JP5756060B2 - Biogas biological desulfurization apparatus and biological desulfurization method - Google Patents

Description

  The present invention relates to a biological desulfurization apparatus and biological desulfurization method for biogas, and more specifically, a technology for efficiently treating hydrogen sulfide contained in biogas generated in the methane fermentation process by converting it to sulfuric acid. About.

  Organic waste or organic wastewater is treated by methane fermentation in the field of water treatment, and biogas mainly composed of methane gas is generated. Although the concentration of biogas varies depending on the method of methane fermentation, it contains 65 to 85% methane, 15 to 35% carbon dioxide, and 1000 to 6000 ppm hydrogen sulfide as main components. Methane in the generated biogas can be used as fuel for the boiler, and steam generated from the boiler can be used effectively in the heating facility. Biogas also serves as fuel for gas engines and can generate electricity.

Hydrogen sulfide contained in biogas is oxidized to sulfurous acid gas (SO ₂ ) during combustion, and the generated sulfurous acid gas becomes sulfuric acid when dissolved in moisture and causes acid rain when released into the atmosphere. In addition, when the combustion gas is cooled in the facility, the condensed moisture turns into sulfuric acid, which causes problems such as corrosion.
Therefore, in order to use biogas, removal of hydrogen sulfide has become an important issue.

  As a method for removing hydrogen sulfide in biogas, there is a dry desulfurization method, in which hydrogen sulfide is removed using a pellet-shaped desulfurization agent mainly composed of iron oxide. In the dry desulfurization method, since hydrogen sulfide chemically reacts with iron oxide, the amount of hydrogen sulfide removed by the desulfurizing agent is approximately proportional to the amount of iron oxide present. When the iron oxide involved in the hydrogen sulfide removal reaction of the desulfurizing agent disappears, the removal performance deteriorates and it is necessary to replace it with a new agent.

Other desulfurization methods include biological desulfurization methods using microorganisms as in the present invention. In the biological desulfurization method, a trace amount of air or oxygen is supplied to a biogas, and hydrogen sulfide is converted by microorganisms into sulfur (S) or sulfuric acid (H ₂ ) in the reaction pathway shown in the following (formula 1) and (formula 2). This is a method of generating and removing SO ₄ ). The microorganisms involved in (Formula 1) and (Formula 2) can adhere to or float on the surface of the filler, and there are many aerobic bacteria that are sulfur-oxidizing bacteria in nature. Since microorganisms are involved, temperature and moisture are essential for the living environment of microorganisms.

H ₂ S + 1 / 2O ₂ → S + H ₂ O (Formula 1)
_{S + 3 / 2O 2 + H} 2 O → H 2 SO 4 ( Equation 2)

(Formula 1) is a reaction in which hydrogen sulfide generates elemental sulfur (S) by sulfur-oxidizing bacteria. This is the main reaction when oxygen is 1/2 mol or less of hydrogen sulfide. When oxygen exceeds 1/2 mol of hydrogen sulfide, the reaction of (Formula 2) is further performed by sulfur-oxidizing bacteria, and sulfuric acid (H ₂ SO ₄ ) is generated. In order to convert all the hydrogen sulfide into sulfuric acid (H ₂ SO ₄ ), 2 mol or more of hydrogen sulfide is theoretically required in the presence of sulfur-oxidizing bacteria.

There exists patent document 1 as an example of biological desulfurization technique.
In this method, when the treatment becomes worse, a part of the removed hydrogen sulfide is precipitated as sulfur and adheres to the filler, and a part is converted to sulfuric acid. A technique is described in which the precipitated sulfur is filled with water in a biological desulfurization tower and peeled off by aeration to recover the treatment performance.
In the case where sulfur is deposited on the carrier, the sulfur-oxidizing bacterium has a disadvantage that the initial hydrogen sulfide removing ability is reduced at an accelerated rate because the biological reaction is inhibited by the formation of sulfur.

  In Patent Document 2, which is another technology, the processing gas in the desulfurization tower is circulated, and the control of the circulation amount is controlled by the pressure value of the pressure adjustment tank installed in the latter stage of the desulfurization tower. When no processed biogas is used in this gas utilization facility, the gas is stored in the pressure adjustment tank, and the gas in the pressure adjustment tank is used as the circulating gas to the desulfurization tower.

  When biogas containing high-concentration hydrogen sulfide flows in this method, biogas is not circulated and the load of hydrogen sulfide is reduced if the biogas processed in the gas utilization facility at the latter stage of the pressure adjustment tank is used. Since it is processed in a high state, there is a drawback that it is impossible to avoid the cause of the sulfur being precipitated and the desulfurization performance being lowered.

The supply of the oxygen-containing gas is adjusted according to the flow rate of the processing gas from the desulfurization tower, and is managed by an oxygen concentration meter installed in the processing gas outflow line at the latter stage of the desulfurization tower.
When the supply amount of the oxygen-containing gas is controlled by this method, oxygen is not consumed when sulfur is deposited, and the oxygen concentration in the processing gas is increased, and the supply amount of the oxygen-containing gas is controlled to be reduced. For this reason, there is a defect that oxygen necessary for conversion to sulfuric acid is insufficient, sulfur deposition is promoted, and processing performance is further deteriorated.

JP 2003-305328 A JP 2006-143780 A

  The problem to be solved by the present invention is that, in view of the above-mentioned problems, the hydrogen sulfide under high load is efficiently treated, and the hydrogen sulfide to be treated is converted into sulfuric acid, thereby eliminating the blockage in the apparatus and cleaning. It is an object of the present invention to provide a biogas biological desulfurization apparatus and a biological desulfurization method that can be processed at low cost by eliminating the above processes.

In order to solve the above problems, the biological desulfurization apparatus and the biological desulfurization method of the present invention have the following technical features.
(1) In a biological desulfurization apparatus for removing hydrogen sulfide biologically by sprinkling a circulating liquid from a biogas generated by methane fermentation of organic waste into a biological desulfurization tower,
A biogas inflow line for introducing biogas from the end of the biological desulfurization tower is provided;
Providing a packed bed made of a filler to which microorganisms adhere in the biological desulfurization tower;
A processing gas outlet line for discharging the processing gas at the other end of the biological desulfurization tower and after the packed bed;
Providing a circulation gas line for circulating a part of the processing gas to an end of the biological desulfurization tower into which the biogas flows;
A hydrogen sulfide concentration meter and a gas flow meter are provided in the biogas inflow line,
Provide a circulating gas amount adjusting mechanism in the circulating gas line,
An arithmetic unit for calculating a hydrogen sulfide load amount from the hydrogen sulfide concentration value of the biogas by the hydrogen sulfide concentration meter and the gas flow value by the gas flow meter is provided,
A circulating gas signal transmission mechanism for operating the circulating gas amount adjusting mechanism so that the hydrogen sulfide concentration of the gas contacting the filler is within a predetermined range based on the calculation result of the hydrogen sulfide load amount of the computing unit. A biological desulfurization apparatus comprising:

(2) providing an oxygen-containing gas inflow line for flowing an oxygen-containing gas into the biogas inflow line and / or the biological desulfurization tower;
A supply adjustment mechanism for the oxygen-containing gas amount is provided in the oxygen-containing gas inflow line,
The biological transmission apparatus according to (1) above, wherein a signal transmission mechanism for an oxygen-containing gas that operates the supply adjustment mechanism for the oxygen-containing gas amount is provided based on the calculation result of the hydrogen sulfide load amount of the computing unit. Desulfurization equipment.

