KR20090129786A - Method and apparatus for bio-hydrogen gas production from organic waste by using inhibitor for methane producing microorganisms and gas purging under low ph condition - Google Patents

Abstract

PURPOSE: An apparatus for bio-hydrogen gas production from organic waste and a method thereof are provided to increase bio hydrogen production by increasing activity of hydrogen production microorganism with low methane conversion of hydrogen due to the hydrogen production microorganism. CONSTITUTION: An apparatus for bio-hydrogen gas production comprises the followings: a bio hydrogen gas production reaction bath(1); an organic waste bath(2) connected with the bio hydrogen gas production reaction bath; a methanogenesis microorganism activity inhibitor bath connected with the bio hydrogen gas production reaction bath; a pH control acid chemical substance storage bath(5) connected with the bio hydrogen gas production reaction bath; a pH control alkali chemical substance bath(6) connected with the bio hydrogen gas production reaction bath; and a hydrogen gas separation device(10) connected with the top of the bio hydrogen gas production reaction bath.

Description

Method and apparatus for Bio-hydrogen gas production from organic waste by using inhibitor for methane producing microorganisms and gas purging under low pH condition}

The present invention relates to an apparatus and method for producing hydrogen with high efficiency from organics present in organic waste using anaerobic fermentation microorganisms. Specifically, in order to suppress the activity of methane-producing microorganisms and increase the activity of hydrogen-producing microorganisms, the pH of the methane-producing microorganisms is injected to suppress the methane conversion of hydrogen by the methane-producing microorganisms. The present invention relates to an apparatus and a method for producing hydrogen with high efficiency by lowering the partial pressure of hydrogen by phosphorus gas purging to increase the activity of hydrogen-producing microorganisms.

At present, more than 96% of hydrogen is produced from fossil fuels, and it is not an environmentally friendly method due to the limited reserves of coal and oil and the emission of environmental pollutants. Recently, there has been increasing interest in biological hydrogen production methods for producing hydrogen from organic waste using microorganisms. In addition, as the regulations on marine emissions for organic wastes are greatly strengthened, it is necessary to treat and recycle the organic wastes, which have been mostly marine discharged, landfilled, or incinerated.

Biological hydrogen production consumes less energy because it is produced at room temperature and atmospheric pressure, and because hydrogen is produced from renewable waste resources, it has advantages in two aspects: reducing environmental pollution and producing clean alternative energy. In the case of hydrogen, the energy content per unit mass is 120 MJ / kg and other energy sources (coal 30 MJ / kg, natural gas 50 MJ / kg, petroleum 45 MJ / kg, diesel 43 MJ / kg, ethanol 21 MJ / kg) It is much higher than), which is more effective in bioenergy production.

In general, the gases produced under anaerobic conditions are hydrogen and methane, but hydrogen is methane because of low production efficiency and conversion to methane by hydrogen-utilizing methanogens. It is true that it has received less attention. However, when methane gas produced by microorganisms is used as energy, the final product is carbon dioxide (CO ₂ ), which is the main culprit of global warming, whereas in the case of hydrogen gas, the final product is water vapor, so it is not suitable for use as eco-friendly renewable energy. It is possible. For this reason, hydrogen energy is in the limelight as the most promising alternative of future clean energy sources.

Biohydrogen production by anaerobic fermentation is 1) faster hydrogen production rate than hydrogen production by photosynthetic microorganisms, 2) hydrogen production occurs even in the absence of light, so hydrogen can be produced without time constraints, 3) rapid growth rate of microorganisms Due to the advantages such as the large size of the facility and the convenience of maintenance, it is evaluated as a suitable technology for mass production of hydrogen industrially. However, hydrogen production by anaerobic fermentation has been pointed out as a problem of low yield of hydrogen production compared to other biological hydrogen production processes. In the case of biohydrogen production research conducted at home and abroad, hydrogen production by photosynthetic microorganisms or algae using solar energy is mostly used. It is focused on.

