JP5284324B2 - Ammonia removal equipment - Google Patents

Description

  The present invention relates to an apparatus for removing ammonia that inhibits methane fermentation in a process of fermenting organic waste to produce useful biogas containing methane gas.

  Conventionally, techniques for producing useful biogas including methane gas by treating methane fermentation of organic waste such as livestock excrement and food waste with microorganisms such as methanogen have been widely proposed. Various techniques for removing ammonia that inhibits methane fermentation have been proposed.

  As an ammonia removal technique, for example, in the organic waste treatment method and treatment system disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2006-205017), an organic process is performed in the pre-process of the methane treatment process (methane fermentation tank). Soybean waste is solubilized, and ammonia fermentation is performed using microorganisms capable of generating ammonia and hydrogen, and the solubilized organic waste is methane removed after removing ammonia and hydrogen produced thereby. A technique for sending to a methane fermentation treatment process (methane fermentation tank) as a raw material has been proposed.

Further, in the method for treating ammonia-containing wastewater disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2006-334472), ammonia is recovered from the ammonia-containing wastewater containing ammonia generated from a semiconductor manufacturing process, a plating process, steelmaking facilities, and the like. As a method, a system using an ammonia stripping method is proposed. In the ammonia stripping method, wastewater is heated and air is blown into it to transfer the ammonia in the wastewater to the aeration gas, and further, the aeration gas is acid-washed to move the ammonia to the liquid side as an ammonium salt. It is to be collected. In Patent Document 2, (1) wastewater containing 500 ppm or more of ammonia is controlled by Moretana (a registered trademark of Fuji Kasui Kogyo Co., Ltd.) while controlling the pH of the waste water with an aqueous solution or dispersion of an alkali hydroxide to a pH of 8 or more and a temperature of 50 ° C. ) Ammonia is released as a gas by gas-liquid contact with an aeration gas supplied to the upper part of the scrubber and supplied from the lower part of the Moretanus scrubber. (2) A gas containing ammonia discharged from the Moretanus scrubber Has proposed a technique in which ammonia is fixed and recovered as an ammonium salt by passing it through another scrubber using an aqueous solution as an absorbent and bringing it into gas-liquid contact.

  In the biogas system of Patent Document 3 (Japanese Unexamined Patent Publication No. 2009-66557), in order to treat the digested liquid after methane fermentation, the digested liquid extracted from the methane fermentation tank is introduced into an ammonia stripping device to remove ammonia. A technique is proposed in which the digested liquid from which ammonia has been removed (denitrified digested liquid) is transferred to a storage tank and discharged from a drain valve provided in the storage tank as organic waste water. In the ammonia recovery process, gaseous or mist-like ammonia is absorbed in water stored in a condenser and recovered as ammonia water. The recovered ammonia water is denitrified and part of it is returned to the condenser so that it can be reused as ammonia-absorbed water.

  In the biogas system of Patent Document 4 (Japanese Unexamined Patent Publication No. 2009-66558), in order to treat the digested liquid after methane fermentation, the digested liquid extracted from the methane fermentation tank is introduced into an ammonia stripping device to remove ammonia. By removing the oxygen dissolved in the digestion solution in the deoxygenation step, the digestion solution after ammonia stripping can be returned to the methane fermenter and reused without giving oxidative stress to the methanogen Proposing technology. In this technology, nitrogen components (ammonia, nitrite nitrogen, etc.) produced by fermentation are dissolved in the digestive juice after methane fermentation, and if the concentration of nitrogen components increases, it will cause methane fermentation inhibition. The ammonia in the digestive liquid is removed so that the digestive liquid can be reused as a diluted liquid in the methane fermentation tank. In addition, deoxygenation of digestive fluid is performed to prevent anaerobic methanogens because their activities are significantly inhibited by the presence of molecular oxygen (oxidative stress).

