KR20220080918A - Bioelectrochemical Method For Bio-gas Conversion of Coal Using an Alternating Current - Google Patents

Abstract

The present invention relates to the improvement of the methane conversion efficiency of bioelectrochemical coal using an electromagnetic field formed from an AC power source in order to solve the above problems of the conventional anaerobic digestion and methane conversion technology of bioelectrochemical coal using an electrostatic field.
When the powdered coal of the present invention and anaerobic sludge containing anaerobic microorganisms are exposed to an electromagnetic field formed by an AC power source, the permanent dipole moment of the coal molecules activates the molecular motion (vibration, rotation, translation), thereby increasing the kinetic energy of the molecules. It increases and the potential energy energy barrier is lowered, thereby facilitating the hydrolysis reaction of coal and the continuous low molecular weight reaction of hydrolysis products.
In addition, when a biostimulant composed of easily decomposable substrates such as yeast extract, glucose, starch, and acetic acid is further injected into the medium containing powdered coal and anaerobic microorganisms, the methanogenic electroactive bacteria injected inside the anaerobic digester where the electromagnetic field is formed It has the effect of promoting growth.
Therefore, the methanogenic electroactive bacteria grown by the fermentable substrate under the electromagnetic field of the present invention can alleviate the accumulation of intermediate products by promoting the continuous low molecular weight of coal hydrolysis products, and as a result, intermediate products for the methanogenic electroactive bacteria. By reducing their toxicity, the methane conversion reaction of coal is improved.

Description

Bioelectrochemical Method For Bio-gas Conversion of Coal Using an Alternating Current

The present invention relates to a bioelectrochemical method for converting coal into biogas using an electromagnetic field, and in particular, anaerobic sludge containing methanogenic anaerobic microorganisms and powdered coal as a substrate are injected into an anaerobic digester including an insulating electrode, It relates to a bioelectrochemical method for converting coal into biogas (methane) by supplying AC power to form an electromagnetic field and driving it.

Coal biological methane conversion technology is an eco-friendly energy conversion technology for methane, in which anaerobic microorganisms metabolize lignin-based hydrophobic organic substances contained in coal and convert it to methane. However, the conventional method for converting coal to methane using anaerobic microorganisms has not been commercialized due to the slow reaction rate and low yield of methane due to the toxicity of intermediate products generated during the decomposition of coal.

In the process of converting coal to methane using the anaerobic microorganisms, particulate coals are hydrolyzed, and then hydrolyzed products go through several stages of fermentation and are gradually converted into low molecular weight substances such as methane precursors such as acetic acid/hydrogen. produces methane. Intermediate products of coal are hydrolysis products or produced in the continuous fermentation process, and are hydrophobic and lipophilic polycyclic aromatic/aliphatic compounds with intricately connected carbon rings, which are metabolized by anaerobic microorganisms. Growth was also inhibited due to difficulty and toxicity of intermediates. Therefore, there is a need for a strategy to alleviate the toxicity of the intermediate product so that the activity of methanogenic bacteria is not inhibited and the fermentation rate for continuous low molecular weight is improved.

Accordingly, as a method of alleviating the inhibitory effect of intermediate products and maintaining the activity of methanogens, the method of lowering the load rate of coal injected into the anaerobic digester or increasing the bioavailability by using surfactant injection, and living organisms such as yeast extract A method of injecting an accelerator has been developed. As an example, Korean Patent Application No. 10-2020-0011558 discloses a technology for forming a high electric field using high voltage, and Korean Patent Application No. 10-2020-0011095 uses various fermentable substances such as glucose as a biostimulant. And, it is disclosed that when an electrostatic field is applied, the methane conversion of coal can be improved than that of a conventional bioelectrochemical anaerobic digester. However, the biostimulant injection method causes the inconvenience and additional cost of periodically injecting, and even if the activity of methanogens is promoted under the electrostatic field conditions, the methanogenic bacteria by intermediate products continuously generated in the process of decomposing coal. There was still a limit to improving the methane conversion rate of coal due to the presence of toxicity.