In order to overcome the limitation of the low yield of the conventional biohydrogen production technology, the present invention maintains a low pH condition to induce the activity of methane-producing microorganisms and increase the activity of hydrogen-producing microorganisms, while at the same time inhibiting the activity of methane-producing microorganisms The present invention provides a method and apparatus for increasing bio-hydrogen production by minimizing the conversion of hydrogen to methane-producing microorganisms by injecting a risk inhibitor and increasing the activity of hydrogen-producing microorganisms by lowering the partial pressure of hydrogen by intermittent gas purging. For the purpose of

The present invention is a bio-hydrogen gas production reactor (1); An organic waste storage tank 2 connected to the bio-hydrogen gas production reactor; A methane generating microbial activity inhibitor reservoir (3) connected to the bio-hydrogen gas production reactor; A pH controlled acid chemical reservoir (5) connected to the biohydrogen gas production reactor; A pH controlled alkali chemicals reservoir (6) connected with said biohydrogen gas production reactor; A gas tank 12 connected to a lower portion of the bio-hydrogen gas production reactor; And a hydrogen gas separation device 10 connected to the upper portion of the bio-hydrogen gas production reactor.

In addition, the present invention provides a method for producing bio-hydrogen gas from the organic waste, comprising the steps of injecting the organic waste into the reactor; Injecting pH adjusting chemicals to adjust the pH of the reactor; Injecting a methane producing microbial activity inhibitor into the reactor; Injecting gas into the organic waste in the reactor to lower the partial pressure of hydrogen in the reactor; And it provides a bio-hydrogen gas production method comprising the step of separating and recovering hydrogen gas in the generated gas.

Using the bio-hydrogen gas production method according to an embodiment of the present invention, it is possible to produce hydrogen with economical, stable and high efficiency, compared to the conventional method for producing bio-hydrogen gas from organic wastes, in particular a continuous gas purging process It is possible to produce highly efficient and stable bio-hydrogen gas even through intermittent gas purging. In addition, it is easy to commercialize by combining the bio-hydrogen gas production method in a unit process.

Hereinafter, a method for producing biohydrogen gas from the organic waste according to the present invention will be described in detail.

The bio-hydrogen production method of the present invention is a methane-producing microorganism by injecting an inhibitor to suppress the activity of the methane-producing microorganism while maintaining a low pH condition in order to induce the activity of methane-producing microorganisms and the increase of activity of the hydrogen-producing microorganism By minimizing the conversion of hydrogen by methane and by intermittent gas purging, it is characterized by lowering the partial pressure of hydrogen to increase the activity of hydrogen-producing microorganisms.

Anaerobic methane-producing microorganisms show the highest activity at pH 8 and hydrogen-producing microorganisms have the highest activity at pH 5, thus decreasing the activity of methane-producing microorganisms and increasing the activity of hydrogen-producing microorganisms. For this reason, it is preferable to keep the reaction pH condition as low as pH 4.5 ~ 5.5.

In addition, when the microorganism produces hydrogen gas under anaerobic conditions, when the partial pressure of hydrogen rises above a certain level due to the build-up of hydrogen in the reactor, the microorganism stops the production of hydrogen and the hydrogen in the reactor. Hydrogen is converted into methane gas by methane-producing microorganisms when the gas is present for a certain time. To prevent this, the methane-producing microorganism activity inhibitor is injected to minimize the methane conversion of hydrogen by methane-producing microorganisms and hydrogen by gas purging. It is desirable to lower the partial pressure.

In order to continuously purge the gas to lower the partial pressure of hydrogen, a large amount of external gas must be continuously injected, which is expensive due to the external gas injection, and even when the generated hydrogen gas is separated, the amount of external gas injected is higher than that of the generated gas. As this increases, the cost of separation is also high. Therefore, it is desirable to lower the hydrogen partial pressure by intermittent gas purging.

Method for producing bio-hydrogen gas from an organic waste according to an embodiment of the present invention,

(1) injecting organic waste into the reactor,

(2) adjusting the pH of the reactor;

(3) injecting a methane generating microbial activity inhibitor into the reactor;

(4) a gas purging process for lowering the partial pressure of hydrogen in the reactor, and

(5) separating and recovering the generated hydrogen gas and measuring the recovered amount of hydrogen gas.

In order to produce biohydrogen gas by the method according to an embodiment of the present invention, the apparatus shown in FIG. 1 may be used. 1 is a schematic diagram of an apparatus for producing biohydrogen gas according to an embodiment of the present invention from organic waste. By using the apparatus, it is easy to commercialize the system by combining the bio-hydrogen gas production method according to an embodiment of the present invention in a unit process.