JP 2006-205017 A JP 2006-334472 A JP 2009-66557 JP 2009-66558

  The use of livestock excrement such as poultry manure as organic waste (biomass), which is a raw material for producing biogas containing methane gas, has been studied, but livestock excreta is nitrogen containing ammonia that inhibits methane production. However, various problems remain for the realization. In the case of a raw material with a high nitrogen concentration, a method has been used to dilute and dilute the raw material with water (hydrolysis) to avoid inhibition of methane fermentation by ammonia, but a large amount of diluted water is required because the nitrogen content is high. As a result, the digested liquid after methane fermentation that occurs after the methane fermentation process also becomes large. Therefore, when the digestive juice is discharged as a waste solution, it may become a problem of environmental pollution, and countermeasures are required. In addition, the running cost for wastewater treatment becomes enormous. In particular, when a biogas production facility is installed in a secluded place where sewerage treatment facilities are not established, a large amount of wastewater is a major cause that hinders the realization of the biogas facility.

  Because of these issues, the reality is that it is difficult to realize despite many proposals to produce biogas from livestock waste containing high concentrations of nitrogen, such as chicken manure. It is in.

  In Patent Document 1, in order to be able to use organic waste containing high-concentration nitrogen as described above as a raw material for wet and dry methane fermentation, the raw material can be used before being supplied to the methane fermentation tank. Solubilization (reduction of the solid content of organic waste is reduced), establishment of temperature conditions capable of generating ammonia and hydrogen, thermal alkali treatment tank and ammonia stripping tank as ammonia removal means (Gas-liquid contact method) is proposed. In these methods, the pH is kept high by adding an alkaline agent, and ammonia is removed by further heating. However, when sending to the methane fermentation in the next step, it is necessary to add acid to neutralize to an appropriate pH (around 7). There is. For this reason, chemicals and heating energy increase running costs. As an ammonia stripping method, gas-liquid contact between a solubilized liquid raw material (organic waste) and air is known as in Patent Documents 2 to 4, but oxygen contained in air is anaerobic. Inhibits methane production (oxygen stress). As a countermeasure against oxygen stress, it is conceivable to provide a deoxygenating means as disclosed in Patent Document 4, but the equipment and its cost increase.

  The present invention has been made in view of the above points, and its purpose is to improve the treatment efficiency of ammonia removal even if the raw material for producing methane is a high-concentration nitrogen-containing livestock effluent, and the like. An object of the present invention is to provide an ammonia removing device that can contribute to shortening of the treatment time and the amount of waste water from the methane fermentation tank, and further eliminates the need for deoxygenating means even when an ammonia stripping method is employed.

  In order to achieve the above-mentioned object, the present invention basically takes out a part of the methanogenic raw material accommodated in the ammonia fermenter while taking it out of the fermenter and circulating it in an anaerobic atmosphere of a closed circulation system. Proposed is a closed circulation system ammonia removal device comprising a mechanism for gasifying and removing ammonia contained in a raw material and a mechanism for returning the raw material from which ammonia has been removed to the ammonia fermentation tank.

  According to the present invention, even if the raw material for producing methane is a high-concentration nitrogen-containing livestock effluent, etc., the ammonia removal treatment efficiency is improved, and particularly the treatment time for ammonia removal is shortened and the amount of wastewater from the methane fermentation tank is reduced. Can contribute. Furthermore, even when the ammonia stripping method is adopted as the ammonia removing means, it is possible to remove ammonia in an anaerobic atmosphere by a closed circulation system, so that a deoxygenating means is not required and equipment costs can be reduced. An ammonia removal apparatus can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS The whole schematic diagram which shows one Example of the system which implements the ammonia removal method of this invention. The schematic diagram which shows the 1st closed circulation system ammonia removal apparatus which performs the 1st step ammonia removal process in the system of FIG. The schematic diagram which shows the 2nd closed circulation system ammonia removal apparatus which performs the 2nd step | paragraph ammonia removal process in the system of FIG.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall schematic diagram showing an embodiment of a system for carrying out the ammonia removing method of the present invention, and FIG. 2 is a diagram of a first closed circulation system ammonia removing apparatus that executes a first stage ammonia removing step in the system. FIG. 3 is a schematic diagram of a second closed circulation system ammonia removal apparatus that executes a second stage ammonia removal step in the system.