On the other hand, when an AC voltage is used as an external voltage source, an electromagnetic field is formed. The electromagnetic field moves as the magnetic field moves in the direction perpendicular to the electric field, and the amplitude changes according to the applied potential. At this time, molecular motion is determined according to the change in frequency, and as the frequency increases, molecular motion (vibration, rotation, translation, etc.) becomes more active and the energy inside the molecule increases, reducing the molecular weight of intermediate products generated in the coal decomposition process. can accelerate

When the electromagnetic field is formed, internal molecular energy increases due to molecular motion (vibration, rotation, translation, etc.) of intermediate products generated in the process of methane conversion of coal, thereby relaxing the energy potential barrier and rapidly reducing the molecular weight. It is expected that methanogenesis will be improved as methanogenic bacteria are readily available.

The patents and references mentioned in this specification are hereby incorporated by reference to the same extent as if each publication were individually and expressly specified by reference.

Korean Patent Publication 10-2020-0095415 Korean Patent Laid-Open Patent 10-2020-0095136

The present invention is to solve the above problems occurring in the bioelectrochemical process for producing methane gas from coal, anaerobic sludge containing anaerobic microorganisms performing methanogenesis and anaerobic powdered coal as a substrate, etc. To provide a bioelectrochemical method for converting coal into methane gas, characterized in that the methane production rate and yield are improved compared to the conventional method using an electrostatic field by supplying AC power to the digester to operate in a state in which an electromagnetic field is formed. There is a purpose.

Other objects and technical features of the present invention are more specifically set forth by the following detailed description of the invention, claims and drawings.

The present invention is a bioelectrochemical method for converting powdered coal into methane gas, comprising: a first step of sieving anaerobic sludge in a sewage treatment plant and then concentrating it to inoculate methanogenic bacteria in an anaerobic digester including an insulated electrode pair; a second step of injecting powdered coal as a substrate into the anaerobic digester; A third step of forming an electromagnetic field by supplying AC power to the insulated electrode pair of the anaerobic digester; and a fourth step of converting the coal into methane gas by stirring the reactants including the anaerobic digester; It provides a bioelectrochemical method for converting coal to methane gas, comprising:

The anaerobic sludge contains methanogenic bacteria, and the methanogenic bacteria dominate as methanogenic electroactive bacteria by an electromagnetic field formed by an alternating current power source, and the methanogenic electroactive bacteria include in vitro transfer emitters and electrotrophic methanobacteria, and It is characterized in that coal is converted into methane gas through direct interspecies electron transfer between in vitro transfer emitters and electrotrophic methane bacteria.

The AC power supplied to the insulated electrode pair has a frequency of 10 to 200 MHz, and the electric field formed by the AC power is 1 to 3 V/cm.

The present invention relates to the improvement of the methane conversion efficiency of bioelectrochemical coal using an electromagnetic field to which an AC power is applied. .

When the powdered coal of the present invention and anaerobic sludge containing anaerobic microorganisms are exposed to an electromagnetic field, a permanent bipolar moment is formed in the coal molecules, and the molecular motion (vibration, rotation, translation) of the coal particles having the bipolar moment formed becomes active. The kinetic energy of the molecule is increased and the potential energy energy barrier is lowered, thereby facilitating the hydrolysis reaction of coal and the continuous low molecular weight reaction of hydrolysis products.

In addition, when a biostimulant composed of easily decomposed substrates such as yeast extract, glucose, starch, and acetic acid is further injected into the medium containing powdered coal and anaerobic microorganisms, the growth of the electroactive bacteria injected inside the anaerobic digester where the electromagnetic field is formed is reduced. has a stimulating effect.

Therefore, the methanogenic electroactive bacteria grown under an electromagnetic field to which an alternating voltage of the present invention is applied can alleviate the accumulation of intermediate products by promoting the continuous low molecular weight of the coal hydrolysis products, and as a result, the toxicity of the electroactive bacteria to the intermediate products is reduced. The methane conversion reaction of coal is continuously performed.

1 is a schematic diagram of an anaerobic digester of the present invention.
Figure 2 shows the cumulative amount of methane generated as a result of operating according to Examples and Comparative Examples in the anaerobic digester of the present invention.
Figure 3 shows the results of operation according to Examples and Comparative Examples in the anaerobic digester of the present invention as a cyclic voltammetry graph.

The present invention injects anaerobic sludge containing powdered coal and anaerobic culturing microorganisms into the anaerobic digester or a biostimulant composed of a substrate that is easily decomposed such as yeast extract, glucose, starch, acetic acid, etc. To provide a bioelectrochemical method for converting coal to methane, characterized in that the operation method converts coal into methane gas.