First, the organic waste stored in the organic waste storage tank 2 is injected into the bio-hydrogen gas production reactor 1 using the influent line 21 and the metering pump 16. At this time, the methane-producing microbial activity inhibitor stored in the methane-producing microbial activity inhibitor storage tank (3) to the bio-hydrogen gas production reactor (1) by using the methane-producing microbial activity inhibitor inlet line 22 and the metering pump (17). Inject. The pH of the reactor is kept low at pH 4.5 to 5.5. When the pH measured by the pH measuring probe (7) is higher than 5.5, it is stored in the pH adjusting acid chemical reservoir (5) through the reactor pH controller (4). Chemicals are injected via a pH-controlled acid chemical inlet line 23 and a metering pump 18 and, if the pH measured by the pH measuring probe 7 is lower than 4.5, pH adjustment via the reactor pH controller 4. The chemicals stored in the alkaline chemical reservoir 6 are injected via the pH adjusting alkaline chemical inlet line 24 and the metering pump 19 to maintain a constant pH in the range of 4.5 to 5.5.

The pH adjusting acid chemical may be HCl, H ₂ SO ₄ , HNO ₃ , H ₃ PO ₄ or H ₂ CO ₃ , the pH adjusting alkali chemicals are NaOH, KOH, Ca (OH) ₂ , CaCO ₃ , MgCO ₃ , Na ₂ CO ₃ or NaHCO ₃ can be used.

The anaerobic fermentation reaction takes place in the biohydrogen gas production reactor 1 where the temperature is kept constant by the reactor temperature controller 8 and mixed by the stirrer 9, and the external gas stored in the gas tank 12 is stored. After the injection amount is adjusted by the gas flow controller 13, the gas is purged into the organic waste (liquid) in the reactor via the gas inflow line 27 and the gas diffusion device 15. The effluent flows out of the reactor via the effluent line 28 and the metering pump 20, and the produced gas is discharged through the gas discharge line 25 and introduced into the hydrogen gas separator 10. The separated hydrogen gas amount is measured by the hydrogen gas amount measuring device 11, and gases other than hydrogen gas are returned to the biohydrogen gas production reactor 1 via the gas flow line 14 via the gas flow controller 14. It is purged with organic waste (liquid) in the reactor via the gas diffusion device 15.

According to one embodiment of the present invention, the organic waste injected in the step (1) is any sludge, wastewater treatment plant generated sludge, digester supernatant and desorption liquid, livestock wastewater and waste, agriculture and forestry wastewater and waste, fishery wastewater and waste, etc. Organic wastewater and waste types can be used.

Microorganisms used to produce hydrogen may also use anaerobic digested sludge from anaerobic digesters in sewage treatment plants rather than pure cultures. Screening can be passed prior to injection.

According to one embodiment of the present invention, the inhibitor injected in the step (3) is 2-bromoethanesulfonic acid (2) which is a similar compound of coenzyme-M that controls the step of producing methane in methane producing microorganisms (2 -bromoethanesulfonic acid (BESA) may be injected. When injecting BESA as an inhibitor, the applicable concentration range is 0.2 to 30 g / L. If the concentration of BESA is less than 0.2g / L there is no inhibitory effect, when the concentration of more than 30 g / L there is no increase in effect due to the increase in the injection amount. Molybdate, azide, aminobenzoic acid or anthraquinone, which are known as other methane-producing microbial inhibitors, are also applicable. However, this is only an example presented to aid the understanding of the present invention, but is not limited thereto.

According to one embodiment of the present invention, since the gas injected in the step (4) can induce the inhibition of the activity of the hydrogen-producing microorganisms when oxygen is included, it is possible to inject a gas containing oxygen 5% or less by volume It is preferable to inject a gas containing no oxygen. Applicable gases include inert gases (helium, nitrogen, argon, carbon dioxide, methane, etc.), and the injection flow rate can be applied from 100 to 10,000 mL / min, but the gas injection flow rate is increased to significantly lower the hydrogen partial pressure and increase the yield of hydrogen production. The more, the more effective. In process (4), gas injection is carried out through a gas diffusion device, which may be a porous acidite, membrane, tubing or diffuser.

According to one embodiment of the present invention, a separation membrane for selectively separating only hydrogen gas may be used as a step for effectively separating and recovering the bio-hydrogen gas generated in the reaction tank in the step (5). However, this is only to be provided to aid the understanding of the present invention, but is not limited thereto. Carbon dioxide, methane, etc. present after hydrogen separation among the gases generated in the reactor can be returned and used as a purging gas.

Hereinafter, the content of the present invention will be described in more detail by the test examples. However, these test examples are only presented to aid the understanding of the present invention, and the scope of the present invention is not limited to these test examples.

