KR20090008987A - Method for high efficiency biological production of methane using hydrogen and carbon dioxide - Google Patents

Abstract

A biological methane manufacturing method of efficiently using hydrogen and carbon dioxide is provided to reduce carbon dioxide massively at a room temperature and a regular pressure by using organic waste and to produce methane usable to new energy source massively. A biological methane manufacturing method of efficiently using hydrogen and carbon dioxide comprises steps of: collecting the organic waste including anaerobe; removing dissolved oxygen included in the organic waste by injecting at least one of inactive gas, mixing gas of the hydrogen and the carbon dioxide and oxygen scavenger in the collected organic waste; using carbon dioxide from the organic waste as unique carbon source and unique energy source by injecting the hydrogen and the carbon dioxide into the organic waste and cultivating the anaerobe; injecting the organic waste in which anaerobe is cultivated in the anaerobic bioreactor(40) in which the porous carrier is filled; and producing the methane by injecting the hydrogen and carbon dioxide into the anaerobic bioreactor and reacting injected gas by anaerobe.

Description

Method for high efficiency biological production of methane using hydrogen and carbon dioxide}

The present invention relates to a method for producing biological methane, and more particularly, to produce biological methane that can mass-reduce carbon dioxide and produce large quantities of methane at high temperature and atmospheric pressure by reacting carbon dioxide with hydrogen through anaerobic bioreaction using organic waste. It is about a method.

Carbon dioxide (CO ₂ ) is one of environmentally hazardous substances that must be removed due to the recent enactment of many laws in each country such as the Kyoto Protocol.

Meanwhile, waste activated sludge (WAS) and food waste (FW) among organic wastes are recognized as essential wastes to be disposed of.

Landfill or incineration techniques can generally be applied for the final treatment of these organic wastes, in addition to anaerobic digestion techniques.

Anaerobic digestion is the process in which organic matter is converted to methane and carbon dioxide by a series of microbiological processes. Anaerobic digestion consists of four stages: the hydrolysis stage, the acid production stage, the acetic acid production stage, and the methane production stage. Methane is produced as the final product at the end of anaerobic digestion.

As such, many studies have been conducted to produce biogas such as methane using organic waste, but all these studies use acetate as a nutrient source in an anaerobic biological process. In other words, the technique used in most studies to produce biogas, such as methane, is a technique that takes advantage of improvements in processes involving fermenters. For example, Korean Patent Laid-Open Publication No. 2002-0038701 discloses a technique of generating biogas using a two-phase methane fermentation reactor as an organic raw material such as animal waste, and in this case, a methane-producing strain is used. The nutrient was acetate. In addition, the Republic of Korea Patent No. 0252811 discloses a technology for generating biogas using a three-phase fermenter containing a crusher as a raw material for food waste, using a variety of aerobic strains and anaerobic strains Treatment was to achieve high efficiency production of methane through shortening of fermentation time. In addition, Korean Patent No. 0461759 discloses a method for producing hydrogen and methane gas with high efficiency after forming sewage sludge as a target raw material and forming granular sludge in a short time by adding a granulation accelerator. In addition, PCT / US2001 / 030969 aims to produce methane with high efficiency at various alkalis and temperatures by applying various organic wastes and applying various bacteria. Examples of the application of two or more single solubilization techniques to the solubilization of organic waste include Korean Patent Publication No. 2005-0088644 and Korean Patent Publication No. 2005-0011391. Korean Patent Publication No. 2005-0088644 discloses a technology for solubilizing sewage sludge using microwave, hot air, and heat absorbing material, and Korean Patent Publication No. 2005-0011391 discloses only two physical methods. Ultrasonic irradiation technology, specifically, sewage sludge as a raw material, using a multi-wavelength and countercurrent ultrasonic irradiation to improve the treatment capacity of the bioreactor, solubilizing the sludge with high efficiency. PCT / US2002 / 025253 classifies target raw materials by particle size, solubilizes them by applying thermal hydrolysis at a temperature of 130 ℃ or higher and a pressure above saturated steam pressure, and then increases the solubilization efficiency of organic waste through alkali treatment. It was. PCT / JP2001 / 08842 tried to reduce the volume of sludge by using excess sludge as a raw material, adding solubilizer to the sludge, applying ultrasonic wave, swelling under reduced pressure, and then microbial treatment.

As mentioned above, many studies have been conducted on producing acetate using raw materials such as organic waste, and producing biogas such as methane through methane production strains. There have been no reports of methane production using production strains. Therefore, there is a demand for a technology for producing a large amount of methane that can be used as a new energy source while reducing the amount of carbon dioxide that is the main cause of greenhouse gases using organic waste.