The bioelectrochemical method for converting coal into methane gas comprises: a first step of sieving and concentrating anaerobic sludge in a sewage treatment plant to seed an anaerobic digester including an insulated electrode pair; a second step of injecting powdered coal as a substrate into the anaerobic digester; A third step of forming an electromagnetic field by supplying AC power to the insulated electrode pair of the anaerobic digester; and a fourth step of converting the coal into methane gas by stirring the reactants including the anaerobic digester.

The anaerobic digester for converting coal to methane gas of the present invention is an anaerobic digester (1) provided with an upper cover (12); DC motor 6 located above the anaerobic digester 1; The upper part is connected to the DC motor (6) and the rotation shaft (14) is installed inside the anaerobic digester (1); agitating blades 7 coupled to the lower portion of the rotating shaft 14 to stir the reactants; an airtight pipe 13 attached to the lower end of the upper cover 12 and connected to the stirring blade 7 by surrounding the rotation shaft 14; It includes a pair of insulating electrodes (insulated electrode 1(2) and insulating electrode 2(3)) coated with a dielectric material installed in an annular shape on the outer wall of the hermetic tube and the inner wall of the anaerobic digester, any one of which is the hermetic tube (13), the other one is installed on the inner wall of the anaerobic digester (1)); an AC voltage source (4) connected to the insulated electrode pair (2, 3) with a wire (5) and applying an AC voltage to form an electromagnetic field (11) and a frequency between the insulated electrode pair (2, 3); and a gas collecting port 10 installed on the upper cover 12 and connected to the pipe of the floating gas collector 15 . In addition, the anaerobic digester 1 of the present invention may further include a liquid sample collecting port 8 and a gas sample collecting port 9 installed on the upper cover 12 .

The size of the electromagnetic field 11 formed inside the anaerobic digestion tank 1 is determined according to the strength of the applied AC voltage and the distance between the insulating electrode 1 ( 2 ) and the insulating electrode 2 ( 3 ). Therefore, if the diameter of the anaerobic reactor 1 is adjusted to a range in which the rotation shaft 14 and the stirring blade 7 can rotate or the intensity of the applied voltage of the AC voltage source 4 is adjusted, the size of the electromagnetic field 11 is increased. can be adjusted In addition, it is preferable that the AC voltage source 4 is capable of frequency conversion.

The insulating electrode 1 (2) and the insulating electrode 2 (3) is a base electrode made of a conductive metal or carbon-based material, a polymer material or a ceramic-based alkyd resin, polyethylene, polypropylene, polycarbonate, polyvinyl chloride, It is selected from dielectric materials such as polyester, polyurethane, epoxy, Teflon and polyvinylidene fluoride, characterized in that such dielectric material is coated. Preferably, the base electrode uses titanium, which is a metal-based material strong against corrosion, and the dielectric material uses a vinyl chloride resin. The thinner the thickness of the dielectric material coated on the base electrode, the more advantageous, but in consideration of durability, it is preferably 0.05 mm or more.

The stirring blade 7 may be positioned between the insulating electrode 1 ( 2 ) and the insulating electrode 2 ( 3 ). The stirring blade 7 is located inside the anaerobic digester 1 and penetrates the upper cover 12 and is coupled to the lower portion of the rotating shaft 14 connected to enable rotation, so that the DC motor 6 rotates the rotating shaft 14 When rotated, the reaction is stirred by rotating inside the anaerobic digester (1). In particular, since the stirring blade 7 is positioned between the insulating electrode 1 ( 2 ) and the insulating electrode 2 ( 3 ), the reactants are effectively mixed and dispersed. Therefore, the electroactive microorganisms inside the anaerobic digester 1 can be uniformly exposed to the formed electromagnetic field 11 .

The anaerobic digester 1 of the present invention may further include a floating gas collector 15 connected through a pipe with the gas collection port 10 provided in the upper cover 12 and filled with acidified saturated brine. The acidified saturated brine has an effect of preventing dissolution of the methane gas collected in the floating gas collector 15 .

