KR101990059B1 - Apparatus and method of producing high purity methane gas using gas recycle - Google Patents

Abstract

According to an embodiment of the present invention, an apparatus of producing high-purity methane comprises: an anaerobic digestion tank which contains hydrogenotrophic methanogens, produces biogas containing methane (CH_4) and carbon dioxide by decomposing acetic acid (CH_3COOH), hydrogen (H_2), and carbon dioxide (CO_2) contained in organic waste introduced from the outside by the hydrogenotrophic methanogens, and discharges high-purity methane by purifying the biogas; a gas collector which is connected to the anaerobic digestion tank, collects the biogas, and provides a feeding gas to the anaerobic digestion tank to circulate gas; a hydrogen (H_2) cylinder which supplies hydrogen to the biogas so as to produce the feeding gas; and a basal anaerobic medium which is connected to the anaerobic digestion tank, and allows the hydrogenotrophic methanogens to be cultured.

Description

High purity methane production apparatus and method using gas circulation {APPARATUS AND METHOD OF PRODUCING HIGH PURITY METHANE GAS USING GAS RECYCLE}

Provided are a high purity methane production apparatus and method using gas circulation.

Anaerobic digestion refers to a biological process in which organic waste is hydrolyzed and acid-produced by various microorganisms under anaerobic conditions and finally converted to CH ₄ and CO ₂ , and can be applied to various organic wastes. Produces biogas, which is energy.

Biogas generally contains about 50-60% of CH ₄ , which is a low-grade fuel used for power generation locally due to storage and supply problems. Therefore, it is necessary to develop technology for advanced utilization of city gas and vehicle fuel by increasing the CH ₄ content through the biogas purification process beyond the current biogas utilization strategy.

Physical and chemical methods of improving biogas include adsorption, pressure swing adsorption, vacuum swing adsorption, membrane separation, and cryogenic separation, but the cost is too high. In addition, even small amounts of methane loss in the process increase greenhouse gas emissions and reduce net energy production.

In order to solve this problem, a method of generating methane by the power-to-gas (P2G) method, which is a method of biologically injecting hydrogen and converting electricity into chemical energy in the form of H ₂ through electrolysis, has been introduced. However, there are some technical limitations to the methane production process. The biggest problem is that the methane-producing bacteria using hydrogen grow slowly, so the microbial concentration time is long.

To solve this problem, Luo and Angelidaki (2014) used a method of rapid stirring to increase the chance of contact between the substrate and the microorganism, thereby reducing the concentration time, but the concentration time was still long and fast. It is disadvantageous in that it is difficult to use in actual process.

High-purity methane production apparatus and high-purity methane purification method using gas circulation according to an embodiment of the present invention is to increase the biogas production.

High-purity methane production apparatus and high-purity methane purification method using gas circulation according to an embodiment of the present invention is to increase the methane content of biogas.

High-purity methane production apparatus and high-purity methane purification method using gas circulation according to an embodiment of the present invention is to shorten the microbial concentration time.

The high purity methane production apparatus and the high purity methane purification method using gas circulation according to an embodiment of the present invention are to improve the utilization rate of the gas circulation method.

In addition to the above object, embodiments according to the present invention can be used to achieve other objects not specifically mentioned.

High-purity methane production apparatus according to an embodiment of the present invention includes hydrogen (hydrogenotrophic methanogens), acetic acid (CH ₃ COOH), hydrogen (H ₂ ), and carbon dioxide contained in the organic waste introduced from the outside (CO ₂ ) is decomposed by methane-producing bacteria using hydrogen to produce biogas containing methane (CH ₄ ) and carbon dioxide, and anaerobic digestion and anaerobic digestion tanks that purify the biogas to discharge high-purity methane. and it is connected, or the biogas is collected, by providing the injected gas to the anaerobic digestion tank hydrogen cylinder (H ₂ cylinder) for supplying hydrogen to the biogas to the gas the gas collector, is generated injected gas (feeding gas) which is circulated, and It is connected to the anaerobic digester, and includes a anaerobic medium (Basal anaerobic medium) for culturing methane producing bacteria using hydrogen.

Anaerobic digesters include acetic acid methanogens (acetoclastic methanogens), methane production bacteria using acetic acid may be the dominant species (dominant species).

Methane-producing bacteria using acetic acid and hydrogen-containing methane-producing bacteria included in the anaerobic digester may be concentrated in a gas circulation mode at a thermophilic temperature.

The thermophilic temperature may be about 35 ° C. to about 75 ° C., and the pH of the anaerobic digester may be about 6.0 to about 8.5.

Methane-producing bacteria using acetic acid were identified as Methanosarcina spp. Or Methanosaeta spp. It may include one or more of.

Hydrogen methane-producing bacteria include Methanoculleus spp., Methanococsus spp., Methanothermococcus spp., Methanospirillum spp., Methanotorris spp., Methanobacterium spp., Or Methanothermobacter spp. It may include one or more of.

The methane content of high purity methane may be about 96% or more.

In the high-purity methane purification method according to an embodiment of the present invention anaerobic digestion of organic waste to produce a sludge containing methane-producing bacteria using hydrogen, the sludge is pre-cultured and introduced into the anaerobic digester, the injection gas stored in the gas collector It is introduced into the anaerobic digester, the hydrogen is consumed in the injected gas by the methane producing bacteria using hydrogen, the anaerobic medium is introduced into the anaerobic digester, and the activity of the methane producing bacteria using hydrogen is increased, discharged from the anaerobic digester The collected gas is collected by the gas collector, and the gas collected by the gas collector is injected by hydrogen discharged from the hydrogen cylinder, and the injected gas is introduced into the anaerobic digester to generate gas. Concentrating methane-producing bacteria using hydrogen by a circulation method, And methane of high purity is discharged by the methane producing bacteria using the concentrated hydrogen, and collecting the high purity methane.