An object of the present invention is to provide a high-efficiency biological methane production method that can produce a large amount of methane that can be used as a new energy source while reducing the mass of carbon dioxide at room temperature and atmospheric pressure using organic wastes.

The present invention to solve the above problems,

(a) collecting organic waste comprising anaerobic microorganisms;

(b) removing dissolved oxygen contained in the organic waste by injecting at least one of an inert gas, a mixed gas of hydrogen and carbon dioxide, and an oxygen scavenger into the collected organic waste;

(c) culturing anaerobic microorganisms using carbon dioxide as the sole carbon source and the only energy source from the organic waste by injecting hydrogen and carbon dioxide into the organic waste;

(d) injecting the organic waste in which the anaerobic microorganisms are cultured into an anaerobic bioreactor filled with a porous carrier; And

(e) injecting hydrogen and carbon dioxide into the anaerobic bioreactor and producing methane by reacting the injected gases by the anaerobic microorganisms.

According to one embodiment of the invention, the filling ratio of the porous carrier in the step (a) is 25 to 45% by volume relative to 100% by volume of the anaerobic bioreactor, the injection molar ratio of hydrogen: carbon dioxide in step (d) Is 4.5: 1 to 5.5: 1.

According to the present invention, a high-efficiency biological methane production method capable of producing large quantities of methane that can be used as a new energy source while reducing carbon dioxide in a large amount at room temperature and atmospheric pressure using an organic waste can be provided.

Next, with reference to the accompanying drawings will be described in detail with respect to the biological methane production method according to a preferred embodiment of the present invention.

Biological methane production method according to the embodiment, the step of collecting an organic waste containing anaerobic microorganisms, by injecting at least one of an inert gas, a mixed gas of hydrogen and carbon dioxide, and an oxygen scavenger to the collected organic waste Removing dissolved oxygen contained in the organic waste, culturing anaerobic microorganisms using carbon dioxide as the sole carbon source and the only energy source from the organic waste by injecting hydrogen and carbon dioxide into the organic waste, culturing the anaerobic microorganisms Injecting the prepared organic waste into an anaerobic bioreactor filled with a porous carrier, and injecting hydrogen and carbon dioxide into the anaerobic bioreactor and reacting the injected gases with the anaerobic microorganism to produce methane. do.

Hereinafter, the biological methane production method according to the embodiment will be described in detail.

First, organic waste such as sewage sludge or food waste is collected. Such organic waste typically contains anaerobic microorganisms.

Next, dissolved oxygen contained in the organic waste is removed by injecting at least one of an inert gas such as argon or nitrogen, a mixed gas of hydrogen and carbon dioxide, and an oxygen scavenger into the organic waste collected. Here, the type of oxygen scavenger is not particularly limited, and any known one may be used.

Next, by injecting hydrogen and carbon dioxide into the organic waste, anaerobic microorganisms are grown from the organic waste using carbon dioxide as the only carbon source and the only energy source. It is preferable that the culture of the anaerobic microorganisms lasts for at least 3 months, but the present invention is not limited thereto, and the incubation time may vary depending on the intended methane production amount. Here, the cultured anaerobic microorganism is a hydrogenotropes community that produces methane from carbon dioxide, not a strain community that produces methane from acetate.

Hereinafter, referring to Figure 1 will be described in more detail the biological methane production method according to the embodiment.

1 is a view schematically showing a biological methane production apparatus configured by applying a biological methane production method according to the present embodiment.

Referring to FIG. 1, the biological methane production apparatus 1 includes a hydrogen storage container 10, a carbon dioxide storage container 20, a gas mixer 30, an anaerobic bioreactor 40, a porous carrier 45, and a gas. Chromatography 50 and flow meter 60.

First, the organic waste in which the anaerobic microorganisms are cultured is introduced into the anaerobic bioreactor 40 in which the porous carrier 45 is filled. Anaerobic bioreactor 40 is preferably formed of an acrylic resin, Pyrex or quartz (quartz) of a transparent material, but the present invention is not limited thereto. As the porous carrier 45, for example, a ceramic ball may be used, but the present invention is not limited thereto. The porous carrier 45 serves to improve the reaction rate and dissolution rate of hydrogen and carbon dioxide in addition to the carrier of the anaerobic microorganism. The filling ratio of the porous carrier 45 is preferably 25 to 45% by volume with respect to 100% by volume of the anaerobic bioreactor 40. If the filling ratio is outside the above range, the amount of methane produced is not preferable.

