JP2011212606A - Biogas treatment method and biogas treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biogas treatment method and apparatus that have low cost and superior treatment efficiency.SOLUTION: In a biogas treatment method, a gas to be treated and a circulation liquid containing oxidative decomposition component to be treated are introduced into a gas-liquid contact column 1, which is equipped with a gas-liquid contact part having an electrically conductive microorganism carrier carrying microorganism, and are brought into gas-liquid contact in the gas-liquid contact part, wherein the oxidative decomposition component to be treated is subjected to oxidative decomposition by the microorganism. In the method, the oxidative decomposition of the oxidative decomposition component to be treated is performed in a condition, in which a positive electrode voltage is applied to the electrically conductive microorganism carrier composed of high temperature firing carbon wherein a ratio (P1/P2) of 1,580 cmpeak intensity (P1) and 1,360 cmpeak intensity (P2) in Raman spectrum is ≥0.85. The invention also includes a biogas treatment apparatus that performs the method.

Description

  The present invention relates to a biological gas processing method and a biological gas processing apparatus, and more particularly, a biological gas processing method for extracting the potential oxidizing power of microorganisms and oxidatively decomposing oxidatively degradable components and The present invention relates to a biological gas processing apparatus.

  Exhaust gas from biogas production facilities, sludge treatment facilities, garbage treatment facilities, composting facilities, etc. includes hydrogen sulfide, odor components, and global warming gas.

  Conventionally, a method of chemically treating these harmful components and removing them from exhaust gas is known, but many chemicals are required and there is a problem of high cost.

  For this reason, for example, Patent Documents 1, 2, and 3 disclose biological gas treatment techniques that utilize aerobic metabolism of microorganisms to oxidize hydrogen sulfide in exhaust gas to sulfuric acid and remove it from the exhaust gas. Yes.

  A conventional biological gas processing technique will be described with reference to FIG.

  FIG. 9 is a schematic view of a biological gas processing apparatus according to the prior art.

  In FIG. 9, reference numeral 101 denotes a conventional biological gas processing apparatus, and reference numeral 102 denotes a packed bed provided in the biological processing apparatus. The packed bed 102 is filled with a microorganism carrier carrying microorganisms.

  Reference numeral 103 denotes a circulating fluid injection unit that injects the circulating fluid into the packed bed 102, and reference numeral 104 denotes a circulating fluid discharge port that discharges the circulating fluid flowing out from the lower portion of the packed bed 102. The circulating fluid discharge port 104 is connected to a circulating fluid tank 105 that stores the circulating fluid. Reference numeral 106 denotes a pump that sends the circulating fluid in the circulating fluid tank 105 to the circulating fluid injection unit 103. The circulating fluid tank 105 is appropriately replenished with circulating fluid from outside the system.

  Reference numeral 107 denotes a target gas introduction unit provided in the lower part of the biological gas processing apparatus 101, and reference numeral 108 denotes a process for contacting the microbial carrier filled in the packed bed 102 and discharging the processing gas that has passed therethrough. It is a gas outlet.

  The biological gas processing apparatus according to the prior art includes an air supply means for supplying air to the gas to be processed, and oxygen in the air becomes an acceptor of electrons generated by oxidative decomposition by microorganisms. As a result, the biological gas treatment proceeds.

  However, in such a conventional biological gas treatment, it is difficult to perform a sufficient treatment, and removal of hydrogen sulfide is often insufficient, and as a result, the exhaust gas that has undergone the biological treatment, Furthermore, it was necessary to cope with such a high-cost chemical treatment.

Japanese Patent Laid-Open No. 2006-143779 JP 2006-143780 A JP 2006-143781 A

  The present inventor has eagerly studied to improve the efficiency of biological gas treatment by extracting the potential oxidizing power of microorganisms without using a high-cost treatment such as a chemical treatment. Completed.

