Processing System

Abstract

To provide a treatment system with improved measures against odors from decomposition gases generated during hydrothermal treatment. [Solution] The system comprises a fermenter 2 that generates biogas by anaerobic fermentation of organic waste, and a hydrothermal treatment device 4 that hydrothermally treats the organic waste. It also has an inlet 7 for mixing the decomposition gas generated in the hydrothermal treatment device 4 with the biogas.

Description

[Technical Field]

[0001] The present invention relates to a treatment system for hydrothermal treatment of organic waste. [Background technology]

[0002] BACKGROUND ART Conventionally, a treatment system is known in which organic waste is fermented by methane fermentation and then hydrothermally treated (see, for example, Patent Document 1).

[0003] The treatment system described in Patent Document 1 includes a digester tank that performs methane fermentation of organic waste, and a hydrothermal carbonization device that hydrothermally carbonizes the dehydrated sludge discharged from the digester tank. In the hydrothermal carbonization device, the dehydrated sludge is treated at high temperature and high pressure in a gas atmosphere that does not contain oxygen or has a low oxygen concentration. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-111869 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in the hydrothermal carbonization apparatus described in Patent Document 1, decomposition gas is generated when dewatered sludge is treated at high temperature and high pressure, and since this decomposition gas has an odor, it is necessary to remove the odor using a deodorization facility before releasing it into the atmosphere. Deodorization facilities that contain activated carbon or the like are often used, but since the decomposition gas has a strong odor, there is room for improvement in removing the odor from the decomposition gas.

[0006] Therefore, there is a demand for a treatment system that can improve odor control for decomposition gases generated during hydrothermal treatment. [Means for solving the problem]

[0007] The treatment system according to the present invention is characterized by comprising a fermenter that subjects organic waste to anaerobic fermentation to produce biogas, and a hydrothermal treatment device that hydrothermally treats the organic waste, and an inlet passage for mixing the decomposition gas generated in the hydrothermal treatment device with the biogas.

[0008] In this configuration, organic waste is hydrothermally treated. This allows the organic matter to be treated under environmentally friendly conditions, producing, for example, charcoal for recycling. However, when organic matter is treated under high temperature and pressure, decomposition gases are generated, which are accompanied by an odor.

[0009] Therefore, by providing an introduction path for mixing the decomposition gas generated in the hydrothermal treatment device with the biogas as in this configuration, the odor of the entire treatment system can be reduced because the decomposition gas is mixed with the biogas and diluted.

[0010] In this way, the treatment system takes into consideration measures to combat the odor of decomposition gases generated during hydrothermal treatment.

[0011] Another characteristic feature of the present invention is that the organic waste to be hydrothermally treated in the hydrothermal treatment device is a treated product that has been fermented in the fermenter.

[0012] If the organic waste to be hydrothermally treated in the hydrothermal treatment device as in this configuration is a treated product that has been fermented in a fermenter, it is possible to shorten the piping length of the inlet path, thereby making the entire treatment system more compact.

[0013] Another characteristic feature is that the inlet passage is connected to the fermenter.

[0014] By returning the decomposition gas generated in the hydrothermal treatment device to the fermenter as in this configuration, the odor of the entire treatment system can be further reduced. This is because the fermenter is an anaerobic fermentation treatment system, so it prevents the intrusion of oxygen-containing outside air and is sealed to prevent gas from leaking to the outside, thereby significantly reducing the risk of the odor of the decomposition gas returned from the inlet line leaking to the outside.

[0015] Another characteristic feature of the present invention is that a condenser for collecting condensed water formed by condensing moisture in the decomposition gas is disposed in the introduction path.

[0016] In this configuration, by separating and collecting the wastewater components consisting of condensed water formed by condensing the water in the decomposition gas in a condenser placed in the inlet line from the gas components, odor control measures for the relatively strong-smelling wastewater components can be implemented separately. As a result, odor control measures for the relatively strong-smelling wastewater components can be considered separately, and odor control measures for the entire treatment system can be made more efficient.

[0017] Another characteristic feature is that a water supply passage is provided for sending the condensed water to the fermenter.

[0018] In this configuration, by providing a water supply channel for sending condensed water, which is a wastewater component with a relatively strong odor, to the fermenter, the wastewater components of the decomposition gas are mixed and diluted in the fermenter, thereby further reducing the odor of the decomposition gas.