  As shown in FIG. 1, this system is roughly divided into a raw material input device 1 for supplying organic waste as a methane generation raw material, a system 101 for executing a first stage ammonia removal process, and a second stage ammonia. The system 102 includes a removal process and peripheral devices (12 to 17).

  In the ammonia removal system according to the present embodiment, even when a high nitrogen concentration organic substance such as livestock excrement such as chicken manure is used as a methanogenic raw material, the ammonia removal efficiency is increased (the time for the ammonia removal process is shortened). In addition, the following treatment is performed in order to effectively reduce the water treatment amount (dilution water amount) and waste water amount of the entire system and to reduce the cost of thermal energy and the like.

  In the first stage ammonia removal system 101, an ammonia conversion step is first executed. In the ammonia conversion process, organic waste containing high nitrogen, which is a raw material for producing methane, is liquefied as the raw material decomposes in the ammonia fermenter 2 at the stage of processing before being sent to the methane fermenter 7 (possible Solubilize).

  The nitrogen component contained in the solubilized raw material is converted into ammonia in the ammonia fermenter 2 by an anaerobic microorganism or the like having the property of generating ammonia. Microorganisms have already been disclosed and well-known in many literatures, and will not be described here. In the ammonia conversion step, ammonia conversion can be performed within 24 hours without using chemicals such as pH adjustment by maintaining an appropriate conversion temperature (for example, about room temperature to 80 ° C.) and stirring conditions.

  In this embodiment, in order to increase the processing efficiency of ammonia removal and methane fermentation of organic waste containing high-concentration nitrogen, in this embodiment, a first stage ammonia removal system (raw material ammonia removal system) 101 before methane fermentation treatment and methane fermentation described later. A second stage ammonia removal system (fermented liquid / digested liquid ammonia removal system) 102 in the process is used in combination. By combining the two-stage ammonia removal system in this way, efficiency and thermal energy costs are reduced.

That is,
(A) In the first stage ammonia removal system 101, the raw material that has been subjected to ammonia conversion treatment in the ammonia fermenter 2 is introduced into the first closed circulation system ammonia removal device (3, 4) and circulated under an anaerobic atmosphere. However, ammonia contained in the raw material is gasified and removed at a concentration level (first concentration level) that does not reach the final target concentration level of methane fermentation. Here, the final target concentration level is a so-called allowable concentration that enables methane production to be generated at a practical level in the methane fermentation tank 7. For example, if the concentration of nitrogen contained in the material is very high, such as chicken manure, and the converted initial ammonia concentration is about 9000 ppm mg / L, ammonia removal is performed until it reaches about 6000 mg / L. Do. Although the structure of the first closed circulation system ammonia removal device (3, 4) will be described later, it is executed at a temperature of methane fermenter temperature to 80 ° C under an anaerobic atmosphere.

  The ammonia removal system 101 in the first stage performs the ammonia conversion process and the ammonia removal process in two steps, but can also be performed simultaneously.

  (B) The raw material subjected to the first stage ammonia removal step (system 101) is introduced into the methane fermentation tank 7, and a part of the raw material (methane fermentation broth) in the state of progress of solubilization is converted into methane. It is taken out to the second closed circulation system ammonia removing device (10, 11) outside the fermenter. The extracted methane fermentation liquor is circulated under an anaerobic atmosphere in the ammonia removal device (10, 11), and the allowable concentration level (for example, 3000 mg) in which ammonia contained in the methane fermentation liquor does not inhibit methane fermentation in the circulation process. / L or less). The methane fermentation broth after the ammonia removal treatment is returned to the methane fermentation tank 7. The configuration of the second closed circulation system ammonia removal device (10, 11) will be described later, but it is a temperature of methane fermentation tank to 80 ° C. in an anaerobic atmosphere as in the first closed circulation system ammonia removal device. It is driven by.

  In both ammonia removal systems 101 and 102, the first stage system 101 is inevitably operated initially, and then the raw material subjected to the first stage ammonia removal process is sent to the second stage system 102. If the raw material is supplied from the ammonia fermenter 2 to the first-stage system 101, then both systems can be operated in parallel. In this way, ammonia removal efficiency can be increased.

