JP2007054730A - Methane gas recovery apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrict expansion on appearance of an organic material and to stably and effectively recover a methane gas even when methane-fermentation is performed without adding water to the organic material in fact in such a case of dry type methane fermentation. <P>SOLUTION: The methane gas recovery apparatus is provided with a tank for storing the organic material; an introduction part provided on an upper part of the tank and introducing the organic material into the tank; and a gas-discharge part provided on the upper part of the tank and discharging the methane gas generated by methane-fermenting the organic material in the tank to the outside of the tank; and a discharge part provided on a lower part of the tank and discharging the residue of the fermented organic material. A vertically extending vibration body is arranged in the tank. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic material recycling technology, and more particularly to a recovery technology for obtaining methane gas by methane fermentation of an organic material.

  To recycle organic materials such as okara, paper, garbage, manure, and organic waste (hereinafter simply referred to as organic materials), a technology to recover methane gas by methane fermentation of such organic materials is proposed. (Patent Documents 1 to 3). The recovered methane gas is used, for example, for power generation. On the other hand, as a fermenter for fermenting organic matter, there is a container type having a common inlet for organic matter and a discharge port for residues of fermented organic matter. However, in this format, the fermented organic matter gives off a strange odor, so when replacing the new organic matter with the post-fermentation residue, there will be a strange odor around the environment, which should be used in environments where there are private houses around the equipment. Is difficult. In addition, it is necessary to replace the new organic matter with the residue after fermentation, and new organic matter cannot be continuously added, resulting in poor work efficiency. On the other hand, there is a tank type in which the upper part of the fermenter is an organic substance inlet and the lower part is a residue outlet (Patent Documents 2 and 3). In this form, it is not necessary to replace the new organic matter with the residue after fermentation, so that the problem of off-flavor can be solved and new organic matter can be continuously added. Note that methane gas generated in the tank is recovered from the upper part of the tank.

JP 11-309493 A JP 2001-347247 A JP 2002-320949 A

  As such a methane fermentation system, dry methane fermentation and wet methane fermentation have been proposed. In the method of fermenting without adding water to the organic matter, which is called dry methane fermentation, the organic matter in the fermenter has a relatively high viscosity. (Abbreviated as methane gas) tends to remain dispersed as fine bubbles in the organic matter during fermentation and is difficult to separate. For this reason, a method called wet methane fermentation in which organic substances are usually pulverized and hydrated is used. In the wet methane fermentation system, the operation is easy to manage, but the content of organic matter is reduced. Therefore, in order to generate the same methane gas, there is a disadvantage that a large capacity tank and a large amount of waste water are generated.

  On the other hand, dry methane fermentation has the advantage that a smaller tank and a smaller amount of drainage are required than wet methane fermentation, but methane gas is difficult to separate from the organic matter being fermented, so the organic matter being fermented is apparently expanded. There is a problem in that the upper surface of the organic matter continues to rise above the tank and may become overflowed and clog a pipe that collects methane gas.

  Therefore, the object of the present invention is to regulate the apparent expansion of organic matter, and to recover methane gas more stably and effectively even when methane fermentation is carried out without virtually adding water to organic matter as called dry methane fermentation. There is to do.

  According to the present invention, a tank that contains organic matter, an introduction portion that is provided at an upper portion of the tank and introduces the organic matter into the tank, and is provided at an upper portion of the tank, wherein the organic matter is methane in the tank. In the methane gas recovery apparatus comprising: an exhaust unit that exhausts methane gas generated by fermentation to the outside of the tank; and a discharge unit that is provided at a lower portion of the tank and discharges the residue of the fermented organic matter. Further, a methane gas recovery device is provided in which a vibrating body extending in the vertical direction is disposed.