The anaerobic sludge can be obtained by natural sedimentation and sieving of anaerobic digestion sludge in a wastewater treatment plant, and after being concentrated to an appropriate concentration, it can be seeded in an anaerobic digester. The microorganisms sown through the anaerobic sludge include electroactive bacteria including in vitro transfer emitters and electrotrophic methane bacteria, and the in vitro transfer emitters and electrotrophic methane bacteria convert powdered coal into methane gas through direct interspecies electron transfer. will switch The direct interspecies electron transfer may occur through electrodes or conductive materials such as carbon and metal, or by direct contact between microorganisms. The direct interspecies electron transfer is an intermediate product (acetic acid, hydrogen, formic acid, etc. ) as a medium to transfer electrons. In the methane conversion reaction of coal, the intermediate products generated during the hydrolysis of coal are mainly polycyclic aromatic and aliphatic polymers that are difficult for microorganisms to decompose. The polycyclic aromatic and aliphatic substances are toxic and may inhibit the activity of microorganisms involved in the coal decomposition process.

The powdered coal is preferably used in the form of powder having a diameter of 1 mm or less by drying and pulverizing the coal. Powdered coal with a diameter of 1 mm or less has a large surface area, which increases the cross-sectional area that anaerobic microorganisms can contact, and facilitates dispersion through stirring inside the anaerobic digester, thereby promoting hydrolysis. The powdered coal is used as a substrate for electroactive bacteria including extracorporeal transfer emitters and electrotrophic methane bacteria contained in anaerobic sludge, and becomes a material for methane production.

Additionally, the bioelectrochemical method for converting coal to methane gas of the present invention may further add an anaerobic medium in the first or second step. The anaerobic medium includes a biodegradable fermentable substrate as a biostimulant, and promotes the continuous fermentation of intermediate products (polycyclic aromatic and aliphatic substances) produced in the hydrolysis and fermentation process of coal for methane gas conversion of powdered coal. There is an effect of improving the conversion efficiency.

The anaerobic medium is a medium for promoting the growth of anaerobic microorganisms, and an alkali component (buffer component) to prevent a sudden change in pH and nutrients such as nitrogen and phosphorus necessary for the growth of anaerobic microorganisms may be included and biodegradable as a biostimulant When possible yeast extract, fermentable substrate glucose, starch, and non-fermentable substrate acetic acid, etc. are included, it may be included so as to have a concentration of 1.0 g / ℓ based on COD.

Electroactive bacteria contained in the anaerobic sludge injected into the anaerobic digester of the present invention is characterized in that it is dominated by the electromagnetic field 11 formed by the AC power supplied to the insulated electrode pair (2, 3), and the insulated electrode pair The AC power supplied to (2,3) has a frequency of 10 to 200 MHz, and the electric field formed by the AC power is 1 to 3 V/cm. Preferably, the AC power has a frequency of 50 to 500,000 Hz, and the electric field formed by the AC power is 1.67 V/cm. If the electric field is less than 1 V/cm or the frequency is less than 50 Hz, the removal of intermediate products is insignificant, so there is no difference in the bioelectrochemical method of converting powdered coal into methane gas by the conventional electrostatic field method and the methane production rate and yield. . Additionally, the distance between the insulated electrode pairs 2 and 3 is preferably 2 to 5 cm, but is not limited thereto.

Since the strength and frequency of the electromagnetic field 11 are affected by the reactant composition inside the anaerobic digestion tank, the intensity, frequency, and voltage between the pair of insulated electrodes 2 and 3 in consideration of the size of the optimal oxidation/reduction current It is desirable to appropriately adjust the distance.

The intensity of the electromagnetic field 11 formed between the insulated electrode pairs 2 and 3 is controlled by adjusting the distance between the facing insulated electrode pairs 2 and 3 and the intensity of the applied voltage using the AC voltage source 4 . can be changed through The frequency means a period of exchanging the electromagnetic field 11 formed between the insulated electrode pairs 2 and 3, and the higher the frequency, the faster the frequency. When the high frequency is used, the molecular motion of polycyclic aromatic and aliphatic polymers and methane precursors, which are intermediate products generated during hydrolysis of coal, increase, and the increased energy due to the increase in molecular motion is thermodynamically transferred between atoms. This causes the link to break easily. Therefore, if the operation is performed while applying a high frequency, it is easy to remove the intermediate product through fermentation, etc. in preparation for the case where the operation is performed while applying a low frequency. have.

Hereinafter, the present invention will be described in detail through drawings and examples.

Example

1. Operation of anaerobic digester

1 shows a schematic diagram of an anaerobic digester for converting coal of the present invention to methane.