  Here, a specific configuration of the first and second stage ammonia removal systems will be described with reference to FIGS. 1, 2, and 3.

  The first closed circulation system ammonia removal device used in the first stage ammonia removal system 101 includes an ammonia diffusion tower 3 and an ammonia scrubber 4. As the stripping tower 3 for gasifying ammonia contained in the solubilized raw material, a moletana, a packed tower, and a spray system are effective, but among them, the spray system is preferable. Here, the spray method will be described as an example.

  In the spray method, the solubilized raw material in which the nitrogen contained in the ammonia fermenter 2 has been converted to ammonia in advance is converted into an ammonia diffusion tower through the pipe 20, the raw material supply valve 21 controlled to open the valve, and the pipe 23 and by driving the pump 22. 3 is stored in the lower part of the ammonia diffusion tower 3. At this time, the raw material supply valve 25 leading to the fermenter 7 is in a closed state.

  When the raw material is stored in the lower part of the ammonia diffusion tower 3, the valve 21 is closed, and the valve 24 is opened or controlled. In this state, the pump 22 is driven, the drive pump 26 of the ammonia scrubber 4 is driven, and the valve 27 leading from the ammonia scrubber 4 to the ammonium sulfate tank 5 is operated to be closed. In this state, the solubilized raw material (ammonia converted raw material) 40 stored in the lower part of the ammonia diffusion tower 3 is showered from the upper part of the diffusion tower 3 through the pump 22 and the pipe 23 as shown in FIG. An anaerobic atmosphere gas (this gas is initially air and oxygen is sent from the scrubber 4 through the fan 28 and the pipe 29 from the bottom of the ammonia diffusion tower 3. However, since it circulates between the closed diffusion tower 3 and the scrubber 4, carbon dioxide, ammonia gas, and water vapor become mainstream and become anaerobic atmosphere gas as it circulates). Thereby, the raw material in the shower form (droplet form: droplet form, granular form) and the anaerobic atmosphere gas are brought into gas-liquid contact, whereby the gas-liquid contact surface area is expanded, thereby efficiently gasifying ammonia. The gasified ammonia is sent to the ammonia scrubber 4, and the anaerobic atmosphere gas after the ammonia is removed by the scrubber 4 is sent to the ammonia diffusion tower 3 via the fan 28 and the gas circulation system pipe 29. Thus, an anaerobic atmosphere gas circulates between the two towers.

  The ammonia scrubber 4 stores an acidic liquid (for example, sulfuric acid) 41 for neutralizing ammonia in a replaceable manner, and collects ammonia by a shower (acid cleaning) of the acidic liquid 41 circulated through the pump 26 and the pipe 32. To do. The acidic liquid 41 collected by the ammonia scrubber 4 is controlled to a pH of 3 to 4 or less, for example, by a chemical liquid injection unit (not shown). When the ammonia concentration in the ammonia-converted raw material is lowered to the first-stage concentration level by the ammonia removal, the first ammonia removal step is completed, the valve 25 leading to the methane fermentation tank 7 is opened, and the pump 22 is driven. Thus, the raw material in the ammonia diffusion tower 3 is sent to the methane fermentation tank 7. When the ammonium sulfate solution at the lower part of the scrubber 4 is replaced, the valve 27 provided at the lower part is opened, and the ammonium sulfate is sent to the ammonium sulfate tank 5 via the pump 30 and stored, and used as a raw material such as fertilizer.

  In the first stage ammonia removal step, the ammonia diffusion tower 3 and the ammonia scrubber 4 constituting the closed circulation system ammonia removal device are provided with a heater and a temperature sensor (both not shown), and a temperature control device between them. 31 is controlled at an isothermal temperature of methane fermenter temperature to 80 ° C. Further, the ammonia diffusion tower 3 and the ammonia scrubber 4 constitute a closed circulation system closed from the outside air, and the inside of each tower is maintained in a gas-liquid equilibrium state. Therefore, since the closed circulation system is in an isothermal and gas-liquid equilibrium state, heat exchange (evaporation and condensation) between the diffusion tower 3 and the scrubber 4 is suppressed. Therefore, it is possible to suppress the evaporation or condensation of water in the ammonia diffusion tower 3 to suppress the fluctuation of moisture in the solubilized raw material, to suppress the evaporation or condensation of water in the ammonia scrubber 4, and to suppress the fluctuation in neutralized water concentration. . That is, energy consumption between the stripping tower and the scrubber is suppressed.