[0019] Another characteristic feature is that the system further includes a water treatment facility for treating wastewater, the organic waste introduced into the fermenter is sludge generated in the water treatment facility, and a branch path branches off from the inlet path and sends the condensed water upstream of the water treatment facility.

[0020] In this configuration, by providing a branch path that sends condensed water, a wastewater component with a relatively strong odor, upstream of the water treatment facility, the wastewater components of the decomposition gas are mixed with the wastewater introduced into the water treatment facility and diluted. This further reduces the odor of the decomposition gas. Furthermore, since the odorous components are treated in the water treatment facility by being adsorbed by sludge, there is no need to install a separate odor treatment facility.

[0021] Another characteristic feature of the present invention is that it further comprises a gas generator that generates electricity using the biogas produced in the fermenter as fuel.

[0022] As in this configuration, even if the biogas produced in the fermenter is supplied to a gas generator as fuel, the volume of decomposition gas is sufficiently small compared to biogas, so there is no reduction in power generation performance. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a block diagram showing a configuration of a processing system according to a first embodiment. [Figure 2] FIG. 10 is a block diagram showing the configuration of a processing system according to a second embodiment. [Figure 3] FIG. 10 is a block diagram showing the configuration of a processing system according to a third embodiment. [Figure 4] FIG. 10 is a block diagram showing the configuration of a processing system according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0024] An embodiment of a treatment system according to the present invention will be described below with reference to the drawings. In this embodiment, a treatment system X that performs methane fermentation treatment and hydrothermal treatment on organic waste will be described as an example. However, the present invention is not limited to the following embodiment, and various modifications are possible within the scope of the present invention.

[0025] The organic waste to be treated in the treatment system X of this embodiment includes sewage sludge, food waste (food biomass) such as food waste, lignocellulosic waste such as used paper and waste paper, agricultural residues, and livestock manure. These organic wastes may be treated individually or in combination. The sludge generated from the water treatment facility 1 that treats wastewater will be described as the organic waste. The wastewater includes sewage, industrial wastewater, domestic wastewater, factory wastewater, etc. Examples of the water treatment facility 1 that treats wastewater include sewage treatment facilities that treat sewage and wastewater treatment facilities that treat wastewater.

[0026] 1 to 4, the treatment system X includes a water treatment facility 1, a methane fermentation tank 2 (an example of a fermentation tank), a dehydrator 3, a hydrothermal treatment device 4, a solid-liquid separator 5, a deodorization facility 6, an introduction path 7, and a gas generator 8. Note that the treatment system X in this embodiment is only required to include at least the methane fermentation tank 2, the hydrothermal treatment device 4, and the introduction path 7.

[0027] The water treatment facility 1 treats wastewater. As an example, the sewage treatment facility includes a first settling tank that settles suspended matter and organic matter contained in the wastewater and removes the sludge (primary sludge) that has settled to the bottom, a biological treatment tank that biologically treats and decomposes the organic matter in the sewage, and a second settling tank that settles the decomposed sludge and separates the treated water from the sludge (secondary sludge).

[0028] The methane fermentation tank 2 is a tank that performs anaerobic fermentation treatment on sludge (an example of organic waste) discharged from the water treatment facility 1. Because the methane fermentation tank 2 performs anaerobic fermentation treatment, it is sealed to prevent the intrusion of oxygen-containing outside air and to prevent gas from leaking to the outside. The solid concentration of the sludge introduced into the methane fermentation tank 2 is, for example, 3 to 9 wt %. In the methane fermentation tank 2, the temperature is about 30 to 42°C and the retention time is about 15 to 30 days for mesophilic fermentation treatment, and the temperature is about 50 to 60°C and the retention time is about 7 to 20 days for thermophilic fermentation treatment.

[0029] The methane fermentation tank 2 generates biogas within the methane fermentation tank 2 through anaerobic fermentation of the sludge. By subjecting the sludge to anaerobic fermentation, the energy contained in the sludge can be recovered as gas energy. Biogas is a gas that is approximately 60% by volume methane and approximately 40% by volume carbon dioxide. The generated biogas is extracted from the methane fermentation tank 2 via a gas discharge path 21 and supplied to the gas generator 8. The biogas supplied to the gas generator 8 is used as fuel for the gas generator 8. The biogas may also be used as fuel for heating the methane fermentation tank 2 and the hydrothermal treatment device 4.