(3) In a biological desulfurization method in which hydrogen sulfide is biologically removed by sprinkling a circulating liquid from a biogas generated by methane fermentation of organic waste into a biological desulfurization tower,
Providing a packed bed made of a filler to which microorganisms adhere in the biological desulfurization tower;
A biogas inflow step of flowing biogas upstream of the packed bed in the biological desulfurization tower;
A process gas outflow step for discharging a process gas downstream of the packed bed in the biological desulfurization tower;
A circulating gas step for circulating a part of the processing gas upstream of the packed bed in the biological desulfurization tower,
The hydrogen sulfide load amount is calculated from the hydrogen sulfide concentration and gas flow rate of the biogas flowing in the biogas inflow step, and the calculation result shows that the hydrogen sulfide concentration of the gas contacting the filler is within a predetermined range. Thus, the biological desulfurization method is characterized in that the amount of circulating gas in the circulating gas step is adjusted.

(4) having an oxygen-containing gas inflow step of flowing an oxygen-containing gas upstream of the packed bed in the biological desulfurization tower;
The biological desulfurization method according to (3), wherein the supply amount of the oxygen-containing gas in the oxygen-containing gas inflow step is adjusted based on the calculation result of the hydrogen sulfide load.

(5) The biological fluid as described in (3) or (4) above, wherein the hydrogen sulfide concentration in the gas is 50 to 1000 ppm upstream of the packed bed in the biological desulfurization tower This is a desulfurization method.

(6) The biological desulfurization method according to (5) above, wherein the hydrogen sulfide concentration in the gas is 150 to 500 ppm.

By treating the biogas using the biological desulfurization apparatus and biological desulfurization method of the present invention, the removed hydrogen sulfide is converted to sulfuric acid to eliminate the problem of clogging due to the precipitation of sulfur, and a highly efficient biological The chemical desulfurization process is maintained.
Further, by calculating the hydrogen sulfide load amount from the hydrogen sulfide concentration and gas flow rate of the biogas, and adjusting the amount of circulating gas and the supply amount of oxygen-containing gas from the hydrogen sulfide load amount, 4.0 kg / (m ³ -It has been confirmed that the sulfuric acid conversion rate can be treated at 100% with respect to the hydrogen sulfide load up to day).

It is the schematic of the biological desulfurization apparatus which concerns on this invention used in verification experiment. It is a graph which shows the relationship between a filler contact gas hydrogen sulfide concentration and a hydrogen sulfide removal rate. It is the schematic which shows an example of the biological desulfurization apparatus of this invention. It is a figure which shows the control flowchart of a circulating gas amount adjustment mechanism. It is a figure which shows the control flowchart of an oxygen containing gas supply adjustment mechanism.

  In the conventional biological desulfurization method, there is no concept for the hydrogen sulfide load amount calculated by the product of the hydrogen sulfide concentration and the gas flow rate, which is a feature of the present invention. For this reason, since a certain amount of oxygen-containing gas is supplied even in a low-load process, the oxygen-containing gas component increases in the biogas, and the methane concentration of the biogas decreases, reducing the value of the fuel. When the hydrogen sulfide concentration is high, there is no operating condition to prevent the precipitation of sulfur, so the hydrogen sulfide in the biogas flowing into the reaction etc. inhibits the oxidation reaction of sulfur oxidizing bacteria with the precipitated sulfur, even if it contains oxygen Even if there is a sufficient amount of gas, the reaction to sulfuric acid cannot be sufficiently performed due to the insufficient amount of oxidized bacteria, and sulfur is deposited. If the support of the biological desulfurization tower is covered with about 30% of sulfur, hydrogen sulfide will be discharged without being processed, resulting in insufficient processing.

  Since the precipitated sulfur is hydrophobic, when it adheres to the filler, it covers the surface of the microorganisms adhering to the filler surface and reduces the activity. Sulfur continues to precipitate toward the depth of the filler, eventually closing the filler in the biological desulfurization tower. Sulfur is difficult to remove from the filler once deposited, and it does not return to the original treatment performance even if the stripping treatment is performed by some means. Therefore, sulfur should be used to maintain the biological desulfurization treatment performance. It is important to devise treatment without depositing.

  The inventors of the present application have examined the conditions for maintaining the treatment performance of biological desulfurization without precipitating sulfur by installing an apparatus in a biogas plant.

Here, the name of the gas to be described later is defined as follows.
・ Biogas: A gas generated by methane fermentation and does not contain oxygen.
-Oxygen-containing gas: A gas containing oxygen.
Diluting gas: A gas that does not contain oxygen, and is a gas that is mixed with biogas to adjust the hydrogen sulfide concentration. In the verification experiment of the present invention, nitrogen gas is used.
Circulating gas: A gas in which a part of the processing gas flows again into the biological desulfurization tower by the circulating gas amount supply control mechanism.
-Filler contact gas: A mixed gas of biogas, dilution gas and oxygen-containing gas, or a mixed gas of biogas, circulating gas and oxygen-containing gas, which flows into the biological desulfurization tower and fills It is the gas that comes into contact with the gas.
・ Processing gas: Gas discharged from a biological desulfurization tower.

The verification experiment according to the present invention was carried out by the following method. The biological desulfurization apparatus used in the verification experiment is shown in FIG.
In order to dilute the biogas hydrogen sulfide concentration with a diluent gas, the desulfurization apparatus of FIG.
The biodesulfurization tower 1 is filled with a filler, and the biogas 0a flowing into the biological desulfurization tower 1 is vented in a downward flow from the top of the biological desulfurization tower 1. Process gas 0c was discharged from the bottom.
Dilution gas 0 g was supplied to the biogas inflow line 2 subsequent to the gas flow meter 4 through the dilution gas inflow line 14.
The oxygen-containing gas 0b was supplied to the biogas inflow line 2 subsequent to the gas flow meter 4 through the oxygen-containing gas inflow line 5.
The circulating liquid was sent from the circulating liquid storage tank 1b below the biological desulfurization tower 1 to the upper part of the biological desulfurization tower 1, and sprinkled on the filler.
The oxygen-containing gas was supplied at 60 L / day so that the conversion of the removed hydrogen sulfide into sulfuric acid and the activity of the microorganisms could be maintained.
The amount of water spraying is sufficient if the filler is in a high-humidity environment. The amount of water sprayed is 200 L / day, which is sufficient for the microorganisms attached to the filler to be active during the treatment.
Similarly, the treatment temperature was set to 35 ° C. so as to be in an environment where microorganisms involved in the reaction could be active.
Each filler contact gas concentration was classified as Run as shown in Table 1, and this verification experiment was performed in parallel by 3 Run using 3 biological desulfurization apparatuses shown in FIG. The evaluation period of the experiment was 30 days.