  When exhausting the gas in the system for maintenance or the like, a part of the gas that has passed through the ammonia scrubber 4 is opened to the atmosphere via the deodorizer 6 to reduce the capacity of the deodorizer in order to prevent odor. To do.

  By increasing the temperature of the raw material at a temperature of methane fermentation tank to 80 ° C. in the first stage ammonia removal system 101, solubilization of the raw material proceeds, and the efficiency of methane fermentation can be improved as a secondary effect.

  As described above, the raw material from which ammonia is removed to about 6000 mg / L, for example, is then sent to the fermenter 7 where it is subjected to methane fermentation using anaerobic microorganisms that generate methane. In order to produce methane in the methane fermentation tank 7, the ammonia concentration can still be an inhibiting factor for methane production. Therefore, a part of the solubilized raw material (methane fermentation liquid) of the methane fermentation tank 7 is placed outside the methane fermentation tank. The second stage ammonia removal step is performed using the second closed circulation system ammonia removal device (ammonia diffusion tower 10 and ammonia scrubber 11).

  In this embodiment, a part of the methane fermentation liquid in the methane fermentation tank 7 is driven to the ammonia diffusion tower 10 through the pipe 34, the valve 56 in the valve open state, the heat exchanger 9, and the heater 8 by driving the pump 33. Supplied. In this case, the valve 55 leading to the stage of the methane fermentation tank (flocculation tank 12) and the valve 54 provided in the return pipe 52 between the outlet side of the stripping tower 10 and the methane fermentation tank 7 are in a closed state, and the return pipe 52 The pump 53 provided in is in a stopped state. The functions of the heat exchanger 9 and the heater 8 will be described later.

  As the ammonia-dispersing tower 10 used in the second stage ammonia removal system 102, the system of moretana, packed tower, and spray may be effective, and any of them may be used. Of these, the moretana system is preferable. To do.

  In the Moretana method, as shown in FIG. 3, a porous shelf 44 for gas-liquid contact is provided in the ammonia diffusion tower 10, but an air-permeable filler can be used instead of the porous shelf. .

  A part of the methane fermentation liquid taken out from the methane fermentation tank 7 is stored in the lower part of the stripping tower 10 (indicated by reference numeral 42), and this methane fermentation liquid 42 is passed from the upper part of the stripping tower 10 through the pump 35 and the pipe 36. It is dropped on the upper surface of the porous shelf stage 44. Anaerobic atmosphere gas from the ammonia scrubber 11 side is fed into the tower from under the stripping tower 10. This anaerobic atmospheric gas is initially air and contains oxygen, similar to that used in the first stage ammonia removal system 101, but circulates between the closed diffusion tower 10 and the scrubber 11. As it circulates, carbon dioxide, ammonia gas, and water vapor become mainstream and become an anaerobic atmosphere gas.

  In the region of the perforated shelf 44, the methane fermentation liquid dripped from above comes into contact with the anaerobic atmosphere gas fed from below (gas-liquid contact), thereby anaerobic from the droplet surface of the methane fermentation liquid. Ammonia is gasified and diffused in the atmospheric gas (circulation gas). The ammonia gas diffused in the stripping tower 10 is supplied to the ammonia scrubber 11 through the circulation gas pipe 38 and the fan 39, and the ammonia gas is absorbed into the acidic liquid by the acidic cleaning of the acidic liquid 43 to remove the ammonia. Is called. The anaerobic atmosphere gas from which ammonia has been removed is returned to the scrubber 11 and used for gas-liquid contact (ammonia stripping by gas-liquid contact between an acidic liquid and ammonia gas) as described above.