Referring to Figure 1, the anaerobic digester of the present invention is an anaerobic digester (1) provided with an upper cover (12); DC motor 6 located above the anaerobic digester 1; The upper part is connected to the DC motor (6) and the rotation shaft (14) is installed inside the anaerobic digester (1); agitating blades 7 coupled to the lower portion of the rotating shaft 14 to stir the reactants; an airtight pipe 13 attached to the lower end of the upper cover 12 and connected to the stirring blade 7 by surrounding the rotation shaft 14; It includes a pair of insulating electrodes (insulated electrode 1(2) and insulating electrode 2(3)) coated with a dielectric material installed in an annular shape on the outer wall of the hermetic tube and the inner wall of the anaerobic digester, any one of which is the hermetic tube (13), the other one is installed on the inner wall of the anaerobic digester (1)); an AC voltage source (4) connected to the insulated electrode pair (2, 3) with a wire (5) and applying an AC voltage to form an electromagnetic field (11) and a frequency between the insulated electrode pair (2, 3); and a gas collecting port 10 installed on the upper cover 12 and connected to the pipe of the floating gas collector 15 . In addition, the anaerobic digester 1 of the present invention may further include a liquid sample collecting port 8 and a gas sample collecting port 9 installed on the upper cover 12 .

The anaerobic digester of the present invention is driven as follows.

Step 1: sieving the anaerobic sludge collected from the anaerobic digester of a sewage treatment plant and then naturally concentrating it and planting it in the anaerobic digester (1);

Second step: injecting powdered coal as a substrate;

Step 3: By supplying an AC voltage of 5.0V from the AC voltage source 4 through the conductive wire 5 connected to the insulating electrode 1 (2) and the insulating electrode 2 (3) installed inside the anaerobic digestion tank (1) Forming an electromagnetic field 11 of 1.67 V/cm inside the anaerobic digester 1, and supplying the frequency from the AC voltage source 4 to 50, 5,000, and 500,000 Hz; and

Produce biogas from the powdered coal by operating the anaerobic digester 1 by rotating the stirring blade 7 with the DC motor 6 at a constant temperature.

The insulating electrode was coated with a vinyl chloride resin using a titanium barrier plate (0.3 mm) of a conductive metal series strong against corrosion as a base electrode. The coated insulating electrode 1 (7 X 7 cm) and insulating electrode 2 (9 X 30 cm) were completed by coating the vinyl chloride resin and then heat-treating it to prevent the coating from peeling off.

Through the Examples and Comparative Examples, the efficacy of the frequency on methane conversion of coal under an electromagnetic field was verified. To this end, an anaerobic digester (1) with an effective volume of 0.5 L was prepared, and insulating electrode pairs (2, 3) coated with dielectric material were installed in an anaerobic digester (1) in an annular shape, and the insulated electrode pairs (2, 3) were The intervals were arranged at intervals of 3 cm. The insulated electrode pair (2, 3) is installed in an annular shape on the inner wall of the anaerobic digester 1 when any one of the two insulated electrode pairs is installed in an annular shape in the airtight pipe 13 (see FIG. 1). A gas collection port 10 is installed on the upper cover 12 of the anaerobic digester of Examples 1, 2, 3 and Comparative Examples, and the amount of gas generated can be measured by connecting to the floating gas collector 15 with a rubber pipe. made to be In addition, a liquid sample collecting port 8 and a gas sample collecting port 9 sealed with a rubber stopper were installed on the upper cover 12 of the anaerobic digester (1). After collecting the biogas (methane gas) from the upper part of the anaerobic digestion tank 1 through the gas sample collection port 9, the composition of the gas was changed using gas chromatography equipped with a thermal conductivity detector and a Porapak-Q separation tube. observed.

For operation, anaerobic sludge was collected from the anaerobic digester of the sewage treatment plant, and the impurities were removed by sieving and naturally concentrated, and seeded by 0.25 L each in the anaerobic digester of Examples and Comparative Examples. In addition, an effective volume of 0.5 ℓ was added by adding a medium for promoting the growth of anaerobic microorganisms. In addition, the concentration of substrate and nutrients at the initial stage of the anaerobic digester operation is Na ₂ PO ₄ 2.45 g / ℓ, Na ₂ HPO ₄ 4.58 g / ℓ, NH ₄ Cl 0.31 g / ℓ, KCl 0.13 g / ℓ, vitamin solution 1 ㎖ /L, the mineral solution was 0.5 mL/L.

Coal used as a substrate is lignite, after removing moisture contained in the coal in a dryer at 105 ° C., crushing it, sieving it through a 1 mm sieve to make powdered coal, Comparative Examples, Examples 1, 2 and Each 5 g / ℓ was injected into the anaerobic digester of Example 3.