  Therefore, an object of the present invention is to provide a biological gas processing method and a biological gas processing apparatus that are low in cost and have high processing efficiency.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

(Claim 1)
A gas to be treated containing an oxidatively decomposable component to be treated and a circulating liquid are introduced into a gas-liquid contact tower having a gas-liquid contact portion having a conductive microorganism carrier carrying microorganisms, and the gas-liquid contact portion introduces gas. A biological gas treatment method in which the oxidatively decomposable component to be oxidatively decomposed by the microorganism is brought into liquid contact,
The voltage ratio of the 1580 cm ^-1 peak intensity in the Raman spectrum (P1) and 1360 cm ^-1 peak intensity (P2) (P1 / P2) is that the positive electrode to the conductive microorganism carrier comprising 0.85 or more high temperature baked carbon A biological gas treatment method characterized by performing oxidative decomposition of an oxidatively decomposable component under application.

(Claim 2)
The oxidatively decomposable component is composed of at least one of a sulfur-based reducing and odorous component, a nitrogen-based reducing and odorous component, a volatile organic compound, or a reducing global warming gas component. The biological gas processing method according to claim 1.

(Claim 3)
Having a gas-liquid contact tower provided with a gas-liquid contact portion having a conductive microorganism carrier carrying microorganisms;
The gas-liquid contact tower includes a process gas inlet for introducing a process gas containing an oxidatively decomposable component, a process gas outlet for discharging the oxidatively decomposed process gas, and an upper portion in the gas-liquid contact tower. A circulating fluid spraying section for spraying the circulating fluid downward from the bottom, and a circulating fluid outlet for discharging the sprayed circulating fluid from below,
A circulation tank for storing the circulation liquid discharged from the circulation liquid outlet to the outside of the gas-liquid contact tower, and a circulation pump for transferring the circulation liquid in the circulation tank to the circulation liquid spraying section via a pipe. A biological gas treatment apparatus that makes gas-liquid contact at the gas-liquid contact portion and oxidatively decomposes the oxidatively degradable component by the microorganism,
The voltage ratio of the 1580 cm ^-1 peak intensity in the Raman spectrum (P1) and 1360 cm ^-1 peak intensity (P2) (P1 / P2) is that the positive electrode to the conductive microorganism carrier comprising 0.85 or more high temperature baked carbon A biological gas processing apparatus comprising a potential applying means for applying.

(Claim 4)
The oxidatively decomposable component is composed of at least one of a sulfur-based reducing and odorous component, a nitrogen-based reducing and odorous component, a volatile organic compound, or a reducing global warming gas component. The biological gas processing device according to claim 3.

  According to the present invention, it is possible to provide a biological gas processing method and a biological gas processing apparatus that are low in cost and have high processing efficiency.

Potential-pH diagram of hydrogen sulfide / sulfuric acid system Micro-Raman spectrum on carbon surface Schematic showing the first embodiment of the biological gas processing apparatus according to the present invention. Schematic which shows the 2nd aspect of the biological gas processing apparatus which concerns on this invention. Schematic which shows the 3rd aspect of the biological gas processing apparatus which concerns on this invention. Figure showing the change in hydrogen sulfide concentration over time Figure showing gas flow rate dependence of hydrogen sulfide concentration Figure showing the treatment potential dependence of hydrogen sulfide concentration Schematic diagram of biological gas processing apparatus according to the prior art

  The gas to be treated to which the biological gas treatment method of the present invention is applied contains an oxidatively decomposable component to be decomposed by oxidation. The oxidatively decomposable component is composed of at least one of a sulfur-based reducing and odorous component, a nitrogen-based reducing and odorous component, a volatile organic compound, or a reducing global warming gas component. Is preferred. Preferred examples of the sulfur-based reducing and odorous component include hydrogen sulfide, methyl sulfides, mercaptans such as methyl mercaptan, carbonyl sulfide, and the like. Examples of the nitrogen-based reducing and odorous component include ammonia, Trimethylamine, skatole, indole and the like can be preferably exemplified, and the volatile organic compound can be preferably exemplified by volatile hydrocarbons or fatty acids, and the reducing global warming gas component can be exemplified by nitrous oxide and methane. Etc. can be preferably exemplified.

