JP5925179B2 - Biological desulfurization apparatus and biological desulfurization method - Google Patents

Description

The present invention relates to a biological desulfurization apparatus and biological desulfurization method for hydrogen sulfide (H ₂ S) -containing gas, and in particular, organic substances such as sewage, livestock manure, human waste, industrial wastewater, sludge, garbage, food residue, etc. The present invention relates to a technology for efficiently treating hydrogen sulfide from a hydrogen sulfide-containing gas generated in the process of methane fermentation.

  Organic waste or organic wastewater is treated by methane fermentation in the water treatment field, and a hydrogen sulfide-containing gas containing methane gas as a main component is generated. Although the concentration of hydrogen sulfide-containing gas varies depending on the method of methane fermentation, it contains 65% to 85% methane, 15% to 35% carbon dioxide, and 400 ppm to 6000 ppm hydrogen sulfide as main components. Methane in the generated hydrogen sulfide-containing gas can be used as fuel for the boiler, and steam generated from the boiler can be used effectively in the heating equipment. In addition, the hydrogen sulfide-containing gas serves as fuel for the gas engine and can generate electricity.

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

  As a method for removing hydrogen sulfide in a hydrogen sulfide-containing gas, there is a dry desulfurization method, in which hydrogen sulfide is removed using a pellet-like 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 small amount of air or oxygen is supplied to a hydrogen sulfide-containing gas, and hydrogen sulfide is converted into sulfur (S) or sulfuric acid by microorganisms in a reaction route represented by the following formulas (1) and (2). In this method, (H ₂ SO ₄ ) is generated and removed. The microorganisms involved in the formulas (1) and (2) can adhere to the surface of the filler or float, 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 (1)
_{S + 3 / 2O 2 + H} 2 O → H 2 SO 4 formula (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.

  Patent Document 1 discloses an example of a biological desulfurization technique. In this method, when the treatment is deteriorated, part of the removed hydrogen sulfide is deposited as sulfur and adheres to the filler, and part is converted to sulfuric acid. Has been. 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. However, when sulfur deposits are present in the filler, there is a drawback that the initial hydrogen sulfide removing ability is reduced at an accelerated rate because the sulfur-oxidizing bacteria are inhibited by the generated sulfur and the biological reaction is inhibited.

JP 2003-305328 A

  The problem to be solved by the present invention is to provide a biological desulfurization apparatus and a biological desulfurization method for a hydrogen sulfide-containing gas capable of efficiently treating hydrogen sulfide under a high load in view of the above-described problems. For the purpose.

  The biological desulfurization apparatus and the biological desulfurization method of the present invention have the following technical features.

(1) In a biological desulfurization apparatus that removes hydrogen sulfide biologically by sprinkling a circulating liquid from a hydrogen sulfide-containing gas into a biological desulfurization tower, a plurality of hydrogen sulfide-containing gas lines are connected via a distributor. An oxygen-containing gas inflow line connected to an inflow gas line and supplying an oxygen-containing gas to the hydrogen sulfide-containing gas line; and a packed bed made of a filler to which microorganisms adhere in the biological desulfurization tower. A plurality of stages are provided, and the inflow gas line is connected to the upstream end of the packed bed in each stage, and the inflow gas line has a hydrogen sulfide-containing gas supply amount adjusting means, and is downstream of the most downstream side of the packed bed. A processing gas outflow line for discharging the processing gas is provided at the end, the hydrogen sulfide-containing gas supplied from the hydrogen sulfide-containing gas line is distributed by the distributor, and the distributed hydrogen sulfide-containing gas is Before through the inflow gas line It supplies to the upstream edge part of the packed bed of each stage .

(2) In the biological desulfurization apparatus according to (1), the hydrogen sulfide-containing gas line has a hydrogen sulfide concentration meter, and the supply amount of the hydrogen sulfide-containing gas is adjusted based on a measurement signal from the hydrogen sulfide concentration meter. A hydrogen sulfide control means for controlling the means is provided.

(3) The biological desulfurization apparatus according to (2), further including a processing gas circulation line for circulating at least a part of the processing gas discharged from the downstream end of the packed bed on the most downstream side, A gas circulation line is connected to an upstream side of the hydrogen sulfide concentration meter of the hydrogen sulfide-containing gas line, the processing gas circulation line has a processing gas circulation amount adjusting means, and the hydrogen sulfide control means has the hydrogen sulfide concentration The processing gas circulation rate adjusting means is controlled based on a measurement signal from the meter.

(4) In the biological desulfurization apparatus according to any one of (1) to (3) above, a part of the hydrogen sulfide-containing gas line, upstream of a connection portion to which the oxygen-containing gas inflow line is connected A hydrogen sulfide-containing gas flow meter is provided on the side, and a hydrogen sulfide concentration meter is provided on the upstream side of the connection part to which the oxygen-containing gas inflow line is connected, which is another part of the hydrogen sulfide-containing gas line. The contained gas inflow line has oxygen-containing gas supply amount adjusting means, and the oxygen-containing gas supply line is controlled based on a load amount calculated by a product of a measurement signal from the hydrogen sulfide-containing gas flow meter and a measurement signal from the hydrogen sulfide concentration meter. A load amount control means for controlling the gas supply amount adjusting means is provided.

(5) A living body that introduces hydrogen sulfide-containing gas generated by methane fermentation of organic waste into a biological desulfurization tower and sprinkles the circulating liquid into the tower to biologically remove hydrogen sulfide. In the biological desulfurization method, the biological desulfurization tower is provided with a plurality of packed layers made of a filler to which microorganisms adhere, and an oxygen supply step for supplying an oxygen-containing gas to the hydrogen sulfide-containing gas, and the oxygen supply step A gas distribution step for distributing the hydrogen sulfide-containing gas that has passed through the gas distribution step, a gas inflow step for flowing the hydrogen sulfide-containing gas distributed in the gas distribution step into the upstream end of the packed bed in each stage, and a most downstream side And a processing gas outflow process for discharging the processing gas from the downstream end of the packed bed, wherein the supply amount of the hydrogen sulfide-containing gas is set to be adjustable in the gas inflow process.

(6) In the biological desulfurization method according to (5), the hydrogen sulfide concentration in the hydrogen sulfide-containing gas before the oxygen supply step is measured, and the supply amount of the hydrogen sulfide-containing gas is based on the measurement result It is characterized by adjusting.

(7) In the biological desulfurization method according to (6), at least a part of the processing gas discharged from the downstream end of the packed bed on the most downstream side is upstream of the place where the hydrogen sulfide concentration is measured. And a processing gas circulation step to be circulated to the side, and based on the measurement result of the hydrogen sulfide concentration, a circulation amount of the processing gas in the processing gas circulation step is adjusted.

(8) In the biological desulfurization method according to any one of (5) to (7) above, the flow rate of the hydrogen sulfide-containing gas before the oxygen supply step, and the hydrogen sulfide-containing gas in the hydrogen sulfide-containing gas before the oxygen supply step The supply amount of the oxygen-containing gas in the oxygen supply step based on the load amount calculated by measuring the hydrogen sulfide concentration and calculating the product of the measurement signal from the hydrogen sulfide-containing gas flow meter and the measurement signal from the hydrogen sulfide concentration meter It is characterized by adjusting.

(9) The biological desulfurization method according to any one of (5) to (8) above, wherein the hydrogen sulfide concentration in the hydrogen sulfide-containing gas that has passed through the oxygen supply step is 400 to 700 ppm. .

(10) In the biological desulfurization method according to any one of (5) to (9), the packed bed includes two stages, an upstream stage and a downstream stage. In the gas inflow process, the inflow to the upstream stage The amount of gas to be used is 50% to 70% of the whole, and the remainder flows into the downstream stage.

(11) In the biological desulfurization method according to any one of (5) to (9), the packed bed is configured of three stages, an upstream stage, a middle stage, and a downstream stage, and in the gas inflow step, The relationship between the amount of gas flowing into each stage is characterized in that “inflow gas amount in upstream stage ≧ inflow gas amount in middle stage ≧ inflow gas amount in downstream stage”.

  By using the biological desulfurization apparatus and the biological desulfurization method of the present invention to distribute and process the hydrogen sulfide-containing gas to the packed bed in a plurality of stages, a highly efficient biological desulfurization process is maintained.

  In particular, by providing a hydrogen sulfide concentration meter and a hydrogen sulfide-containing gas flow meter in the hydrogen sulfide-containing gas line, by distributing the hydrogen sulfide-containing gas for each of the plurality of packed beds and controlling the supply amount of the hydrogen sulfide-containing gas, The treatment load of the uppermost packed bed is reduced, making it difficult for sulfur to precipitate, and the entire packing material is used efficiently, enabling efficient removal of hydrogen sulfide and conversion to sulfuric acid even at high loads. It becomes.