The prepared anaerobic digester was installed in a constant temperature room at 35 degrees Celsius. The stirring blade (7) mounted on the DC motor (6) was rotated at 200 rpm to start operation.

In each anaerobic digester (1) in Examples 1, 2 and 3, an AC voltage of 5.0V was applied using an AC voltage source (4) to form an electromagnetic field of 1.67 V/cm, and the frequencies were 50, 5,000, 500,000 Hz. In the comparative example, a DC voltage of 5.0 V was applied using a DC voltage source to form an electrostatic field of 1.67 V/cm. The initial VSS and total COD of the anaerobic digester used in Examples and Comparative Examples were 18.9±0.3 g/L and 17.2±0.2 g/L, respectively.

In addition, in order to correct the amount of methane generated from the anaerobic sludge itself, an anaerobic digester was separately prepared and operated as a correction example in the same manner as in Examples 1, 2, 3 and Comparative Examples.

Examples 1, 2, 3 and the anaerobic digester of Comparative Examples by applying a voltage of 5.0 V to the insulating electrode pair (2, 3) to form an electric field of 1.67 V / cm. An AC voltage of 5.0 V was applied to the anaerobic digestion tank of Examples 1, 2, and 3 as an AC voltage source 4, respectively, and the frequencies were 50, 5,000, and 500,000 Hz. The anaerobic digester of Comparative Example 1 was used in the same standard as in Example, but 5.0 V was applied as a DC voltage source.

2. Generation of biogas

1) Comparison of results of coal-biogas (methane) conversion between the electrostatic field method and the electromagnetic field method

While operating the anaerobic digester of Examples 1, 2, and 3, Comparative Examples and Corrected Examples, the components and the amount of biogas generated were measured.

2 shows coal-biogas (methane) conversion results (cumulative methane generation amount) according to the operating time of Examples and Comparative Examples of the present invention. The line including the black circle shows the result of the cumulative methane generation of the comparative example, which was operated by applying a DC voltage of 5.0 V using a DC voltage source to form an electrostatic field of 1.67 V/cm, and the line including the red inverted triangle shows the results for the cumulative methane generation of Example 1, which was operated with an electromagnetic field of 1.67 V/cm by applying an AC voltage of 5.0 V, but operated at a frequency of 50 Hz, and the line including the green square indicates an AC voltage of 5.0 V The result of the accumulated methane generation in Example 2 was shown, which was applied to form an electromagnetic field of 1.67 V/cm, but operated at a frequency of 5,000 Hz, and the line including the yellow square was applied with an AC voltage of 5.0 V and an electromagnetic field of 1.67 V/ cm, but shows the results for the cumulative methane generation of Example 3 operated with a frequency of 500,000 Hz.

Cumulative amount of methane generated from coal in the bioelectrochemical anaerobic digester (comparative example) in which an electrostatic field was formed by supplying DC power and the bioelectrochemical anaerobic digester (Examples 1, 2 and 3) in which an electromagnetic field was formed by supplying AC power ( As a result of comparing cumulative methane production), it was confirmed that both results showed a very short lag period, followed by a sharp increase in the cumulative methane production. In the case of Comparative Example, a total of 161.4 ml of biogas (methane) was generated after 8 hours of operation, and in the case of Example 1 (frequency of 50 Hz), a total of 160.9 ml of biogas was generated as a result of 8 hours of operation, Example 2 ( In the case of a frequency of 5,000 Hz), a total of 172.2 ml of biogas was generated as a result of 8 hours of operation, and in the case of Example 3 (frequency of 500,000 Hz), it was confirmed that a total of 185.2 ml of biogas was generated as a result of 8 hours of operation. In the case of Example 1, it was confirmed that the biogas production amount was similar to that of Comparative Example, but in Examples 2 and 3, the biogas production was increased to 6.7% and 14.7%, respectively, compared to Comparative Example (see Table 1).

In addition, as a result of analyzing the final methane yield generated from 1 g of coal, 64.4 ml/g Lignite in Example 1 (frequency 50 Hz) and 68.9 ml/g in Example 2 (frequency 5,000 Hz) of the reactor in which an electromagnetic field was formed In the case of g Lignite, Example 3 (frequency 500,000 Hz), 74.1 ml/g Lignite occurred maximally in Example 3, which had a high frequency, which was larger than 64.5 ml/g Lignite of the reaction tank (comparative example) in which an electrostatic field was formed. was found to be high.