  According to this methane gas recovery device, by arranging the vibrating body, the organic matter around the vibrating body is vibrated, and fine bubbles including the generated methane gas gather together, and grow into large bubbles, It becomes easy to move upward. Further, the surface of the vibrating body has a portion where pressure is increased and a portion that is depressurized, bubbles tend to gather in the decompressed portion, and an airway in which bubbles containing methane gas are likely to rise in the vertical direction along the vibrating body is formed, The methane gas generated by being dispersed in the organic matter is promoted to be defoamed and degassed from the organic matter, so that the methane gas is easily gathered above the tank.

  Further, the organic matter is vibrated even in a wide range from the periphery of the vibrating body, and the movement of the bubbles becomes active and moves so as to collect in the vibrating body, and the movement of the bubbles stirs the organic matter. As a result, methane fermentation is promoted. Therefore, apparent expansion of organic matter due to fermentation can be regulated, and methane gas can be recovered more stably and effectively.

  Here, it is preferable that the vibrating body extends from the vicinity of the bottom of the tank to at least a height that is at least half the depth of the organic matter housed in the tank, and is to be put into the tank. It is preferable to extend to the position of the upper surface of the whole unfermented organic matter. The vibrator may be configured to extend in the vertical direction by arranging a plurality of vibrators in the vertical direction.

  In the present invention, it is possible to employ a configuration in which stirring means for stirring the organic matter is disposed in the upper part of the tank. According to this configuration, when the organic substance is charged, the height of the organic substance in the tank is made uniform, and the organic substance rising above the tank is stirred to degas the methane gas dispersed in the tank. -It can promote deaeration and suppress organic overflow.

  Further, in the present invention, it is possible to employ a configuration provided with a decompression means for decompressing the inside of the tank. According to this configuration, by depressurizing the inside of the tank, the expansion of the organic matter due to the methane gas is regulated within a range that does not hinder, and the degassing / degassing of the methane gas can be further promoted. Further, the number of installed vibrators per unit volume of organic matter can be reduced.

  Further, in the present invention, a plurality of the vibrators are disposed, and when the organic matter in the tank does not reach a predetermined height, the plurality of vibrators are sequentially operated one by one, When the organic substance reaches the predetermined height, it is possible to employ a configuration in which a plurality of the vibrators are simultaneously operated. According to this configuration, it is easy to prevent overflow even when viscosity or the like increases depending on the type of organic matter, and defoaming / degassing is difficult, or when methane gas is generated at a rate exceeding expectations.

  As described above, according to the present invention, even when the water content called dry methane fermentation is 90% or less and practically does not add water to organic matter, the apparent expansion of the organic matter is regulated, and it is more stable and effective. Methane gas can be recovered. This makes it possible to utilize the advantages of dry methane fermentation that less waste water and a smaller fermenter can be made at the same scale than wet methane fermentation.

<Device configuration>
FIG. 1 is a configuration diagram of a methane gas recovery apparatus A according to an embodiment of the present invention. FIG. 2A is a plan view of the methane gas recovery apparatus A. The methane gas recovery device A is provided in a tank 10 that stores organic matter, an upper portion of the tank 10, an introduction unit 20 that introduces the organic matter into the tank, and an upper portion of the tank 10, and the organic matter undergoes methane fermentation in the tank 10. The exhaust part 21 which exhausts the methane gas generated by this out of the tank 10 and the discharge part 22 which is provided in the lower part of the tank 10 and exhausts the residue of the fermented organic substance are provided.

  The tank 10 includes a cylindrical main body 11 and a lid 12 that closes an upper opening end of the main body 11. The lower part of the main body 11 is tapered and the tip (lower end) is opened to constitute the discharge part 22. A screw conveyor 22a that can be rotationally driven by a driving means (not shown) is disposed in the discharge section 22, and organic residue accumulated in the tank 10 is discharged out of the tank 10 by the screw conveyor 22a. It should be noted that the periphery of the discharge unit 22 is normally sealed by a sealing means (not shown) so that a strange odor does not drift.