The hydrogen sulfide concentration in the biogas was measured with a hydrogen sulfide concentration meter 3 installed in the biogas inflow line 2.
For other gases that cannot be measured with a hydrogen sulfide concentration meter, the filler contact gas was collected from a biogas inflow line 2 between the biogas flow meter 4 and the top of the biological desulfurization tower 1 using a suction pump into a Tedra bag. . The processing gas 0c was collected from the processing gas outflow line 7 into a tedra bag using a suction pump.
The concentration of hydrogen sulfide in the gas collected in the Tedra bag was measured using a hydrogen sulfide detector tube (Gastec gas detector tube: 4H). Regarding the value of the hydrogen sulfide concentration meter 3 and the value of the detection tube for hydrogen sulfide, it was confirmed that the same concentration value was shown for the same gas.

The treatment performance was evaluated by calculating the amount of hydrogen sulfide removed per unit filler from the hydrogen sulfide removal rate. With a set hydrogen sulfide load of 2.0 kg / (m ³ · day), the hydrogen sulfide removal rate is 90% or more (1.8 kg / (m ³ · day or more as the amount of hydrogen sulfide removed per unit filler)) The treatment was judged to be good.
The calculation method of the hydrogen sulfide removal rate is shown in the following (Formula 3), and the calculation method of the hydrogen sulfide removal amount per unit filler is shown in the following (Formula 4).
Hydrogen sulfide removal rate [%] = (filler contact gas hydrogen sulfide concentration−treatment gas hydrogen sulfide concentration)) [ppm] / filler contact gas hydrogen sulfide concentration [ppm] × 100 (Equation 3)
Hydrogen sulfide removal amount per unit filler [kg / (m ³ · day)] = set hydrogen sulfide load [kg / (m ³ · day)] × removal rate [%] / 100 (Formula 4)

In order to understand the conversion status of sulfuric acid, the concentration of sulfuric acid in the circulating fluid was also investigated.
The circulating fluid was collected from the circulating fluid reservoir at the bottom of the biological desulfurization tower by a drain cock once a day.
The amount of the circulating fluid collected was set to 100 mL so that the amount of the circulating fluid was not significantly affected and the experimental conditions were affected, and the sulfuric acid concentration was measured by an ion chromatography method.
As for the circulating fluid, the blow water was drained every day, and the same amount of make-up water as the amount of blow water was supplied to keep the circulating fluid amount constant.

The sulfuric acid conversion rate is calculated from the sulfuric acid conversion amount per day and the amount of removed hydrogen sulfide per day. The calculation method of the sulfuric acid conversion amount per day is shown in the following (Formula 5), and the removal sulfurization per day. The amount of hydrogen is shown in the following (formula 6), and the sulfuric acid conversion rate is shown in the following (formula 7).
Sulfuric conversion amount _{[kg-H 2 SO 4 /} day] = ( day of sulfuric acid concentration - sulfuric acid concentration of the previous _{day) [kg-H 2 SO 4} / (L · day)] × circulating fluid quantity [L] (Equation 5)
Removal hydrogen sulfide amount [kg-H ₂ S / day] = hydrogen sulfide removal amount per unit filler [kg / (m ³ · day)] × filling capacity [m ³ ] (Formula 6)
Sulfuric acid conversion rate [%] = (sulfuric acid conversion amount × (32/96) [kg-S / day]) / (removed hydrogen sulfide amount [kg-H ₂ S / day] × (32/34) [kg-S / Kg-H ₂ S]) × 100 (Formula 7)

The amount of oxygen required for biological desulfurization will be described.
Oxygen consumed in the biological desulfurization system includes an oxygen amount necessary for sulfation by microorganisms (O 2 _{O 3} ) and an oxygen amount necessary for respiration of microorganisms (O _R ). Oxygen-containing gas supply amount supplied to the biological desulfurization tower of the present invention _[kg-O 2 / day] _is a _O O + O _R.
The amount of oxygen required for sulfation (O 2 _{O 3} ) is expressed by the following (formula 8).
_{O O [kg-O 2 /} day] = removal of hydrogen sulfide amount _{[kg-H 2 S / day} ] × 32/34 [kg-O 2 / kg / H 2 S] × 2 ( Equation 8)
O 2 _O when oxidizing hydrogen sulfide into sulfuric acid with a hydrogen sulfide load of 2 kg / (m ³ · day) using 1 m ³ of filler is 3.8 [kg-O ₂ / day from (Equation 8). ].

The oxygen required for biological desulfurization is supplied in gaseous form.
When pure oxygen gas is supplied as an oxygen-containing gas at 25 ° C., the amount of pure oxygen gas is expressed by the following (formula 9).
Pure oxygen gas amount ^{_{[m 3 -O 2 / day]}} = O O [kg-O 2 /day]/32×22.4×(273+25)/273/1000 ( Equation 9)

When air (containing 21 v / v% oxygen; 25 ° C.) is used as the oxygen-containing gas, the amount of air containing O 2 _O is expressed by the following (formula 10).
Air amount [m ³ −air / day] = pure oxygen gas amount [m ³ −O ₂ / day] × (100/21) (Formula 10)

Regarding the amount of microorganisms, it was experimentally found that the adhesion amount per 1 m ^{3 of} filler was 1 kg-SS / m ³ and the respiration rate was 5 to 10 mg-O ₂ / (g-SS · hr).
Microorganisms adhering per filler 1 m ³ is 1kg-SS, _{O R} is _{0.12~0.24kg-O} 2 / day.
Thus, O _R, while O _O sufficiently smaller than the, in order not to inhibit microbial activity, 1.5 to 3 oxygen content of volumes of O _O by our experiments It has been found that a gas supply rate is preferred.
When the amount of oxygen to be supplied is less than 1.5 times that of O 2 _O , the sulfation of microorganisms is delayed, and when it becomes 3 or more times that of O 2 _O, a large amount of unreacted oxygen-containing gas is contained in the processing gas. The concentration of methane in the inside decreases and the value of the fuel decreases.

Table 1 shows the gas treatment conditions in the verification experiment.
The hydrogen sulfide concentration in the biogas was 6000 ppm, the biogas flow rate was 1 m ³ / day, and the set hydrogen sulfide load was 2 kg / (m ³ · day).
The supply amount of the oxygen-containing gas was 1.5 times the amount of O 2 _O.

RunK-1-1 treated only biogas and did not use dilution gas. The contact time was 340 seconds.
In RunK-1-2 to RunK-1-11, a dilution gas was supplied in the range of 1 to 59 m ³ / day, and the filler contact gas hydrogen sulfide concentration was adjusted in the range of 100 to 6000 ppm.
In Run K-1-2, when the filler contact gas flow rate is 2 m ³ / day, the contact time is 170 sec. In Run K-1-1, when the filler contact gas flow rate is 60 m ³ / day, the contact time is 170 m. The time was 6 seconds.