In the step of introducing methane-producing bacteria using hydrogen into the anaerobic digester, the anaerobic digester may further include methane-producing bacteria using acetic acid.

In the step in which the injection gas is introduced into the anaerobic digester, the injection gas may have a ratio of carbon dioxide and hydrogen of 1: 4.

The temperature of the anaerobic digester may be about 35 ° C. to about 75 ° C., and the pH of the anaerobic digester may be about 6.0 to about 8.5.

In the stage where high purity methane is discharged, the methane content of the high purity methane may be about 96% or more.

High-purity methane production apparatus and high-purity methane purification method using the gas circulation according to an embodiment of the present invention can increase the biogas production, increase the methane content of the biogas, shorten the microbial concentration time The utilization rate of the gas circulation system can be improved.

1 is a view schematically showing a high purity methane production apparatus according to the embodiment.
Figure 2a is a graph showing the amount of methane production over time of the anaerobic digester according to the Examples and Comparative Examples.
Figure 2b is a graph showing the hydrogen consumption rate with time of the anaerobic digester according to the Examples and Comparative Examples.
Figure 3a is a graph showing the gas content over time of the anaerobic digester according to a comparative example.
Figure 3b is a graph showing the gas content over time of the anaerobic digester according to the embodiment.
Figure 4a is a graph showing the distribution of archaea at the neck level according to the mesophilic microorganisms and thermophilic microorganisms according to the Examples and Comparative Examples.
Figure 4b shows the distribution of archaea at the genus level according to mesophilic microorganisms and thermophilic microorganisms according to Examples and Comparative Examples.
5 is a graph showing the gas components and hydrogen consumption rate of the anaerobic digester according to the embodiment.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily practice the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. The drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. In addition, in the case of well-known technology, a detailed description thereof will be omitted.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the other hand, when a part is "just above" another part, there is no other part in the middle. Conversely, when a part of a layer, film, region, plate, etc. is "below" another part, this includes not only the other part "below" but also another part in the middle. On the other hand, when a part is "just below" another part, it means that there is no other part in the middle.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise.

1 is a view schematically showing a high purity methane production apparatus according to the embodiment.

Referring to FIG. 1, the high purity methane production apparatus 100 according to the embodiment may include a hydrogen cylinder 120 for injecting hydrogen into the biogas 110, an anaerobic medium 140, and a gas for storing the injected gas 130. Collector 150, the anaerobic digestion tank 160, the high-purity methane 170 is discharged.

The high-purity methane production apparatus 100 is a device in which high-purity methane (CH ₄ ) 170 is generated by purifying biogas 110 generated from organic waste, and a fed-batch culture type in which the medium is intermittently supplied. (fed-batch culture).

The organic waste may be, for example, but not limited to wastewater or sewage. Organic waste may be decomposed through anaerobic digestion using microorganisms and sludge and biogas 110 may be generated. For example, organic waste can be decomposed and converted to acetic acid (CH ₃ COOH), hydrogen (H ₂ ) and carbon dioxide (CO ₂ ), and then acetic acid and hydrogen can be converted to methane by archaea groups such as methane-producing bacteria. .

Biogas 110 is generated during the anaerobic digestion of organic waste. The biogas 110 generated generally comprises about 60% methane (CH ₄ ) and about 40% carbon dioxide (CO ₂ ). Methane may be utilized as an energy source, and high purity methane having a high content of methane may be obtained through biogas 110 purification. At this time, the content of high purity methane may be about 96% or more.

Biogas 110 is supplied through an upflow anaerobic sludge blanket (UASB) process. The upflow anaerobic sludge bed process is a method in which sludge flows in from the bottom of the anaerobic digester and flows upward. Sludge can biologically form sludge phases such as granules and particles. Sludge introduced into the anaerobic digester rises to the top, and the sludge-like particles and microorganisms come into contact with each other, and gas is generated. In this case, the generated gas may be methane, and methane may be discharged from the anaerobic digester.

Sludge refers to suspended solids produced by decomposition of organic waste, and may be, for example, but not limited to, microorganism, organic matter, and the like. At this time, the organic material may be glucose, and microorganisms may decompose it to produce methane.

 The microorganism may include methane-producing bacteria, bacteria, and the like, and may include, for example, but not limited to, hydrogen-producing methane-producing methaneogens and acetic acid-acetoclastic methanogens.

The anaerobic digester 160 includes methane producing bacteria using hydrogen and methane producing bacteria using acetic acid.

Methane-producing bacteria using acetic acid are dominant species, and about 70% of methane generated can be produced by acetic acid methaneogens, and about 30% of hydrogen-producing methane-producing methanogens. Can be generated by

Methane-producing bacteria using acetic acid break down acetic acid to produce methane and carbon dioxide.

Methane-producing bacteria using acetic acid may generate methane and carbon dioxide through Scheme 1 below.

Scheme 1

CH ₃ COOH → CH ₄ + CO ₂ (△ G = -31KJ)

Referring to Scheme 1, it can be seen that the reaction in which acetic acid is produced from methane and carbon dioxide is a spontaneous reaction.

Methane producing bacteria using acetic acid, for example, Methanosarcina spp., Methanosaeta spp. And the like, but are not limited thereto.

Methane producing bacteria decompose hydrogen and carbon dioxide to produce methane.

Methane producing bacteria using hydrogen can generate methane through the following scheme 2.

Scheme 2

4 H _{2 +} CO ₂ → CH ₄ + 2H ₂ O (△ G = -130KJ)

Referring to Scheme 2, it can be seen that the reaction of hydrogen and carbon dioxide to methane is a spontaneous reaction.

Hydrogen methane-producing bacteria include Methanoculleus spp., Methanococsus spp., Methanothermococcus spp., Methanospirillum spp., Methanotorris spp., Methanobacterium spp., Methanothermobacter spp. And the like, but are not limited thereto.