  In addition, a hydrogen sulfide-containing gas flow meter and a hydrogen sulfide concentration meter are provided in the hydrogen sulfide-containing gas line, and in order to obtain a mixed gas hydrogen sulfide concentration suitable for the biological desulfurization method, the processing gas circulation is determined from the value of the hydrogen sulfide meter. The amount of hydrogen sulfide-containing gas supplied to each stage of the packed bed is controlled to effectively remove hydrogen sulfide, especially for hydrogen sulfide-containing gas containing high-concentration hydrogen sulfide. it can.

It is a figure which shows the hydrogen sulfide removal pattern of a conventional system. It is a figure which shows the hydrogen sulfide removal pattern of this invention. It is a figure which shows the outline of the biological desulfurization apparatus of this invention. It is a figure which shows the outline of the biological desulfurization apparatus of this invention, and is a figure which shows the example which processes a hydrogen sulfide containing gas by an upward flow. It is a figure which shows the outline of the biological desulfurization apparatus of this invention, and is a figure which shows the example which connected the process gas circulation line to the hydrogen sulfide containing gas line. 1 is a diagram showing an outline of an experimental apparatus of Example 1. FIG. It is a figure which shows the experimental apparatus outline | summary of Example 2. FIG. It is a figure which shows the experimental apparatus outline | summary of Example 4. FIG. It is a figure which shows the daily change which concerns on Example 5. FIG.

The basic concept of the biological desulfurization apparatus and desulfurization method of the present invention will be described.
First, the inventors conducted an experiment of removing hydrogen sulfide from a synthetic hydrogen sulfide-containing gas having a hydrogen sulfide concentration of 1500 ppm using a conventional desulfurization apparatus. The packed bed of 5 cm diameter and carrier was divided into an upstream stage and a downstream stage. In both the upstream and downstream stages, a biological desulfurization apparatus was used in which each carrier filling height was 100 cm and each carrier filling capacity was 2 L. The outline of this apparatus is shown in “Comparative example of Example 1” on the right side of FIG.

The treatment status at a hydrogen sulfide concentration of 1500 ppm, a hydrogen sulfide-containing gas amount of 1 L / min, a hydrogen sulfide amount of 3 g / day, and a hydrogen sulfide load of 0.7 kg / (m ³ · day) was closely observed.
As a result of the conventional system (comparative example), the filling height passes from 0 cm to 200 cm, and the biological treatment is performed for 2 minutes in the upstream stage, 2 minutes in the downstream stage, and 4 minutes in total. FIG. 1 shows a hydrogen sulfide removal pattern in the case where the entire amount of hydrogen sulfide-containing gas is flowed from the uppermost stream side of the packed bed (load ratio: 100%). When the hydrogen sulfide concentration of the inflowing hydrogen sulfide-containing gas is 1500 ppm, 620 ppm in the upstream stage of the desulfurization unit (filling height 100 cm) and 250 ppm in the processing gas (filling height 200 cm), the hydrogen sulfide cannot be treated. Was.

  In addition, since the biological reaction rate is slow when the hydrogen sulfide concentration is 1500 ppm, in order to further reduce the hydrogen sulfide concentration of the processing gas in the case of the conventional method, the hydrogen sulfide load amount of the hydrogen sulfide-containing gas amount is reduced, It has been found that it is necessary to increase the processing time.

Next, as a result of intensive studies, the inventors have found that it is possible to increase the processing efficiency by distributing and supplying the hydrogen sulfide-containing gas to be supplied to each stage of the packed bed composed of a plurality of stages. For example, the hydrogen sulfide concentration is 1500 ppm, the hydrogen sulfide amount is 3 g / day, the hydrogen sulfide load is 0.7 kg / (m ³ -filled carrier · day), and the hydrogen sulfide-containing gas is distributed to the upstream and downstream stages. And supplied. The outline of this apparatus is shown in “Example 1” on the left side of FIG.

  Specifically, the upstream stage has a hydrogen sulfide-containing gas amount of 0.7 L / min, the hydrogen sulfide amount is 2.1 g / day, the load ratio is 70% of the total load of 3 g / day, and the downstream stage has hydrogen sulfide. FIG. 2 shows a hydrogen sulfide removal pattern when the gas content is 0.3 L / min, the hydrogen sulfide amount is 0.9 g / day, and the load ratio is 30% of the total load. As shown in FIG. 2, by distributing the hydrogen sulfide-containing gas, the hydrogen sulfide concentration of the processing gas becomes 0 ppm, and the processing is completely performed. In the upstream stage, the load was reduced to 70% of the conventional method, and the biological treatment time was extended to 3 minutes, so that it could be reduced to 150 ppm at the outlet (filling height 100 cm). Further, 30% of the total load flows into the downstream stage, so that the residence time of the downstream stage is 2 minutes. Although the hydrogen sulfide concentration just below the inlet (filling height 105 cm) in the downstream stage increased to 550 ppm, it was confirmed that the treatment could be performed up to 0 ppm even with a residence time of 2 minutes.

  The biological desulfurization apparatus and the desulfurization method of the present invention have been made based on such an experiment, and a desulfurization apparatus capable of stably treating a gas containing a high concentration of hydrogen sulfide even under a high load. This is a desulfurization method.

Here, the name of the gas to be described later is defined as follows.
-Hydrogen sulfide-containing gas: A gas containing hydrogen sulfide.
-Oxygen-containing gas: A gas containing oxygen, which is air, pure oxygen, or a gas whose oxygen concentration is adjusted by an oxygen generator.
-Mixed gas: A gas in which hydrogen sulfide-containing gas and processing gas are mixed.
・ Processing gas: Gas discharged from the biological desulfurization tower.

Further, symbols used in the calculation formulas and the like shown in this specification are defined as follows.
・ RH ₂ S: Hydrogen sulfide removal rate [%]
CH ₂ S (in): hydrogen sulfide concentration in hydrogen sulfide-containing gas [ppm]
CH ₂ S (out): Hydrogen sulfide concentration in the process gas [ppm]
V ₂₅ : Volume [m ³ ] occupied by 1 mol of gas at 25 ° C.
・ SH ₂ S: Hydrogen sulfide treatment amount per day [kg / day]
・ Q _in : hydrogen sulfide-containing gas amount [m ³ / day]
・ Q _R : Process gas circulation rate [m ³ / day]
・ V _filler : Filling capacity [m ³ ]
_LR : Hydrogen sulfide load [kg / (m ³ · day)]
・ V _R : Circulating fluid volume [L]
・ TH ₂ S: Hydrogen sulfide removal amount [kg-H ₂ S / day]
· _TS-H 2 S: Sulfur content in the removed hydrogen sulfide [kg-S / day]
・ O 2 _O : Required oxygen amount for sulfation by microorganisms [kg-O ₂ / day]
・ O _R : Oxygen required for respiration of microorganisms [kg-O ₂ / day]
· _OPO 2: pure oxygen demand ^[m 3 _-O 2 / day]
・ OAir: Air volume [m ³ -air / day]

The hydrogen sulfide removal rate RH ₂ S [%] can be expressed by the following formula (3).
RH ₂ S = 100 × (CH ₂ S (in) −CH ₂ S (out)) / CH ₂ S (in)
Formula (3)

The volume V ₂₅ [m ³ ] occupied by 1 mol of gas at 25 ° C. is expressed by Equation (4) using 02.4 ° C. (273 K) and 22.4 L of volume occupied by 1 mol of gas at 1 atmosphere.
V ₂₅ = 22.4 × (298/273) Formula (4)

The daily hydrogen sulfide treatment amount SH ₂ S [kg / day] is expressed by the formula (5) using a hydrogen sulfide molecular weight of 34 g / mol.
SH ₂ S = (Q _in + Q _R ) × CH ₂ S (in) × 10 ⁻⁶ × 34 / V ₂₅ formula (5)
The hydrogen sulfide load L _R [kg / (m ³ · day)] per unit filler is expressed by the equation (6). _LR is simply referred to as a hydrogen sulfide load.
L _R = SH ₂ S / V _filler formula (6)

Hydrogen sulfide removal amount _{TH 2 S [kg-H 2} S / day] is represented by the formula (7) with _{L R} and RH ₂ S and V _filler.
TH ₂ S = L _R × RH ₂ S × V _Filler Formula (7)
The sulfur amount TS-H ₂ S [kg-S / day] contained in the removed hydrogen sulfide is represented by the formula (8) using the molecular weight of sulfur of 32 g / mol and the molecular weight of hydrogen sulfide of 34 g / mol.
TS-H ₂ S = TH ₂ S × 32/34 Formula (8)

  An example of a biological desulfurization apparatus filled with a filler to which microorganisms according to the present invention are attached is shown in FIG. FIG. 3 is an apparatus diagram in which a hydrogen sulfide-containing gas is processed in a downward flow. Implementation is not limited to this embodiment.

  FIG. 4 shows an apparatus diagram in which piping is installed to treat the hydrogen sulfide-containing gas 0a in an upward flow using the present invention. 3 and 4 will be described in common.