Test Example 1: Inhibition of methane-producing microbial activity and pH-enhancing activity of hydrogen-producing microorganisms by pH control and gas purging

Digested sludge from the anaerobic digester of Jungnang Sewage Treatment Plant in Seoul was planted and injected into the reactor. The reaction temperature was 35 ° C., the stirring speed was 160 rpm, and the volume of the reactor was 500 mL. Digested sludge was the only carbon source injected, with a concentration of 2,000 mgCOD / L.

In order to increase the yield of hydrogen production by intermittent gas purging, the organic waste (liquid) in the reaction gas was gas purged under various pH conditions to increase the activity of hydrogen-producing microorganisms. The gas injected for gas purging was argon and gas purging was performed once a day for 15 minutes at a flow rate of 2 L / min. The total driving period was 20 days.

The pH of the organic waste in the reactor was adjusted to pH 5, 7, 9 using 1 N concentrations of HCl and NaOH to compare the degradation of methane-producing microorganisms and the increase of hydrogen-producing microorganisms at different pH conditions. The amount of gas generated was measured using a water displacement apparatus, and each biogas content was measured using gas chromatography (GC-TCD).

Table 1 shows the biogas production yield after gas purging the organic waste (liquid) in the reaction vessel under various pH conditions. The biogas production yield is expressed as the production yield by calculating the "COD of biogas generated" as "% of COD of removed waste sludge".

pH Methane gas production yield (%) Hydrogen gas production yield (%) 5 64.44 0.17 7 70.76 0.05 9 53.63 0.06

When the pH was kept low to 5, the yield of hydrogen gas production was relatively high compared to the conditions of pH 7 and 9. Therefore, it was confirmed that the activity of hydrogen-producing microorganisms was increased at low pH. However, the yield of hydrogen gas from organic waste is very low, at 0.17%, suggesting that there is a limit to increasing the yield of bio-hydrogen by pH control and gas purging alone.

<Test Example 2: Inhibition of methane-producing microbial activity and hydrogenation-producing effect by low concentration of methane-producing microbial activity inhibitor and gas purging

Digested sludge was planted under the same conditions as in Test Example 1 and injected into the reactor. Argon gas purging of the organic waste (liquid) in the reactor to induce increased activity of hydrogen-producing microorganisms. Gas purging was performed once a day for 15 minutes at a flow rate of 2 L / min.

At the same time, 10 g / L of BESA (2-bromoethanesulfonic acid) was injected as an inhibitor of methane-producing microorganisms to induce deactivation of methane-producing microorganisms following the injection of the inhibitor.

Table 2 shows the biogas production yield after gas purging the organic waste (liquid) in the reactor under various pH conditions and injecting the methane generating microbial activity inhibitor. As in Test Example 1, the biogas production yield was expressed by calculating the "COD of generated biogas" in% compared to "COD of removed waste sludge". The pH of the organic waste in the reactor was adjusted to pH 5, 7, 9 using 1 N concentrations of HCl and NaOH to compare the degradation of methane-producing microorganisms and the increase of hydrogen-producing microorganisms at different pH conditions.

pH Methane gas production yield (%) Hydrogen gas production yield (%) 5 2.14 17.69 7 5.03 6.44 9 3.61 5.70

When the methane activity inhibitor is injected and gas purged to discharge the hydrogen gas generated in the reactor to lower the partial pressure of hydrogen and keep the pH low at 5, it is most effective to suppress the activity of the methane-producing microorganisms and to increase the activity of the hydrogen-producing microorganisms. It was confirmed to make. In particular, very high biohydrogen gas production yield (17.69%) and very low biomethane gas production yield (2.14%) were obtained.

In addition, the yield of hydrogen gas production at pH 7, 9 conditions (similar to 6.44 and 5.70%, respectively), similar to the pH (pH 7.0 to 8.5) of typical organic wastes, was significantly higher than the yield of hydrogen gas production at pH 5 conditions of low pH. Low was confirmed.

Therefore, in order to increase the yield of bio-hydrogen gas production from organic waste, a method of injecting a methane generating microbial activity inhibitor and purging the organic waste (liquid) in the reactor to keep the partial pressure of hydrogen low and at the same time keep the pH of the organic waste low It was confirmed to be effective.

1 is a schematic diagram of an apparatus for producing biohydrogen gas from organic waste according to one embodiment of the present invention.