Methane-producing bacteria using acetic acid and methane-producing bacteria using hydrogen may coexist, and methane-producing bacteria using hydrogen may use the product produced by methane-producing bacteria using acetic acid. Hydrogen can be used as an electron donor of hydrogen-producing methaneogens under anaerobic conditions, and methane can be produced. As a result, the amount of methane produced may increase.

Is injected into a hydrogen (H ₂₎ is biogas 110 is discharged from the hydrogen cylinder _{(H 2 cylinder) (120)} , has a content of the bio-gas 110 it may be adjusted. Injecting hydrogen into the biogas 110 may have a ratio of CO ₂ and H _{2 in} a ratio of 1: 4, and a feeding gas 130 may be generated. The injection gas may consist of, for example, about 15% carbon dioxide, about 62% hydrogen, and about 23% methane, but is not limited thereto. The injection gas 130 may be introduced into the anaerobic digester 160 through the gas collector 150.

Anaerobic medium (BA medium, basal anaerobic medium) (140) may include, but is not limited to pre-cultured microorganisms. Anaerobic medium 140 may enter the anaerobic digester 160.

Methane-producing bacteria can be proliferated by the anaerobic medium introduced into the anaerobic digester 160. Anaerobic medium 140 is continuously introduced into the anaerobic digester 160, methane producing bacteria can be concentrated in the anaerobic digester 160 while consuming hydrogen in the anaerobic conditions, the amount of methane can be increased. At this time, the gas circulation process may be performed. Gas circulation can increase mass transfer between gas and liquid, which can dissolve gases that are less soluble in water, such as H _2, with less energy.

The anaerobic digester 160 may have a temperature of about 35 ° C. to about 75 ° C., and a pH of about 6.0 to about 8.5. Under these conditions, it provides an optimal environment for methane producing bacteria to grow, and the amount of methane produced can be increased.

Anaerobic digester 160 includes a glass fiber filter (pore size 20㎛) at the bottom, the gas can be introduced through the glass fiber filter. First, the injection gas 130 may be stored in the gas collector 150, the injection gas stored in the gas collector 150 may be introduced into the anaerobic digester 160, and the gas discharged from the anaerobic digester 160 may be discharged. It may be moved to the gas collector 150. By repeating this process, gas circulation can occur. At this time, methane producing bacteria may be concentrated, and methane of high purity may be produced.

Methane is an environmentally friendly gas that can be used as an energy source and can be applied to various fields such as power generation facilities.

In the high-purity methane purification method according to the embodiment, the step of introducing the pre-cultured sludge into the anaerobic digester 160, introducing the injection gas 130 stored in the gas collector 150 into the anaerobic digester, anaerobic medium 140 It includes the step of, collecting the gas discharged from the anaerobic digester 160, the above-described process is repeated and the step of concentrating the microorganism, and collecting the methane.

For details overlapping with the components, environment, and conditions of the above-described anaerobic digester, detailed description may be omitted.

First, a step of introducing the pre-cultured sludge into the anaerobic digester 160 is performed. Sludge from an anaerobic digester in a sewage treatment plant contains microorganisms, for example methane producing bacteria. Separately prepared continuous digestion tank reactor is supplied with glucose and anaerobic medium at a temperature of about 35 ℃ to about 75 ℃, pH about 6.8 to about 7.6 and microorganisms can be cultured for about 3 months. In this case, glucose is injected at an organic loading rate (OLR) of about 8 kg / m ³ d, whereby CO ₂ and CH ₄ are continuously generated in the anaerobic digester. As such, the biogas 110 may be generated by decomposing the methane producing bacteria and the biogas 110 may be collected in the gas collector 150.

Next, the step of introducing the injection gas 130 stored in the gas collector 150 into the anaerobic digester 160 is performed. At this time, the temperature of the anaerobic digester 160 may be about 35 ℃ to about 75 ℃, pH may be about 6.0 to about 8.5. The injection gas 130 is a gas in which the ratio of carbon dioxide and hydrogen is 1: 4 while injecting hydrogen into the biogas 110, and hydrogen is consumed by methane-producing bacteria to be converted into methane.

Subsequently, the step of introducing the anaerobic medium 140 is performed. The fresh anaerobic medium 140 is periodically introduced into the anaerobic digester 160 at about 30 mL / Ld, thereby increasing the activity of methane-producing bacteria and increasing methane production.

Subsequently, the step of capturing the gas discharged from the anaerobic digester 160 and the above-described process are repeated and the step of concentrating the microorganism is performed. The gas discharged from the anaerobic digester 160 may be collected by the gas collector 150 and flow back into the anaerobic digester 160, and the above-described process may be repeated. As this gas cycle is repeated, the concentration of microorganisms may occur, and the amount of methane produced may increase while methane producing bacteria consume hydrogen.

As for the method for concentrating microorganisms, a method according to a stirring method and temperature conditions may be performed. For example, the method may be mechanical stirring at mesophilic temperature, gas circulation at mesophilic temperature, and gas circulation at thermophilic temperature.

Conventionally, a method for concentrating a microorganism, which increases the chance of contact between a substrate and a microorganism by performing mechanical agitation at a high speed, has been disclosed. However, the concentration of the microorganism may be long, and energy for mechanical agitation may be consumed.

The microbial concentration method through the gas circulation method at the thermophilic temperature may consume less energy, and the concentration time of the microorganisms may be shortened.

Finally, a step of collecting methane is performed. Gas in which the content of methane is increased in a gas circulation method may be discharged from the anaerobic digester 160, and high purity methane may be discharged. At this time, the discharged gas may be about 96% or more high purity methane gas.

When the microorganism is concentrated in a gas circulation manner at a thermophilic temperature in the anaerobic digester 160, the concentration period may be shortened, and methane of high purity may be generated.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are merely examples of the present invention, and the present invention is not limited to the following Examples.

