Treatment system and treatment method for organic waste

Abstract

[Problem] To provide a treatment system and a treatment method for organic waste. [Solution] The present invention comprises: a digestion tank 3 for digesting organic waste W1 from the inside of a water treatment facility 51A; a digested sludge circulation line L3 for circulating, to the digestion tank 3, a portion of the digested sludge W11 treated in the digestion tank 3 as circulating digested sludge W11a; a thermal reformer 2 for introducing an outside dehydrated cake 52B from a water treatment facility 51B outside the water treatment facility 51A, and performing a thermal reforming treatment; a controller 50 for controlling the operating conditions for the thermal reformer 2; and a thermally reformed substance introduction line L12 for introducing, into the digestion tank 3, a thermally reformed substance W12B reformed by the thermal reformer 2, wherein the controller 50 controls the pressure in a thermal reforming tank 11 of the thermal reformer 2 to be kept equal to or higher than the saturated water vapor pressure.

Description

Organic waste treatment system and treatment method

[0001] The present invention relates to a system and method for treating organic waste.

[0002] For example, anaerobic digestion using anaerobic organisms is known as a method for treating organic waste such as food waste, livestock manure, and sewage sludge in water treatment facilities. In this anaerobic digestion process, organic waste such as sludge is put into a digestion tank and undergoes solubilization, hydrolysis, and acid fermentation, followed by methane fermentation, where the solids are decomposed into methane gas and carbon dioxide, thereby reducing the volume of the solids. The methane gas is used as energy.

[0003] Before anaerobic digestion, sludge may be subjected to thermal solubilization. Thermal solubilization is a process in which sludge (organic waste) is heated to a predetermined temperature to hydrolyze the solid content. For example, Patent Document 1 describes a technology in which sludge containing organic materials is thermally solubilized by supplying high-temperature steam to the sludge.

[0004] Special Publication No. 2003-500208

[0005] However, when a digestion tank is installed to treat dehydrated cake as a method for treating organic waste such as sewage sludge, there is a problem in that the digestion tank is large, and it is difficult for each local government to install a digestion tank at each treatment plant.

[0006] Therefore, when dehydrated cake is transported from other treatment plants and processed in one place, if a large amount of dehydrated cake is brought in, the amount of steam required for thermal reforming increases, and this heat is supplied to the digestion tank, which poses a problem of raising the temperature of the digestion tank.This is because the entire process from the thermal reformer to the digestion tank is sealed, and if a large amount of steam is required for solubilization, the temperature of the solubilized sludge transported to the digestion tank rises.

[0007] On the other hand, methods for cooling the thermally solubilized sludge whose temperature has risen are also being considered, but this requires separate equipment and utilities such as electricity.In addition, it is possible to lower the temperature by releasing steam from the sealed thermal reforming device, but this results in energy loss and, if steam is released to the outside, the device will no longer be sealed but will be open, which could cause problems such as the spread of odors to the outside.

[0008] The present invention provides an organic waste treatment system and method that can treat organic waste such as sewage sludge in one place, not only within a water treatment facility but also dehydrated cake from off-site water treatment facilities.

[0009] The organic waste treatment system of the present invention comprises a digestion tank that digests organic waste from within a water treatment facility; a digested sludge circulation line that circulates a portion of the digested sludge treated in the digestion tank as circulated digested sludge to the digestion tank; a thermal reforming device that introduces off-site dehydrated cake from the water treatment facility outside the water treatment facility and thermally reforms it; a control device that controls the operating conditions of the thermal reforming device; and a thermally reformed product introduction line that introduces the thermally reformed product reformed in the thermal reforming device into the digestion tank, and is characterized in that the control device controls the pressure in the thermal reforming tank of the thermal reforming device to maintain it at or above the saturated water vapor pressure.