The packed bed 1a may be provided in a plurality of stages in the desulfurization tower, and specifically, the packed bed preferably has 2 to 4 stages. The filler for this packed bed will be described.
The filler to which microorganisms adhere is only required to be a material having chemical resistance that can be used under strong acidity of pH 1 or lower. For example, the material is preferably an organic substance such as polyethylene, polypropylene, vinyl chloride, and polyurethane. . Further, the shape of the filler is preferably a cylindrical shape, a reticulated skeleton pipe, a ball shape, or a sea urchin shape. The specific surface area is preferably in the range of 50 m ² / m ^{3 to} 1000 m ² / m ³ . The porosity is preferably in the range of 80% to 96%.

  The distributor 6 only needs to be able to branch the flowing gas into a plurality of flows. Specifically, when branching in two directions, a pipe connector such as cheese is used or there is a three-way valve, and when branching in three directions, there is a four-way valve valve.

  The watering line 11 should just be able to water the circulating liquid 0d to a filler. In order to maintain the wet state of the filler, a watering line 11 may be installed at each upstream end of the plurality of packed beds.

  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 the replenishing water 0f is replenished and the amount of water in the circulating fluid reservoir 1b. Must be constant.

When adjusting the supply amount of the hydrogen sulfide-containing gas 0a, the hydrogen sulfide control means is a signal transmission means for the first calculation result by the hydrogen sulfide concentration signal input means 16, the hydrogen sulfide concentration calculator 12, and the hydrogen sulfide concentration calculator. 15 and controls the hydrogen sulfide-containing gas supply amount adjusting means 7.
Further, when the processing gas circulation amount is adjusted, as shown in FIG. 5, the hydrogen sulfide control means performs the second calculation result by the hydrogen sulfide concentration signal input means 16, the hydrogen sulfide concentration calculator 12, and the hydrogen sulfide concentration calculator. The signal transmission means 21 for controlling the processing gas circulation amount adjusting means 20 is controlled.

  The hydrogen sulfide concentration meter 4 may use a measurement method by a potentiostatic electrolytic method, a silver nitrate potentiometric titration method, an ion electrode method, a gas chromatograph method, or the like.

  The hydrogen sulfide concentration signal input means 16 is a means for physically inputting or electrically inputting the measurement signal or measurement value of the hydrogen sulfide concentration meter 4 to the hydrogen sulfide concentration calculator 12 or the load amount calculator 13. Specifically, there is a manual input physically, and an electric input may be electrically input via a cable or the like, or may be input by wireless transmission using radio waves or the like.

  The hydrogen sulfide concentration calculator 12 incorporates a program, and can control the hydrogen sulfide-containing gas supply amount adjusting means 7 and the processing gas circulation amount adjusting means 20 within a set range.

  Regarding the control of the hydrogen sulfide-containing gas supply amount, the signal transmission means 15 of the first calculation result by the hydrogen sulfide concentration calculator physically transfers the calculation result of the hydrogen sulfide concentration calculator 12 to the hydrogen sulfide-containing gas supply amount adjusting means 7. Or a manual output as a physical means, an output via a cable or the like as an electrical means, or a wireless output using a radio wave or the like.

  The hydrogen sulfide-containing gas supply amount adjusting means 7 is a means for physically adjusting or electrically adjusting the hydrogen sulfide-containing gas supply amount. Specifically, the hydrogen sulfide-containing gas supply amount adjusting means 7 physically includes valves, dampers, etc. In particular, there are blowers and pumps.

A biological desulfurization method using control of the supply amount of hydrogen sulfide-containing gas will be described using the apparatus shown in FIGS.
When the number of stages of the packed bed is two stages, an upstream stage and a downstream stage, Example 1 (hydrogen sulfide concentration range in hydrogen sulfide-containing gas; 200 ppm to 1500 ppm) and Example 3 (sulfurization in hydrogen sulfide-containing gas) From the experimental results of hydrogen concentration (400 ppm to 700 ppm), the hydrogen sulfide-containing gas amount to the upstream stage is 50% to 70% of the total, and the hydrogen sulfide-containing gas amount to the downstream stage is the hydrogen sulfide-containing gas to the upstream stage It was found that the remaining amount, ie 50% to 30% of the total, was the best treatment.
Accordingly, it has been found that it is important that “the inflow gas flow rate to the upstream stage ≧ the inflow gas flow rate to the downstream stage”.

  Example 4 (concentration of hydrogen sulfide in a hydrogen sulfide-containing gas; 400 ppm to 700 ppm) in the case where the number of stages of the packed bed is three stages of an upstream stage, a middle stream stage, and a downstream stage using the apparatus shown in FIGS. Was investigated.

Specifically, when the amount of gas flowing into the upstream stage is 50% of the whole, the amount of gas flowing into the middle stage is 25% to 35% of the whole, and the amount of gas flowing into the downstream stage is 25% of the whole. When the amount of gas flowing into the upstream stage is 40% of the whole, the amount of gas flowing into the middle stage is 30% to 40% of the whole, and the amount of gas flowing into the downstream stage is 30% of the whole. % To 20%. When the amount of gas flowing into the upstream stage is 33% of the total, the amount of gas flowing into the middle stage is 33% of the whole, and the amount of gas flowing into the downstream stage is 33% of the whole. When processing was found to be good.
Accordingly, it has been found that it is important that the relationship between the amounts of gas flowing into the respective stages is “upstream inflow gas amount ≧ middle flow inflow gas amount ≧ downstream flow inflow gas amount”.

  In the present invention having the hydrogen sulfide control means, that is, controlling the hydrogen sulfide-containing gas supply amount adjusting means 7 by the hydrogen sulfide concentration, the hydrogen sulfide load amount increases as the inflow gas flow rate increases. For this reason, the concept of distribution can be applied to the load calculated by the product of the measurement signal from the hydrogen sulfide-containing gas flow meter and the measurement signal from the hydrogen sulfide concentration meter.

  Regarding the control of the processing gas circulation amount, the signal transmission means 21 of the second calculation result by the hydrogen sulfide concentration calculator physically outputs the calculation result of the hydrogen sulfide concentration calculator 12 to the processing gas circulation amount adjustment means 20. An electrical output means, specifically a manual output physically, and an electrical output via a cable etc., or a radio transmission using radio waves etc. Also good.

  The processing gas circulation amount adjusting means 20 is a means for physically adjusting or electrically adjusting the circulation amount of the processing gas 0c. Specifically, there are a valve, a damper and the like physically. There are blowers and pumps.

A biological desulfurization method using control of the processing gas circulation rate will be described using the apparatus shown in FIG.
When the hydrogen sulfide-containing gas 0a having a hydrogen sulfide concentration exceeding 700 ppm is processed, the processing efficiency is further improved by circulating a part of the processing gas 0c. FIG. 5 shows an apparatus diagram in which piping is installed so as to circulate a part of the processing gas 0c to process the hydrogen sulfide-containing gas 0a.

  When the hydrogen sulfide-containing gas 0a having a hydrogen sulfide concentration exceeding 700 ppm is treated, the biological treatment time is long and the biological reaction rate becomes extremely slow, so that untreated hydrogen sulfide flows out. Furthermore, when the hydrogen sulfide concentration is lower than 400 ppm, the biological treatment time is shortened and hydrogen sulfide cannot be sufficiently treated. Accordingly, the present inventors have found that it is preferable to treat the hydrogen sulfide concentration in the hydrogen sulfide-containing gas 0a in the range of 400 ppm to 700 ppm in consideration of the biological reaction rate and the biological treatment time.

A biological desulfurization method using control of the supply amount of the oxygen-containing gas 0b will be described using the apparatus shown in FIGS.
The load amount control means comprises a hydrogen sulfide concentration signal input means 16, a hydrogen sulfide-containing gas flow rate signal input means 17, a load amount calculator 13, and a signal transmission means 14 of the calculation result by the load amount calculator, and supplies oxygen-containing gas. The amount adjusting means 9 is controlled.

  As the hydrogen sulfide-containing gas flow meter 3, an orifice flow meter, a volumetric flow meter, a vortex flow meter, a flow rate flow meter, or the like can be used, and the positive displacement flow meter uses an actual dry gas meter or an actual wet meter. In addition, the actual dry gas meter may be of a membrane type or a rotor type.

  The hydrogen sulfide-containing gas flow rate signal input means 17 is a means for physically inputting or electrically inputting the measurement signal of the hydrogen sulfide-containing gas flow meter 3 to the load amount calculator 13, specifically physically. Is manually input, and may be input electrically via a cable or by wireless transmission using radio waves or the like.

  The load amount calculator 13 has a built-in program, and can control the oxygen-containing gas supply amount adjusting means 9 within a set range.

  The calculation result signal transmission means 14 by the load amount calculator is a means for physically outputting or electrically outputting the hydrogen sulfide load amount calculation result to the oxygen-containing gas supply amount adjusting means 9 by the load amount calculator 13. Specifically, there is a manual output physically, and an electrical output via a cable or the like, or a radio transmission using radio waves or the like may be performed.

  The oxygen-containing gas supply amount adjusting means 9 is a means for physically outputting or electrically outputting. Specifically, there are a valve, a damper and the like physically, and an electric blower and a pump.