[0030] The fermentation residue of the sludge after anaerobic fermentation treatment in the methane fermenter 2 is discharged to the outside from the methane fermenter 2. The fermented sludge (an example of a treated product) discharged to the outside from the methane fermenter 2 is supplied to the dehydrator 3. The solid concentration of the fermented sludge is, for example, 1.5 to 5% by mass. The dehydrator 3 is a machine that dehydrates the fermented sludge discharged from the methane fermenter 2. The dehydrator 3 can be any of a belt press dehydrator, a centrifugal dehydrator, a screw press dehydrator, a filter press dehydrator, a belt concentrator, and a centrifugal concentrator. Of course, the dehydrator 3 can also be configured using other dehydrators.

[0031] The dehydrator 3 turns the fermented sludge into dehydrated sludge (an example of a treated product) with a moisture content of, for example, about 80% by mass. The dehydrated filtrate separated from the fermented sludge by the dehydrator 3 is sent to a separated liquid treatment device (not shown). This separated liquid treatment device is, for example, a device that subjects the dehydrated filtrate to acidic coagulation and sedimentation treatment.

[0032] Organic waste such as dewatered sludge is supplied to a hydrothermal treatment device 4. The hydrothermal treatment device 4 hydrothermally treats the organic waste such as dewatered sludge whose moisture content has been reduced by the dehydrator 3. The hydrothermal treatment treats the organic waste such as dewatered sludge at high temperature and high pressure in a gas atmosphere that does not contain oxygen or has a low oxygen concentration, or in a state where oxygen is blocked, thereby carbonizing the dewatered sludge.

[0033] In the hydrothermal treatment device 4, first, organic waste such as dewatered sludge supplied from the dehydrator 3 is preheated. The preheated organic waste such as dewatered sludge is subjected to high-temperature, high-pressure treatment in a reactor (not shown). The reactor is a container that performs high-temperature, high-pressure treatment in a gas atmosphere that does not contain oxygen or has a low oxygen concentration, or in a state where oxygen is blocked. As an example, the reactor performs high-temperature, high-pressure treatment on organic waste such as dewatered sludge in a gas atmosphere with an oxygen concentration of 5% by volume or less. This high-temperature, high-pressure treatment is performed in the reactor provided in the hydrothermal treatment device 4, and the oxygen concentration in the reactor is maintained at approximately 0% by volume during this treatment. In the reactor, the carbonized sludge (sludge slurry) and the organic waste such as dewatered sludge supplied to the reactor are mixed and stirred.

[0034] The reactor is surrounded by a jacket (not shown), and a heat transfer medium heated by thermal energy from the waste heat of the gas generator 8 flows through this jacket. The heat transfer medium heats the sludge slurry in the reactor to, for example, 200°C. At this time, the pressure inside the reactor is set to a pressure equivalent to that of subcritical water corresponding to the temperature inside the reactor plus the pressure of the gas generated by the decomposition of the components of the material to be treated. The temperature of the sludge slurry in the reactor is not limited to 200°C and may be any temperature within the range of, for example, 160°C to 250°C. The pressure inside the reactor is set to a gauge pressure of approximately 0.6 MPa to 3 MPa. Therefore, in the hydrothermal treatment device 4, high-temperature, high-pressure treatment is performed when the temperature of the organic waste, such as dewatered sludge, is between 160°C and 250°C, and the gauge pressure inside the reactor is between 0.6 MPa and 3 MPa.

[0035] The decomposition gas generated by the decomposition of the components of the material to be treated in the reactor is mixed with the biogas via the inlet path 7. That is, the treatment system X of this embodiment has an inlet path 7 for mixing the decomposition gas generated in the reactor of the hydrothermal treatment device 4 with the biogas. This decomposition gas is generated when organic matter is treated at high temperature and high pressure, and therefore has an odor. Therefore, by providing an inlet path 7 for mixing the decomposition gas generated in the hydrothermal treatment device 4 with the biogas as in this embodiment, the odor of the entire treatment system X can be reduced. This is because the decomposition gas is mixed with and diluted by the biogas.