Example 1 Example 2 Example 3 comparative example Voltage application method 5.0 V AC
(1.67 V/cm electromagnetic field) 5.0 V AC
(1.67 V/cm electromagnetic field) 5.0 V AC
(1.67 V/cm electromagnetic field) 5.0 V DC
(1.67 V/cm electrostatic field) Frequency (Hz) 50 5,000 500,000 - Final methane production (ml) 160.9 172.2 185.2 161.4 Maximum methane generation rate (ml/d) 31.2 29.1 33.9 32.0 lag phase (d) 0.31 0.24 0.21 0.24 Final methane yield (ml/g Lignite) 64.4 68.9 74.1 64.5

The above results show that the operation of the electromagnetic field method using an alternating current power supply has better biogas generation than the electrostatic field method using a DC power source.

In the case of the example in which the electromagnetic field was formed, the molecular motion (vibration, rotation, translation) by the electric field was increased compared to Comparative Example 1 in which the electrostatic field was formed. Therefore, bioelectrochemical decomposition of polycyclic aromatic and aliphatic substances generated in the hydrolysis and fermentation process of coal is promoted, which leads to improved in vitro electron transfer of electroactive bacteria, and thus it is judged that the production of biogas is improved. .

According to the result of FIG. 2 , it is confirmed that the cumulative amount of biogas generated increases in proportion to the frequency. The above results show that the molecular motion (vibration, rotation, translation) is active in the decomposition process of coal according to the magnitude of the frequency, and the conversion of polycyclic aromatic and aliphatic compounds generated during the hydrolysis of coal into low-molecular substances by continuous fermentation is promoted. means that

In summary, the bioelectrochemical anaerobic digester (Example) that formed the electromagnetic field according to the present invention had a high cumulative biogas generation amount compared to the bioelectrochemical anaerobic digester (Comparative Example) that formed an electrostatic field, and the frequency was set to 500,000 Hz. In the case of setting the frequency, it was confirmed that the accumulated methane production increased by 15% compared to 50 Hz. The above result means that the molecular motion (vibration, rotation, translation) of polycyclic aromatic and aliphatic substances generated in the hydrolysis step of coal increases as the frequency increases, thereby increasing the molecular weight reduction effect. It means that adding , is advantageous when converting coal to methane.

According to the result of FIG. 2 , it is confirmed that the amount of biogas generated no longer increases after about 6 days of operation. The above result is judged because the activity of anaerobic microorganisms, such as electroactive bacteria, is reduced because the coal decomposition intermediate product is no longer decomposed and accumulated after 6 days of operation.

2) Analysis of dominance of electroactive bacteria according to frequency size

3 shows the results of comparing the degree of activity of electroactive bacteria by performing cyclic voltammetry analysis in Examples and Comparative Examples of the present invention. The black line shows the analysis result of the cyclic current voltammetry of the comparative example, which was operated by applying a DC voltage of 5.0 V using a DC voltage source to form an electrostatic field of 1.67 V/cm, and the red line shows the analysis result of the AC voltage 5.0 V applied. The cyclic voltammetry analysis result of Example 1 was shown in which an electromagnetic field of 1.67 V/cm was formed but the frequency was 50 Hz, and the green line was applied with an AC voltage of 5.0 V to form an electromagnetic field of 1.67 V/cm but the frequency was lowered. The cyclic voltammetry analysis result of Example 2 operated at 5,000 Hz is shown, and the yellow line is an electromagnetic field of 1.67 V/cm by applying an AC voltage of 5.0 V, but operating at a frequency of 500,000 Hz. The results of the analysis of cyclic voltammetry are shown. The cyclic voltammetry was performed as a method of monitoring the oxidation/reduction current while increasing or decreasing the voltage in the internal solution of the anaerobic digester in stages. As the size of the measured oxidation/reduction current peak increases, it means that the degree of activity of the electroactive bacteria is dominant.