The control of the oxygen supply amount will be described using the apparatus shown in FIGS.
The amount of oxygen consumed in the biological desulfurization system includes the amount of oxygen necessary for sulfation by microorganisms (O 2 _{O 3} ) and the amount of oxygen necessary for respiration of microorganisms (O _R ). The oxygen-containing gas supply amount supplied to the biological desulfurization tower 1 of the present invention is represented by _O 2 O + OR ₂ .

O 2 _O is the amount of oxygen necessary to oxidize the inflowing hydrogen sulfide load (L _R ) to sulfuric acid. From Formula (1), 2 mol of oxygen, that is, the amount of hydrogen sulfide, is equivalent to 1 mol of hydrogen sulfide. On the other hand, oxygen twice as much as the molar ratio is required. The required oxygen amount O _{2 O} [kg-O ₂ / day] for sulfation is represented by the formula (9) using _LR , oxygen molecular weight; 32 g / mol, hydrogen sulfide molecular weight; 34 g / mol.
O _O = 2 × L _R × 32/34 (9)
As an example, temperature and 35 ° C. of hydrogen sulfide-containing gas _L R with a filler of 1 m ^3; when treated with ^{1.0kg / (m 3 · day)} , the amount of hydrogen sulfide entering the 29.4mol- H ₂ S / day, and O _{2 O} required for sulfation of hydrogen sulfide is 1.9 kg-O ₂ / day, that is, 58.8 mol-O ₂ / day based on the formula (9).

O _R is an amount of oxygen required to respiration of microorganisms. Specifically, the adhesion amount per 1 m ^{3 of} filler is 1 kg-SS / m ³ and the respiration rate is 5 mg-O ₂ / (g-SS · hr) to 10 mg-O ₂ / (g-SS · hr). ), That is, 3.8 mmol / (g-SS · day) to 7.5 mmol / (g-SS · day).
Microorganisms adhering per filler 1 m ³ is 1kg-SS, _{O R} is _0.12kg-O 2 / day to _0.24kg-O 2 / day, i.e. _3.8mol-O 2 / day to 7 the _.5mol-O 2 / day.

In order to promote the reaction of the formulas (1) and (2) without inhibiting the activity of microorganisms due to oxygen deficiency, the amount of hydrogen sulfide is 22.6 mol-O ₂ / day with respect to 29.4 mol-H ₂ S / day. Day to 66.3 mol-O ₂ / day, that is, the theoretical oxygen amount (O 2 _O + O _R ) is required to be 2.13 to 2.26 times in terms of molar ratio with respect to 1 mol of hydrogen sulfide. In addition, a theoretical value is a case where oxygen dissolution efficiency is 100%.

  The actual oxygen dissolution efficiency is about 20% to 85% as confirmed by experiments. Considering the actual oxygen dissolution efficiency, when the molar ratio of the theoretical oxygen amount to the hydrogen sulfide amount is 2.13 times, the molar ratio is 2.5 to 10.5 times the hydrogen sulfide amount 1 When an oxygen amount is required and the molar ratio of the theoretical oxygen amount is 2.26 times, an oxygen amount of 2.7 times to 11.3 times as much as the hydrogen sulfide amount is required. That is, the theoretical molar ratio of the oxygen amount to the hydrogen sulfide amount is generally 2.5 times to 11.6 times.

  If an excessive oxygen-containing gas 0b is supplied, a large amount of unreacted oxygen-containing gas 0b is contained in the processing gas 0c, and the concentration of methane gas in the processing gas 0c is lowered, reducing the value of fuel. Accordingly, it is preferable that the oxygen content in the oxygen-containing gas supply amount adjusting means 9 is 2.5 times to 11.6 times, preferably 2.5 times to 7 times as much as the molar ratio of hydrogen sulfide.

  The oxygen-containing gas 0b used in the present invention may be air, pure oxygen, or a gas whose oxygen concentration is adjusted by an oxygen generator.

In the present invention, when pure oxygen is used as the oxygen-containing gas 0b, the required amount of pure oxygen at 25 ° C. (298 K) OPO ₂ [m ³ —O ₂ / day] is an oxygen molecular weight from O 2 _O ; 32 g / mol, gas The volume occupied by 1 mol (0 ° C. (273 K), 1 atm); shown in formula (10) using 22.4 L.
OPO ₂ = O _{2 O} × 22.4 × (298/273) / 32 Formula (10)

In the present invention, when air (oxygen concentration; 21 v / v%, 25 ° C.) is used as the oxygen-containing gas, the required amount of air OAir [m ³ —O ₂ / day] at 25 ° C. is expressed using OPO _2. It is represented by (11).
OAir = OPO ₂ × (100/21) Formula (11)

  In Example 1, the hydrogen sulfide-containing gas is distributed and supplied to the upstream end of the packed bed, and as a comparative example of Example 1, the hydrogen sulfide-containing gas is supplied only to the uppermost stream end of the packed bed. Experiments on the processing performance were conducted in parallel. The hydrogen sulfide-containing gas was classified as Run according to the hydrogen sulfide concentration, and this experiment was performed while comparing Example 1 and the comparative example of Example 1. The evaluation period for each run was 10 days, and the total evaluation period was 90 days.

The experimental apparatus used was the biological desulfurization apparatus shown in FIG. An outline of the experimental apparatus of Example 1 is shown in Table 1. The inner diameter of the experimental device is 5 cm.
The filler was filled so that the filling height per layer was 1 m, and the number of packed bed stages was two stages, upstream and downstream. The total filling height was 2 m, and the total filling capacity was 4.2 L. The filler used was a cylindrical one of φ15 mm × h15 mm.
The circulating liquid was sent from the circulating liquid storage tank at the bottom of the desulfurization tower to the upper part of the desulfurization tower by a pump, and sprinkled in parallel with the gas direction. The amount of sprinkling of the circulating liquid was 200 L / day. The processing temperature was set to 35 ° C.
The hydrogen sulfide-containing gas is a biogas generated in a methane fermentation tank. The hydrogen sulfide-containing gas components were hydrogen sulfide concentration; 100 ppm, methane concentration; 80%, carbon dioxide concentration; 20%, and were constant throughout the experiment.
Air (containing 21 v / v% oxygen; 25 ° C.) was used as the oxygen-containing gas. The air supply amount was adjusted to 43.1 L / day by the oxygen-containing gas supply amount adjusting means so that oxygen at a molar ratio of 2.5 times the hydrogen sulfide amount was supplied.

  Table 2 shows the experimental conditions. In the series of Example 1, the hydrogen sulfide-containing gas was allowed to flow downward from each upstream end of the packed bed via a distributor. In the hydrogen sulfide-containing gas, the hydrogen sulfide-containing gas amount to the upstream stage was 70% of the whole, and the hydrogen sulfide-containing gas amount to the downstream stage was 30% of the whole. The distribution of the hydrogen sulfide-containing gas was performed by controlling the hydrogen sulfide-containing gas supply amount adjusting means via the hydrogen sulfide control means.

In the series of comparative examples of Example 1, the hydrogen sulfide-containing gas was allowed to flow downward from the most upstream end of the packed bed.
Further, the hydrogen sulfide-containing gas used in the comparative example of Example 1 and Example 1 is a gas obtained by mixing biogas generated in a methane fermentation tank and 100% hydrogen sulfide gas. The 100% hydrogen sulfide gas used was stored in a gas cylinder.
The supply amount of 100% hydrogen sulfide gas mixed with the biogas was adjusted so that the hydrogen sulfide concentration in the hydrogen sulfide-containing gas was a constant concentration in the range of 200 ppm to 1500 ppm.

Hydrogen-containing gas flow sulfide was adjusted by opening of the valve so that a certain amount in the range of 2.4 m ³ / day to 18.1 m ³ / day.

  The hydrogen sulfide concentration in the hydrogen sulfide-containing gas was measured with a hydrogen sulfide concentration meter installed in the hydrogen sulfide-containing gas inflow line. For other gases that cannot be measured with a hydrogen sulfide concentration meter, the processing gas was collected from a processing gas outflow line into a tedla bag using a suction pump. The hydrogen sulfide concentration in the gas collected in the Tedra bag was measured using a hydrogen sulfide concentration detector tube (Gastec gas detector tube; 4H).

  The results of Example 1 are shown in Table 3. The values in the table are the values on the 10th day of evaluation. In the evaluation of the treatment performance, the hydrogen sulfide removal rate was calculated by the equation (3), and the treatment was good at 95% or more.

In Run 1-1 and Run 1-2, the hydrogen sulfide concentration in the hydrogen sulfide-containing gas was set to 200 ppm and 300 ppm, respectively.
In Example 1, the hydrogen sulfide concentration in the process gas was 55 ppm for Run 1-1, 25 ppm for Run 1-2, and the hydrogen sulfide removal rates were Run 1-1; 73% and Run 1-2; 92%.
In the comparative example of Example 1, the hydrogen sulfide concentration in the process gas was 60 ppm for Run 1-1, 30 ppm for Run 1-2, and the hydrogen sulfide removal rates were Run 1-1; 70% and Run 1-2; 90%. .