Table 2 shows the experimental results regarding the influence of the filler contact gas hydrogen sulfide concentration on the biological desulfurization treatment. The values of the experimental results in the table are the values on the 30th day of evaluation.
In Run K-1-1, on the 30th day from the start of evaluation, the processing gas hydrogen sulfide concentration was detected at 5850 ppm. The hydrogen sulfide removal rate at this time was 3%, and the amount of hydrogen sulfide removed per unit filler was 0.05 kg / (m ³ · day). The sulfuric acid conversion was 30%, and sulfur was precipitated.

In RunK-1-2 to RunK-1-9, the hydrogen sulfide removal rate increased as the filler contact gas flow rate increased.
In Run K-1-6 to Run K-1-9, when the filler contact gas hydrogen sulfide concentration is operated in the range of 150 to 500 ppm, the hydrogen sulfide removal rate is 90% or more, and the amount of hydrogen sulfide removed per unit filler is 1 It was possible to process at 8 kg / (m ³ · day) or more. The sulfuric acid conversion rate was 100%.

In RunK-1-10 to RunK-1-11, when the dilution gas flow rate is increased, the hydrogen sulfide removal rate decreases, the removal rate becomes 75% or less, and the hydrogen sulfide removal amount per unit filler is 1.5 kg. / (M ³ · day) or less. However, the sulfuric acid conversion rate was maintained at 100%.

The relationship between the filler contact gas hydrogen sulfide concentration in Table 2 and the hydrogen sulfide removal rate is shown in FIG.
When the filler contact gas hydrogen sulfide concentration was lower than 120 ppm, the hydrogen sulfide removal rate was 75% or less.
When the filler contact gas hydrogen sulfide concentration was processed in the concentration range of 150 ppm to 500 ppm, the hydrogen sulfide removal rate could be processed at 90% or more.
When the hydrogen sulfide concentration of the filler contact gas was 600 ppm or more, the hydrogen sulfide removal rate decreased as the hydrogen sulfide concentration increased.

As shown in Table 2, in RunK-1-1, the filler contact gas hydrogen sulfide concentration was 6000 ppm, and at this time, the amount of hydrogen sulfide removed per unit filler was 0.05 kg / (m ³ · day). It was.
In RunK-1-7 and RunK-1-8, the hydrogen sulfide concentration of the filler contact gas was 300 ppm and 200 ppm, respectively, and the amount of hydrogen sulfide removed per unit filler was 2.0 kg / (m ³ · day). .

The contact time between the gas and the filler became shorter as the filler contact gas flow rate increased.
In RunK-1-1-1 to RunK-1-8, when the contact time is shortened, the amount of hydrogen sulfide removed per unit filler increases, and in RunK-1-8, the contact time is 11 sec. Hydrogen sulfide removed per unit filler The amount was 2.0 kg / (m ³ · day).
However, in Run K-1-9, the contact time was 8 sec, and the amount of hydrogen sulfide removed per unit filler was 1.8 kg / (m ³ · day).
Furthermore, when the contact time was 6 sec in Run K-1-10, the amount of hydrogen sulfide removed per unit filler decreased to 1.5 kg / (m ³ · day).

Therefore, although the removal amount of hydrogen sulfide per unit filler increases as the contact time becomes shorter, the removal amount of hydrogen sulfide per unit filler decreases as the contact time becomes shorter.
This is because when the contact gas flow rate of the filler is increased and the contact time is shortened, microorganisms attached to the filler cannot sufficiently treat hydrogen sulfide, and untreated hydrogen sulfide flows out of the system.

Hereinafter, an embodiment of the present invention will be described based on the verification experiment result. An example of the biological desulfurization apparatus of the present invention is shown in FIG.
In the present invention, in a biological desulfurization apparatus that biologically removes hydrogen sulfide by sprinkling a circulating liquid into a biological desulfurization tower 1 from biogas generated by methane fermentation of organic waste. A biogas inflow line 2 for injecting biogas from the end of the biological desulfurization tower is provided, and a packed bed 1a made of a filler to which microorganisms adhere is provided in the biological desulfurization tower, and the biological desulfurization A processing gas outflow line 7 for discharging the processing gas is provided at the other end of the tower and after the packed bed, and an end of the processing gas into which the biogas flows in the biological desulfurization tower A circulation gas line 8 for circulation is provided, a hydrogen sulfide concentration meter 3 and a gas flow meter 4 are provided in the biogas inflow line 2, and a circulation gas amount adjusting mechanism 9 is provided in the circulation gas line. Sulfidation in biogas by hydrogen concentration meter An arithmetic unit 11 for calculating the hydrogen sulfide load amount from the elementary concentration value and the gas flow rate value by the gas flow meter is provided, and the circulating gas amount adjusting mechanism is provided according to the calculation result of the hydrogen sulfide load amount of the arithmetic unit. A signal transmission mechanism 12 for circulating gas to be operated is provided.

  The inventors of the present invention conducted a long-term continuous experiment using the biological desulfurization apparatus of the present invention, and were efficient and stable even under conditions where the concentration of hydrogen sulfide in biogas and the flow rate of biogas varied. Then, the method that can be processed was examined.

  An example of a biological desulfurization apparatus that biologically removes hydrogen sulfide from biogas generated by methane fermentation of organic waste is shown in FIG. 3, but the present invention is not limited to this embodiment.

The biogas inflow line 2 for flowing in the biogas 0a is directly connected to the top of the biological desulfurization tower 1, and the biogas inflow line 2 is provided with a hydrogen sulfide concentration meter 3 and a gas flow meter 4. .
The fluidized hydrogen concentration value is input from the hydrogen sulfide concentration signal input line 15 to the calculator, and the gas flow rate value is input from the gas flow signal input line 16 to the calculator.
The oxygen-containing gas inflow line 5 is directly connected to the biogas inflow line 2, and the supply amount of the oxygen-containing gas 0 b was adjusted by the oxygen-containing gas supply adjusting mechanism 6.

The packing material to which microorganisms adhere is made of polyethylene, has a cylindrical shape of φ15 mm × h15 mm, has a specific surface area of 1000 m ² / m ³ , and is packed in the packed bed 1 a of the biological desulfurization tower 1.
The processing gas outflow line 7 is directly connected to the lower part of the biological desulfurization tower 1, and the processing gas 0c is discharged out of the system.

The circulating gas line 8 was branched from the processing gas outflow line 7 and directly connected to the top of the biological desulfurization tower 1 to circulate a part of the processing gas 0c.
The amount of circulating gas was adjusted by the circulating gas amount adjusting mechanism 9.
The circulating fluid 0d from the circulating fluid reservoir 1b was sprinkled from the upper part of the biological desulfurization tower 1. In order to adjust the sulfuric acid concentration in the circulating fluid 0d from the circulating fluid reservoir 1b, a part of the circulating fluid is intermittently discharged as blow water 0e, and makeup water 0f is replenished and the amount of water in the circulating fluid reservoir 1b. Was kept constant.

