a high organic matter content, and may include, but is not limited to, livestock manure, food wastewater, etc.

[0034] In one aspect, in the first reactor, liquid wastewater is used as a substrate and fermentation (liquid phase fermentation) is performed using microorganisms. At this time, organic acids such as acetic acid are produced (acetogenesis) in the first reactor, and gases or gas phases such as carbon dioxide and hydrogen are also produced.

[0035] In one aspect, the organic acid may include acetic acid, butyric acid, stearic acid, propionic acid, citric acid, and the like.

[0036] In one aspect, the microorganisms utilized in the first reactor may include one or more of Clostridium, Enterobacter, Lactobacillus, Escherichia, Ruminococcus, Propionibacterium, Acetobacterium, Butyribacterium, and Streprococcus.

[0037] In addition, any microorganism that can produce acetic acid and / or ethanol from carbon dioxide can be used in the first reactor without limitation.

[0038] In addition, the microorganisms utilized in the first reactor may include microorganisms having hydrogen production capabilities. For example, one or more of Clostridium, Sporanaerobacter, Coprococcus, Enterococcus, Morella, Thermoanaerobacterium, and Enterobacter may be included.

[0039] In addition, any microorganism capable of producing hydrogen under anaerobic conditions may be used in the first reactor without limitation.

[0040] In one aspect, among the fermentation products produced in the first reactor, the gaseous fermentation product can be introduced into the second reactor.

[0041] In the second reactor, synthesis gas fermentation can be performed, and organic acids including acetic acid are produced by utilizing carbon dioxide and hydrogen present in the gas phase, for example, outside the reactor.

[0042] At this time, the carbon dioxide and carbon used in the synthesis gas fermentation may include those existing in the atmosphere, and may further include carbon dioxide and / or hydrogen included in the gas phase flowing in from the first reactor.

[0043] Additionally, in one aspect, the second reactor can be supplied with hydrogen from the second hydrogen supply tank (70).

[0044] Meanwhile, unlike the present invention, when liquid phase fermentation and synthesis gas fermentation are not performed separately and external carbon dioxide is supplied during liquid phase fermentation using organic wastewater, there is a problem in that the efficiency of acetic acid production is reduced because it is difficult to find an appropriate balance between microorganisms involved in liquid phase fermentation and microorganisms involved in synthesis gas fermentation.

[0045] In one aspect, the first reactor and the second reactor may be connected to a microbial production microbial culture device (80). Specifically, the seed microbial culture device I (81) may be connected to the first reactor, and the seed microbial culture device II (82) may be connected to the second reactor, and the microorganisms stabilized and cultured in these culture devices may be supplied to the first reactor and the second reactor, so that the supplied microorganisms may perform fermentation in the first reactor and the second reactor.

[0046] In one aspect, the device for producing biomethane of the present invention may further include a fourth reactor (40) and a hydrogen supply tank (50).

[0047] In this case, the gas phase of the fermentation product produced in the third reactor can be introduced into the fourth reactor.

[0048] In one aspect, the fermentation performed in the third reactor may utilize fermentation products introduced from the first reactor and the second reactor.

[0049] In one aspect, the fermentation products generated in the first and second reactors may be directly introduced into the third reactor, or may be introduced into the third reactor via a mixing tank (60). In this case, a concentration process of the fermentation products supplied to the third reactor may be performed in the mixing tank.

[0050] The fermentation performed in the third reactor may be anaerobic fermentation. Through the fermentation, not only methane but also hydrogen, carbon dioxide, etc. may be produced.

[0051] Carbon dioxide generated in the third fermentation tank can be captured by a separate capture device (not shown) and used as a substrate for acetic acid fermentation.

[0052] In one aspect, the biogas produced in the third reactor can be purified and membrane separated to obtain high-purity biomethane, or the gas phase produced in the third reactor can be supplied to the fourth reactor and then methanated in the fourth reactor to obtain high-purity biomethane.

[0053] At this time, the microorganisms used in the third reactor may be one or more of Methanobacterium, Methanococcus, Methanosarcina, Methanothhrix, Methanolobus, Methanococcoides, and Methnoplanus, but are not limited thereto.

[0054] In one aspect, the internal temperature of the third fermentation tank may be 20 to 60°C, specifically 25 to 60°C, or 25 to 55°C, or 25 to 57°C, or 30 to 57°C, or 30 to 55°C.

[0055] Under the above temperature conditions, methane production efficiency can be excellent.

[0056] In one aspect, the gas phase flowing from the third reactor to the fourth reactor may include carbon dioxide, methane, and hydrogen.

[0057] Additionally, the hydrogen supply tank (50) can supply hydrogen to the fourth reaction tank.

[0058] In the fourth reactor, high-purity methane can be produced by utilizing the gas supplied from the third reactor and the hydrogen supply tank.

[0059] The hydrogen supply tank (50) can supply hydrogen so that the mole fraction of hydrogen and carbon dioxide (hydrogen:carbon dioxide) present in the fourth reactor becomes 3 to 5:1. The hydrogen supply tank can supply hydrogen so that the mole fraction of hydrogen:carbon dioxide in the fourth reactor becomes 3.5 to 4.5:1, or 3.8 to 4.5:1, or 3.8 to 4.3:1, or 3.8 to 4.2:1.

[0060] The fourth reactor may contain methanogenic bacteria.