In Run1-3 to Run1-6, the hydrogen sulfide concentration in the hydrogen sulfide-containing gas was set to 400 ppm to 700 ppm.
In Example 1, the hydrogen sulfide concentration in the process gas was in the range of 5 ppm to 35 ppm, and the hydrogen sulfide removal rate was 95% to 99% for Run1-3 to Run1-6.
In the comparative example of Example 1, the hydrogen sulfide concentration in the process gas was in the range of 20 ppm to 140 ppm, and the hydrogen sulfide removal rate was 95% to 96% for Run1-3 and Run1-4. In Run 1-6, it was 92% to 80%.

In Run 1-7 to Run 1-9, the hydrogen sulfide concentration in the hydrogen sulfide-containing gas was set to 800 ppm to 1500 ppm.
In Example 1, the hydrogen sulfide concentration in the process gas was in the range of 160 ppm to 500 ppm, and the hydrogen sulfide removal rate became 80% to 67% with the increase of the hydrogen sulfide concentration.
In the comparative example of Example 1, the hydrogen sulfide concentration in the process gas was in the range of 333 ppm to 1000 ppm, and the hydrogen sulfide removal rate was 58% to 33%.

  In Example 1, the removal rate is always higher than in the comparative example. In particular, the hydrogen sulfide removal rate was 95% or higher when the hydrogen sulfide concentration was 400 ppm to 700 ppm, and the hydrogen sulfide removal rate was 95% or more in the comparative example of Example 1 with the hydrogen sulfide concentrations of 400 ppm and 500 ppm. It was found that processing superior in processing performance can be obtained by processing with the distribution method.

  In Example 2, the process gas is circulated and mixed with the hydrogen sulfide-containing gas and then supplied to each upstream end of the packed bed via a distributor, and the process gas is circulated as a comparative example of Example 2. Comparison between Example 2 and Comparative Example of Example 2 in parallel with two towers of the biological desulfurization apparatus shown in FIG. 7 regarding the processing performance in the case of supplying to the uppermost stream end of the packed bed after mixing with the hydrogen sulfide-containing gas I went there. It was classified as Run according to the circulation amount of the processing gas. In this experiment, the evaluation period for each run was 10 days, and the total evaluation period was 80 days.

An outline of the experimental apparatus of Example 2 is shown in Table 4. The inner diameter of the experimental device is 5 cm.
The filler was filled so that the filling height per layer was 1 m, and the number of packed bed stages was two stages, upstream and downstream. The total filling height was 2 m, and the total filling capacity was 4.2 L. The filler used was a cylindrical one of φ15 mm × h15 mm.
The circulating liquid was sent from the circulating liquid storage tank at the bottom of the desulfurization tower to the upper part of the desulfurization tower by a pump, and sprinkled in parallel with the gas direction. The amount of sprinkling of the circulating liquid was 200 L / day. The processing temperature was set to 35 ° C.
The hydrogen sulfide-containing gas is a biogas generated in the same methane fermentation tank as in Example 1. The hydrogen sulfide-containing gas components were hydrogen sulfide concentration; 100 ppm, methane concentration; 80%, carbon dioxide concentration; 20%, and were constant throughout the experiment.
Air (containing 21 v / v% oxygen; 25 ° C.) was used as the oxygen-containing gas. The air supply amount was adjusted to 43.1 L / day by the oxygen-containing gas supply amount adjusting means so that oxygen at a molar ratio of 2.5 times the hydrogen sulfide amount was supplied.

  Table 5 shows the experimental conditions. In the series of Example 2, the hydrogen sulfide-containing gas was allowed to flow in a downward flow from each upstream end of the packed bed via the distributor after mixing with the processing gas. As for the hydrogen sulfide-containing gas, the amount of hydrogen sulfide-containing gas to the upstream stage was 70% of the whole, and the amount of hydrogen sulfide-containing gas to the downstream stage was 30%. The distribution of the hydrogen sulfide-containing gas was performed by controlling the hydrogen sulfide-containing gas supply amount adjusting means via the hydrogen sulfide control means.

In the series of comparative examples of Example 2, the hydrogen sulfide-containing gas was allowed to flow downward from the uppermost stream end of the packed bed after mixing with the processing gas. In both the comparative example of Example 2 and Example 2, a part of the processing gas was circulated to the upstream portion of the hydrogen sulfide concentration meter and mixed with the hydrogen sulfide-containing gas.
Both series process gas circulation rate was adjusted by opening of the valve so that a certain amount in the range of 1.2 m ³ / day to 9.6 m ³ / day in Run2-2～Run2-8. Run 2-1 did not circulate the processing gas.

The hydrogen sulfide-containing gas is a biogas having the same properties as in Example 1.
The supply amount of 100% hydrogen sulfide gas mixed with biogas was adjusted so that the hydrogen sulfide concentration in the hydrogen sulfide-containing gas was 1500 ppm.
The flow rate of the hydrogen sulfide-containing gas was adjusted by the valve opening so as to be a constant amount of 2.4 m ³ / day.
Circulating gas amount ^was adjusted by the opening degree of the valve so that a certain amount in the range of 1.2m ³ /day~9.6m 3 / day.

  The results of the examples are shown in Table 6. The values in the table are the values on the 10th day of evaluation.

Run 2-1 does not circulate the processing gas, and the results of the examples are the same as the results of Run 1-9 for both the present invention and the comparative example.
For Run 2-2, the processing gas circulation rate was set to 1.2 m ³ / day.
In Example 2, the treatment gas hydrogen sulfide concentration was 300 ppm, and the hydrogen sulfide removal rate was 80%.
In the comparative example of Example 2, the treatment gas hydrogen sulfide concentration was 500 ppm and the hydrogen sulfide removal rate was 67%.

In Run 2-3, the processing gas circulation rate was 2.4 m ³ / day.
In Example 2, the treatment gas hydrogen sulfide concentration was 160 ppm, and the hydrogen sulfide removal rate was 89%.
In the comparative example of Example 2, the treatment gas hydrogen sulfide concentration was 333 ppm and the hydrogen sulfide removal rate was 78%.

In Run 2-4 to Run 2-7, the processing gas circulation rate was in the range of 2.8 m ³ / day to 7.2 m ³ / day.
In Example 2, the treatment gas hydrogen sulfide concentration was 15 ppm to 35 ppm, and the hydrogen sulfide removal rate was 98% to 99%.
In the comparative example of Example 2, the treatment gas hydrogen sulfide concentration was 20 ppm to 140 ppm, and the hydrogen sulfide removal rate was 91% to 99%.

In Run 2-8, the processing gas circulation rate was 9.6 m ³ / day.
In Example 2, the treatment gas hydrogen sulfide concentration was 45 ppm, and the hydrogen sulfide removal rate was 97%.
In the comparative example of Example 2, the treatment gas hydrogen sulfide concentration was 100 ppm, and the hydrogen sulfide removal rate was 93%.

Even in Example 2, the removal rate is always higher than that of the comparative example of Example 2. In particular, when the circulating flow rate was in the range of 2.8 m ³ / day to 9.6 m ³ / day, the hydrogen sulfide removal rate was 95% or more, and the treatment was good, whereas in the comparative example of Example 2, it was 3. It was found that the hydrogen sulfide removal rate was 95% or more in the range of 6 m ³ / day to 6.6 m ³ / day, and that a result superior in processing performance could be obtained by processing by the distribution method.

As shown in Example 1, since the hydrogen sulfide removal effect of the distribution method is high, in Example 3, the treatment performance when the hydrogen sulfide-containing gas distribution ratio was changed was examined. Specifically, the processing performance when the hydrogen sulfide-containing gas distribution ratio was changed when the hydrogen sulfide concentration was constant within the range of 400 ppm to 700 ppm was investigated.
Each hydrogen sulfide concentration in the hydrogen sulfide-containing gas was classified as Run. The evaluation period at a constant concentration was 10 days, and the total evaluation period was 40 days.

As the experimental apparatus, the biological desulfurization apparatus of Example 1 shown in FIG. 6 was used, and five identical towers were operated in parallel. The experimental apparatus is No. 1. 1 to No. The removal performance was compared by setting the gas amount ratio to different conditions.
An outline of the experimental apparatus of Example 3 is shown in Table 7. The outline of the experimental apparatus is the same as in Example 1.
The air supply amount was adjusted to 46.7 L / day by the oxygen-containing gas supply amount adjusting means so that oxygen at a molar ratio of 2.5 times the hydrogen sulfide amount was supplied.