[0010] The organic waste treatment method of the present invention is characterized by comprising: a digestion process for digesting first organic waste, which is sludge within a water treatment facility; a sludge circulation process for circulating a portion of the digested sludge treated in the digestion process as circulated sludge to the digestion tank; a thermal modification process for thermally modifying off-site dehydrated cake from the water treatment facility outside the water treatment facility; a steam supply process for introducing the thermally modified product modified in the thermal modification device into the digestion tank for digestion, and further supplying steam as a heat source into a thermal modification tank that thermally modifies the sludge; a measurement process for measuring the pressure within the thermal modification tank; and a pressure control process for releasing gas within the thermal modification tank into an outlet pipe through which solubilized sludge discharged from the thermal modification tank flows by opening and closing a pressure regulating valve.

[0011] According to the present invention, when treating organic waste such as sewage sludge, dehydrated cake from not only in-house water treatment facilities but also off-site water treatment facilities can be collected and treated in one place. This also reduces variations in the thermal modification treatment and makes it possible to reduce energy consumption during the digestion treatment of thermally modified sludge.

[0012] Fig. 1 is a conceptual diagram of an organic waste treatment system of embodiment 1. Fig. 2 is a treatment flow diagram of the organic waste treatment system of embodiment 1. Fig. 3 is a cross-sectional view of a thermal reforming device of embodiment 1. Fig. 4 is a cross-sectional view of another thermal reforming device of embodiment 1. Fig. 5 is a treatment flow diagram of an organic waste treatment system of embodiment 2.

[0013] [Embodiment 1] Fig. 1 is a schematic diagram of an organic waste treatment system according to embodiment 1. Fig. 2 is a treatment flow diagram of the organic waste treatment system of embodiment 1. Fig. 3 is a cross-sectional view of a thermal reforming device of embodiment 1. As shown in Fig. 1, in the organic waste treatment system (hereinafter simply referred to as "treatment system") 100A of embodiment 1, when treating organic waste such as sewage sludge, the organic waste W is treated in an on-site water treatment facility (hereinafter referred to as "on-site water treatment facility" or "water treatment facility (on-site)") 51A. １ In addition, off-site dewatered cake 52B from an off-site water treatment facility (hereinafter referred to as "off-site water treatment facility" or "water treatment facility (off-site)") 51B is treated in a single digestion tank 3.

[0014] That is, as shown in FIG. 1, the organic waste treatment system 100A according to this embodiment treats organic waste W, which is sludge from an on-site water treatment facility 51A. １ Introducing Line L １ and a digestion tank 3 into which the digested sludge W is introduced and digested. １１ Discharge line L ２ and digested sludge W １１ Part of the digested sludge W １１ａ The digested sludge circulation line L circulates the digestion sludge to the digestion tank 3 as ３ and a thermal reforming device 2 equipped with a thermal reforming tank 11 for thermally reforming the off-site dewatered cake 52B from the off-site water treatment facility 51B, and a thermally reformed product W thermally reformed in the thermal reforming tank 11.１２Ｂ The thermally reformed product is introduced into the digestion tank 3 through a thermal reformed product introduction line L １２ Here, in the present invention, "thermal reforming" refers to a state in which sludge (dehydrated cake) is solubilized by the heat of steam (S) supplied from the outside, but also includes a state in which the sludge is not completely solubilized. In FIG. 1, reference numeral 4 denotes a steam supply device, S denotes high-temperature steam, L ６ is the outside dehydrated cake feeding line (also called the "feeding line"), L １１ is the steam introduction line, L １３ is the gas exhaust line (described later), L １４ is biogas (CH ４ ) and the biogas lines that discharge them are shown.

[0015] As shown in FIG. 2, the digested sludge W treated in the digestion tank 3 １１ After being dehydrated by the sludge dehydrator 6, the sludge is discharged as dehydrated cake 52A through the dehydrated cake discharge line L ４ The dehydrated filtrate 53 from the sludge dewatering machine 6 is discharged to the outside as a dried product through the drain line L ５ The water is discharged as return water through the

[0016] Here, the off-site dewatered cake 52B that has undergone sludge treatment in a water treatment facility 52B that does not have a digestion tank is transported by a transport means (for example, a truck, etc.) and brought in. The off-site dewatered cake 52B that has been brought in is fed from a feeding section 55, and is fed through a feeding line L ６ The fuel is introduced into the thermal reforming tank 11 via the

[0017] Steam S is introduced into the thermal reforming tank 11 by the steam supply device 4 to thermally reform the sludge. The thermally reformed (partially thermally solubilized) sludge is then thermally reformed in the thermal reforming tank 11. １２Ｂ is a thermal reformate introduction line L １２ It is introduced via.