Table 2 compares the electrochemical analysis results using the cyclic voltammetry in the bioelectrochemical anaerobic digester (Comparative Example) forming an electrostatic field and the bioelectrochemical anaerobic digester (Examples 1, 2 and 3) forming an electromagnetic field did it

Example 1 Example 2 Example 3 comparative example Voltage application method 5.0 V AC
(1.67 V/cm electromagnetic field) 5.0 V AC
(1.67 V/cm electromagnetic field) 5.0 V AC
(1.67 V/cm electromagnetic field) 5.0 V DC
(1.67 V/cm electrostatic field) Frequency (Hz) 50 5,000 500,000 - Final methane production (ml) 160.9 172.2 185.2 161.4 Final methane yield (ml/g Lignite) 64.4 68.9 74.1 64.5 E _pa (V) 0.054 0.109 0.228 0.058 I _pa (㎃) 0.446 0.561 0.603 0.456 E _pc (V) -0.459 -0.372 -0.228 -0.443 I _pc (㎃) 0.357 0.464 0.488 0.369

As a result of comparing the magnitude of the oxidation/reduction peak current, I _pa =0.446 mA and I _pc =0.357 mA of the reactor in which an electromagnetic field was formed at a frequency of 50 Hz (Example 1) were the reaction tank in which an electrostatic field was formed (Comparative Example) I On the other hand, values similar to _pa = 0.456 mA and I _pc =0.369 mA are shown, whereas in the case of the reactor (Example 2) in which an electromagnetic field is formed at a frequency of 5,000 Hz, I _pa = 0.561 mA and I _pc =0.464 mA, and the frequency is 500,000 In the case of the reactor in which the electromagnetic field was formed at Hz (Example 3), it was confirmed that I _pa = 0.603 mA and I _pc = 0.488 mA, which was larger than the reactor (Comparative Example) in which an electrostatic field was formed (see Table 2). The above result means that an electromagnetic field is formed by applying AC power, but as the size of the frequency increases, the electroactive bacteria are abundantly dominant in the reaction tank. As the size of the frequency increases, the cumulative amount of biogas generation increases. to be. As in Tables 1 and 2, when the same electromagnetic field of 1.67 V/cm was formed and only the frequency was increased, it was confirmed that both the final methane production (accumulated biogas production) and the final methane yield from 1 g of coal were increased. . The above result means that when AC power is applied to form an electromagnetic field, but a large frequency is formed, the amount of biogas generated increases because the electroactive bacteria are abundantly dominant in the reaction tank.

Specific examples described herein are meant to represent preferred embodiments or examples of the present invention, and the scope of the present invention is not limited thereby. It will be apparent to those skilled in the art that modifications and other uses of the present invention do not depart from the scope of the invention as set forth in the claims herein.

1: Anaerobic reactor 2: Insulated electrode 1
3: Insulated electrode 2 4: AC voltage source
5: Conductor 6: DC motor
7: Stirring blade 8: Liquid sample collection port
9: gas sample collection port 10: gas collection port
11: electromagnetic field 12: top cover
13: airtight pipe 14: rotation shaft
15: Floating gas collector

Claims (6)

A bioelectrochemical method for converting powdered coal into methane gas, comprising:
A first step of sieving the anaerobic sludge in a sewage treatment plant, concentrating it, and planting it in an anaerobic digester including an insulated electrode pair;
a second step of injecting powdered coal as a substrate into the anaerobic digester;
A third step of forming an electromagnetic field by supplying AC power to the insulated electrode pair of the anaerobic digester; and
a fourth step of converting the coal into methane gas by stirring the reactants including the anaerobic digester;
A bioelectrochemical method for converting coal into methane gas, comprising:
The bioelectrochemical method for converting coal to methane gas according to claim 1, wherein the anaerobic sludge includes methanogenic bacteria, and the methanogenic bacteria are predominantly methanogenic electroactive bacteria by an electromagnetic field formed by an AC power source. .
[Claim 3] The method of claim 2, wherein the methanogenic electroactive bacteria include in vitro transport emitters and electrotrophic methanobacteria, and the conversion of coal to methane gas through direct interspecies electron transfer between the in vitro transport emitters and electrotrophic methanobacteria. A bioelectrochemical method for converting coal into methane gas, characterized in that
The method of claim 1, wherein the AC power supplied to the insulated electrode pair has a frequency of 10 to 200 MHz, and the electric field formed by the AC power is 1 to 3 V/cm. Bioelectrochemical method.
The bioelectrochemical method for converting coal into methane gas according to claim 1, wherein an anaerobic medium is further added in the first or second step.
6. Coal according to claim 5, wherein the anaerobic medium contains a biodegradable fermentable substrate to promote continuous fermentation of intermediate products produced in the hydrolysis and fermentation process of coal for methane gas conversion of coal. Bioelectrochemical method for conversion to methane gas.

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