Table 8 shows the experimental conditions. Both the gas processing direction and the processing system are the same as those in the first embodiment.
The ratio range of the gas amount was in the range of 80% to 40% in the upstream stage and in the range of 20% to 60% in the downstream stage. The distribution of the hydrogen sulfide-containing gas was performed by controlling the hydrogen sulfide-containing gas supply amount adjusting means via the hydrogen sulfide control means. The ratio of the gas amount of each experimental apparatus is No. In No. 1, the upstream stage is 80% against the downstream stage 20%. In No. 2, the upstream stage is 70% with respect to the downstream stage 30%. In No. 3, the upstream stage is 60% and the downstream stage is 40%. In No. 4, 50% of the upstream stage is compared with 50% of the downstream stage. 5, the upstream stage is 40% with respect to the downstream stage 60%.

The supply amount of 100% hydrogen sulfide gas mixed with the biogas was adjusted so that the hydrogen sulfide concentration in the hydrogen sulfide-containing gas was a constant concentration in the range of 400 ppm to 700 ppm.
The flow rate of the hydrogen sulfide-containing gas was adjusted by the valve opening so as to be a constant amount in the range of 5.6 m ³ / day to 9.8 m ³ / day.

  The results of Example 3 are shown in Table 9. The values in the table are the values on the 10th day of evaluation.

The hydrogen sulfide concentration in Run 3-1 to Run 3-5 was 400 ppm.
In Run 3-1, the ratio of the gas amount was set to the upstream stage; 80%, and the downstream stage; 20%. As a result, the treatment gas hydrogen sulfide concentration was 32 ppm, and the hydrogen sulfide removal rate was 92%.
In Run 3-2, the ratio of the gas amount was set to 70% for the upstream stage and 30% for the downstream stage. As a result, the treatment gas hydrogen sulfide concentration was 16 ppm, and the hydrogen sulfide removal rate was 96%.
In Run 3-3, the ratio of the gas amount was set to the upstream stage; 60%, and the downstream stage; 40%. As a result, the treatment gas hydrogen sulfide concentration was 16 ppm, and the hydrogen sulfide removal rate was 96%.
In Run 3-4, the ratio of the gas amount was set to the upstream stage; 50%, and the downstream stage; 50%. As a result, the treatment gas hydrogen sulfide concentration was 16 ppm, and the hydrogen sulfide removal rate was 96%.
In Run 3-5, the gas amount ratio was set to 40% for the upstream stage and 60% for the downstream stage. As a result, the treatment gas hydrogen sulfide concentration was 40 ppm, and the hydrogen sulfide removal rate was 90%.

The hydrogen sulfide concentration was 500 ppm for Run 4-1 to Run 4-5, 600 ppm for Run 5-1 to Run 5-5, and 700 ppm for Run 6-1 to Run 6-6.
In Run 4-1, Run 5-1, and Run 6-1, the ratio of gas amounts was set to 80% upstream stage and 20% downstream stage. At any hydrogen sulfide concentration, the hydrogen sulfide removal rate was 90% to 92%.
In Run 4-2 to Run 4-4, Run 5-2 to Run 5-4, and Run 6-2 to Run 6-4, the ratio of the gas amounts is in the range of upstream stage; 50% to 70%, downstream stage; 30% to 50%. did. At any hydrogen sulfide concentration, the hydrogen sulfide removal rate was in the range of 95% to 97%.
In Run 4-5, Run 5-5, and Run 6-5, the ratio of gas amounts was set to 40% for the upstream stage and 60% for the downstream stage. The hydrogen sulfide removal rate decreased to 85% to 90% at any hydrogen sulfide concentration.

The following can be seen through the third embodiment. when the n-th stage of the ratio of gas volume and r _n, the ratio of the amount of gas can be satisfactorily processed when a r _n ≧ r _{n + 1,} and hydrogen sulfide towards the subsequent increases the ratio of gas volume than the preceding stage Cannot be completely removed.

  Therefore, the ratio of the gas amount is 50% to 70% in the upstream stage; the processing performance is good in the range of the remainder (50% to 30%) in the downstream stage and the upstream stage, and superior results are obtained. Gakata.

  In Example 4, the processing performance when the number of stages of the packed bed was 3 was examined. The evaluation period for each run was 7 days, and the total evaluation period was 70 days.

As the experimental apparatus, the biological desulfurization apparatus shown in FIG. 8 was used. An outline of the experimental apparatus of Example 4 is shown in Table 10. The outline of the experimental apparatus is almost the same as that of the first embodiment.
The number of packed bed stages was three, the total packed height was 3 m, and the total packed volume was 6.3 L.
The air supply amount was adjusted to 70 L / day by the oxygen-containing gas supply amount adjusting means so that oxygen at a molar ratio of 2.5 times the hydrogen sulfide amount was supplied.

Table 11 shows the experimental conditions. Both the gas processing direction and the processing system are the same as those in the first embodiment.
The ratio of the gas amount was in the range of 50% to 33% in the upstream stage, in the range of 40% to 20% in the middle stream stage, and in the range of 33% to 15% in the downstream stage. The distribution of the hydrogen sulfide-containing gas was performed by controlling the hydrogen sulfide-containing gas supply amount adjusting means via the hydrogen sulfide control means.

The supply amount of 100% hydrogen sulfide gas mixed with biogas was adjusted so that the hydrogen sulfide concentration in the hydrogen sulfide-containing gas was 700 ppm.
The flow rate of the hydrogen sulfide-containing gas was adjusted by the valve opening so as to be a constant amount of 8.4 m ³ / day.

  The results of Example 4 are shown in Table 12. The values in the table are the values on the seventh day of evaluation.

In Runs 7-1 to 7-4, the ratio of the gas amount in the upstream stage was fixed to 50%, and the distribution ratio in the midstream stage and the downstream stage was changed. In Runs 7-1 to 7-3, “upstream inflow gas amount ≧ middle flow inflow gas amount ≧ downstream inflow gas amount”, but in this case, a removal rate of 97% to 98% is obtained. It was. Specifically, in Run 7-1, the hydrogen sulfide removal rate was 98% when the ratio of the gas amount in the midstream and downstream stages was 35% and 15%, respectively. In Run 7-2, the hydrogen sulfide removal rate was 97% when the ratio of the gas amount in the middle and downstream stages was 30% and 20%, respectively. In Run 7-3, the hydrogen sulfide removal rate was 97% when the ratio of the gas amount in the middle and downstream stages was 25% and 25%, respectively.
In Run 7-4, the ratio of the gas amount in the midstream and downstream stages was 20% and 30%, respectively. Compared with “upstream inflow gas amount ≧ middle flow inflow gas amount ≧ downstream inflow gas amount”, the hydrogen sulfide removal rate decreased to 90%.

In Runs 7-5 to 7-7 and Run 7-9, “the amount of inflow gas in the upstream stage ≧ the amount of inflow gas in the middle stage ≧ the amount of inflow gas in the downstream stage” and the hydrogen sulfide removal rate was 97%. .
In Run 7-8, the hydrogen sulfide removal rate was 90% when the ratio of the gas amount was set to 40% upstream, 25% downstream, and 35% downstream.
In Run 7-10, the hydrogen sulfide removal rate was 80% when the ratio of the gas amount was set to the upstream stage; 30%, the midstream stage; 30%, the downstream stage; 40%.

The distribution ratio of the nth stage is represented as rn. Specifically, the ratio of the amount of gas r ₁ upstream _stage, the middle stage r _2, representing a downstream stage and r _3. Although not shown in Table 12, the hydrogen sulfide-containing gas concentrations of 400 ppm, 500 ppm, and 600 ppm were also examined, and it was found that high removal performance was obtained when the gas amount ratio was r ₁ ≧ r ₂ ≧ r _3. It was.

  As shown in the fourth embodiment, the hydrogen sulfide removal rate is obtained by setting the relationship of the amount of gas flowing into each stage as “inflow gas amount in upstream stage ≧ inflow gas amount in middle stage ≧ inflow gas quantity in downstream stage”. Was 97% to 98%, and the processing performance was good. In particular, the ratio of the gas amount is the upstream stage: 33% to 50%, the middle stage; 40% to 30%, the downstream stage; the hydrogen sulfide removal rate in the range of the remainder of the upstream stage and the middle stage (15% to 33%) Was 95%, and it was found that a result superior in processing performance was obtained.

The hydrogen sulfide loading was 0.6 kg / (m ³ · day) to 5.0 kg / (m ³ · day). In Example 5, the amount of hydrogen was controlled as the amount of oxygen-containing gas by the amount of hydrogen sulfide, whereas in the comparative example of Example 5, air was always supplied as a fixed amount of oxygen-containing gas. In the present embodiment, each hydrogen sulfide load was classified as Run. The evaluation period at a constant hydrogen sulfide load was 1 day, and the total evaluation period was 9 days.

  Experiments were conducted on Run 8-1 to Run 8-9 while comparing the biological desulfurization apparatus of Example 1 shown in FIG. 6 with two towers in parallel and comparing the comparative example of Example 5 and Example 5. . Table 13 shows an outline of the experimental apparatus of Example 5. The outline of the experimental apparatus is the same as in Example 1.