에 의해 계산된다. 폐수 속에 들어있는 메탄은 낮은 용해성 및 낮은 유출비율로 인해 무시될 수 있다. Q_Eff 가스는 용적 가스 효율을 말하며,

는 가스 유출물 속 물의 용적 유량이며, xCH₄는 가스 유출물 속 메탄의 몰분율이며,

는 용적 수소를 말한다. 수소의 소비율은

에 의해 계산된다.

는 유출 가스 속 수소의 질량흐름이다. 특정 수소소모율(U)은 평형상태를 유지하는 수소소비효율 하에서

로 계산된다.

는 수소이용률을 말하며, V는 혐기성 소화조의 작용 부피, X는 미생물균의 농도이다.In embodiments, the concentration of organic acid was determined by high performance liquid chromatography (HPLC, Finnigan Spectra SYS-TEM) with an ultraviolet (210 nm) sensor (UV1000, Thermo Electron) and a 100 × 7.8 mm fatty acid analysis column (Bio-Rad Lab.). LC, Thermo Electron Co., USA) is analyzed by using 0.005 MH ₂ SO ₄ as the mobile phase eluent. Liquid samples were pretreated with 0.45 mm membrane filter before injection. The amount of methane and carbon dioxide in the gas was determined by GC (Gow Mac series 580, Gow-Mac Instrument Co.) equipped with a 2 m × 2 mm stainless steel column containing a thermal conductivity detector (TCD) and Porapak Q (80/100 mesh). , USA). To determine the hydrogen content in the gas, gas chromatography (GC, Gow Mac series 580, Gow-Mac Instrument Co., Ltd.) equipped with a stainless steel column with a thermal conductivity detector and a 5 A molecular sieve of 1.8 m 3.2 mm (inner diameter). , USA). Total volatile solids and alkalinity were determined by Yun et al. It is measured in the same way as reported in (2016). The mixed samples obtained from the anaerobic digester according to Comparative Example 2, Comparative Example 3 and Example 3 were prepared using Ultraclean Soil DNA Kit (Cat # 12800-50; Mo Bio Laboratory Inc., USA) and UltraClean Microbial DNA Isolation Kit (Mo Bio Laboratories). , CA, USA). 16S rRNA genes are amplified with the Fast Start High Fidelity PCR System (Roche) for PCR as previously described with the highly bacterial specific primer set 8F / 519R primer. The PCR product was then purified by AMPure beads (Beckman coulter). The products were purified and quantified, and then sequencing was performed using a 454 pyrosequencing Genome Sequencer FLX Titanium (Life Sciences, CT, USA) according to the manufacturer's order by a commercial sequence facility (Macrogen, Seoul, Korea). Sequences were analyzed with MOTHUR for preprocessing. The method of trimming the bar code with the filter media with voids was performed according to the method reported by Yun (2016). Subsequent sequences were compared with the NCBI BLAST database (www.ncbi.nlm.ni h.gov). Samples of mixed solution collected from two inoculum (medium and thermophilic), anaerobic digesters of Comparative Examples 3 and 3 after 40 days to assess archaea group structure were analyzed using the 454 GS-FLX sequencer. Analyzed with the previous area, pyrosequence. A total of 94,910 high quality sequence reads and 132 engineered classification units (OTUs) were obtained from a single lane of an 8 lane pico-titer plate (Table 1). A log-shaped thinning curve at a distance of 0.03 is considered to be a reliable analysis (data not shown) since a reasonable number of sequences have been analyzed. Biomethanation yield (Y _CH4 ) is the amount of methane produced per amount of hydrogen consumed in an anaerobic digester,

Is calculated by. Methane in the waste water can be ignored due to its low solubility and low runoff rate. Q _Eff Gas refers to volumetric gas efficiency,

Is the volumetric flow rate of water in the gas effluent, xCH ₄ is the mole fraction of methane in the gas effluent,

Refers to volumetric hydrogen. The consumption rate of hydrogen

Is calculated by.

Is the mass flow of hydrogen in the effluent gas. The specific hydrogen consumption rate (U) is at the equilibrium of hydrogen consumption efficiency

Is calculated.

Is the hydrogen utilization rate, V is the working volume of the anaerobic digester, X is the concentration of microorganisms.

Example  One - Anaerobic digestion  Device

Referring to Figure 1, the anaerobic digestion apparatus is composed of fed-batch culture (fed-batch culture).

The anaerobic digester is round and made of acrylic plastic. The digester was built with a volume of about 6.3L, an internal diameter of about 140mm and a height of about 460mm.

The gas flowing into the anaerobic digester is stored in the gas collection tank, and the gas with a controlled ratio of CO ₂ and H ₂ is introduced by separately injecting hydrogen into the gas.

The gas from the anaerobic digester is collected in the gas collector and then flows back into the digester.

As such, the injected gas can be continuously introduced into and discharged from the anaerobic digester and recycled, and the gas can be recycled to lower the ratio of CO ₂ and increase the ratio of CH ₄ to increase the amount of CH ₄ gas available as an energy source. have.

Comparative example 1-mesophilic  Microbial culture

A continuous fire tank reaction tank (CSTR) was prepared, and sludge from an anaerobic digester in a sewage treatment plant was prepared. Sludge contains methane producing bacteria which are microorganisms.

The volume of the continuous digestion tank reactor is about 6 liters.

The continuous digestion tank reactor was supplied with glucose and anaerobic medium (BA medium) and operated for about 15 kg COD / m ³ d, hydraulic retention time (HRT) for about 15 days. . At this time, the continuous digestion tank reactor was maintained at pH 7.2 ± 0.4.

In a continuous digestion tank reactor, the microorganisms are incubated for about three months at about 35 ° C., which is a moderate temperature.