  Preferred examples of the gas to be treated include exhaust gas discharged from a biogas plant, a water treatment facility, a sludge treatment facility, a waste treatment facility, a composting facility, an organic matter processing facility, and the like.

  Oxidative degradation of oxidatively degradable components by microorganisms usually requires oxygen as an electron acceptor. However, by performing aeration as in the past and only supplying oxygen to the gas-liquid contact portion, the stage where oxygen is dissolved in the circulating liquid, the stage where oxygen in the dissolved liquid diffuses and reaches the microorganisms, Before the supplied oxygen can be used to develop oxidative degradation of microorganisms, such as when oxygen is taken into the metabolic pathways of microorganisms, oxidative degradation becomes inefficient and the process gas A large amount of oxidatively decomposable component remains inside.

  The present inventor diligently studied to improve the efficiency of biological gas treatment by moving away from the conventional oxidative decomposition method that depends only on oxygen and extracting the potential oxidizing power of microorganisms, and supporting microorganisms. As a carrier to be used, a conductive microbial carrier having conductivity was used, and a state in which a “voltage to be a positive electrode” was applied was formed, resulting in an electron acceptor.

  With this configuration, the microorganisms can donate electrons generated by oxidative degradation to both oxygen and the conductive microorganism carrier, so that potential oxidation that could not be expressed when relying only on oxygen was not possible. It becomes possible to express force and improve the efficiency of biological gas processing.

  The above-mentioned “voltage as a positive electrode” is a potential at which a conductive microorganism carrier can preferably accept electrons generated by oxidative degradation, and is −1.5 to +1.5 V (the standard is Ag or a standard hydrogen electrode). / AgCl electrode is also possible), but it is preferably set to a range of about +0.3 to 1.0 V within the above range depending on the bacterial flora and pH.

  Since the potential in the decomposition reaction according to the oxidatively decomposable component can be obtained by general electrochemical theoretical calculation, it is also preferable to set the potential within the above range based on this result.

  For example, the decomposition reaction of the oxidatively decomposable component is performed by setting the potential to the noble side of the boundary line of the oxidatively decomposable component region in the potential-pH diagram of the oxidatively decomposable component / decomposition product system Progresses. In order to suitably obtain the driving force of the decomposition reaction, it is preferable to set the potential to the noble side by 0.1 V or more from the boundary line.

  As a specific example, FIG. 1 shows a potential-pH diagram of a hydrogen sulfide / sulfuric acid system.

  When the component to be oxidatively decomposed is hydrogen sulfide and the decomposition product by oxidative decomposition is sulfuric acid, in FIG. 1, the potential is set to the noble side from the boundary line L of the hydrogen sulfide region (shaded portion). The decomposition reaction proceeds, and the driving force of the decomposition reaction can be suitably obtained by setting the potential to the noble side of 0.1 V or more from the boundary line.

  Furthermore, the present inventor has selected a conductive microbial carrier in order to stably and sufficiently advance the electron transfer between the microorganism and the conductive microbial carrier and significantly improve the efficiency of biological gas treatment. went.

  Conventionally, many studies have been conducted on the electrode electron transfer reaction of microorganisms immobilized on electrodes. However, since the electron transfer occurs only within a limited distance and it is difficult to obtain the affinity between the microorganism and the electrode (specifically, the adsorptive and non-destructive properties of the microorganism), It has been considered difficult to allow the electron transfer reaction to proceed stably and sufficiently.

  As a result, at present, research on a method for immobilizing an enzyme extracted from a living body, not a microorganism, on an electrode has become the mainstream.