Table 14 shows the experimental conditions of the comparative example of Example 5 and Example 5. The gas treatment direction was downward flow, and the treatment method was a single-pass method, and the hydrogen sulfide-containing gas was distributed to the upstream and downstream stages of the packed bed.
The ratio of the gas amount was 70% for the upstream stage and 30% for the downstream stage. The distribution of the hydrogen sulfide-containing gas was performed by controlling the hydrogen sulfide-containing gas supply amount adjusting means via the hydrogen sulfide control means.

The supply amount of 100% hydrogen sulfide gas mixed with biogas was adjusted so that the hydrogen sulfide concentration in the hydrogen sulfide-containing gas was 500 ppm.
The hydrogen sulfide-containing gas flow rate was adjusted by the valve opening so as to be a constant amount in the range of 3.6 m ³ / day to 30 m ³ / day.
The air supply amount is adjusted at any time by the oxygen-containing gas supply amount adjusting means in accordance with the variation of the hydrogen sulfide load in Example 5, whereas in the comparative example of Example 5, the air is supplied so that a constant amount of oxygen is always supplied. The supply amount was adjusted by the oxygen-containing gas supply amount adjusting means.

  Table 15 shows the results of the comparative example of Example 5 and Example 5. Moreover, the daily change of the comparative example of Example 5 and Example 5 is shown in FIG.

In Run8-1～Run8-8, hydrogen sulfide loading was investigated in the range of ^{0.6kg / (m 3 · day)} ~5kg / (m 3 · day). The hydrogen sulfide-containing gas flow rate was 3.6 m ³ / day to ³⁰ m ³ / day, that is, the amount of hydrogen sulfide was 2.5 g / day to 21 g / day.
In Example 5, the oxygen supply amount was 6 g / day to 50 g / day, that is, the air supply amount was 54 L / day to 455 L / day, and the molar ratio was constant at 2.5 times. The removal rate of hydrogen sulfide was 100% for Run 8-1 to Run 8-4, and 98% to 90% for Run 8-5 to Run 8-8.
In the comparative example of Example 5, the oxygen supply amount was 26 g / day, that is, the air amount was constant at 240 L / day, and the molar ratio was 11.6 times to 1.3 times. The removal rate of hydrogen sulfide was 100% for Run 8-1 to Run 8-4, and 98% to 50% for Run 8-5 to Run 8-8.

In Run 8-9, the hydrogen sulfide load was reduced to 1.4 kg / (m ³ · day). The flow rate of the hydrogen sulfide-containing gas was 8.5 m ³ / day, that is, the amount of hydrogen sulfide was 6 g / day. In Example 5, the oxygen supply amount was 14 g / day, that is, the air supply amount was 128 L / day, and the molar ratio of the oxygen amount to the hydrogen sulfide amount was 2.5 times. The hydrogen sulfide removal rate and the sulfuric acid conversion rate were both 100% and the methane concentration was 59%, whereas in the comparative example of Example 5, the oxygen supply amount was 26 g / day, that is, the air supply amount was 240 L / day. When the molar ratio of the oxygen amount to the hydrogen sulfide amount was 4.6 times, the hydrogen sulfide removal rate was 85%, the sulfuric acid conversion rate was 70%, and the methane concentration was 58%. Both hydrogen removal rate and sulfuric acid conversion rate decreased.

Therefore, in the present invention, as shown in Example 5, the hydrogen sulfide removal rate is 95 up to 4 kg / (m ³ · day) by supplying oxygen so that the molar ratio is constant with respect to the hydrogen sulfide load. It was found to be a hydrogen sulfide removal method that provides a higher removal rate than the comparative example.
Throughout this experiment period, no precipitation of sulfur was observed in Example 5, whereas in the comparative example of Example 5, sulfur was deposited and adhered to the filler. In Example 5 in which almost no precipitation of sulfur was observed, the treatment was recovered because the activity of the microorganism was maintained, whereas in the comparative example of Example 5 in which sulfur was deposited, the activity of the microorganism was decreased and the treatment was not performed. It did not recover. Therefore, it has been found that it is preferable to supply air so that the molar ratio of the oxygen amount to the hydrogen sulfide amount is constant.

Next, attention is focused on the sulfuric acid conversion rate. In Example 5, hydrogen sulfide loading in the range of Run8-1~Run8-7 is in the range of ^{0.6kg / (m 3 · day)} ~5kg / (m 3 · day), sulfuric acid conversion is 100% Met. In Run 8-8, the hydrogen sulfide load was 5 kg / (m ³ · day), and the sulfuric acid conversion rate was 95%. In the comparative example of Example 5, when Run 8-1 to Run 8-4, the molar ratio of the oxygen amount to the hydrogen sulfide amount was 11.6 times to 2.5 times, and the sulfuric acid conversion rate was 100%. In the case of Run 8-5 to Run 8-8, the molar ratio of the oxygen amount to the hydrogen sulfide amount was 2.1 times to 1.3 times, and the sulfuric acid conversion rate tended to decrease to 80% to 30%.
Therefore, in order to make the sulfuric acid conversion rate 100%, the molar ratio of the oxygen amount to the hydrogen sulfide amount is preferably 2.5 times or more.

Paying attention to the methane concentration in the biogas, in Example 5, the air supply amount was adjusted so that the molar ratio of the oxygen amount to the hydrogen sulfide amount was 2.5 times constant, and Run 8-1 to Run 8-9. Throughout, the methane concentration was constant at 59%.
In the comparative example of Example 5, a constant amount of air was supplied. In Run 8-1, the molar ratio of the oxygen amount to the hydrogen sulfide amount was 11.6 times, and the methane concentration was 55%. In Run 8-2 to Run 8-8, the molar ratio of the oxygen amount to the hydrogen sulfide amount was 7 to 1.3 times, and the methane concentration was 58% to 59%. Therefore, when a certain amount of air is supplied when the hydrogen sulfide load is low, the concentration of methane gas in the biogas decreases, and the value as biogas decreases. Therefore, it is preferable to supply air so that the molar ratio of the oxygen amount to the hydrogen sulfide amount is less than seven times.

  In Example 6, the effect of biologically desulfurizing using oxygen-containing gases having different oxygen concentrations was examined. This example was divided according to the molar ratio of the amount of oxygen to the amount of hydrogen sulfide to be treated. The evaluation period was 10 days, and the total evaluation period was 40 days.

As the experimental apparatus, the biological desulfurization apparatus of Example 1 shown in FIG. 6 was used, and three identical towers were operated in parallel. The experimental apparatus is No. 1. 1 to No. 3, the oxygen concentration in the oxygen-containing gas was set to different conditions, and the removal performance was compared.
Table 16 shows an outline of the experimental apparatus of Example 6. The outline of the experimental apparatus is the same as in Example 1. The hydrogen sulfide-containing gas is a biogas generated in the same methane fermentation tank as in Example 5. The hydrogen sulfide-containing gas component had a hydrogen sulfide concentration of 100 ppm, a methane concentration of 60%, and a carbon dioxide concentration of 40%, and was constant throughout the experiment.

Table 17 shows the experimental conditions of Example 6. The gas direction was a downward flow, and the treatment method was a transient method, and the hydrogen sulfide-containing gas was distributed to the upstream and downstream stages of the packed bed.
The ratio of the gas amount was 70% for the upstream stage and 30% for the downstream stage. The distribution of the hydrogen sulfide-containing gas was performed by controlling the hydrogen sulfide-containing gas supply amount adjusting means via the hydrogen sulfide control means.

The supply amount of 100% hydrogen sulfide gas mixed with biogas was adjusted so that the hydrogen sulfide concentration in the hydrogen sulfide-containing gas was 500 ppm.
The flow rate of the hydrogen sulfide-containing gas was adjusted by the valve opening so that the flow rate was 12.1 m ³ / day, and the amount of hydrogen sulfide was 8.4 g / day.
Air (containing 21 v / v% oxygen; 25 ° C.) was used as the oxygen-containing gas. The oxygen concentration in the air oxygen-containing gas was adjusted to 21%, 50%, and 90% using an oxygen generator. Each experimental apparatus was supplied with oxygen-containing gases having different oxygen concentrations. 1 was 21%, No. 1 2 is 50%, no. 3 was 90%. The oxygen-containing gas was supplied by adjusting the oxygen-containing gas supply amount adjusting means.
The oxygen-containing gas supply amount was adjusted according to the molar ratio of the oxygen amount to the amount of hydrogen sulfide to be treated. Specifically, an oxygen-containing gas having an oxygen concentration of 21% is 70 L / day to 860 L / day, an oxygen-containing gas having an oxygen concentration of 50% is 30 L / day to 360 L / day, and an oxygen-containing gas having an oxygen concentration of 90% Then, it adjusted in the range of 17L / day-200L / day.

  The results of Example 6 are shown in Table 18.