As a result, mesophilic methane producing bacteria were cultured. Alkalinity was maintained at 3.5 g CaCO ₃ / L.

As a result of specific methanogenic activity (SMA) test contained in the culture sludge, it was confirmed that the 0.30L CH ₄ g / VSS.

Example 2-thermophilic  Microbial culture

A continuous fire tank reaction tank (CSTR) was prepared, and sludge from an anaerobic digester in a sewage treatment plant was prepared. Sludge contains methane producing bacteria which are microorganisms.

The volume of the continuous digestion tank reactor is about 6 liters.

Continuous digestion tank reactor was supplied with glucose and anaerobic medium (BA medium), operated for 1.5 kg COD / m ³ d, hydraulic retention time of about 15 days. At this time, the continuous digestion tank reactor was maintained at pH 7.2 ± 0.4.

In the continuous digestion tank reactor, the microorganisms are incubated at 55 ° C. for thermophilic temperature for about 3 months.

As a result, thermophilic methane producing bacteria were cultured.

As a result of specific methanogenic activity (SMA) test, 0.31L CH ₄ g / VSS was confirmed.

Comparative example 2-mesophilic  Temperature, mechanical Stirring  Anaerobic Digester

An anaerobic digestion apparatus according to Example 1 was prepared, and mechanical agitation was performed at about 35 ° C., which is a mesophilic temperature, as a growth condition of methane-producing bacteria.

Cultured sludge 2.3 g VSS / L according to Comparative Example 2 is injected into the anaerobic digester. The initial pH of the anaerobic digester is adjusted to about 7.1. Nitrogen gas is injected into the anaerobic digester for about 10 minutes, providing anaerobic conditions.

Injection gas (H ₂ : CO ₂ = 80: 20) is injected daily at a hydrogen injection rate (HIR) of about 1.6 LH ₂ / Ld.

Anaerobic medium (BA medium) was injected at a hydraulic retention time of 33 days at about 30mL / Ld.

The injection gas introduced into the anaerobic digester is mixed by mechanical stirring at 200 rpm for about one day. Injected gas to be mixed in between is stored in the gas collector. This process was repeated for 40 days to concentrate the microorganisms (methane-producing bacteria).

Comparative example 3-mesophilic temperature Gas cycle anaerobic Digester

The anaerobic digestion apparatus according to Example 1 was prepared, and gas circulation was performed at 35 ° C., which is a mesophilic temperature, under the growth conditions of methane-producing bacteria.

About 2.3 g VSS / L of cultured sludge according to Comparative Example 2 is injected into the anaerobic digester. The initial pH of the anaerobic digester is adjusted to about 7.1. Nitrogen gas is injected into the anaerobic digester for about 10 minutes, providing anaerobic conditions.

Injection gas (H ₂ : CO ₂ = 80: 20) is injected daily at a hydrogen injection rate (HIR) of 1.6 LH ₂ / Ld.

Anaerobic medium (BA medium) was injected at a hydraulic retention time of 33 days at about 30mL / Ld.

The injection gas is first filled in the gas collection tank, and then injected into the anaerobic digester by about 100 L / Ld through a glass fiber filter (pore size 20 µm) located at the bottom of the anaerobic digester. At this time, the pump may operate by injecting at 200 rpm. This process was repeated for 40 days to concentrate the microorganisms (methane-producing bacteria).

Example 3-thermophilic  Temperature, gas circulation anaerobic Digester

The anaerobic digestion apparatus according to Example 1 is prepared, and gas circulation is performed at 55 ° C., which is a thermophilic temperature, under the growth conditions of methane-producing bacteria.

About 2.3 g VSS / L of cultured sludge according to Example 3 is injected into the anaerobic digester. The initial pH of the anaerobic digester is adjusted to about 7.1. Nitrogen gas is injected into the anaerobic digester for about 10 minutes, providing anaerobic conditions.

Injection gas (H ₂ : CO ₂ = 80: 20) is injected daily at a hydrogen injection rate (HIR) of 1.6 LH ₂ / Ld.

Anaerobic medium (BA medium) was injected at a hydraulic retention time of 33 days at about 30mL / Ld.

The injected gas is first filled in the gas collection tank, and then injected into the anaerobic digester by recirculation by about 100 L / Ld through a glass fiber filter (pore size 20 µm) located at the bottom of the anaerobic digester. At this time, the pump may operate by injecting at 200 rpm. This process was repeated for 40 days to concentrate the microorganisms (methane-producing bacteria).

Experimental Example 1-methane production  And hydrogen consumption test

Anaerobic digestion tanks according to Comparative Example 2, Comparative Example 3 and Example 3 were prepared, and methane production and hydrogen consumption experiments were performed, which are illustrated in FIGS. 2A and 2B.

Figure 2a is a graph showing the amount of methane production over time of the anaerobic digester according to Comparative Example 2, Comparative Example 3 and Example 3. The horizontal axis represents time d, and the vertical axis represents methane production rate (methane production rate / hydrogen consumption rate).

Figure 2b is a graph showing the hydrogen consumption rate with time of the anaerobic digester according to Comparative Example 2, Comparative Example 3 and Example 3. The horizontal axis represents time d, and the vertical axis represents hydrogen consumption rate (LH ₂ / Ld).

Referring to FIGS. 2A and 2B, initially, all anaerobic digesters show an increase in hydrogen consumption rate, but the rate of reaching maximum hydrogen consumption rate is different.

Comparative Examples In the case of anaerobic digestion according to the second, the ratio of hydrogen reached 0.17LH ₂ / Ld to around 5, and after 10 days 0.35LH ₂ / Ld, 30 days later, found that the reach 1.51LH ₂ / Ld have. Hydrogen consumption rate 1.51LH ₂ / Ld is a value corresponding to 94% of the hydrogen injection rate.