  However, the enzyme immobilization method cannot be easily performed, and requires complicated processes such as an enzyme extraction process from a living body and an enzyme coating process on the electrode surface. Furthermore, when the enzyme is peeled off or denatured during use, it is very difficult to regenerate and it will be replaced. For these reasons, it has not been put into practical use except for some uses such as biosensors. In particular, it is extremely difficult to use in a large-scale bioreactor that treats exhaust gas. In addition, it is impossible to reconstruct complex metabolic pathways of microorganisms even when using an electrode in which only a specific enzyme is immobilized, and it is still possible to oxidize and decompose various oxidatively degradable components in exhaust gas. It is extremely difficult.

The present inventor continues research on the electron transfer reaction between a microorganism and a carrier, and high-temperature baking obtained by baking or re-baking an organic substance in a reducing atmosphere, preferably at 1250 ° C. or higher, more preferably at 1400 ° C. or higher. Among carbon, the ratio (P1 / P2) of 1580 cm ⁻¹ peak intensity (P1) to 1360 cm ⁻¹ peak intensity (P2) in the Raman spectrum is 0.85 or more, preferably 1.00 or more, more preferably 1. When 20 or more high-temperature calcined carbons are selected and used as a conductive microbial carrier, the electron transfer between the microorganism and the conductive microbial carrier is stably and sufficiently advanced to significantly increase the efficiency of biological gas treatment. It has been found that it can be improved. This selection is important in the present invention because the organic material is not necessarily provided with the above characteristics if it is fired at high temperature or refired.

  Under a reducing atmosphere means in a gas that does not contain an oxygen element, and preferred examples of the gas that does not contain an oxygen element include nitrogen.

The conductivity of the high-temperature calcined carbon is imparted by the graphitic crystal structure that forms the high-temperature calcined carbon. By measuring the ratio (P1 / P2) of 1580 cm ⁻¹ peak intensity (P1) and 1360 cm ⁻¹ peak intensity (P2) in the Raman spectrum, the structure mainly on the carbon surface (several to several tens of atomic layers) is obtained. The resulting measurement is obtained. In particular, in the present invention in which high-temperature calcined carbon is used as a conductive microorganism carrier, surface conductivity is important in order to efficiently perform electron transfer with the supporting microorganism. If the Raman spectroscopic spectrum is used, the surface conductivity as a conductive microorganism carrier can be suitably evaluated. On the other hand, X-ray diffraction reflecting the crystal structure inside carbon is not suitable for such evaluation.

  A micro Raman spectrum on the carbon surface is shown in FIG.

In this spectrum, a peak (1580 cm ⁻¹ ) indicating the graphite quality and a peak (1360 cm ⁻¹ ) indicating the carbon quality appear.

  If the carbonaceous material is sufficiently graphitized, the peak indicating the graphite quality is high and the peak indicating the carbonaceous material is low. Since conductivity is mainly given by the graphite, it is preferable that the peak indicating the graphite is high and the peak indicating the carbon is low as described above.

As described above, the conductive microbial carrier may be a high-temperature calcined carbon having a ratio (P1 / P2) of 1580 cm ⁻¹ peak intensity (P1) to 1360 cm ⁻¹ peak intensity (P2) in a Raman spectroscopic spectrum of 0.85 or more. For example, excellent conductivity can be obtained, and the application of the above-mentioned “voltage as a positive electrode” can be preferably performed on the entire packed layer of the conductive microorganism carrier. Thus, the efficiency of biological gas treatment can be significantly improved.

  Moreover, since the high temperature baked carbon becomes microporous due to the combustion of organic matter, the high temperature baked carbon has a huge specific surface area, that is, the number of microorganisms that can be supported is greatly increased. The above-described problem in which electron transfer occurs only within a limited range can be sufficiently covered by an increase in the number of supported microorganisms.

The high-temperature calcined carbon of the present invention preferably has a BET specific surface area measured by nitrogen adsorption of 1 m ² / g (nitrogen adsorption amount) or more.

  Furthermore, it is known that carbon is excellent in affinity with microorganisms, but high-temperature calcined carbon is also excellent in affinity between microorganisms and electrodes, and can support microorganisms simply by being immersed in a microorganism-containing solution. It has excellent adsorptivity and non-destructiveness that prevents the destruction of microorganisms even when a potential is applied.