[0018] In this embodiment, the control device 50 controls the pressure inside the thermal reforming tank 11 to be maintained at or above the saturated steam pressure. When off-site dehydrated cake 52B is transported from another treatment plant (off-site water treatment facility 51B) and collected and treated in large quantities at one location, the input amount of steam S required for thermal reforming increases. As a result, the increased heat quantity of the input steam is introduced into the digester 3, causing the temperature of the digester 3 to rise.

[0019] That is, when thermal reforming is performed at a low temperature (for example, 120°C) to prevent the heat rise as described above, if the vapor pressure of the corresponding water vapor S is set to 0.1 MPa (gauge pressure), the thermal reformed product W １２Ｂ As a result, the extrusion pressure of the thermal reformate W from the thermal reforming tank 11 is reduced. １２Ｂ It becomes difficult to discharge the wastewater into the digestion tank 3.

[0020] Therefore, in this embodiment, the internal pressure of the tank of the thermal reforming device 2 is controlled to a set pressure of 0.2 to 0.3 MPa, so that the thermally reformed sludge W from the thermal reforming tank 11 can be reduced. １２Ｂ This makes it easy to discharge.

[0021] An example of this control will be further explained with reference to Figures 2 and 3. As shown in Figure 2, the organic waste treatment system 100A includes a digestion tank (apparatus) 3 for digesting first organic waste W1, which is sludge from an on-site water treatment facility 51A, and a digested sludge W1 treated in the digestion tank 3. １１ Discharge line L ２ and discharge line L ２ Digested sludge W １１ Part of the circulating sludge W １１ａ The sludge circulation line L circulates the sludge to the digestion tank 3 as ３ The off-site dewatered cake 52B from the off-site water treatment facility 51B is fed to the off-site dewatered cake input line L ６ and a thermal reforming device 2 for thermally reforming the fuel, a control device 50 for controlling the operating conditions of the thermal reforming device 2, and a thermal reformate W reformed in the thermal reforming device 2. １２Ｂ The thermally reformed product introduction line L introduces the above into the digestion tank 3. １２ The control device 50 controls the pressure in the thermal reforming tank 11 of the thermal reforming device 2 so as to maintain it at or above the saturated water vapor pressure.

[0022] Here, the processing temperature in the thermal reforming tank 11 is controlled to 110 to 150°C. Also, the gauge pressure at a processing temperature of 120°C is controlled to approximately 0.1 to 0.4 MPa. That is, in the control device 50, the control set value (X) in the thermal reforming tank 11 is set higher than 0.1 MPa (X = 0.2 to 0.3 MPa). This control is performed by controlling the gas discharge line L, as will be described later. １３ The pressure is adjusted by a pressure adjusting valve 31a installed in the

[0023] (Treatment system 100A) An example of the configuration of an organic waste treatment system 100A according to the present invention will be described with reference to Figure 2. As shown in Figure 2, the thermal reforming device 2 of the organic waste treatment system 100A includes a mixing pot 12 that performs pretreatment on the off-site dehydrated cake 52B from outside the site, a thermal reforming tank 11 that performs thermal reforming treatment on the off-site dehydrated cake 52B discharged from the mixing pot 12, and a steam introduction line L between the thermal reforming tank 11 and the mixing pot 12. １１ (Steam introduction line L １１－１ , steam introduction line L １１－２ ) through water vapor S (S １ , S ２ ) and a gas discharge line L for discharging the gas 31 in the thermal reforming tank 11. １３ and the gas exhaust line L １３ and a pressure adjusting valve 31a for opening and closing the pressure adjusting valve 31b.