  A central portion of the lid portion 12 is opened, and a cylindrical introduction portion 20 is formed here. The introduction part 20 is provided with a lid 20a that can be opened and closed. The organic matter to be processed is thrown into the tank 10 from the introduction unit 20 with the lid 20a opened. The exhaust part 21 is a pipe and penetrates the lid part 12 and the lower end part thereof is exposed into the tank 10. Methane gas generated in the tank 10 passes through the exhaust part 21 and the pipe 21a and is stored in the chamber 1. The chamber 1 is provided with a bag or the like for storing methane gas. In the middle of the pipe 21a, a valve 21b for blocking and allowing passage of methane gas in the pipe 21a is provided.

  A plurality (three in this case) of vibration units 30 extending in the vertical direction are arranged in the tank 10. The vibration unit 30 includes a drive unit 31 and a vibrating body 32, has a rod shape as a whole, and is supported by the main body 11 of the tank 10 via a support member 33. The vibrating body 32 includes a shaft member extending in the vertical direction having an eccentric weight in a hollow member, and a motor that rotationally drives the shaft body in the vibrating body 32 is built in the driving unit 31. . When the shaft is rotated by driving the motor, the vibrating body 32 vibrates. Note that the configuration of the vibrating body is not limited to this, and various types such as those driven by air can be adopted. As will be described later, an airway in which bubbles are likely to rise in the vertical direction is easily formed in the tank 10 around the vibrating body. It only has to be.

  A plate-like vibrating blade 32 a extending in the vertical direction is fixed to the peripheral surface of the vibrating body 32. A plurality of vibrating blades 32a are provided for one vibrating body 32 and project radially (in the radial direction) from the vibrating body 32 in a plan view. The protrusion length is preferably about 5 cm to 10 cm. If it is 5 cm or less, the formation range of the airway is narrowed, and if it is 10 cm or more, the vibrating portion including the vibrating blade 32a, the vibrating body 32, and the like is strengthened, so that the energy required for vibration increases too much. The plurality of vibrating blades 32a are made of, for example, a metal plate, an FRP plate, or the like, and vibrate due to the vibration of the vibrating body 32 (see the arrow in FIG. 2A), thereby forming an airway in the vertical direction and exciting organic matter. Is increased. For example, as shown in the enlarged cross-sectional view of FIG. 1, the support member 33 has a space in which a stopper member 33 a attached to the vibration body 32 is accommodated so as not to hinder the vibration of the vibration unit 30. The vibration unit 30 is supported so that it can move a certain amount vertically and horizontally. Although not shown, by using a spring-shaped spring instead of the stopper member 33a, fixing the support member 33 to the outer periphery of the spring-shaped spring, and fixing the vibrating body 32 to the center of the spring-shaped spring, The vibration unit 30 can also be supported.

  Next, a rotating blade 40 is disposed in the upper part of the tank 10 as a stirring means for stirring the organic matter in the tank 10. The rotary blade 40 is disposed above the vibration unit 30 and is attached to a shaft 42 connected to the output shaft of the motor 41 disposed on the lid portion 12, and rotates by the rotational drive of the motor 41 ( (See arrow in FIG. 2 (a)). The rotary blade 40 may be driven not to rotate but to repeat normal rotation and reverse rotation. In the case of this embodiment, three units of a motor 41, a shaft 42, and a rotor blade 40 are provided, and a plurality of rotor blades 40 are attached to each shaft 42, respectively.

  By driving the rotary blade 40, when the organic substance is charged, the height of the organic substance in the tank 10 is made uniform, and the organic substance rising upward from the tank 10 is stirred to disperse the methane gas dispersed therein. Defoaming and deaeration can be promoted, and overflow of organic matter can be suppressed.

  Next, an exhaust unit 50 different from the exhaust unit 21 is provided in the lid 12 of the tank 10. The exhaust part 50 is a pipe, and penetrates the lid part 12 and its lower end is exposed into the tank 10. The methane gas generated in the tank 10 can also be stored in the chamber 1 through the exhaust part 50 and the pipe 50a. A valve 50b that blocks and allows passage of methane gas in the pipe 50a is disposed in the middle of the pipe 50a. Further, a pump 51 which is a decompression unit for decompressing the inside of the tank 10 is disposed in the middle of the pipe 50a. The recovery of methane gas from the exhaust unit 21 is natural recovery by the fermentation pressure of methane gas, but the recovery of methane gas from the exhaust unit 50 is forcibly recovered by suction of the pump 51.