  In the present invention, preferred specific examples of the high-temperature calcined carbon used as the conductive microorganism carrier can include bamboo charcoal or charcoal, granules obtained by refiring activated carbon, and carbon fiber aggregates. As described below, a packed bed Bamboo charcoal or charcoal that can prevent an increase in pressure loss when forming is particularly suitable.

  In the present invention, the bamboo charcoal or charcoal (which may be a crushed piece thereof) forming the conductive microorganism carrier preferably has a shape that does not increase the pressure loss when the packed bed is formed. Specifically, the packing density A method of making sparse is preferable. As a method for reducing the packing density, there are a method for increasing the particle size of bamboo charcoal or charcoal, a method for using bamboo charcoal or charcoal having a shape that inevitably becomes sparse when filled.

  In the method of increasing the particle size of bamboo charcoal or charcoal, it is meaningful to define the minimum particle size because a smaller particle size can be a limiting factor for the desulfurization effect. In the present invention, in the case of crushed bamboo charcoal or charcoal, the particle size (diameter) is preferably 1 cm or more, more preferably 3 cm or more, and further preferably 5 cm or more. The particle diameter means a diameter converted into a circle when the crushed bamboo charcoal or charcoal is not circular.

  In the method of using bamboo charcoal or charcoal having a shape that inevitably becomes sparse when filled, it is possible to use bamboo charcoal or charcoal fired in the form of raw materials. For example, in the case of bamboo charcoal, if cylindrical bamboo charcoal having a length of about 5 cm to 10 cm is used as a filler as it is, the gap is large in the filled state, and the pressure loss does not become a limiting factor for the desulfurization effect. In addition, if the bamboo raw material obtained by cutting the bamboo raw material into a line, plain weaving into a lattice, and then firing it is used to laminate them, the gap is large in the filled state, and the pressure loss is It is not a limiting factor for the desulfurization effect. A method of alternately laminating reticulated bamboo charcoal layers and cylindrical bamboo charcoal layers can also be exemplified as a preferred embodiment.

  FIG. 3 is a schematic view showing a first embodiment of the biological gas processing apparatus according to the present invention.

  In FIG. 3, 1 is a gas-liquid contact tower, and 2 is a packed bed provided in the gas-liquid contact tower. The packed layer 2 is filled with a conductive microorganism carrier carrying microorganisms.

  Reference numeral 3 denotes a potential application electrode provided in contact with the conductive microorganism carrier so that potential can be applied thereto, 4 is a counter electrode, and 5 is a reference electrode.

  Further, 6 is a circulating fluid injection part for injecting the circulating fluid into the packed bed 2, and 7 is a circulating fluid outlet for discharging the circulating fluid flowing out from the lower part of the packed bed 2. The circulating fluid discharge port 7 is connected to a circulating fluid tank 8 that stores the circulating fluid. Reference numeral 9 denotes a circulation pump that sends the circulating fluid in the circulating fluid tank 8 to the circulating fluid injection unit 6. The circulating fluid tank 8 is appropriately replenished with circulating fluid from outside the system. In the present invention, the circulating fluid can be used for the purpose of discharging a product resulting from the decomposition reaction out of the system or for supplying microorganisms to the conductive microorganism carrier. The product by the decomposition reaction is, for example, sulfuric acid or the like if the component to be oxidatively decomposed is a sulfur-based reducing and odorous component. In addition, when a circulating fluid is used for the purpose of supplying microorganisms to the conductive microorganism carrier, a microorganism-containing solution containing microorganisms such as methane fermentation digestive fluid can be used as the circulating fluid.

  Reference numeral 10 denotes a gas introduction section to be treated provided in the lower part of the gas-liquid contact tower 1, and 11 denotes a treatment for contacting the conductive microorganism carrier filled in the packed bed 2 and discharging the processing gas that has passed through the carrier. It is a gas outlet.