  In the present embodiment, the ammonia scrubber 11 also adopts the Moretana method, and the porous shelf 45 is loaded in the scrubber 11 tower. The shelf 45 may use a breathable filler. As the scrubber 11, moretana, packed tower and spray system are effective, and any of them may be used. At the time of ammonia removal in the second stage, ammonia is removed at the pH of the methane fermentation broth (around 7-8) without using any chemical for pH adjustment.

  Further, the second closed circulation system ammonia diffusion tower 10 and the ammonia scrubber 11 are also controlled isothermally (the methane fermentation tank temperature to 80 ° C.) via the temperature control device 51 as in the first stage ammonia removal system. Both are kept in a vapor-liquid equilibrium state (isothermal / vapor-liquid equilibrium state). Since the advantages of the isothermal / gas-liquid equilibrium state are the same as those described in the first ammonia removal system, description thereof will be omitted.

The fermentation liquor 42 supplied to the ammonia stripping tower 10 is (1) circulated through the path of the stripping tower 10 and the pipe 36 until the final target concentration level (second stage, for example, 3000 mg / L or less) is reached, thereby removing ammonia. After being removed, it is returned to the methane fermentation tank 7 via the return pipe 52, or (2) after the ammonia is removed by circulation through the path of the stripping tower 10 and the pipe 36 for a specified number of times (one or more times). Then, it is returned to the methane fermentation tank 7 via the return pipe 52.

  When the methane fermentation liquid from the ammonia diffusion tower 10 is returned to the methane fermentation tank 7, the pump 33 is stopped, the valve 54 of the return pipe 52 is opened, and the pump 53 is driven. After this fermentation broth return, the valve 54 is closed, the pump 53 is stopped, the pump 33 is driven again, and the methane fermentation liquor is supplied from the methane fermentation tank 7 to the ammonia stripping tower 10, and then the ammonia removal step described above. I do.

  By repeating such a series of steps, the ammonia concentration in the methane fermentation tank 7 can be reduced to a final target concentration level (for example, 3,000 mg / L) or less.

  In the present embodiment, the pipe 37 for sending the methane fermentation liquid from the methane fermentation tank 7 to the diffusion tower 10 of the closed circulation system ammonia removal mechanism is provided with the heat exchanger 9 and the heater 8 from the upstream side to the downstream side to dissipate. A pipe for returning the methane fermentation liquid from the tower 10 to the methane fermentation tank 7 is connected to the methane fermentation tank 7 via the heat exchanger 9. In order to improve the thermal efficiency of the second stage ammonia removal system (methane fermentation liquid ammonia removal system) 102, the methane fermentation liquid extracted from the methane fermentation tank 7 passes through the regenerative heat exchanger 9 and the heater 8. After the temperature is raised, it is introduced into the diffusion tower 10. Further, the methane fermentation liquor returned from the stripping tower 10 to the methane fermentation tank 7 is lowered to the temperature at which the methane fermentation tank 7 is charged by the regenerative heat exchanger 9 described above. By doing in this way, the ammonia removal efficiency improvement and the temperature rise in the methane fermentation tank 7 are suppressed.

  Moreover, the heat of the fermentation liquor whose temperature has been adjusted by the heater 8 and the heat exchanger 9 is used to maintain the temperature of the methane fermentation tank, and efficient energy use can be achieved.

  A part of the methane fermentation broth (so-called digestive juice) is reused as water to keep the water content of the methane fermentation broth appropriately (returning the digestive juice back to the fermentor will be described later). Since ammonia produced at the time of methane fermentation is contained, ammonia removal is performed using the second closed circulation system ammonia removal system 102. After the ammonia concentration has decreased to a level that can be used as dilution water, the digested liquid in the methane fermentation tank 7 is sent to the water tank 16 for reuse via the solid-liquid separator 13 by opening the valve 55. It is done.