[0061] The above methanogenic bacteria may include microorganisms having the ability to produce methane from hydrogen, and may include, but are not limited to, one or more of Methanobacterials, Methanococcales, Methanomicrobials, and Methanosarcinaceae.

[0062] In one aspect, it may be desirable for the methanogenic bacteria to be dominant in the fourth reactor. For example, it may be desirable to inactivate microorganisms that compete with the methanogenic bacteria to produce other products.

[0063] The internal temperature of the fourth reactor may be 55 to 80°C, and specifically, 55 to 78°C, or 57 to 78°C, or 58 to 75°C, or 60 to 75°C.

[0064] Additionally, the internal pressure of the fourth reactor may be atmospheric pressure to about 10 bar, and a state of pressure applied rather than atmospheric pressure may be more preferable in that it increases hydrogen solubility.

[0065] In one aspect, the fourth reactor may be equipped with a stirring system (not shown) to increase the solubility of the gas. The stirring system may be operated at a speed of about 1000 rpm or less to stir the material in the fourth reactor, for example, stirring may be performed at 200 rpm or more, 300 rpm or more, 400 rpm or more, 500 rpm or more, 600 rpm or more, 700 rpm or more, 800 rpm or more, or 900 rpm or more, and stirring may be performed at 1000 rpm or less, 900 rpm or less, 800 rpm or less, 700 rpm or less, 600 rpm or less, 500 rpm or less, 400 rpm or less, 300 rpm or less, or 200 rpm or less.

[0066] In addition, in one aspect, the fourth reactor may be equipped with a microbubble generator (not shown). The microbubble generator may supply gas (e.g., hydrogen) flowing into the fourth reactor from the outside in the form of microbubbles to the fourth reactor. By supplying gas in the form of microbubbles through the microbubble generator, the fourth reactor may expect improved reactivity between gases (e.g., between hydrogen and carbon dioxide).

[0067] High purity methane can be produced under the above temperature and pressure conditions.

[0068] In one aspect, the fourth reactor may be connected to a nutrient supply tank that supplies nutrients to the fourth reactor (not shown).

[0069] In addition, the third and fourth reactors may be connected to a sludge storage tank (not shown) to store sludge generated in each reactor, filter the unused portion, and circulate it to each reactor, or to supply the organic matter storage portion required for methane gas production to the reactor.

[0070] Additionally, in one aspect, the third and fourth reactors may be provided with discharge pipes for discharging liquid components generated or overflowed within each reactor.

[0071] In one aspect, each of the reaction tanks and supply tanks constituting the above device may be provided with a connecting pipe connecting them.

[0072] In addition, the present invention, in one aspect, is a system or method for producing biomethane from waste by utilizing the above device.

[0073] In this specification, "waste" is used as a broad concept that includes byproducts generated throughout the life cycle of living organisms on Earth, including humans and animals, and materials that are no longer necessary for living or activities. For example, waste includes garbage, combustion ash, manure, sludge, waste oil, waste acid, waste alkali, waste materials, and animal carcasses, and its form is not limited. For example, it is a concept that includes liquids such as livestock manure, sludge such as food waste, solids such as waste wood, and gases such as carbon dioxide emitted from industrial plants.

[0074]

[0075] [Explanation of symbols]

[0076] 10: Reactor 1

[0077] 20: Reactor 2

[0078] 30: Reactor 3

[0079] 40: Reaction Tank 4

[0080] 50: Hydrogen supply tank

[0081] 60: Mixed group

[0082] 70: Second hydrogen supply tank

[0083] 80: Organic acid producing microorganism cultivation device

[0084] 81: Seed Microorganism Culture I

[0085] 82: Seed Microorganism Culture Device II

Claims

1. A first reactor (10) for producing a fermentation product containing an organic acid from a liquid phase containing wastewater; A second reactor (20) for producing a fermentation product containing an organic acid from a gaseous phase; and A device for producing biomethane, comprising a third reactor (30) for producing methane from fermentation products derived from the first reactor (10) and the second reactor (20).

2. In paragraph 1, A device for producing biomethane, wherein a gaseous fermentation product among the fermentation products produced in the first reactor (10) is introduced into the second reactor (20).

3. In paragraph 1, The above biomethane production device is, It further includes a fourth reaction tank (40); and a hydrogen supply tank (50). Among the fermentation products produced in the third reactor (30), the gas phase flows into the fourth reactor (40). The above hydrogen supply tank (50) is a device for producing biomethane that supplies hydrogen to the fourth reaction tank (40).

4. In paragraph 1, The above biomethane production device is, The fermentation product produced from the first reactor (10) above, A device for producing biomethane, further comprising a mixing tank (60) for mixing fermentation products produced from the second reactor (20).

5. In paragraph 1, A device for producing biomethane, wherein the organic acid comprises acetic acid.

6. In paragraph 2, A device for producing biomethane, wherein the gas phase comprises at least one of hydrogen and carbon dioxide.

7. In paragraph 1, A device for producing biomethane, wherein the internal temperature of the third fermentation tank (30) is 20 to 60°C.

8. In paragraph 3, A device for producing biomethane, wherein the internal temperature of the fourth fermentation tank (40) is 55 to 80°C.

9. In paragraph 3, The above hydrogen supply tank (50) is A device for producing biomethane that supplies hydrogen so that the mole fraction (hydrogen:carbon dioxide) of hydrogen and carbon dioxide present in the fourth reactor (40) is 3 to 5:

1.

10. A method for producing biomethane from waste by using the device of any one of clauses 1 to 9.

Images