Here, the biogas inflow line is directly connected to the top of the biological desulfurization tower, but may be directly connected from the side of the biological desulfurization tower. In this case, the processing gas outflow line is directly connected to the side surface of the biological desulfurization tower located between the packed bed and the circulating liquid storage tank.
Further, in FIG. 3, the biogas flows downward, but the biogas inflow line is directly connected to the side surface located between the packed bed of the biological desulfurization tower and the circulating liquid storage tank, and the upward flow The gas may be flowed with. In this case, the process gas outflow line may be directly connected to the side of the biological desulfurization tower between the packed bed and the top of the biological desulfurization tower, or may be directly connected to the top of the biological desulfurization tower.

The oxygen-containing gas supply adjustment mechanism may supply gas using supply means such as a blower, and the supply amount may be adjusted by controlling the number of rotations of the blower with an inverter. You may control by the opening degree of a valve | bulb.
The oxygen-containing gas is a gas containing oxygen, and air, pure oxygen, or a gas whose oxygen concentration is adjusted by an oxygen generator may be used.

The oxygen-containing gas inflow line may be directly connected to the biogas inflow line, may be directly connected to the top of the biological desulfurization tower, or may be directly connected from the side of the biological desulfurization tower.
In FIG. 3, the oxygen-containing gas flows in a downward flow. However, when the biogas flows in an upward flow, the oxygen-containing gas inflow line is connected to the packed bed of the biological desulfurization tower and the circulating liquid storage tank. You may connect directly to the side surface located in between.

The filler to which microorganisms adhere can be any material that can be used under strong acidity of pH 1 or lower. For example, organic materials such as polyethylene, polypropylene, vinyl chloride, and polyurethane are preferable.
The shape of the filler is preferably a cylinder, a reticulated skeleton pipe, a ball or a sea urchin. The specific surface area is preferably in the range of 50 to 1000 m ² / m ³ . The porosity is preferably in the range of 80 to 96%.

  As the gas flow meter, an orifice flow meter, a volumetric flow meter, a vortex flow meter, a flow rate type flow meter, etc. can be used, and the positive displacement flow meter can use a measured dry gas meter or a measured wet type, Further, the actual dry gas meter may be a membrane type or a rotor type.

  For the hydrogen sulfide concentration meter, a measurement method by a potentiostatic electrolytic method, a silver nitrate potentiometric titration method, an ion electrode method, a methylene blue absorptiometry, a gas chromatograph method, or the like may be used. Moreover, you may measure the hydrogen sulfide by a detection tube.

  The method for controlling the oxygen-containing gas supply adjustment mechanism and / or the circulating gas amount supply adjustment mechanism is based on the gas flow rate and / or the hydrogen sulfide concentration value obtained by the above-described method. It may be controlled by a typical signal.

  In FIG. 3, the processing gas outflow line is a mechanism for discharging the gas processed in the downward flow, but when the biogas flows in the upward flow, it is positioned between the top of the biological desulfurization tower and the packed bed. It may be directly connected to the side of the biological desulfurization tower.

The circulating gas line may be branched from the process gas outflow line or directly connected to the end of the biological desulfurization tower. Moreover, you may connect directly to the side surface located between the top part of a packed tower, and a packed bed.
In FIG. 3, the circulation gas line is circulated to the top of the biological desulfurization tower. However, when the inside of the desulfurization tower is treated with an upward flow, the circulation line is disposed between the packed bed and the circulating liquid storage tank. You may comprise so that it may connect directly to the side surface of a chemical desulfurization tower.
The circulating gas amount adjusting mechanism may supply gas using supply means such as a blower. The supply amount may be adjusted by controlling the number of rotations of the blower with an inverter, and installing a valve in the subsequent stage of the blower. You may control by the opening degree of a valve | bulb.

  One end of the sprinkling line is preferably directly connected to the side of the biological desulfurization tower at a position sufficiently lower than the level of the circulating liquid stored in the circulating liquid storage tank, and the other end of the sprinkling line is biological It may be directly connected to the side of the biological desulfurization tower located between the top of the desulfurization tower and the packed bed, or may be directly connected to the top of the biological desulfurization tower. The circulating fluid is connected to the watering line by liquid feeding means such as a pump.

  The computing unit is preferably capable of calculating the hydrogen sulfide load from the hydrogen sulfide concentration in the biogas and the biogas flow rate, and the oxygen-containing gas supply amount is preferably controlled based on the hydrogen sulfide load, and the filler contact gas sulfide It is preferable to adjust the amount of circulating gas so that the hydrogen concentration range is 50 to 1000 ppm, preferably 150 to 500 ppm.

The inventors of the present application calculate the hydrogen sulfide load obtained from the product of the hydrogen sulfide concentration in the biogas and the biogas flow rate, and automatically adjust the supply amount of the oxygen-containing gas based on the value of the hydrogen sulfide load. Thus, an optimum amount was supplied without including an excess oxygen-containing gas supply amount.
Specifically, the hydrogen sulfide concentration and biogas flow rate in the biogas are input to the sequential calculator, the hydrogen sulfide load is calculated sequentially by the calculator, and the calculation formula stored in advance is based on the hydrogen sulfide load. Accordingly, the oxygen-containing gas supply adjusting mechanism was feedforward controlled so that an appropriate amount of oxygen-containing gas could be supplied.

  In addition, the inventors of the present application have studied a method capable of biological desulfurization treatment with an appropriate filler contact gas hydrogen sulfide concentration. Specifically, when the hydrogen sulfide concentration in the biogas is equal to or higher than a set concentration (for example, 500 ppm or more as a concentration), the circulating gas amount adjusting mechanism is operated, and the filler contact gas hydrogen sulfide concentration is set to a predetermined concentration (for example, The circulating gas amount was calculated so as to be 300 ppm), and the circulating gas amount supply adjusting mechanism was feedforward controlled so as to supply a predetermined circulating gas amount.

An example of a control flowchart of the circulating gas amount adjusting mechanism is shown in FIG.
FIG. 4- (a) shows a flowchart of a method for controlling the circulating gas amount adjusting mechanism with the hydrogen sulfide load.
The hydrogen sulfide load is calculated from the hydrogen sulfide concentration in the biogas and the biogas flow rate. Based on the hydrogen sulfide load, the circulating gas amount is calculated and the circulating gas amount adjusting mechanism is operated.
As another control method of the circulating gas amount adjusting mechanism, there is a method of controlling by the hydrogen sulfide concentration, which is shown in FIG.
In this system, the circulating gas amount is calculated based on the hydrogen sulfide concentration in the biogas and the circulating gas amount adjusting mechanism is operated.

Next, an example of a control flowchart of the oxygen-containing gas supply adjusting mechanism is shown in FIG.
The hydrogen sulfide load amount is calculated from the hydrogen sulfide concentration in the biogas and the biogas flow rate, the oxygen-containing gas supply amount is calculated based on the hydrogen sulfide load amount, and the oxygen-containing gas supply adjustment mechanism is operated.