[0024] 3 is a system diagram of the thermal reforming device 2. As shown in FIG. 3, the thermal reforming device 2 of this embodiment includes a pressure sensor 32 that measures the pressure in the thermal reforming tank 11, a pressure control means 33 that adjusts the opening of the pressure control valve 31 a so that the measured value of the pressure sensor 32 becomes a target value, and a pressure control means 33 that controls the temperature of the thermal reformed product W from the thermal reforming tank 11. １２Ｂ the outlet pipe 24 for discharging the sludge, a liquid level sensor 34 for measuring a physical quantity correlated with the liquid level of the sludge in the thermal reforming tank 11, a liquid level control valve 24a for opening and closing the outlet pipe 24, and a liquid level control means 35 for adjusting the opening of the liquid level control valve 24a so that the measurement value of the liquid level sensor 34 becomes the target value.

[0025] An example of the processing flow of the organic waste processing system 100A will be described with reference to FIG. 2. First, the organic waste W to be newly processed on-site is １ is fed into the digestion tank 3. １ Examples of the waste include organic sludge such as sewage sludge and septic tank sludge, food waste, garbage, livestock manure, etc. １ is fermented (digested) into methane by anaerobic methane-fermenting bacteria.

[0026] The operating temperature of the digester 3 is set appropriately taking into consideration the type of methane fermentation bacteria, doubling time, etc. As methane fermentation proceeds, mainly CH ４ , CO ２ A biogas G, which is a digestion gas consisting of the biogas G, is generated. A part or all of this biogas G is sent out as fuel for the steam boiler of the steam supply device 4. The steam supply device 4 generates high-temperature steam S using this biogas G as fuel, and the high-temperature steam S (S １ , S ２ ) to supply.

[0027] Instead of using a steam boiler, biogas G can be supplied to a digester gas generator to generate electricity, and high-temperature steam recovered from the exhaust heat of the digester gas generator (consisting of a digester gas engine and a generator) can be supplied to the thermal reforming tank 11 and the mixing pot 12.

[0028] Digested sludge W, which is organic waste digested in the digestion tank 3 １１ is the discharge line L ２ The digested sludge is stored in the digested sludge storage tank 5 via the digested sludge storage tank 5. １１ Part of W １１ａ is the circulation line L ３ The remaining sludge W １１ The digested sludge is temporarily stored in a digested sludge storage tank 5 and then sent to a sludge dehydrator 6. The sludge dehydrator 6 is composed of, for example, a centrifugal dehydrator (decanter), a screw compression dehydrator, a belt press dehydrator, etc. The dehydrated filtrate 53 discharged from the sludge dehydrator 6 is sent to a water treatment system (not shown).

[0029] The thermal reforming device 2 thermally reforms the input off-site dewatered cake 52B, and produces thermally reformed sludge W １２Ｂ is the thermal reformate introduction line L １２ The wastewater is then sent to the digestion tank 3 via the

[0030] In addition, the digested sludge W １１ In some cases, the entire amount of digested sludge W may be sent to the sludge dewatering machine 6. In other cases, the digested sludge storage tank 5 may not be provided, and the digested sludge W may be sent from the digestion tank 3. １１ It is also possible to send the sludge directly to the sludge dewatering machine 6. The residence time of the sludge in the thermal reforming device 2 is, for example, about 10 to 60 minutes.

[0031] (Thermal Reforming Apparatus 2) Next, the configuration of the thermal reforming apparatus will be described in detail with reference to Figures 3 and 4. Figure 3 is a cross-sectional view of the thermal reforming apparatus of the first embodiment. Also, Figure 4 is a cross-sectional view of another thermal reforming apparatus of the first embodiment. As shown in Figure 3, in the thermal reforming apparatus 2A of this embodiment, pretreatment of the off-site dehydrated cake 52B is performed in the mixing pot 12, and steam S is mixed in the mixing pot 12. １ The pre-treated off-site dehydrated cake 52B is subjected to thermal reforming treatment in the thermal reforming tank 11. The steam supply device 4 of this embodiment supplies the first steam (S １ ) is supplied to the outside dehydrated cake 52B in the mixing pot 12, and second steam (S ２ ) to supply.