[0036] Meanwhile, the sludge slurry obtained by hydrothermal treatment in the reactor is cooled and supplied to the solid-liquid separator 5. The solid-liquid separator 5 separates the sludge slurry supplied from the hydrothermal treatment device 4 into solid and liquid. The solid-liquid separator 5 is a machine that dewaters the sludge slurry supplied from the hydrothermal treatment device 4. The solid-liquid separator 5 is not particularly limited, but is preferably a filter press dehydrator. The sludge slurry is in a state where fine carbonized particles are dispersed in water. For this reason, a filter press dehydrator is suitable, as it has fine filter openings and can achieve a high solid recovery rate even when compressed at high pressure. Of course, the solid-liquid separator 5 can also be configured using other dehydrators, such as a centrifugal dehydrator or a screw press dehydrator.

[0037] The sludge slurry obtained by solid-liquid separation in the solid-liquid separator 5 becomes a solid material consisting of carbonized sludge with a moisture content of, for example, 35% by mass or less. This solid material is supplied to a curing vessel (not shown) consisting of a curing hopper, where it is dried by contact with oxygen-containing air and subjected to low-temperature oxidation treatment. This reduces the exothermic ignition property of the solid material (carbonized sludge), and the resulting carbonized material can be recycled as fertilizer or solid fuel.

[0038] Odors generated from the sludge slurry, the solids and dewatered filtrate discharged from the solid-liquid separator 5, and odorous gases generated within the solid-liquid separator 5 and the curing vessel are supplied to the deodorizing equipment 6 for deodorization. The deodorizing equipment 6 has an activated carbon filter that adsorbs odorous components (so-called malodorous components, mainly hydrogen sulfide, ammonia, volatile organic compounds, etc.), and releases gas with reduced odorous component concentrations (reduced to a level that meets regulations in the area where the deodorizing equipment 6 is installed) into the atmosphere. Meanwhile, the dewatered filtrate discharged from the solid-liquid separator 5 may be returned to the methane fermentation tank 2, or may be subjected to acidic coagulation and sedimentation treatment in the above-mentioned separated liquid treatment device (not shown).

[0039] In this way, organic waste is hydrothermally treated in the hydrothermal treatment device 4. This allows organic matter to be treated under environmentally friendly conditions without using organic solvents, and for example, carbonized material can be produced and recycled. On the other hand, decomposition gas is generated when organic matter is treated at high temperature and high pressure, and this decomposition gas is accompanied by an odor. Therefore, by providing an inlet 7 for mixing the decomposition gas generated in the hydrothermal treatment device 4 with biogas, as in this embodiment, the odor of the entire treatment system X can be reduced. This is because the decomposition gas is mixed with and diluted by the biogas. In this way, the treatment system X is designed to address the odor of the decomposition gas generated by hydrothermal treatment.

[0040] Furthermore, even if the decomposition gas is mixed and supplied to a gas generator 8 that uses the biogas produced in the methane fermentation tank 2 as fuel, the volume of the decomposition gas is sufficiently small compared to the biogas, so there is no reduction in power generation performance.

[0041] (First embodiment) A first embodiment of the introduction line 7 will be described below with reference to FIG. 1 . The introduction line 7 is a mixing introduction pipe for mixing the decomposition gas generated in the hydrothermal treatment device 4 with the biogas produced in the methane fermentation tank 2. In this embodiment, the introduction line 7 is connected to the methane fermentation tank 2. A condenser 71 is disposed in the introduction line 7, which collects condensed water obtained by condensing the moisture in the decomposition gas. A water supply line 72 is also provided for sending the condensed water to the methane fermentation tank 2. The introduction line 7 may be connected to either the gas phase or liquid phase of the methane fermentation tank 2. However, in the case of the liquid phase, it is necessary to increase the supply pressure in consideration of the hydraulic head difference. Therefore, it is preferable to connect the introduction line 7 to the gas phase. However, when the introduction line 7 is connected to the liquid phase, water-soluble gases such as ammonia are dissolved in the liquid phase and reduced, so the introduction line 7 can be appropriately selected during design. When the introduction line 7 is connected to the liquid phase, the decomposition gas passes through the liquid phase and reaches the gas phase, where it is mixed with the biogas.