Next, based on the knowledge obtained by other biological desulfurization techniques, the performance when the biological desulfurized gas was circulated to the upper part of the biological desulfurization tower and processed was examined.
In the biological desulfurization apparatus of FIG. 3, the biological desulfurization tower 1 is made of polyethylene, has a specific surface area of 1000 m ² / m ³ , and is filled with a cylindrical filler of φ15 mm × h15 mm to 2 m. did. The gas flowing into the biological desulfurization tower was allowed to flow downward from the top of the biological desulfurization tower 1. Activated sludge was used as the circulating liquid, stored in a circulating liquid storage tank at the lower part of the biological desulfurization tower, sent to the upper part of the biological desulfurization tower by a pump, and sprinkled in parallel with the gas direction.

In this experiment, biogas having a hydrogen sulfide concentration of 6000 ppm was used.
Here, in test section 1, the hydrogen sulfide concentration in the biogas is 6000 ppm, in test section 2, the hydrogen sulfide concentration in the biogas is 3000 ppm, and in test section 3, the hydrogen sulfide concentration in the biogas is 1500 ppm.
The methane concentration in the biogas was 80% and the carbon dioxide concentration was 20%, which was almost constant throughout the implementation period.

Table 3 shows the gas treatment conditions in Test Zone 1. Hydrogen sulfide concentration: 6000 ppm of biogas was supplied at 1 m ³ / day, and the amount of circulating gas was adjusted in the range of 9 to 49 m ³ / day.
Table 4 shows the gas treatment conditions in Test Zone 2. Hydrogen sulfide concentration: 3000 ppm of biogas was supplied at 2 m ³ / day, and the amount of circulating gas was adjusted in the range of 8 to 48 m ³ / day.
Table 5 shows the gas treatment conditions in the test section 3. Hydrogen sulfide concentration: 1500 ppm of biogas was supplied at 4 m ³ / day, and the amount of circulating gas was adjusted in the range of 6 to 46 m ³ / day.

In this experiment, an oxygen-containing gas adjusted to 30 v / v% oxygen and 70 v / v% nitrogen was used, and the oxygen-containing gas supply amount was 60 L / day.
The amount of water spraying is sufficient if the filler is in a high-humidity environment. The amount of water sprayed is 200 L / day, which is sufficient for the microorganisms attached to the filler to be active during the treatment.
Similarly, the treatment temperature was set to 35 ° C. so as to be in an environment where microorganisms involved in the reaction could be active.
Each of the filler contact gas flow rates was classified as Run, and this experiment was performed in parallel using three biological desulfurization apparatuses shown in FIG. The evaluation period of the experiment was 30 days.

The hydrogen sulfide concentration in the biogas was measured with a hydrogen sulfide concentration meter 3 installed in the biogas inflow line 2.
For other gases that cannot be measured with a hydrogen sulfide concentration meter, the filler contact gas is drawn from a biogas flow gas line 2 between the biogas flow meter 4 and the top of the biological biological desulfurization tower 1 using a suction pump. Collected in a Tedra bag. The processing gas 0c was collected from the processing gas outflow line 7 into a tedra bag using a suction pump.
The concentration of hydrogen sulfide in the gas collected in the Tedra bag was measured using a hydrogen sulfide detector tube (Gastec gas detector tube: 4H).

The experimental results will be described.
The experimental results in Test Group 1 are shown in Table 6, the experimental results in Test Group 2 are shown in Table 7, and the experimental results in Test Group 3 are shown in Table 8. The values of the experimental results in the table are the values on the 30th day of evaluation.
Regarding the results of test section 1, Run J-1-1 had a filler contact gas flow rate of 10 m ³ / day and a contact time of 34 sec. The treatment gas hydrogen sulfide concentration during this period averaged 3000 ppm. The hydrogen sulfide removal rate at this time was 50%, the hydrogen sulfide removal amount per unit filler was 1.0 kg / (m ³ · day), and the sulfuric acid conversion rate was 100%.

The contact time when the filler contact gas flow rate was increased to 12 m ³ / day with Run J-1-2 was 28 sec. The treatment gas hydrogen sulfide concentration during this period averaged 450 ppm. The hydrogen sulfide removal rate at this time was 93%, and the amount of hydrogen sulfide removed per unit filler was 1.9 kg / (m ³ · day). The sulfuric acid conversion rate was 100%.

When the amount of circulating gas is increased (Run J-1-3 to Run J-1-7), the hydrogen sulfide removal rate is 90% or more until the filler contact gas flow rate is 40 m ³ / day (Run J-1-7). The amount of hydrogen sulfide removed per filler was 1.8 kg / (m ³ · day) or more. The contact time at this time was 8 to 23 sec. The sulfuric acid conversion rate was 100%.

However, when the filler contact gas flow rate is increased to 50 m ³ / day (Run J-1-8), the contact time becomes 6 sec, the hydrogen sulfide removal rate decreases to 65%, and the amount of hydrogen sulfide removed per unit filler is It decreased to 1.3 kg / (m ³ · day). The sulfuric acid conversion rate at this time was 100%.

RunJ-1-9 was treated with biogas as it was as a conventional method. The treatment gas hydrogen sulfide on the 30th day of evaluation reached 5850 ppm, the hydrogen sulfide removal rate was 3%, and the hydrogen sulfide removal amount per unit filler was 0.05 kg / (m ³ · day). The sulfuric acid conversion rate was 30% and sulfur was precipitated.

In the test section 2 and the test section 3, the processing performance shows the same tendency as the test section 1, and the hydrogen sulfide removal rate is 90% or more when the filler contact gas flow rate is in the range of 12 to 40 m ³ / day, which is compared with the conventional method. Thus, the processing method according to the present invention had good processing performance even at high loads.

The hydrogen sulfide load that can be treated by the circulating gas method was verified. As the experimental apparatus, the same biological desulfurization apparatus as in Example 1 was used. Table 9 shows the gas treatment conditions and the experimental results of the experiment on the hydrogen sulfide load that can be treated by the circulating gas system.
The gas flowing into the biological desulfurization tower flowed downward from the top of the biological desulfurization tower.
The circulating liquid was sent to the upper part of the biological desulfurization tower by a pump and sprinkled in parallel with the gas direction.
Biogas having a hydrogen sulfide concentration of 3000 ppm was used, and the amount of circulating gas was adjusted so that the treatment gas was circulated and the filler contact gas concentration was 300 ppm.
The methane concentration in the biogas was 80% and the carbon dioxide concentration was 20%, which was almost constant throughout the implementation period.
The supply amount of oxygen-containing gas in this experiment was 60 L / day.
The amount of water spraying is sufficient if the filler is in a high-humidity environment. The amount of water sprayed is 200 L / day, which is sufficient for the microorganisms attached to the filler to be active during the treatment.
Similarly, the treatment temperature was set to 35 ° C. so as to be in an environment where microorganisms involved in the reaction could be active.
Each of the filler contact gas flow rates was classified as Run, and this experiment was performed in parallel using three biological desulfurization apparatuses shown in FIG. The evaluation period of the experiment was 30 days. The values of the experimental results in the table are the values on the 30th day of evaluation.