  In this case, if the moisture content of the raw material of the methane fermentation tank 7 is 70% or less, the amount of water brought in by the raw material is balanced with the amount of water contained in the solid residue separated by the solid-liquid separation device 17, It is possible to minimize the digestive drainage discharged to the outside (nearly zero in some cases). The desorbed water separated by the solid-liquid separator 13 is stored in the water tank 16 and returned to the methane fermentation tank 7 as a recycle liquid, and the desorbed liquid that is not reused passes through the waste water treatment facility 17 and the like. To be discharged. Even if the desorbed liquid is returned to the methane fermenter, concentration of ammonia can be prevented, so that the desorbed liquid can be reused and the amount of drainage can be reduced.

  When digestion liquid with less fiber is processed in the solid-liquid separation device 13, in order to improve the recovery rate of solid content, a condensing tank 12 is installed in the previous stage of the solid-liquid separation device, and a polymer flocculant and rice cake are collected. Alternatively, sawdust or the like may be added to improve the solid content recovery rate.

  The solid matter separated by the solid-liquid separator is processed in a carbonization furnace or composting equipment via a hopper stirrer to obtain a carbide or compost.

According to this example,
(1) Since ammonia removal, which is a factor in inhibiting methane fermentation, is performed by using a two-stage ammonia removal system in the methane fermentation pre-stage and methane fermentation stage, organic waste containing high-concentration nitrogen is used. Even in this case, no water is added or the amount of dilution water from the outside is reduced as much as possible, and the ammonia removal can be executed with good efficiency (reduction of time and energy consumption) and sufficient margin. As a result, the amount of waste water, which was a major impediment, could be greatly reduced, and a methane production facility using organic waste containing high-concentration nitrogen at a practical level could be realized.

Needless to say, the present invention is applicable not only to high nitrogen content but also to low nitrogen content organic waste.
(2) Further, even when an ammonia stripping method is adopted as an ammonia removal means, it is possible to remove ammonia in an anaerobic atmosphere by a closed circulation system, so that a deoxygenation means is not required and equipment costs are reduced. Can be achieved.
(3) Moreover, since the space between the ammonia diffusion tower and the ammonia scrubber can be maintained in an isothermal and gas-liquid equilibrium state, the ammonia carrier gas (circulation gas) used for water evaporation of the material solubilized in the ammonia removal step and ammonia removal ) Can be suppressed and energy consumption during ammonia removal can be suppressed.
(4) Since the digestive juice can be recycled by returning it to the methane fermentation tank, the amount of waste water can be suppressed as much as possible.
(5) When returning the methane fermentation liquor subjected to the ammonia removal step to the methane fermentation tank, the temperature of the methane fermentation tank can be maintained at a preferable temperature using a heater and a regenerative heat exchanger. And energy consumption can be achieved.

DESCRIPTION OF SYMBOLS 2 ... Ammonia fermenter, 3, 4 ... 1st closed circulation system ammonia removal apparatus (ammonia diffusion tower, ammonia scrubber), 7 ... Methane fermenter, 8 ... Heater, 9 ... Heat exchanger, 10, 11 ... 2nd A closed circulation system ammonia removal device (ammonia diffusion tower, ammonia scrubber), 31 ... temperature control device, 51 ... temperature control device, 101 ... first stage ammonia removal system, 102 ... second stage ammonia removal system.

Claims (1)

A portion of the methane product ingredients contained in the ammonia fermenter, the ammonia contained in the raw material while circulating under anaerobic atmosphere closed circulation system taken out of the fermenter comprises a machine structure to remove gasified,
Mechanism for removing gasifying the ammonia, the ammonia stripping column to the gas by the gas-liquid contact with anaerobic atmosphere gas the raw material in the column of anaerobic atmosphere,
An ammonia scrubber that removes ammonia by acid cleaning the ammonia gas with an acidic liquid in an anaerobic atmosphere;
A gas circulation mechanism for circulating an anaerobic atmosphere gas between the ammonia diffusion tower and the ammonia scrubber to convey the ammonia gas diffused in the ammonia diffusion tower to the ammonia scrubber;
A closed circulation system ammonia removing apparatus comprising a temperature control device for isothermal control between the ammonia diffusion tower and the ammonia scrubber in a gas-liquid equilibrium state .

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