[0042] The cracked gas generated in the hydrothermal treatment device 4 is at high temperature and pressure, and therefore exchanges heat with the outside air as it flows through the inlet line 7, generating condensed water. The condenser 71 is composed of a sealed drain tank or the like provided in the piping of the inlet line 7 and can store the condensed water. The condensed water stored in the condenser 71 is introduced into the upper space of the methane fermentation tank 2 via the water supply line 72 by driving the pump P. This water supply line 72 may be connected to either the gas phase or liquid phase of the methane fermentation tank 2. However, in the case of the liquid phase, it is necessary to increase the supply pressure in consideration of the hydraulic head difference, so it is preferable to connect it to the gas phase (upper space). The condenser 71 actively separates the moisture in the cracked gas, preventing moisture from accumulating in the piping of the inlet line 7 and obstructing the flow of gas. The condenser 71 may be, for example, a drain pot provided with a cooling jacket around the periphery of a cyclone separator to promote cooling. However, there are no particular limitations on the condensed water that can be collected by condensing the moisture in the cracked gas.

[0043] Returning the decomposition gas generated in the hydrothermal treatment device 4 to the methane fermentation tank 2 as in this embodiment can further reduce the odor of the entire treatment system X. This is because the methane fermentation tank 2 is sealed to prevent the intrusion of oxygen-containing outside air and to prevent gas leakage to the outside due to the anaerobic fermentation process, significantly reducing the risk of the odor of the decomposition gas returned from the inlet line 7 leaking to the outside. Furthermore, by separating and collecting the wastewater component consisting of condensed water formed by condensing the water in the decomposition gas in the condenser 71 disposed in the inlet line 7 from the gas component, odor control measures for the relatively strong-smelling wastewater component can be implemented separately. As a result, odor control measures for the relatively strong-smelling wastewater component can be considered separately, thereby improving the efficiency of odor control measures for the entire treatment system X. Furthermore, by providing a water supply line 72 for sending condensed water, a relatively strong-smelling wastewater component, to the methane fermentation tank 2 as in this embodiment, the decomposition gas and the wastewater component are mixed and diluted in the methane fermentation tank 2. This further reduces the odor of the decomposition gas.

[0044] Furthermore, in this embodiment, dehydrated sludge (an example of a material to be treated) that has been fermented in the methane fermenter 2 and dehydrated in the dehydrator 3 is treated as organic waste and hydrothermally treated in the hydrothermal treatment device 4. Specifically, the fermented sludge that has been fermented in the methane fermenter 2 is dehydrated in the dehydrator 3 to reduce its moisture content and is then supplied to the hydrothermal treatment device 4. Note that the fermented sludge that has been fermented in the methane fermenter 2 may be directly supplied to the hydrothermal treatment device 4 without going through the dehydrator 3. In this way, if the organic waste to be hydrothermally treated in the hydrothermal treatment device 4 is a material that has been fermented in the methane fermenter 2, it is possible to shorten the piping length of the inlet path 7, and the overall treatment system X can be made more compact.

[0045] Second Embodiment A second embodiment of the introduction path 7 will be described below with reference to Fig. 2. In this embodiment, only the differences from the first embodiment will be described, and in order to facilitate understanding of the invention, similar members will be denoted by the same reference numerals.

[0046] In this embodiment, a duct for introducing decomposition gas from the hydrothermal treatment device 4 is directly connected to a duct for discharging biogas from the methane fermentation tank 2. The other configurations are the same as those in the first embodiment, and therefore description thereof will be omitted. In this embodiment as well, if the decomposition gas generated in the hydrothermal treatment device 4 is returned to the methane fermentation tank 2, the odor of the entire treatment system X can be further reduced. Furthermore, even if the decomposition gas is directly mixed with the biogas and supplied to the gas generator 8, the power generation performance is not reduced because the volume of the decomposition gas is sufficiently smaller than that of the biogas.

[0047] (Third embodiment) A third embodiment of the introduction path 7 will be described below with reference to Fig. 3. In this embodiment, only the differences from the first embodiment will be described, and in order to facilitate understanding of the invention, similar members will be denoted by the same reference numerals.