The experimental results will be described.
RunJ-4-1 is biogas flow ^2m 3 / day circulating gas amount with respect to ^18m 3 / day supply, a filler-contacting gas flow was treated with ^{20 m} 3 / day. The contact time was 17 sec, and the hydrogen sulfide load was 2.0 kg / (m ³ · day).
Hydrogen sulfide was not detected from the treated gas, the amount of hydrogen sulfide removed per unit filler was 2.0 kg / (m ³ · day), and the sulfuric acid conversion rate was 100%.

RunJ-4-2 is biogas flow ^3m 3 / day circulating gas volume ^27m 3 / and day supplied to, and the filler-contacting gas flow was treated with ^{30 m} 3 / day. The contact time was 11 sec, and the hydrogen sulfide load was 3.0 kg / (m ³ · day).
Hydrogen sulfide was not detected from the treated gas, the amount of hydrogen sulfide removed per unit filler was 3.0 kg / (m ³ · day), and the sulfuric acid conversion rate was 100%.

In Run J-4-3, a circulating gas amount of 31.5 m ³ / day was supplied to a biogas flow rate of 3.5 m ³ / day, and the filler contact gas flow rate was treated at 35 m ³ / day. The contact time was 10 sec, and the hydrogen sulfide load was 3.5 kg / (m ³ · day).
The processing gas hydrogen sulfide was 150 ppm, the hydrogen sulfide removal rate was 95%, and the amount of hydrogen sulfide removed per unit filler was 3.3 kg / (m ³ · day). The sulfuric acid conversion rate was 100%.

In RunJ-4-4, biogas flow rate of the circulating gas volume and ^36m 3 / day fed to 4.0 m ³ / day, a filler-contacting gas flow was treated with ^{40 m} 3 / day. The contact time was 8 sec, and the hydrogen sulfide load was 4.0 kg / (m ³ · day). The concentration of hydrogen sulfide in the process gas was 300 ppm, the hydrogen sulfide removal rate was 90%, and the amount of hydrogen sulfide removed per unit filler was 3.6 kg / (m ³ · day). The sulfuric acid conversion rate was 100%.

In RunJ-4-5, the circulating gas amount to the biogas flow rate 4.2m ³ / day 37.8m ³ / to day supply, the filler contact the gas flow rate processed by ^42m 3 / day. The contact time was 7 sec, and the hydrogen sulfide load was 4.2 kg / (m ³ · day). The concentration of hydrogen sulfide in the process gas was 2500 ppm, the hydrogen sulfide removal rate was 17%, and the amount of hydrogen sulfide removed per unit filler was 0.7 kg / (m ³ · day). The sulfuric acid conversion rate was also significantly reduced to 20%.

Therefore, by applying the circulating gas method according to the present invention, the biogas flow rate and the circulating gas amount are constantly supplied so that the hydrogen sulfide concentration of the filler contact gas that can be processed at a high load in Example 1 is 300 ppm. As a result, it was found that the sulfuric acid conversion rate could be 100% when the hydrogen sulfide loading was 4.0 kg / (m ³ · day).

The experiment apparatus used the same apparatus as Example 1, and verified about the effect of this invention regarding the control method of oxygen-containing gas supply amount.
The gas flowing into the biological desulfurization tower flowed downward from the top of the biological desulfurization tower.
Activated sludge was used as seed sludge, stored in a circulating liquid storage tank at the bottom of the biological desulfurization tower, sent to the upper part of the biological desulfurization tower by a pump, and sprinkled in parallel with the gas direction.
Air (21 v / v% as oxygen) was used as the oxygen-containing gas.

The hydrogen sulfide concentration in the biogas in this experiment fluctuated daily as follows for each hour.
0:00 to 8:00 (period 1): 1000 ppm
8:00 to 20:00 (period 2): 6000 ppm
20: 00 to 0:00 (period 3): 1000 ppm
The flow rate of biogas was fixed at 1 m ³ / day throughout the experiment.
The methane concentration in biogas was 65% and the carbon dioxide concentration was 35%, which were almost constant throughout the implementation period.

Table 10 shows the experimental conditions and results regarding the method for controlling the oxygen-containing gas supply rate.
The oxygen-containing gas supply amount in the present invention is controlled by the hydrogen sulfide load amount.
The oxygen-containing gas supply amount was set to supply 1.5 times the amount of O 2 _O , and the oxygen-containing gas supply amount was changed in accordance with the fluctuation of the hydrogen sulfide load. That is, in the period 1 and the period 3, when the hydrogen sulfide load was 0.3 kg / (m ³ · day), 10 L / day of the oxygen-containing gas was supplied based on the above (Expression 8) to (Expression 10).
In period 2, when the hydrogen sulfide load was 2.0 kg / (m ³ · day), an oxygen-containing gas of 60 L / day was supplied based on (Expression 8) to (Expression 10).

On the other hand, the oxygen supply system of the control series decided to supply oxygen-containing gas at a certain ratio with respect to the biogas flow rate.
That is, since the oxygen-containing gas supply amount supplied in this experiment was the same as the oxygen-containing gas supply amount supplied in the present invention, a constant supply was made at 35 L / day throughout the experiment.

The amount of circulating gas was controlled so that the filler contact gas hydrogen sulfide concentration was 300 to 500 ppm.
The amount of water spraying is sufficient if the filler is in a high-humidity environment. The amount of water sprayed is 200 L / day, which is sufficient for the microorganisms attached to the filler to be active during the treatment. Similarly, the treatment temperature was set to 35 ° C. so as to be in an environment where microorganisms involved in the reaction could be active. Each of the filler contact gas concentrations was classified as Run, and this experiment was performed in parallel using two biological desulfurization apparatuses shown in FIG. The evaluation period was 30 days. The values of the experimental results in the table are the values on the 30th day of evaluation.

The experimental results will be described.
In periods 1 and 3 of the present invention, when the oxygen-containing gas supply rate was 10 L / day, the hydrogen sulfide removal rate was 100% and the sulfuric acid conversion rate was 100%.
In period 1 and period 3 of the control series, when the oxygen-containing gas supply rate was 35 L / day, the hydrogen sulfide removal rate was 100% and the sulfuric acid conversion rate was 100%.
In period 2 of the present invention, when the oxygen-containing gas supply rate was 60 L / day, the hydrogen sulfide removal rate was 100% and the sulfuric acid conversion rate was 100%.
In period 2 of the control series, when the oxygen-containing gas supply rate was 35 L / day, the hydrogen sulfide concentration in the treated gas was 1000 ppm, the hydrogen sulfide removal rate was 83%, and the sulfuric acid conversion rate was 80%.

In the period 1 and the period 3 in the present invention, if the oxygen-containing gas supply rate is 10 L / day with respect to the biogas flow rate of 1 m ³ / day, the sulfuric acid conversion rate is 100%, and no more oxygen is required. The methane concentration in the biogas during this period was 65%, and the methane concentration in the treated gas was 64.3%.
In period 1 and period 3 in the control series, the oxygen-containing gas supply rate is 35 L / day with respect to the biogas flow rate of 1 m ³ / day, which is 3.5 times that of the present invention, and untreated oxygen is present in the process gas. Included in extra. In this period, the methane concentration in the biogas is 65%, the methane concentration in the treated gas is 62.8%, the value of the biogas as fuel decreases, and there is a risk of misfires such as boilers. .