[0032] The mixing pot 12 is connected to the input line L of the outside dewatered cake 52B. ６ The mixing pot 12 is connected to the downstream end of the input line L ６ a substantially cylindrical pot body 14 disposed as part of the pot body 14; and a first steam (S １ ) and a first steam pipe 15 for supplying the water vapor.

[0033] The pot body 14 has a large diameter in the center and gradually narrows toward the upper and lower ends. A flange 13 at one end (lower end) of the pot body 14 is bolted to a flange 7a of the supply pipe 7. The opening diameter at the lower end of the pot body 14 is approximately the same as the inner diameter of the supply pipe 7, and the opening diameter at the upper end is approximately the same as the inner diameter of the lower end of the discharge nozzle 20 (described below). In this embodiment, two first steam pipes 15 are provided, and they are inserted into the pot body 14 so as to be offset from each other in the axial direction of the pot body 14 and extend in a direction perpendicular to the axial direction of the pot body 14. The tip of the first steam pipe 15 is fitted into a steam pipe support portion 16 recessed in the inner peripheral surface of the pot body 14.

[0034] The thermal reforming tank 11 is a sealed cylindrical body. When the set temperature (target temperature) of the gas phase in the thermal reforming tank 11 is set to, for example, 110°C to 150°C, preferably, for example, 120°C to 140°C, the set pressure is approximately 0.2 to 0.7 MPa, preferably 0.3 MPa to 0.5 MPa.

[0035] A large-diameter drain section 18 is attached coaxially to the lower end of the thermal reforming tank 11, and a discharge nozzle 20 is coaxially disposed within the drain section 18. The discharge nozzle 20 is composed of a tubular member with an open lower end and is connected to the upstream end of the mixing pot 12. A flange 21 at the lower end of the discharge nozzle 20 is bolted to a flange 22 at the upper end of the pot body 14. The upper end of the discharge nozzle 20 is formed with a slightly larger diameter than the pipe diameter near the lower end, and is disposed at the bottom of the thermal reforming tank 11. The upper end of the discharge nozzle 20 is closed and does not open. A plurality of small-diameter nozzle holes 23 are drilled at equal intervals in the circumferential direction around the upper end (discharge end) of the discharge nozzle 20, which is formed with a large diameter. That is, the plurality of nozzle holes 23 are formed at equal intervals around the axis O of the thermal reforming tank 11. The diameter of the nozzle holes 23 is, for example, approximately 15 millimeters.

[0036] The thermal reforming material W is stored on the peripheral wall of the thermal reforming tank 11. １２Ｂ The outlet pipe 24 is connected to the thermal reformate introduction line L１２ The outlet pipe 24 is fitted with a liquid level control valve 24a that opens and closes the outlet pipe 24. The liquid level control valve 24a is, for example, an air-operated ball valve.

[0037] A liquid level sensor 34 is attached to the side of the thermal reforming tank 11. The liquid level sensor 34 measures a physical quantity correlated to the liquid level of the sludge in the thermal reforming device 2A. The liquid level sensor 34 in this embodiment is of a differential pressure type, and is equipped with a sensor that measures the pressure of the gas phase in the thermal reforming tank 11 and a sensor that measures the pressure of the liquid phase (sludge) in the thermal reforming tank 11. The measurement result of the liquid level sensor 34 is output to the liquid level control means 35.

[0038] The liquid level control means 35 adjusts the opening of the liquid level adjustment valve 24a in accordance with the measurement value of the sludge liquid level sensor 34, and adjusts the liquid level of the sludge to a target value. The liquid level control means 35 sends a control signal to the drive unit of the liquid level adjustment valve 24a.

[0039] At the top of the thermal reforming tank 11, there is a gas discharge line L through which the gas 31 is discharged. １３ and a pressure sensor 32 are attached. １３ One end of the gas exhaust line L is connected to the top 11a of the thermal reforming tank 11. １３ The other end of the thermal reformate W is supplied to the liquid level control valve 24a installed in the outlet pipe 24. １２Ｂ The gas discharge line L １３ This gas exhaust line L １３ The pressure regulation valve 31a is, for example, an air-operated regulation valve.