In Run 9-1, the oxygen supply amount was set to 8 g / day so that the molar ratio of the oxygen amount to the amount of hydrogen sulfide to be processed was 1 time. Regardless of the oxygen concentration in the oxygen-containing gas, the hydrogen sulfide removal rate was 100%, the sulfuric acid conversion rate was 75%, and the methane concentration was 60%.
In Run 9-2, the oxygen supply rate was set to 20 g / day so that the molar ratio of the oxygen demand to the amount of hydrogen sulfide to be processed was 2.5 times. Regardless of the oxygen concentration in the oxygen-containing gas, the hydrogen sulfide removal rate and the sulfuric acid conversion rate were both 100%. The methane concentration was 59% for air with an oxygen concentration of 21% and 60% for air with an oxygen concentration of 50% and 90%. All the biogas treated in this period could be used as fuel without any problems.
In Run 9-3, the oxygen supply amount was 55 g / day so that the molar ratio of the oxygen amount to the amount of hydrogen sulfide to be treated was 7 times. Regardless of the oxygen concentration in the oxygen-containing gas, the hydrogen sulfide removal rate was 100%, and the sulfuric acid conversion rate was 100%. The methane concentration is 58% for air with an oxygen concentration of 21%, 59% for air with an oxygen concentration of 50% and 90%, and any biogas treated in this period can be used as a fuel without any problems. did it.
In Run 9-4, the oxygen supply amount was set to 95 g / day so that the molar ratio of the oxygen amount to the amount of hydrogen sulfide to be processed was 12 times. Regardless of the oxygen concentration in the oxygen-containing gas, the hydrogen sulfide removal rate was 100%, and the sulfuric acid conversion rate was 100%. The methane concentration was 55% for air with an oxygen concentration of 21%, 58% for air with an oxygen concentration of 50%, and 59% for air with an oxygen concentration of 90%.
Here, when the methane concentration in the biogas was 55%, it was insufficient as a boiler fuel, but it could be used as a fuel without problems in air with an oxygen concentration of 50% and 90%.

From the experimental results of this example, when the oxygen concentration in the oxygen-containing gas becomes high, even if the oxygen-containing gas supply amount to be supplied is small, it can be processed without impairing the value as a biogas.
Therefore, if the molar ratio of the oxygen amount to the hydrogen sulfide amount is adjusted to be 2.5 to 7 times, the utility value of the treated biogas is maintained regardless of the oxygen concentration in the oxygen-containing gas.

  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 biological desulfurization apparatus and biological desulfurization method for hydrogen sulfide-containing gas that can be processed at low cost.

0a Hydrogen sulfide containing gas 0b Oxygen containing gas 0c Treatment gas 0d Circulating fluid 0e Blowing water 0f Makeup water 1 Biological desulfurization tower 1a Packed bed 1b Circulating fluid reservoir 2 Hydrogen sulfide containing gas line 3 Hydrogen sulfide containing gas flow meter 4 Hydrogen sulfide concentration meter 5 Inflow gas line 6 Distributor 7 Hydrogen sulfide-containing gas supply amount adjusting means 8 Oxygen-containing gas inflow line 9 Oxygen-containing gas supply amount adjusting means 10 Process gas outflow line 11 Sprinkling line 12 Hydrogen sulfide concentration calculator 13 Load Quantity calculator 14 Signal transmission means 15 of calculation result by load quantity calculator 15 Signal transmission means 16 of first calculation result by hydrogen sulfide concentration calculator 16 Hydrogen sulfide concentration signal input means 17 Hydrogen sulfide-containing gas flow rate signal input means 18 Process gas Circulation line 19 Blower 20 Process gas circulation amount adjusting means 21 Signal transmission hand of second calculation result by hydrogen sulfide concentration calculator

Claims (11)

In a biological desulfurization apparatus that biologically removes hydrogen sulfide by sprinkling a circulating liquid from a hydrogen sulfide-containing gas into a biological desulfurization tower,
Connect hydrogen sulfide-containing gas lines to multiple inflow gas lines via distributors,
An oxygen-containing gas inflow line for supplying an oxygen-containing gas to the hydrogen sulfide-containing gas line is connected;
In the biological desulfurization tower, a plurality of packed layers made of a filler to which microorganisms adhere are provided,
The inflow gas line is connected to the upstream end of the packed bed in each stage,
The inflow gas line has a hydrogen sulfide-containing gas supply amount adjusting means,
A processing gas outflow line for discharging a processing gas is provided at the downstream end of the packed bed on the most downstream side, and the hydrogen sulfide-containing gas supplied through the hydrogen sulfide-containing gas line is distributed by the distributor, and the distribution is performed. A biological desulfurization apparatus, wherein the hydrogen sulfide-containing gas is supplied to the upstream end of the packed bed of each stage through the inflow gas line . The biological desulfurization apparatus according to claim 1,
The hydrogen sulfide-containing gas line has a hydrogen sulfide concentration meter,
A biological desulfurization apparatus comprising hydrogen sulfide control means for controlling the hydrogen sulfide-containing gas supply amount adjusting means based on a measurement signal from the hydrogen sulfide concentration meter. The biological desulfurization apparatus according to claim 2,
A processing gas circulation line for circulating at least a part of the processing gas discharged from the downstream end of the packed bed on the most downstream side;
The processing gas circulation line is connected to the upstream side of the hydrogen sulfide concentration meter of the hydrogen sulfide-containing gas line,
The processing gas circulation line has a processing gas circulation amount adjusting means,
The biological desulfurization apparatus, wherein the hydrogen sulfide control means controls the processing gas circulation rate adjusting means based on a measurement signal from the hydrogen sulfide concentration meter. The biological desulfurization apparatus according to any one of claims 1 to 3,
A hydrogen sulfide-containing gas flow meter that is a part of the hydrogen sulfide-containing gas line and is upstream of a connection portion to which the oxygen-containing gas inflow line is connected;
The hydrogen sulfide-containing gas line is another part, and a hydrogen sulfide concentration meter is provided on the upstream side of the connection portion to which the oxygen-containing gas inflow line is connected,
The oxygen-containing gas inflow line has oxygen-containing gas supply amount adjusting means,
Load amount control means for controlling the oxygen-containing gas supply amount adjusting means based on the load amount calculated by the product of the measurement signal from the hydrogen sulfide-containing gas flow meter and the measurement signal from the hydrogen sulfide concentration meter is provided. Biological desulfurization equipment characterized by. Biological desulfurization in which hydrogen sulfide-containing gas generated by methane fermentation of organic waste is introduced into a biological desulfurization tower, and the circulating liquid is sprinkled into the tower to remove hydrogen sulfide biologically. In the method
In the biological desulfurization tower, a plurality of packed layers made of a filler to which microorganisms adhere are provided,
An oxygen supply step of supplying an oxygen-containing gas to the hydrogen sulfide-containing gas;
A gas distribution step of distributing the hydrogen sulfide-containing gas that has undergone the oxygen supply step into a plurality of portions;
A gas inflow step of flowing the hydrogen sulfide-containing gas distributed in the gas distribution step into the upstream end of the packed bed of each stage;
A process gas outflow step of discharging the process gas from the downstream end of the packed bed on the most downstream side,
In the gas inflow step, the biological desulfurization method is characterized in that the supply amount of the hydrogen sulfide-containing gas is set to be adjustable. The biological desulfurization method according to claim 5,
A biological desulfurization method comprising measuring a hydrogen sulfide concentration in a hydrogen sulfide-containing gas before the oxygen supply step, and adjusting a supply amount of the hydrogen sulfide-containing gas based on the measurement result. The biological desulfurization method according to claim 6,
A process gas circulation step of circulating at least a part of the process gas discharged from the downstream end of the packed bed on the most downstream side to the upstream side of the place where the hydrogen sulfide concentration is measured;
A biological desulfurization method characterized by adjusting a circulation amount of a treatment gas in the treatment gas circulation step based on a measurement result of the hydrogen sulfide concentration. The biological desulfurization method according to any one of claims 5 to 7,
The flow rate of the hydrogen sulfide-containing gas before the oxygen supply step and the hydrogen sulfide concentration in the hydrogen sulfide-containing gas before the oxygen supply step are measured, and the measurement signal from the hydrogen sulfide-containing gas flow meter and the hydrogen sulfide concentration A biological desulfurization method, comprising: adjusting a supply amount of an oxygen-containing gas in the oxygen supply step based on a load amount calculated by a product of measurement signals from a meter. The biological desulfurization method according to any one of claims 5 to 8,
A biological desulfurization method, wherein the hydrogen sulfide concentration in the hydrogen sulfide-containing gas that has undergone the oxygen supply step is 400 to 700 ppm. The biological desulfurization method according to any one of claims 5 to 9,
The packed bed is composed of two stages, an upstream stage and a downstream stage,
In the gas inflow step, the amount of gas flowing into the upstream stage is 50% to 70% of the whole, and the rest flows into the downstream stage. The biological desulfurization method according to any one of claims 5 to 9,
The packed bed is composed of three stages, an upstream stage, a midstream stage, and a downstream stage,
In the gas inflow process, biological desulfurization characterized in that the relationship between the amount of gas flowing into each stage is “the amount of inflow gas in the upstream stage ≧ the amount of inflow gas in the middle stage ≧ the amount of inflow gas in the downstream stage”. Method.

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