Controlling the oxygen-containing gas supply amount with the hydrogen sulfide load amount as in the present invention allows an appropriate amount of oxygen-containing gas to be supplied following the load, and the hydrogen sulfide removal performance and sulfuric acid conversion rate are also 100%. And stable processing.
Therefore, it was confirmed that the method of controlling the supply amount of oxygen-containing gas to biogas is superior in that it is processed according to the fluctuation of the hydrogen sulfide load.

Next, the removal performance when the amount of oxygen was increased in the target comparison was examined.
Table 11 shows gas treatment conditions and experimental results of a comparative experiment regarding the method of controlling the oxygen-containing gas supply rate.

The experimental conditions of the present invention are the same as in Example 2.
In the control series, the oxygen-containing gas supply amount was changed from 35 L / day to 60 L / day, and a constant supply was made. The value of the experimental result in the table is the value on the 30th day of the evaluation period.

The experimental results will be described.
In periods 1 and 3 of the present invention, when the oxygen-containing gas supply rate was 10 L / day, the hydrogen sulfide removal rate was 100% and the sulfuric acid conversion rate was 100%. In period 2, when the oxygen-containing gas supply rate was 60 L / day, the hydrogen sulfide removal rate was 100% and the sulfuric acid conversion rate was 100%.
In period 1 and period 3 of the control series, when the oxygen-containing gas supply rate was 60 L / day, the hydrogen sulfide removal rate was 100% and the sulfuric acid conversion rate was 100%. In period 2, when the oxygen-containing gas supply rate was 60 L / day, the treatment could be performed with a hydrogen sulfide removal rate of 100%, and the sulfuric acid conversion rate could also be treated with 100%.

If the oxygen-containing gas supply amount in the period 1 and period 3 of the present invention (10 L / day with respect to the biogas flow rate of 1 m ³ / day), the sulfuric acid conversion rate is 100%, and no more oxygen is required. The methane concentration in the biogas during this period was 65%, and the methane concentration in the treated gas was 64.3%.
In contrast, the supply amount of oxygen-containing gas in the period 1 and period 3 of the control series is 6 times that of the present invention (60 L / day relative to the biogas flow rate of 1 m ³ / day), and the control process gas Some untreated oxygen is contained inside. In this period, the methane concentration in the biogas is 65%, the methane concentration in the treated gas is 61.0%, the value of the biogas as a fuel decreases, and there is a risk of misfire of boilers and the like.

  As described above, according to the present invention, hydrogen sulfide under a high load is efficiently treated, and the hydrogen sulfide to be treated is converted into sulfuric acid, thereby eliminating clogging in the apparatus and eliminating steps such as cleaning. It is possible to provide a biogas biological desulfurization apparatus and a biological desulfurization method that can be processed at low cost.

0a Biogas 0b Oxygen-containing gas 0c Treatment gas 0d Circulating fluid 0e Blow water 0f Make-up water 0g Diluted gas 1 Biological desulfurization tower 1a Packed bed 1b Circulating fluid reservoir 2 Biogas inflow line 3 Hydrogen sulfide concentration meter 4 Gas flow rate Total 5 Oxygen-containing gas inflow line 6 Oxygen-containing gas supply adjusting mechanism 7 Process gas outflow line 8 Circulating gas line 9 Circulating gas amount adjusting mechanism 10 Sprinkling line 11 Calculator 12 Circulating gas signal transmission mechanism 13 Oxygen-containing gas signal transmission mechanism 14 Dilution gas line 15 Hydrogen sulfide concentration signal input line 16 Gas flow signal input line

Claims (6)

In a biological desulfurization apparatus that biologically removes hydrogen sulfide by sprinkling a circulating liquid from biogas generated by methane fermentation of organic waste into a biological desulfurization tower,
A biogas inflow line for introducing biogas from the end of the biological desulfurization tower is provided;
Providing a packed bed made of a filler to which microorganisms adhere in the biological desulfurization tower;
A processing gas outlet line for discharging the processing gas at the other end of the biological desulfurization tower and after the packed bed;
Providing a circulation gas line for circulating a part of the processing gas to an end of the biological desulfurization tower into which the biogas flows;
A hydrogen sulfide concentration meter and a gas flow meter are provided in the biogas inflow line,
Provide a circulating gas amount adjusting mechanism in the circulating gas line,
An arithmetic unit for calculating a hydrogen sulfide load amount from the hydrogen sulfide concentration value of the biogas by the hydrogen sulfide concentration meter and the gas flow value by the gas flow meter is provided,
A circulating gas signal transmission mechanism for operating the circulating gas amount adjusting mechanism so that the hydrogen sulfide concentration of the gas contacting the filler is within a predetermined range based on the calculation result of the hydrogen sulfide load amount of the computing unit. A biological desulfurization apparatus comprising: Providing an oxygen-containing gas inflow line for flowing an oxygen-containing gas into the biogas inflow line and / or the biological desulfurization tower;
A supply adjustment mechanism for the oxygen-containing gas amount is provided in the oxygen-containing gas inflow line,
2. The biological desulfurization according to claim 1, further comprising an oxygen-containing gas signal transmission mechanism for operating the oxygen-containing gas amount supply adjustment mechanism based on a calculation result of the hydrogen sulfide load amount of the computing unit. apparatus. In the biological desulfurization method of removing hydrogen sulfide biologically by sprinkling the circulating liquid into the biological desulfurization tower from the biogas generated by methane fermentation of organic waste,
Providing a packed bed made of a filler to which microorganisms adhere in the biological desulfurization tower;
A biogas inflow step of flowing biogas upstream of the packed bed in the biological desulfurization tower;
A process gas outflow step for discharging a process gas downstream of the packed bed in the biological desulfurization tower;
A circulating gas step for circulating a part of the processing gas upstream of the packed bed in the biological desulfurization tower,
The hydrogen sulfide load amount is calculated from the hydrogen sulfide concentration and gas flow rate of the biogas flowing in the biogas inflow step, and the calculation result shows that the hydrogen sulfide concentration of the gas contacting the filler is within a predetermined range. Thus, the biological desulfurization method characterized by adjusting the amount of circulating gas in the circulating gas step. An oxygen-containing gas inflow step for flowing an oxygen-containing gas upstream of the packed bed in the biological desulfurization tower;
The biological desulfurization method according to claim 3, wherein the supply amount of the oxygen-containing gas in the oxygen-containing gas inflow step is adjusted based on the calculation result of the hydrogen sulfide load.   The biological desulfurization method according to claim 3 or 4, wherein the hydrogen sulfide concentration in the gas is 50 to 1000 ppm upstream of the packed bed in the biological desulfurization tower.   The biological desulfurization method according to claim 5, wherein the hydrogen sulfide concentration in the gas is 150 to 500 ppm.

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