[0040] The pressure sensor 32 measures the pressure of the gas phase in the thermal reforming tank 11. The measurement result of the pressure sensor 32 is output to the pressure control means 33. The pressure control means 33 adjusts the opening of the pressure adjustment valve 31a so that the measurement value of the pressure sensor 32 becomes the target value. In other words, the pressure of the gas phase in the thermal reforming tank 11 is controlled by the pressure control means 33. By controlling the measurement value of the pressure sensor 32 to become the target value (set pressure), the saturated water vapor pressure in the gas phase in the thermal reforming tank 11 can be kept constant, and therefore the temperature in the gas phase can be kept at a temperature corresponding to the saturated water vapor pressure.

[0041] The steam supply device 4 of this embodiment supplies high-temperature second steam S in the thermal reforming tank 11, separately from the mixing pot 12 and the steam pipe 15. ２ The water vapor injection pipe 25 is attached to the peripheral wall near the bottom of the thermal reforming tank 11. The water vapor injection pipe 25 is perforated with a plurality of water vapor injection holes 26. The diameter of the water vapor injection holes 26 is, for example, about 6 mm. Here, the high-temperature second water vapor S ２ The temperature range is preferably, for example, 110°C to 180°C.

[0042] According to this embodiment, in the thermal reforming tank 11, which continuously supplies dehydrated cake from outside to the thermal reforming device 2A to perform thermal reforming, the temperature inside the tank is set to a range of, for example, 120 to 140°C, and the pressure inside the thermal reforming tank 11 is controlled to be maintained at or above the saturated water vapor pressure, solubilized sludge can be discharged from the thermal reforming tank 11 without installing a pump for sending sludge to the digestion tank near the outlet of the thermal reforming tank.

[0043] (Method for Treating Organic Waste) Next, a method for treating organic waste will be described. The method for treating organic waste includes a supplying step, a measuring step, and a control step.

[0044] The supply step is a step of supplying steam generated in the steam boiler of the steam supply device 4 as a heat source into the thermal reforming device 2A (the thermal reforming tank 11 and the mixing pot 12). After the pressure inside the thermal reforming tank 11 reaches a predetermined pressure, the off-site dehydrated cake 52B is introduced into the thermal reforming device 2A, and thermal reforming is started within a predetermined temperature range.

[0045] In addition, the high-temperature first steam S １ and high-temperature second steam S ２ The total amount of supply is the thermal reforming tank 11, the gas discharge line L １３ Taking into consideration the heat radiation and exhaust from the dehydrated cake 52B, it is preferable to supply a slightly larger amount than that required for heating the dehydrated cake 52B. Specifically, when the amount of high-temperature steam required for heating is 100% by mass, the increment is, for example, 3% by mass to 50% by mass. １ The temperature range is preferably, for example, 110°C to 180°C.

[0046] Input line L ６ The dehydrated cake 52B transported outside the facility is mixed with the high-temperature first steam S injected from the steam injection holes 17 of the first steam pipe 15 in the mixing pot 12. １ By directly mixing with the molten metal, the molten metal is heated and steam condenses, which reduces the viscosity. ６ The temperature of the outside dehydrated cake 52B in the mixing pot 12 is approximately 25 to 35°C. The outside dehydrated cake 52B, whose viscosity has been reduced in the mixing pot 12, is poured into the thermal reforming tank 11 as treated sludge through the discharge nozzle 20. The treated sludge poured into the thermal reforming tank 11 is heated by the high-temperature second steam S injected from the steam injection holes 26 of the steam injection pipe 25. ２ After a predetermined residence time, the product is discharged from the outlet pipe 24 and fed to the thermal reformate introduction line L １２ The wastewater is transported to the digestion tank 3 via the

[0047] The measurement step is a step of continuously measuring the pressure of the gas phase portion in the thermal reforming tank 11 by the pressure sensor 32. The measurement value of the pressure sensor 32 is sent to the pressure control means 33.