  It should be noted that a cover is installed at the lower end of the pipes of the exhaust parts 21 and 50 so that the scattered organic matter does not easily enter the pipe, and the lower end of the pipe is prevented from entering the pipe due to the rise of the organic matter. A float valve may be installed.

  Next, an overflow sensor 60 is disposed in the tank 10. The overflow sensor 60 is a float switch that detects the upper surface level of the organic matter in the tank 10, a sensor that uses pressure, light, ultrasonic waves, or the like. A jacket heater (not shown) is disposed outside the main body 10 of the tank 10. The heater promotes methane fermentation by heating as necessary to keep the organic matter at 35 to 38 degrees Celsius.

<Operation of the device>
Next, the operation of the methane gas recovery apparatus A having such a configuration will be described with reference to FIGS. The methane gas recovery apparatus A operates under the control of a control means (not shown) such as a computer. This embodiment assumes the case of dry methane fermentation.

<Input of organic substances and discharge of residues>
Referring to FIG. 3A, new deaerated unfermented organic matter X ′ is periodically introduced from the introduction unit 20. The introduced organic substance X ′ is constantly homogenized in the height direction while being stirred by the rotating blade 40 rotating at a speed of several times per minute, and acid-producing fermentation is promoted.

  The amount of the organic substance X ′ introduced into the tank 10 is preferably such that the upper end portion of the organic substance X ′ immediately after the pressure reduction by the pump 51 and the operation of the vibrating body 32 is in contact with the lower end of the rotor blade. By setting the amount to this level, the increased portion of the organic matter X ′ expanded by methane fermentation is agitated by the rotor blade 40, so that the load on the rotor blade can be prevented from being continued, and the stirring energy is reduced. Less.

  The organic substance X ′ may be preliminarily subjected to pretreatment such as removal of foreign substances, pulverization treatment, pre-fermentation (acid-producing fermentation), reduction of fermentation-inhibiting substances, etc., and heated to 35 to 38 degrees Celsius. Good.

  For example, when a new organic substance X ′ is introduced, the residue X ″ can be discharged about 1/30 of its raw material equivalent capacity with respect to the input amount. A part of the discharged residue X ″ is Although it can be reintroduced into the tank 10 together with the new organic substance X ′ and used as an inoculum, as described later, methane-fermenting bacteria that become an inoculum along the airway formed around the vibrating body 32 are also bubbles. It is not necessary to re-inject a part of the discharged residue X ″ into the upper part of the tank. As a result, the discharged residue X ″ is used as a compost product by aerobic fermentation. You can also

<Recovery of methane gas 1>
With reference to FIG.3 (b), the organic substance X in the tank 10 ferments by methane fermentation, and the gas which has methane gas as a main component is generated. The fermentation period is, for example, 30 days. The generated methane gas passes through the exhaust part 21 and is guided to the chamber 1 and stored. When collecting from the exhaust part 21, the valve 21b is opened and the valve 50b is closed (see FIG. 1). Since the fermented organic substance X has a relatively high viscosity, even if methane gas is generated, it tends to be dispersed as fine bubbles inside the organic substance X, and the methane gas is difficult to be degassed and degassed. In particular, since the methane gas generated on the lower side of the tank 10 has a distance to reach the exhaust part 21, it is more difficult to degas and deaerate. If the degassing of the methane gas is not successful, the whole organic substance X expands upward and clogs the exhaust part 21 (overflow).