  FIG. 4 is a schematic view showing a second embodiment of the biological gas processing apparatus according to the present invention.

  In the second aspect, air is injected into the gas to be treated, whereby oxygen in the injected air functions as an acceptor of electrons generated by the oxidative decomposition reaction in addition to the conductive microorganism carrier. Therefore, it is possible to exhibit higher processing capability.

  FIG. 5 is a schematic view showing a third embodiment of the biological gas processing apparatus according to the present invention.

  In the third aspect, the biological gas processing apparatus according to the present invention is provided in the subsequent stage of the conventional aeration type biological processing apparatus that does not apply potential. The biological gas processing apparatus according to the present invention can be easily combined with a conventional biological processing apparatus, and by using them together, it is possible to exhibit a higher processing capacity.

  In the present invention, the electron transfer between the microorganism and the conductive microorganism carrier is not limited to the direct electron transfer, and may be, for example, via a mediator having redox activity.

  Examples of the present invention will be described below, but the present invention is not limited to such examples.

(Comparative Example 1)
The wood piece was fired at 1000 ° C. in a reducing atmosphere to obtain charcoal having a ratio (P1 / P2) of 1580 cm ⁻¹ peak intensity (P1) to 1360 cm ⁻¹ peak intensity (P2) in a Raman spectroscopic spectrum of 0.80. . The obtained charcoal was crushed into an ellipsoidal granular material having an average major axis of 2 to 5 cm and an average minor axis of 1 to 2 cm, and subjected to the following measurements and tests.

<Measurement of physical properties>
1. Measurement of Raman spectral peak ratio 1580 cm ⁻¹ peak intensity (P1) and 1360 cm ⁻¹ peak intensity (P2) on the surface of a granular material are measured using a microscopic Raman spectroscopic analyzer (U-1000 Raman system manufactured by Jobin-Yvon). The intensity ratio (P1 / P2) was calculated.

2. Measurement of BET specific surface area The BET specific surface area of the granular material was measured by a nitrogen adsorption method.

3. Measurement of surface conductivity At room temperature, the above-mentioned granular material is crushed and filled into a groove of a container having a length of 140 mm, a width and a depth of 10 mm to form a filling electrode, and both end portions in the longitudinal direction of the groove The electrode of the voltmeter was inserted into the filling electrode with an interval of 50 mm in the longitudinal direction, and the surface conductivity of the filling electrode was measured by a DC four-terminal method at an energization value of 10 mA. In the present invention, the surface conductivity is preferably 1 kΩcm or less, more preferably 200 Ωcm or less, and most preferably 100 Ωcm or less.

<Biodesulfurization test>
The above-mentioned granular material is filled in a packed portion having a layer height of about 100 mm and an inner diameter of about 100 mm provided in the biological gas processing apparatus for testing, and a voltage of 28 ° C. and +0.2 (V vs Ag / AgCl) is applied. In the filling section, the following gas to be treated and the following circulating liquid were brought into contact with each other in a countercurrent to conduct a biodesulfurization test. No air was injected into the gas to be treated.

  The treatment gas after the desulfurization treatment was subjected to gas chromatography analysis to determine the hydrogen sulfide concentration.

Gas to be treated: Milking cow manure methane fermentation treatment facility (4t / day) Biogas from the fermenter was used. The composition ratio (volume) is CH ₄ : 53%, CO ₂ : 47%, H ₂ S: 1800 to 2000 ppm. The flow rate of introduced biogas was 150 ml / min. As the circulating liquid, methane fermentation digestive liquid was circulated.

  The results are shown in Table 1.

Example 1
Bamboo pieces were fired at 1250 ° C. in a reducing atmosphere to obtain bamboo charcoal having a ratio (P1 / P2) of 1580 cm ⁻¹ peak intensity (P1) to 1360 cm ⁻¹ peak intensity (P2) in a Raman spectrum. It was. The obtained bamboo charcoal was crushed into an ellipsoidal granular material having an average major axis of 2 to 5 cm and an average minor axis of 1 to 2 cm, and subjected to the same measurements and tests as in Comparative Example 1.