For the anaerobic digestion tank according to the third comparison, the ratio of hydrogen reached 0.5LH ₂ / Ld to around 5, and the 10th 1.10LH ₂ / Ld, is around 22 to check to reach the 1.52LH ₂ / Ld, The hydrogen consumption rate of 1.52 LH ₂ / Ld corresponds to 95% of the hydrogen injection rate.

Exemplary case of anaerobic digestion according to Example 3, to check in or about 5 to hydrogen ratio reaches 0.99LH ₂ / Ld, and reaches the 1.37LH ₂ / Ld, there 1.52LH ₂ / Ld 12 or about 11 or about, It can be seen that the maximum hydrogen consumption rate is reached at the fastest speed.

Therefore, the methane production rate initially shows a higher value than the theoretical value of 0.25, but it can be confirmed that as time passes by 0.22 to 0.23. This may be inferred due to the overproduction of methane by microorganisms decomposing organic matter remaining at the beginning of operation.

Experimental Example 2-methane Of hydrogen, hydrogen and carbon dioxide

Anaerobic digester according to Comparative Example 3 and Example 3 was prepared, the gas content was confirmed, which is shown in Figures 3a and 3b.

Figure 3a is a graph showing the gas content over time of the anaerobic digester according to Comparative Example 3. The horizontal axis represents time d and the vertical axis represents gas content (%).

Figure 3b is a graph showing the gas content over time of the anaerobic digester according to Example 3. The horizontal axis represents time d and the vertical axis represents gas content (%).

Referring to Figure 3a and b, in the anaerobic digester according to Example 3, it can be seen that the content of methane increases to 43% after 4 hours, 74% after 8 hours, 92% after 14 hours.

On the other hand, in the anaerobic digester according to Comparative Example 3, it can be seen that the content of methane increases to 49% after 8 hours, 84% after 16 hours, 91% after 22 hours.

Therefore, it can be seen that methane of high purity is produced more rapidly in an anaerobic digester cultured in a gas circulation mode at a thermophilic temperature.

In the case of acetic acid, 48 mg COD / L was measured in the anaerobic digester according to Comparative Example 2, 32 mg COD / L in the anaerobic digester according to Comparative Example 3, and 80 mg COD / L in the anaerobic digester according to Example 3 It became.

This confirms that homoacetogenic bacteria convert hydrogen and carbon dioxide to acetic acid.

Experimental Example 3-pyrosequencing  analysis

Anaerobic digester according to Comparative Example 3 and Example 3 was prepared, and the structure of archaea was analyzed using Pyrosequencing method, which is shown in Table 1, Figure 4a and 4b. The experiment was conducted on anaerobic digester according to Comparative Example 3, anaerobic digester according to Example 3, mesophilic inoculum and thermophilic inoculum.

Table 1 is a table showing the results of the gene library of archaea through Next Generation Sequencing (NGS) analysis method. The analysis was carried out at the beginning and end of the enrichment run.

Figure 4a shows the distribution of archaea at the neck level according to mesophilic and thermophilic microorganisms. The horizontal axis represents the percentage of archaea and the vertical axis represents four test subjects.

Figure 4b shows the distribution of archaea at the genus level according to mesophilic microorganisms and thermophilic microorganisms.

sample Reads OTUs Shannon Simpson Mesophilic
inoculum 27,739 35 0.9424 ± 0.0197 0.6832 ± 0.0072 Thermophilic
inoculum 30,789 34 0.9693 ± 0.0139 0.5228 ± 0.0052 Comparative Example 3 24,154 34 0.7037 ± 0.0191 0.7581 ± 0.0072 Example 4 12,228 29 1.1678 ± 0.0276 0.5605 ± 0.0110

Referring to Table 1, 94,910 base sequences were read and 132 OTUs were found.

Referring to FIG. 4A, Methanomicrobiales is 11.6% in mesophilic inoculum and 4.8% in thermophilic inoculum, while 50.1% in anaerobic digester according to Comparative Example 3 and 41.3% in anaerobic digester according to Example 3 You can see that it exists.

In addition, Methanosarcinales was most predominantly observed at 42.5% in mesophilic inoculum and 53.6% in thermophilic inoculation, while 0.9% in anaerobic digester according to Comparative Example 3 and 21.2% in anaerobic digester according to Example 3 Observed, it can be seen that the amount is measured to be measured significantly less than the inoculum.

Referring to Figure 4b, it can be seen that the various archaea are classified as Methanosaeta spp. And Methanosarcina spp. Species. Methanosaeta, a methane-producing bacterium using acetic acid, occupies 0.5% in the anaerobic digester according to Comparative Example 3 and 0.6% in the anaerobic digester according to Example 3.

In addition, methanogenic bacteria such as Methanoculleus, Methanococcus, Methanothermococcus, Methanospirillum, Methanotorris, Methanobacterium, Methanothermobacter, Methanosarcina can be confirmed that the methane producing bacteria using hydrogen are all settled in the anaerobic digester according to Comparative Example 3 and Example 3.

Thus, this result means that methane production by hydrogen is not selectively enhanced.

On the other hand, feedstocks made with acetic acid can prevent the production of CH4 using acetic acid in anaerobic conditions and remove Methanosaeta spp.

Experimental Example 4-archaea OTUs  analysis

Anaerobic digestion tanks according to Comparative Example 2, Comparative Example 3 and Example 3 were prepared, and the predominant archaea OTUs analysis was performed in these reactors, which are shown in Table 2.

Table 2 shows the results of analysis of the dominant archaea OTUs (operational taxonomic units) in the anaerobic digester according to Comparative Example 2, Comparative Example 3 and Example 3. Species-level alignments were shown through 16 representative OTUs, indicating the type of methane producing bacteria, optimal methane producing bacteria, mesophilic inoculum, thermophilic inoculum, and similarities.