[0048] The control step is a step of controlling the opening degree of the pressure regulating valve 31a so that the pressure of the gas phase in the thermal reforming tank 11 measured in the measurement step becomes a target value. When the pressure in the thermal reforming tank 11 exceeds the target value, the opening degree of the pressure regulating valve 31a is increased to discharge the gas (gas containing water vapor) in the thermal reforming tank 11 to the gas discharge line L １３ When the pressure in the thermal reforming tank 11 falls below the target value, the pressure in the thermal reforming tank 11 is increased by reducing the opening of the pressure control valve 31a or by fully closing the valve. By controlling the pressure in the gas phase of the thermal reforming tank 11 to the target value, the thermal reformed sludge W from the thermal reforming tank 11 is released. １２Ｂ This makes it easy to discharge.

[0049] According to the thermal reforming apparatus 2A described above, based on the measured pressure of the gas phase in the thermal reforming tank 11, the gas in the thermal reforming tank 11 (gas containing water vapor) is introduced into the thermal reforming product introduction line L １２ Since the refrigerant is discharged to the outside of the thermal reforming tank 11 through the refrigerant passage 14, the pressure inside the thermal reforming tank 11 can be kept constant.

[0050] In addition, the gas exhaust line L １３ The gas (exhaust heat) discharged to the outside of the thermal reforming tank 11 through the １２Ｂ Since the thermal reformate W １２Ｂ This allows the amount of energy consumed to heat the digester 3 to be reduced.

[0051] In this embodiment, the gas (exhaust heat) in the thermal reforming tank 11 is discharged through a gas discharge line L １３ The thermal reformate W in the outlet pipe 24 is １２Ｂ Since the heat loss is small, the thermal reformed product W １２Ｂ That is, the thermally modified product W １２Ｂ can be used as a heating source for the digester 3.

[0052] Furthermore, the thermal reforming device 2A can maintain a constant liquid level in the thermal reforming tank 11 by adjusting the opening of the liquid level control valve 24a, which reduces variations in the thermal reforming process, thereby reducing the amount of energy consumed when digesting the thermally reformed sludge.

[0053] In conventional organic waste treatment facilities, if the dehydrated sludge (dehydrated cake) is not thermally reformed, it is incinerated. However, in the future, in order to combat global warming, ２ There is a demand for reduction, and now the trend is to avoid incineration of dehydrated cake. In a water treatment facility equipped with a digestion treatment facility as in this embodiment, dehydrated cake from outside the facility can be collected and treated, thereby contributing to measures against global warming.

[0054] 4 shows a modified example of the thermal reforming device. In the thermal reforming device 2A shown in FIG. 3, the thermal reformed material W inserted into the outlet pipe 24 of FIG. １２Ｂ In contrast, in the thermal reforming device 2B shown in FIG. 4, the thermal reformed product W of the outlet pipe 24 is introduced into the inlet pipe 24b. １２Ｂ The tip of the pipe inlet portion 24b inserted into the interior through which the gas is introduced is cut obliquely downward. In other words, if the outlet pipe 24 is circular, the cut surface will be elliptical, and the outlet pipe 24 is disposed so that the elliptical opening faces the bottom of the thermal reforming tank 11.

[0055] 4, if the inner diameter of the pipe of the thermal reforming tank 11 is D, the length between the side wall 11c (point a) of the thermal reforming tank 11 and the lower end (point b) of the tip of the pipe inlet portion 24b inserted into the outlet pipe 24 is X, the inner diameter of the outlet pipe 24 is d, and the angle of the tip of the pipe inlet portion 24b is θ, it is preferable to have the following relationship: X: 0 to 1 / 2D θ: 30 to 85 degrees d: inner diameter 65 mm to 1 / 2D WL: (sludge volume) / (tank volume)=1 / 5 to 4 / 5

[0056] Here, the reason for setting d: inner diameter 65 mm to 1 / 2D is as follows: The solid concentration of the discharged sludge is high, at 5 to 20 wt%, so it is difficult to discharge it with an inner diameter of 65 mm or less, while if it is 1 / 2D or more, it becomes difficult to manufacture the tank.