Next, methane is produced by injecting hydrogen and carbon dioxide into the anaerobic bioreactor 40 and reacting the injected gases with the anaerobic microorganisms. Specifically, hydrogen and oxygen are dissolved in water contained in the organic waste and then converted into methane by reacting with each other by anaerobic microorganisms. Here, it is preferable that the injection molar ratio of hydrogen: carbon dioxide is 4.5: 1 to 5.5: 1. If the injection molar ratio is less than 4.5: 1, the amount of hydrogen used for the reduction of carbon dioxide is too small, which is not preferable because it has little effect on the methane production. Too little to produce less methane, which is undesirable. In addition, hydrogen and carbon dioxide may be injected into the anaerobic bioreactor 40 separately from the hydrogen storage container 10 and the carbon dioxide storage container 20, respectively, mixed in the gas mixer 30 as shown in FIG. It may be injected in the form of. Here, the optimum flow rate of the mixed gas of hydrogen and carbon dioxide may vary depending on the size of the anaerobic bioreactor 40, the particle size of the porous carrier 45 and the filling ratio.

Next, methane, by-products produced in the anaerobic bioreactor 40, and / or unreacted gases such as hydrogen or carbon dioxide are discharged to the outside of the anaerobic bioreactor 40. Some or all of the gases discharged to the outside are subjected to the gas chromatography 50 and the flow meter 60, respectively, and the components thereof may be analyzed and the gas flow rate may be measured. In addition, carbon dioxide among the discharged gases may be separated in a separate separator (not shown) and re-injected into the anaerobic bioreactor 40.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example

Example 1 Organic Waste Collection, Anaerobic Microbial Culture and Identification of Cultured Anaerobic Microorganisms

Organic waste was harvested and inert gases (argon and nitrogen) were used immediately to remove dissolved oxygen contained in the organic waste. Subsequently, the organic wastes of FIG. Injected into the biological methane production apparatus (1). In the present embodiment, the anaerobic bioreactor 40 was formed of a transparent acrylic resin, and a reactor having a diameter of 10.5 cm and a length of 97 cm was used. As the porous carrier 45, a ceramic ball having a volume of 0.325 cm ³ , a density of 1.8-2.0 g / cm ³ , and a surface area of 2.23 m ² / g was used. The flow rate of the mixed gas consisting of hydrogen and carbon dioxide was 100 ml / min.

In order to confirm that only hydrogenopros colonies exist in the anaerobic bioreactor 40, gas and acetate, optionally mixed 1: 1 with hydrogen and carbon dioxide on a molar ratio basis, are injected into the anaerobic bioreactor 40, After looking at the methane production characteristics are shown in Figure 2 the results. As shown in FIG. 2, there was no change in acetate concentration over time, and the amount of methane increased with decreasing hydrogen and carbon dioxide concentrations. From these results, it can be seen that a high concentration of hydrogenotropes is present in the organic waste cultured with anaerobic microorganisms. As a result of direct examination of the hydrogenotropes community in organic waste using PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) method, it was confirmed that the hydrogenotropes community was cultured at high concentration.

Example 2: Changes in Biological Methane Production Rate According to Filling Ratio of Porous Carrier

As in Example 1, the cultured organic waste, the anaerobic bioreactor 40, and the porous carrier 45 were used to observe the change of the methane production rate according to the filling ratio of the porous carrier 45. Specifically, methane production rate was measured while changing the filling ratio of the porous carrier 45 from 0% to 100% by volume with respect to 100% by volume of the anaerobic bioreactor 40, and the results are shown in FIG. Here, the flow rate of the mixed gas consisting of hydrogen and carbon dioxide was 100ml / min.

As shown in FIG. 3, the production rate of methane was the highest when the porous carrier 45 was filled in 40 vol% with respect to 100 vol% of the anaerobic bioreactor 40. In particular, when filling the porous carrier 45 or more by 80% by volume or more, the mixed gas of hydrogen and carbon dioxide injected from the anaerobic bioreactor 40 does not flow inside the anaerobic bioreactor 40 but is stagnant or only in one place. While showing the phenomenon of flowing, the organic waste introduced into the anaerobic bioreactor 40 shows the phenomenon of corruption. This is believed to be because the filling of a large amount of the porous carrier 45 interferes with the flow of the injected mixed gas.

Example 3: Methane Production Rate Change According to Mixing Ratio of Hydrogen and Carbon Dioxide

As in Example 1, the culture rate of the organic waste, the anaerobic bioreactor 40, and the porous carrier 45 were used to measure the change in methane production rate according to the mixing ratio of hydrogen and carbon dioxide. The filling ratio of the porous carrier 45 was 40% by volume with respect to 100% by volume of the anaerobic bioreactor 40 reflecting the results of Example 2. In addition, the flow volume of the mixed gas which consists of hydrogen and carbon dioxide was 100 ml / min in all cases.