<Description of main parts of drawing>

1: Bio-hydrogen gas production reactor

2: organic waste storage tank

3: methane generating microbial activity inhibitor reservoir

4: reactor pH controller

5: pH-controlled acid chemical reservoir

6: pH-controlled alkaline chemical reservoir

7: pH measuring probe

8: reactor temperature controller

9: stirrer

10: hydrogen gas separation device

11: hydrogen gas amount measuring device

12: gas tank

13,14: gas flow regulator

15: gas diffusion device

16,17,18,19,20: Metering pump

21: influent line

22: methane-producing microbial activity inhibitor inlet line

23: pH-controlled acid chemical inlet line

24: pH Regulating Alkaline Chemical Inlet Line

25: gas discharge line

26: gas return line

27: gas inlet line

28: runoff line

Claims (17)

Biohydrogen gas production reactor 1; An organic waste storage tank 2 connected to the bio-hydrogen gas production reactor; A methane generating microbial activity inhibitor reservoir (3) connected to the bio-hydrogen gas production reactor; A pH controlled acid chemical reservoir (5) connected to the biohydrogen gas production reactor; A pH controlled alkali chemicals reservoir (6) connected with said biohydrogen gas production reactor; A gas tank 12 connected to a lower portion of the bio-hydrogen gas production reactor; And Bio-hydrogen production apparatus comprising a hydrogen gas separation device (10) connected to the top of the bio-hydrogen gas production reactor. The method of claim 1, wherein the device, And a gas conveying line (26) connecting the hydrogen gas separation device and the lower part of the bio-hydrogen gas production reactor. The method of claim 1, wherein the device, A pH measuring probe (7) connected to the biohydrogen gas production reactor, and a pH measuring probe (4) connected to the pH measuring probe, a pH adjusting acid chemical reservoir (5) and a pH adjusting alkaline chemical reservoir (6). Bio-hydrogen production apparatus comprising. The method of claim 1, wherein the device, And a gas diffusion device (15) at a portion of the gas tank (12) connected to a lower portion of the biohydrogen gas production reactor. The method of claim 2, wherein the device, Bio-hydrogen production further includes a gas diffusion device 15 in a portion where the gas tank 12 is connected to the lower portion of the bio-hydrogen gas production reactor and a portion in which the gas return line 26 is connected to the lower portion of the bio-hydrogen gas production reactor. Device. 6. The biohydrogen production apparatus according to claim 4 or 5, wherein the gas diffusion device is a porous acid stone, a membrane, a tubing or an acid pipe. The biohydrogen production apparatus of claim 1, wherein the hydrogen gas separation device comprises a gas separation membrane capable of separating hydrogen gas. As a method of producing biohydrogen gas from organic waste, Injecting organic waste into the reactor; Injecting a pH controlled acid chemical or a pH controlled alkali chemical to adjust the pH of the reactor; Injecting a methane producing microbial activity inhibitor into the reactor; Injecting gas into the organic waste in the reactor to lower the partial pressure of hydrogen in the reactor; And Biohydrogen gas production method comprising the step of separating and recovering hydrogen gas in the produced gas. The method of claim 8, wherein the organic waste is sewage and wastewater treatment plant-generated sludge, digester supernatant and leachate, livestock wastewater and waste, agriculture and forestry wastewater and waste, or fishery wastewater and waste. The method of claim 8, wherein the methane-producing microbial activity inhibitor is 2-bromoethanesulfonic acid (BESA), molybdate, azide, aminobenzoic acid or anthraquinone (anthraquinone) biohydrogen gas production method. The method of claim 10, wherein the injection of 2-bromoethanesulfonic acid (BESA) at a concentration of 0.2 to 30 g / L is carried out. The method of claim 8, wherein the pH of the reactor is maintained at 4.5 to 5.5. The method of claim 12, wherein the pH adjusting acid chemical is HCl, H ₂ SO ₄ , HNO ₃ , H ₃ PO ₄ or H ₂ CO ₃ , The pH adjusting alkali chemicals are NaOH, KOH, Ca (OH) ₂ Method for producing biohydrogen gas, which is CaCO ₃ , MgCO ₃ , Na ₂ CO ₃ or NaHCO ₃ . The method of claim 8, wherein the gas injected to lower the partial pressure of hydrogen is an inert gas containing 5% or less of oxygen by volume. The method of claim 14, wherein the inert gas is helium, nitrogen, argon, carbon dioxide, or methane. The method of claim 8, wherein the gas injected to lower the partial pressure of hydrogen is injected at a flow rate of 100 to 10,000 mL / min. The biohydrogen gas production method of claim 8, wherein the remaining gas from the gas generated in the reactor is separated, and the remaining gas is returned to the organic waste in the reactor to lower the partial pressure of hydrogen in the reactor.

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