  The results are shown in Table 1.

(Example 2)
The granular material made of charcoal obtained in Comparative Example 1 was refired at 1400 ° C. in a reducing atmosphere, and the ratio of the 1580 cm ⁻¹ peak intensity (P1) to the 1360 cm ⁻¹ peak intensity (P2) in the Raman spectrum (P1 / P2) obtained 1.20 charcoal. The obtained charcoal was subjected to the same measurement and test as in Comparative Example 1.

  The results are shown in Table 1.

(Example 3)
And fired at 1400 ° C. the bamboo strips in a reducing atmosphere, to obtain a charcoal ratio (P1 / P2) of 1.20 of 1580 cm ^-1 peak intensity (P1) and 1360 cm ^-1 peak intensity in the Raman spectrum (P2) It was. The obtained bamboo charcoal was crushed into an ellipsoidal granular material having an average major axis of 2 to 5 cm and an average minor axis of 1 to 2 cm, and subjected to the same measurements and tests as in Comparative Example 1.

  The results are shown in Table 1.

Example 4
The activated carbon coconut husk material was re-fired at 1400 ° C. in a reducing atmosphere, the ratio of the 1580 cm ^-1 peak intensity in the Raman spectrum (P1) and 1360 cm ^-1 peak intensity (P2) (P1 / P2) is 0.90 1.0 refired coconut charcoal was obtained. The average particle size of the obtained refired coconut shell charcoal was about 5 mm. A biodesulfurization test was performed using the same biodesulfurization apparatus as in Comparative Example 1, and the following items were evaluated. During each test, air was not injected into the gas to be treated.

<Evaluation items>
1. Change in hydrogen sulfide concentration over time The change in hydrogen sulfide concentration over time in the gas to be treated and in the treatment gas was measured over 4 days.

  The results are shown in FIG.

2. Dependence of hydrogen sulfide concentration on gas flow rate Varying the flow rate of the gas to be treated (28 ° C) with a hydrogen sulfide concentration of 2200 ppm (average: fluctuation range of 1800-2500 ppm) and supplying it to the filling section, the detected current value and sulfurization in the treatment gas The flow rate dependence of the hydrogen concentration was measured.

  The results are shown in FIG.

3. Treatment potential dependence of hydrogen sulfide concentration Gas to be treated (28 ° C.) having a hydrogen sulfide concentration of 2200 ppm (average: fluctuation range of 1800 to 2500 ppm) is supplied to the filling portion, and the potential applied to the refired coconut charcoal is changed in the filling portion. Thus, the potential dependence of the hydrogen sulfide concentration in the process gas was measured.

  The results are shown in FIG.

<Evaluation>
From FIG. 6, it was confirmed that the biological gas treatment was stable over time in the test period of 4 days.

  Further, from FIG. 7, it can be confirmed that the current value increases, that is, the reaction amount increases as the flow rate of the gas to be processed increases. It can be seen that the hydrogen sulfide concentration decreases particularly in the region where the flow rate is relatively low.

  Furthermore, it can be seen from FIG. 8 that the hydrogen sulfide concentration is sufficiently lowered by applying a potential of +0.1 (V vs Ag / AgCl) or more.

(Example 5)
Using the same apparatus as in Example 4, when 5 ml / min of air was injected into the gas to be processed at a flow rate of 150 ml / min and supplied to the filling section, the hydrogen sulfide concentration in the processing gas was 0 ppm (detection tube It was not detected in).

(Example 6)
Gas after the conventional biological desulfurization treatment as shown in FIG. 22 (hydrogen sulfide concentration of about 2000 to 2200 ppm) was supplied at a flow rate of 150 ml / min without injecting air using the same apparatus as in Example 4. In this case, the hydrogen sulfide concentration in the process gas was 0 ppm (not detected in the detector tube).