Methane production rate was measured over time while gradually increasing the mixing ratio of hydrogen: carbon dioxide from 2: 1 to 8: 1 on a molar ratio basis, and the results are shown in FIG. 4. As can be seen in Figure 4, when the mixture of hydrogen and carbon dioxide in a ratio of 5: 1 it can be seen that the methane production rate is the highest. From a stoichiometric point of view, the ratio of hydrogen to carbon dioxide is 4: 1 optimal. However, the ratio of 5: 1, which is larger than 4: 1, is considered to be the optimum mixing ratio due to the solubility of hydrogen in water.

Example 4 Changes in Cumulative Methane Production Over Time at Optimal Operating Conditions

Changes in cumulative methane production over time were measured using the same cultured organic waste, anaerobic bioreactor 40, and porous carrier 45 as in Example 1. The filling ratio of the porous carrier 45 was 40 vol% to 100 vol% of the anaerobic bioreactor 40 reflecting the result of Example 2, and the mixing ratio of hydrogen and carbon dioxide was 5 to reflect the result of Example 3 : 1 was set. In addition, the flow volume of the mixed gas which consists of hydrogen and carbon dioxide was 100 ml / min. The temperature of the anaerobic biological reactor (40) was adjusted to 37 ㅁ 1 ℃, pH was 6.8-7.0.

As shown in FIG. 5, in the case of using hydrogenoprox present in organic waste at a high concentration, the injected carbon dioxide is partially discharged to the outlet in the anaerobic bioreactor 40 at the beginning of operation, but is discharged to the outlet at the end of operation. Carbon dioxide is not emitted but only methane is produced. That is, in the early stage of operation, the mixed gas of hydrogen and carbon dioxide injected was not reacted in a large amount in the anaerobic bioreactor 40 and discharged as it is, but the productivity of methane was low. It can be seen that as the amount is reduced, a large amount of methane is produced. The reduction of the emission of hydrogen and carbon dioxide over time means that these mixed gases are reacted by the hydrogenopros community in the anaerobic bioreactor 40, thereby improving the methane production capacity.

According to the biological methane production method according to the present invention having the configuration as described above, it is possible to produce a large amount of methane with high efficiency at room temperature and atmospheric pressure using the organic waste. Here, normal temperature means the low temperature range of 0-100 degreeC. In addition, the biological methane production method according to the present invention can be used to reduce the carbon dioxide which is the main culprit of the greenhouse gas can efficiently remove the carbon dioxide contained in the flue gas (analysis) through the anaerobic biological process.

In the foregoing description, a preferred embodiment according to the present invention has been described with reference to the drawings, but this is only an example, and those skilled in the art may understand that various modifications and equivalent other embodiments are possible. There will be. Therefore, the protection scope of the present invention should be defined by the appended claims.

1 is a view schematically showing a biological methane production apparatus configured by applying a biological methane production method according to the present embodiment.

2 is a graph showing the cultivation degree of anaerobic microorganisms over time in the biological methane production method according to the present embodiment.

3 is a graph showing the methane production rate according to the filling ratio of the porous carrier in the biological methane production method according to the present embodiment.

4 is a graph showing the methane production rate according to the injection ratio of hydrogen and carbon dioxide in the biological methane production method according to the present embodiment over time.

5 is a graph showing the cumulative methane production and the reaction characteristics of hydrogen and carbon dioxide over time when applying the optimum operating conditions in the biological methane production method according to the present embodiment.

<Explanation of symbols for the main parts of the drawings>

1: biological methane production apparatus 10: hydrogen storage container

20: carbon dioxide storage container 30: gas mixer

40: anaerobic bioreactor 45: porous carrier

50: gas chromatography 60: flow meter

Claims (2)

(a) collecting organic waste comprising anaerobic microorganisms; (b) removing dissolved oxygen contained in the organic waste by injecting at least one of an inert gas, a mixed gas of hydrogen and carbon dioxide, and an oxygen scavenger into the collected organic waste; (c) culturing anaerobic microorganisms using carbon dioxide as the sole carbon source and the only energy source from the organic waste by injecting hydrogen and carbon dioxide into the organic waste; (d) injecting the organic waste in which the anaerobic microorganisms are cultured into an anaerobic bioreactor filled with a porous carrier; And (e) injecting hydrogen and carbon dioxide into the anaerobic bioreactor and producing methane by reacting the injected gases by the anaerobic microorganisms. The method of claim 1, The filling ratio of the porous carrier in step (a) is 25 to 45% by volume relative to 100% by volume of the anaerobic bioreactor, and in step (d), the injection molar ratio of hydrogen: carbon dioxide is 4.5: 1 to 5.5: 1. Biological methane production method, characterized in that.

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