  Therefore, the vibration unit 30 is operated. Due to the vibration of the vibrating blade 32a of the operated vibration unit 30, an airway in which methane gas bubbles easily rise in the vertical direction along the vibrating body 32 is formed around the vibration blade 32a. Further, on the surface of the vibrating body 32 (and the vibrating blade 32a), a portion where the pressure is increased and a portion where the pressure is reduced are generated, and bubbles are easily collected in the reduced pressure portion. Accordingly, an airway in which bubbles containing methane gas easily rise in the vertical direction along the vibrating body 32 is formed, and it is promoted that the methane gas generated by being dispersed in the organic matter is defoamed and degassed from the organic matter. It becomes easy to gather upwards.

  2B and 2C are explanatory views of airway formation by the vibrating body 32. FIG. FIG. 2B shows a mode in which the vibrating body 32 does not vibrate, and the organic substance X exists in the tank 10 without a gap. Therefore, when the vibrating body 32 is vibrated, a negative pressure space Y is temporarily formed around the vibrating body 32 and the vibrating blade 32a fixed to the vibrating body 32, as shown in FIG. Methane gas gathers in the part and forms large bubbles, so bubbles rise. Since the vibrating body 32 extends in the vertical direction, large bubbles are formed at a number of locations, and an airway is formed in which the bubbles rise substantially continuously.

  In order to form such an airway, the vibrating body 32 preferably extends from the vicinity of the bottom of the tank 10 to a height that is at least half the depth of the organic matter contained in the tank 10. It is preferable to extend to the position of the upper surface of all organic matter in an unfermented state that is scheduled to be put into 10. Each vibrating body 32 does not necessarily have to be a single rod-shaped member, and is configured so that a plurality of vibrating members are arranged in the vertical direction and extend in the vertical direction, and is substantially the same as the single bar-shaped member. It can also be.

  Since the vibration of the organic substance X by the vibrating blade 32a is rapidly attenuated as the distance from the vibrating blade 32a increases, fine bubbles in the organic substance X are gathered by the vibration of the vibrating blade 32a depending on the output of the vibrating body 32a. The largest growth is in the range of about several tens of centimeters from the vibrating blade 32a. For this reason, it is desirable to arrange the vibrators 32 at a relatively fine pitch.

  Moreover, it is not necessary to always vibrate the vibrating body 32, and it is sufficient to vibrate intermittently according to the degree of expansion of the organic substance X or the like. When the vibration unit 30 is operated, the methane gas can be recovered at a more constant speed by operating the three vibration units 30 one by one, for example, clockwise or counterclockwise in plan view. . Further, since the organic substance X is degassed and degassed around the vibrating body 32 in operation and expansion is suppressed, the upper surface of the organic substance X existing around the operating vibration body 32 is lower than other parts. A slight inclination is generated on the upper surface of the organic substance X. As a result, a rapid load is less likely to be applied to the stirring blade 40. FIG. 3B shows a state in which one vibration unit 30 is operated (right side in FIG. 3).

  In this manner, the methane gas dispersed in the organic substance X is promoted to be degassed from the organic substance X, and the methane gas is easily collected above the tank 10. Furthermore, the organic substance X is vibrated and stirred by pulsation, whereby methane fermentation of the organic substance X is promoted. Therefore, the expansion | swelling which leads to the overflow of the organic substance X is controlled, and methane gas can be collect | recovered more effectively. Note that the vibration frequency of the vibrating body 32 is set to 200 to 240 Hz, for example.

<Methane gas recovery 2>
In the present embodiment, the inside of the tank 10 can be depressurized to further promote the degassing of methane gas. When the inside of the tank 10 is depressurized, fine bubbles containing methane gas generated by fermentation expand, the fine bubbles gather together and gradually increase, and the ascending force increases. It becomes easy to do. However, there is a high risk of overflow if the pressure is reduced suddenly.

  Methane gas is recovered from the exhaust 50 as shown in FIG. The valve 50b is opened, the valve 21b is closed, and the pump 51 is operated (see FIG. 1). By the operation of the pump 51, the methane gas in the tank 10 is sucked and guided to the chamber 1, and the tank 10 is depressurized. Then, the organic substance X also apparently expands, and there is a risk of overflow as described above. However, by vibrating the vibrating body 32, degassing of methane gas from the surroundings of the vibrating body 32 is promoted. Therefore, the apparent expansion of the organic substance X due to the reduced pressure is controlled within a range where there is no hindrance. In addition, when the pressure reduction is intermittently performed, the organic substance X repeatedly expands and contracts, so that fine bubbles are likely to be large and more difficult to overflow.