OTUs Type of methanogens Best matched methanogens Mesophilic inoculum Thermophilic inoculum Comparative Example 3 Example 3 Accession # Similarity (%) One




Hydrogenotroph Methanoculleus chikugoensis 11.3 0.0 19.5 0.5 NR_028152.1 100 2 Methanothermococcus 1.6 0.5 15.7 1.9 NR_074182.1 97 4 thermolithotrophicus 2.3 2.1 2.1 28.1 NR_044720.1 91 5 Methanospirillum hungatei 1.4 1.9 1.9 1.5 NR_074177.1 98 7 Methanotorris formicicus 0.1 0.0 16.9 0.1 NR_028646.1 97 8 Methanobacterium thermaggregans 0.6 5.8 0.0 15.9 NR_104880.1 95 12 Methanobacterium formicicum 2.6 0.0 1.2 0.0 JQ973735.1 93 13 Methanothermobacter thermoflexus 0.0 9.2 0.0 8.3 NR_028249.1 91 15 Methanobacteriom sp. AL-2l 0.1 0.8 0.0 0.0 NR_102889.1 97 24 Methanobacterium oryzae 4.4 0.8 0.8 1.8 NR_028171.1 99 9
Acetoclastic Methanosaeta concilii GP6 8.5 2.9 0.0 0.0 NR_104707.1 100 10 Methanosaeta thermophila 2.3 27.1 0.1 0.1 NR_074214.1 98 14 Methanosaeta harundinacea 6Ac 2.2 1.0 0.2 0.1 NR_102896.1 98 6 Acetoclastic
&
Hydrogenotroph Methanosarcina thermophila 8.1 8.5 0.1 13.2 NR_044725.1 97 11 Methanosarcina barkeri 9.4 10.8 18.2 1.0 AB973360.1 96

These results clearly show three patterns.

The first is that methane-producing bacteria that convert acetic acid to CH4 gradually decrease in both mesophilic and thermophilic states, and secondly, that hydrogen-producing methane-producing bacteria change significantly. The microorganisms frequently seen in mesophilic inoculum are increased in the anaerobic digester according to Comparative Example 3, and in the anaerobic digester according to Example 2, Methanothermococcus thermolithotrophicus and Methanobacterium thermaggregans are seen only 2.1% and 5.8% in thermophilic inoculum. . Third, when Methanosarcina species prevails, Methanosarcina thermophila present in 8.1% in mesophilic inoculation and 8.5% in thermophilic inoculum is rapidly reduced to 0.1% in anaerobic digester according to Comparative Example 3 and anaerobic digester according to Example 3 It can be seen that the sharp increase to 13.2%.

Example 4-thermophilic  Long-term operation of temperature, gas circulation

The anaerobic digestion apparatus according to Example 1 is prepared, and gas circulation is performed at 55 ° C., which is a thermophilic temperature, under the growth conditions of methane-producing bacteria.

About 2.3 g VSS / L of sludge cultured according to Example 3 is injected into an anaerobic digester. The initial pH of the anaerobic digester is adjusted to about 7.1. Nitrogen gas is injected into the anaerobic digester for about 10 minutes, providing anaerobic conditions.

Injecting gas _{(H 2: CO 2 = 80} : 20) from the hydrogen injection rate (HIR) was injected to increase gradually from 1.6LH ₂ / Ld to 20.8LH ₂ / Ld.

The recycled injection gas was injected at an increase from about 100 L / Ld to about 300 L / Ld for about 198 days.

Experimental Example 5-hydrogen consumption rate , Methane production rate, gas composition analysis

The anaerobic digester according to Example 4 was prepared, and the hydrogen consumption rate, methane production rate, gas composition, and the like were measured, which are shown in Table 3 and FIG. 5.

Table 3 is a table showing the hydrogen injection rate (HIR), gas circulation rate, methane production rate (MPR), sludge concentration, specific hydrogen consumption rate (SHCR) of the anaerobic digester according to Example 4.

5 is a graph showing the gas components and hydrogen consumption rate of the anaerobic digester according to Example 4. The horizontal axis represents time (d), the left vertical axis represents gas constituents (%), and the right vertical axis represents hydrogen consumption rate (LH ₂ / Ld).

operation (d) 1-20 21-38 39-56 57-74 75-90 91-106 107-
126 127-
148 149-
164 165-
176 177-
198 HIR
(LH ₂ / Ld) 1.6 3.2 4.8 6.4 6.4 9.6 12.8 16.0 20.8 20.8 19.2 Gas recycle rate (L / Ld) 100 100 100 100 200 200 200 200 200 300 200 MPR
(L CH ₄ / Ld) 0.4 ± 0.0 0.7 ± 0.0 1.0 ± 0.1 1.4 ± 0.0 1.5 ± 0.1 2.4 ± 0.1 2.9 ± 0.1 3.9 ± 0.2 4.3 ± 0.1 4.8 ± 0.3 4.5 ± 0.2 Sludge concentration 2.3 ± 0.2 2.5 ± 0.3 2.6 ± 0.2 2.9 ± 0.3 2.8 ± 0.0 2.9 ± 0.1 3.2 ± 0.3 3.6 ± 0.0 4.3 ± 0.1 4.4 ± 0.0 4.4 ± 0.3 SHCR
(gCODg / VSSd) 1.3 2.4 3.4 3.8 4.2 6.2 7.5 8.3 8.6 8.4 8.4