[0048] The treatment system X in this embodiment has a branch path 9 that branches off from the inlet path 7 and sends condensed water to the upstream side of the water treatment facility 1. A drainage pit 91 that stores condensed water is arranged in the branch path 9, and the condensed water is mixed with the wastewater introduced into the water treatment facility 1 by the driving force of a pump P. The other configurations are the same as those of the first embodiment, and therefore description thereof will be omitted. As in this embodiment, by providing the branch path 9 that sends condensed water, which is a wastewater component with a relatively strong odor, to the upstream side of the water treatment facility 1, the wastewater components of the decomposition gas are mixed with and diluted by the wastewater introduced into the water treatment facility 1. This makes it possible to further reduce the odor of the decomposition gas. Furthermore, since the odorous components are treated in the water treatment facility 1 by being adsorbed by sludge, etc., there is no need to provide a separate odor treatment facility.

[0049] (Fourth embodiment) A fourth embodiment of the introduction path 7 will be described below with reference to Fig. 4. In this embodiment, only the differences from the first embodiment will be described, and in order to facilitate understanding of the invention, similar members will be denoted by the same reference numerals.

[0050] In the treatment system X of this embodiment, the methane fermentation tank 2 and the hydrothermal treatment device 4 are provided in separate systems. The other configurations are the same as those of the first embodiment, so a description thereof will be omitted. Even in this case, the organic waste supplied to the hydrothermal treatment device 4 can be sewage sludge transported from another system, food waste (food-related biomass) such as food waste, lignocellulosic waste such as used paper and waste paper, agricultural residues, and livestock manure. This embodiment also produces the same effects as the first embodiment.

[0051] [Other embodiments] (1) The water treatment facility 1 in the above-described embodiment may be omitted. In this case, the organic waste to be supplied to the methane fermentation tank 2 is transported and carried in from another system. (2) The dehydrator 3 in the above-described embodiment may be omitted. In this case, the organic waste supplied to the hydrothermal treatment device 4 will have a higher moisture content, but by increasing the treatment time and treatment energy in the hydrothermal treatment device 4, a similar sludge slurry can be produced. (3) The solid-liquid separator 5 in the above-described embodiment may be omitted. In this case, the carbonized material can be used in cases where a low moisture content as described above is not required. (4) The gas generator 8 in the above-described embodiment may be omitted. In this case, the biogas may be used as fuel in other facilities, or may be stored in a tank and distributed. (5) The deodorizing equipment 6 in the above-described embodiment may be an incinerator, a biological deodorizing device, a wet deodorizing device, or the like. (6) The methane fermenter 2 in the above-described embodiment is not particularly limited as long as it is a fermenter that can generate biogas by anaerobic fermentation treatment. [Industrial Applicability]

[0052] The present invention can be used in a treatment system for hydrothermal treatment of organic waste. [Explanation of symbols]

[0053] 1: Water treatment facility 2: Methane fermentation tank (fermenter) 4: Hydrothermal treatment equipment 7:Introduction path 8: Gas generator 9: Fork in the road 71:Flocculator 72: Water supply channel X: Processing System

Claims

1. a fermenter that performs anaerobic fermentation of organic waste to produce biogas; a hydrothermal treatment device for hydrothermally treating organic waste, an introduction path for mixing the decomposition gas generated in the hydrothermal treatment device with the biogas; In the treatment system, a condenser for collecting condensed water formed by condensing moisture in the decomposition gas is disposed in the introduction path.

2. 2. The treatment system according to claim 1, wherein the organic waste to be hydrothermally treated in the hydrothermal treatment device is a treated product that has been fermented in the fermenter.

3. The treatment system according to claim 1 , wherein the inlet channel is connected to the fermenter.

4. The treatment system according to claim 1 , further comprising a water supply line for supplying the condensed water to the fermenter.

5. Further provided with a water treatment facility for treating wastewater; The organic waste introduced into the fermenter is sludge generated in the water treatment facility, The treatment system according to claim 1 , further comprising a branch line branching from the inlet line and sending the condensed water to an upstream side of the water treatment facility.

6. The treatment system according to claim 1 , further comprising a gas generator that generates electricity using the biogas produced in the fermenter as fuel.

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