  As described above, it is desirable to arrange the vibrating bodies 32 at a relatively fine pitch when trying to degas and deaerate the vibrating bodies 32 alone, but a large number of vibrating bodies 32 are arranged. When the pressure is reduced, the tendency of the fine bubbles in the entire tank 10 to gather and grow greatly increases. The increased bubbles increase the force of ascending, and are more likely to gather while rising around the vibrating blade 32 a where the apparent viscosity is reduced due to vibration or the like, and are likely to rise along the vibrating body 32. As a result, the pitch at which the vibrating bodies 32 are disposed can be increased, and the number of vibrating bodies 32 can be reduced.

<Process immediately before overflow>
As described above, despite the fact that the three vibration units 30 are operated one by one in sequence, the organic matter X expands significantly upward, and exceeds the upper end of the rotor blade 40 as shown in FIG. The increase in the defoaming / degassing effect by the stirring blade 40 cannot be expected, and in this state, the possibility of overflow is increased. Therefore, the overflow sensor 60 in the tank 10 detects whether or not the organic matter X in the tank 10 has reached a predetermined height. In the case of this embodiment, the overflow sensor 60 is installed so as to detect the organic substance X when the upper surface of the organic substance X reaches the upper end position of the rotor blade 40.

  When the overflow sensor 60 detects the organic substance X, all three vibration units 30 are operated. Thereby, defoaming and deaeration of the organic substance X is promoted, and the expansion of the organic substance X is suppressed. In addition, preferably, in addition to this, measures such as reducing the decompression width, lowering the temperature setting of the tank 10, and discharging a certain amount of the organic substance X (close to the residue) from which the fermentation has been almost completed are discharged. Take. Note that a plurality of overflow sensors 60 may be installed in the vertical direction, and the above-described measures for preventing overflow from occurring at each position may be taken sequentially. FIG. 4B shows a case immediately before the overflow during the operation of “methane gas recovery 2” described above, but the same applies to the case of “methane gas recovery 1” described above.

It is a lineblock diagram of methane gas recovery device A concerning one embodiment of the present invention. (A) is a top view of the methane gas collection | recovery apparatus A, (b) And (c) is explanatory drawing of the airway formation by the vibrating body 32. FIG. (A) And (b) is operation | movement explanatory drawing of the methane gas collection | recovery apparatus A. FIG. (A) And (b) is operation | movement explanatory drawing of the methane gas collection | recovery apparatus A. FIG.

Explanation of symbols

A Methane gas recovery device 10 Tank 20 Introduction part 21 Exhaust part 22 Discharge part 32 Vibrating body 40 Rotor blade 51 Pump

Claims (4)

A tank containing organic matter;
An introduction part provided at an upper part of the tank, for introducing the organic substance into the tank;
An exhaust unit that is provided in an upper part of the tank and exhausts methane gas generated by methane fermentation of the organic matter in the tank;
In the methane gas recovery device, which is provided at the lower part of the tank and includes a discharge unit for discharging the fermented organic matter residue,
A methane gas recovery apparatus, wherein a vibrating body extending in a vertical direction is disposed in the tank.   The methane gas recovery apparatus according to claim 1, further comprising an agitation unit for agitating the organic matter in an upper part of the tank.   The methane gas recovery apparatus according to claim 1, further comprising a decompression unit that decompresses the inside of the tank.   A plurality of the vibrators are disposed, and when the organic matter in the tank does not reach a predetermined height, the plurality of vibrators are sequentially operated one by one, and the organic matter in the tank is placed at the predetermined height. The methane gas recovery apparatus according to any one of claims 1 to 3, wherein a plurality of the vibrators are simultaneously operated when the height is reached.

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