Referring to Table 3 and FIG. 5, it can be seen that the initial hydrogen injection rate gradually increased, starting with 1.6 LH ₂ / Ld, and thus the hydrogen consumption rate and methane production rate increased. And it can be seen that the content of methane increases to 96% after 20 days. When the hydrogen consumption rate is increased to 4.8 LH ₂ / Ld, the hydrogen consumption rate and methane production rate gradually increase to reach 4.7 ± 0.2 LH ₂ / Ld and 1.0 ± 0.1 L CH _{4 /} Ld. On the other hand, when the hydrogen consumption rate is 6.4 LH ₂ / Ld, the methane ratio is sharply reduced to 76% for methane and 19% for hydrogen in the exhaust gas. In this state, the hydrogen consumption rate and the methane production rate are maintained at 5.9 ± 0.2 LH ₂ / Ld and 1.4 ± 0.0 L CH ₄ / Ld. This result is consistent with previous findings that mass transfer between gas and liquid is a major limiting factor in the methane production of hydrogen. Thus, the gas circulation rate increases from 100 L / Ld to 200 L / Ld in 74 days, which can be seen as overcoming the gas and liquid mass transfer limitations. At this time, the content of methane continues to increase to reach around 96%. Methane production rate is maintained at 3.9 ± 0.2 L CH ₄ / Ld until hydrogen injection rate 16.0 LH ₂ /Ld.However, when hydrogen injection rate is 20.8 LH ₂ / Ld, the ratio of methane is reduced to 81%. This increases to 15% and 4%. Increasing the gas circulation rate to 300 L / Ld, the hydrogen consumption rate is limited at 19.7 ± 0.8 LH ₂ / Ld. This can be confirmed that the mass transfer between the gas and the liquid is limited and did not overcome this at 300L / Ld. At this time, the pH was maintained at about 7.1 to 7.3, which is suitable for methane production. Acetic acid is produced by homoacetogenic bacteria and this acetic acid is measured as about 100 to 120 mg COD / L as the main organic acid. It shows that the specific hydrogen consumption rate (SHCR) reaches 8.4-8.6 g COD · g / VSSd, similar to other papers with a specific hydrogen consumption rate of 8.8 g COD · g / VSSd for hydrogen-methane production. Therefore, this particular hydrogen consumption rate suggests that biomass concentration is more restrictive than mass transfer between gas and liquid. As a result of operating the gas cycle back to 200 L / Ld, the hydrogen consumption and specific hydrogen consumption were measured to be 19.0–0.3 LH ₂ / Ld and 8.4 g COD · g / VSSd. At this time, the methane ratio of the produced biogas reaches 96%.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

100: high purity methane production apparatus 110: biogas
120: hydrogen cylinder 130: injection gas
140: anaerobic medium 150: gas collector
160: anaerobic digester 170: high purity methane

Claims (12)

Acetic acid (CH ₃ COOH), hydrogen (H ₂ ), and carbon dioxide (CO ₂ ), including hydrogen-generated methanogens and acetic acid methane-producing bacteria (acetoclasticmethanogens) ) Is decomposed by methane-producing bacteria using hydrogen and methane-producing bacteria using acetic acid (acetoclasticmethanogens) to produce biogas containing methane (CH ₄ ) and carbon dioxide, and purifying the biogas to obtain high-purity methane. Anaerobic digester,
A gas collector connected to the anaerobic digester, wherein the biogas is collected and the gas is circulated by providing an injection gas to the anaerobic digester;
A hydrogen cylinder (H ₂ cylinder) for supplying hydrogen to the biogas so that the feeding gas is generated, and
An anaerobic medium connected with the anaerobic digester and allowing methane producing bacteria to be cultured using the hydrogen
Including,
The anaerobic digester is the dominantspecies of methane-producing bacteria (acetoclasticmethanogens) using the acetic acid
High purity methane production unit.

delete In claim 1,
Methane-producing bacteria using the acetic acid and the methane-producing bacteria using hydrogen contained in the anaerobic digester is concentrated in a gas circulation method at a thermophilic temperature methane production apparatus.
In claim 3,
The thermophilic temperature is 35 ℃ to 75 ℃, the pH of the anaerobic digester is 6.0 to 8.5 high purity methane production apparatus.
In claim 1,
The methane producing bacteria using acetic acid is Methanosarcina spp., Or Methanosaeta spp. High purity methane production unit comprising at least one of.
In claim 1,
Methane-producing bacteria using hydrogen include Methanoculleus spp., Methanococcus spp., Methanothermococcus spp., Methanospirillum spp., Methanotorris spp., Methanobacterium spp., Or Methanothermobacter spp. High purity methane production unit comprising at least one of.
In claim 1,
Methane content of the high purity methane is 96% or more high purity methane production apparatus.
Anaerobic digestion of organic waste to produce sludge containing methane-producing bacteria using hydrogen, and the sludge is pre-cultured and introduced into an anaerobic digester,
Injecting gas stored in the gas collector is introduced into the anaerobic digester, the hydrogen in the injected gas is consumed by the methane producing bacteria using the hydrogen, methane is produced,
Anaerobic medium is introduced into the anaerobic digester to increase the activity of methane producing bacteria using the hydrogen,
Collecting the gas discharged from the anaerobic digester into the gas collector,
The gas collected in the gas collector is again produced by the hydrogen discharged from the hydrogen cylinder, the injection gas is introduced into the anaerobic digester, the process of generating the gas is repeated, by a gas circulation method Methane-producing bacteria are concentrated using the hydrogen, and
Methane of high purity is discharged by methane producing bacteria using the concentrated hydrogen and collecting the high purity methane
High purity methane production method comprising a.
In claim 8,
In the step of introducing the methane producing bacteria using the hydrogen into the anaerobic digester,
The anaerobic digester further comprises a methane producing bacteria using acetic acid.
In claim 8,
In the step of introducing the injection gas into the anaerobic digester,
The injection gas is a high-purity methane production method of the ratio of carbon dioxide and hydrogen 1: 4.
In claim 8,
The temperature of the anaerobic digester is 35 ℃ to 75 ℃, pH of the anaerobic digester is 6.0 to 8.5 high purity methane production method.
In claim 8,
In the step of exhausting the high purity methane,
The methane content of the high purity methane is 96% or more high-purity methane production method.

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