(Example 7)
Using an apparatus similar to that in Example 4, a filling unit to which an exhaust gas generated from a sludge storage facility was applied as a process gas and a potential of 25 ° C. and +0.4 (V vs Ag / AgCl) was applied at a flow rate of 100 ml / min. The odor component was oxidatively decomposed. The concentration of odorous components in the gas to be processed and in the processing gas was measured with the detection tube. The composition of the odor component in the gas to be treated and in the treatment gas is shown below.

  Composition of odor components in gas to be treated: hydrogen sulfide 250 ppm, methyl mercaptan 10 ppm, ammonia 470 ppm

  Composition of odor components in process gas: hydrogen sulfide 10ppm, methyl mercaptan 0.2ppm, ammonia 15ppm

(Example 8)
Using the same apparatus as in Example 4, a gas generated from a milking cow manure treatment facility was used as a gas to be treated, and a potential of 25 ° C. and −0.2 (V vs Ag / AgCl) was applied at a flow rate of 100 ml / min. Then, the nitrous oxide was oxidatively decomposed. The nitrous oxide concentration in the gas to be treated and in the treatment gas was measured by GC-ECD analysis. The nitrous oxide concentration in the gas to be processed and in the processing gas is shown below.
Nitrous oxide concentration in gas to be treated: 12,000ppb
Nitrous oxide concentration after treatment: 750 ppb

1: Gas-liquid contact tower 2: Packed layer 3: Potential application electrode 4: Counter electrode 5: Reference electrode 6: Condensate water injection part 7: Condensate water discharge port 8: Circulating liquid tank 9: Pump 10: Gas to be treated introduction part 11 : Process gas outlet

Claims (4)

A gas to be treated containing an oxidatively decomposable component to be treated and a circulating liquid are introduced into a gas-liquid contact tower having a gas-liquid contact portion having a conductive microorganism carrier carrying microorganisms, and the gas-liquid contact portion introduces gas. A biological gas treatment method in which the oxidatively decomposable component to be oxidatively decomposed by the microorganism is brought into liquid contact,
The voltage ratio of the 1580 cm ^-1 peak intensity in the Raman spectrum (P1) and 1360 cm ^-1 peak intensity (P2) (P1 / P2) is that the positive electrode to the conductive microorganism carrier comprising 0.85 or more high temperature baked carbon A biological gas treatment method characterized by performing oxidative decomposition of an oxidatively decomposable component under application.   The oxidatively decomposable component is composed of at least one of a sulfur-based reducing and odorous component, a nitrogen-based reducing and odorous component, a volatile organic compound, or a reducing global warming gas component. The biological gas processing method according to claim 1. Having a gas-liquid contact tower provided with a gas-liquid contact portion having a conductive microorganism carrier carrying microorganisms;
The gas-liquid contact tower includes a process gas inlet for introducing a process gas containing an oxidatively decomposable component, a process gas outlet for discharging the oxidatively decomposed process gas, and an upper portion in the gas-liquid contact tower. A circulating fluid spraying section for spraying the circulating fluid downward from the bottom, and a circulating fluid outlet for discharging the sprayed circulating fluid from below,
A circulation tank for storing the circulation liquid discharged from the circulation liquid outlet to the outside of the gas-liquid contact tower, and a circulation pump for transferring the circulation liquid in the circulation tank to the circulation liquid spraying section via a pipe. A biological gas treatment apparatus that makes gas-liquid contact at the gas-liquid contact portion and oxidatively decomposes the oxidatively degradable component by the microorganism,
The voltage ratio of the 1580 cm ^-1 peak intensity in the Raman spectrum (P1) and 1360 cm ^-1 peak intensity (P2) (P1 / P2) is that the positive electrode to the conductive microorganism carrier comprising 0.85 or more high temperature baked carbon A biological gas processing apparatus comprising a potential applying means for applying.   The oxidatively decomposable component is composed of at least one of a sulfur-based reducing and odorous component, a nitrogen-based reducing and odorous component, a volatile organic compound, or a reducing global warming gas component. The biological gas processing device according to claim 3.

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