[0057] The upper edge angle θ of the pipe inlet portion 24b in a side view is not particularly limited, and the cut shape can be appropriately modified as long as it has a tip opening shape that can face the bottom 11b of the thermal reforming tank 11. For example, 30 to 85 degrees is preferable, and 45 to 75 degrees is more preferable. In this embodiment, the upper edge angle θ of the pipe inlet portion 24b in a side view is approximately 60 degrees.

[0058] Here, if the side view edge angle θ of the pipe inlet portion 24b is outside the range of 30 degrees to 85 degrees, the ratio of the area of ​​the discharge outlet to the area of ​​the flow path of the outlet pipe 24 is not favorable in terms of sludge discharge.

[0059] In addition, for example, an embodiment can be adopted in which the circular pipe (with an upward-facing funnel-shaped outlet opening portion) used in Figure 3 is rotated 180 degrees and the funnel-shaped outlet opening portion is arranged so as to face the bottom 11b of the thermal reforming tank 11.

[0060] Furthermore, the protruding length X of the outlet pipe 24 inserted into the thermal reforming tank 11 is preferably equal to or less than 1 / 2 of the tank inner diameter D of the thermal reforming tank 11. Here, by making the protruding length X equal to or less than 1 / 2 of the tank inner diameter D of the thermal reforming tank 11, maintenance of the discharge port of the outlet pipe 24 becomes easier, which is preferable.

[0061] Furthermore, WL is preferably set to, for example, 1 / 5 to 4 / 5, where WL is the volume of sludge / the volume of the tank.

[0062] By limiting the values ​​as described above, when thermally solubilizing in the temperature range of 150°C or less, the thermally modified product W having high viscosity can be obtained. １２Ｂ Therefore, the thermal reformate W from the inside of the thermal reforming tank 11 must be discharged. １２Ｂ Furthermore, by setting the value within the range, a gas phase can be provided in the tank 11, and the temperature and pressure of the tank 11 can be easily controlled.

[0063] [Embodiment 2] Figure 5 is a treatment flow diagram of an organic waste treatment system of embodiment 2. Note that the same components as those in embodiment 1 are given the same reference numerals and their description will be omitted. As shown in Figure 5, an organic waste treatment system 100B is different from the organic waste treatment system 100A of embodiment 1 in that it treats digested sludge W. １１ A sludge dewatering machine 6 dewaters a portion of the sludge to produce on-site dewatered cake 51A, and a dewatered cake introduction line L that introduces on-site dewatered cake 52A from the sludge dewatering machine 6 into the thermal reforming device 2 (2A, 2B). ７ The dehydrated cake introduction line L ７ is the outside dewatered cake feeding line L ６ The on-site dehydrated cake 52A and the off-site dehydrated cake 52B are introduced into the thermal reforming tank 11. In the thermal reforming tank 11, the on-site dehydrated cake 52A and the off-site dehydrated cake 52B are mixed and thermally reformed.

[0064] As a result, the on-site dewatered cake 52A and the off-site dewatered cake 52B are integrated and subjected to thermal reforming treatment in the thermal reforming tank 11.

[0065] Although the embodiment of the present invention has been described above, appropriate design changes are possible within the scope of the present invention. For example, the gas discharge line L １３ The thermal reforming tank 11 may be configured to communicate with the digestion tank 3 so that the gas in the thermal reforming tank 11 is released into the digestion tank 3.

[0066] Furthermore, the thermal reforming device 2 (2A, 2B) of this embodiment is an example, and is not particularly limited as long as it has a configuration that provides substantially the same effects as this configuration.

[0067] The present invention can be applied to organic waste treatment systems and treatment methods in general.

[0068] 100A, 100B Organic waste treatment system 2 (2A, 2B) Thermal reforming device 3 Digestion tank 4 Steam supply device 11 Thermal reforming tank 12 Mixing pot 15 First steam pipe 24 Outlet pipe 24a Liquid level control valve 24b Pipe inlet 25 Steam injection pipe 31 Gas 31a Pressure control valve 32 Pressure sensor 33 Pressure control means 34 Liquid level sensor 35 Liquid level control means 51A On-site water treatment facility (on-site water treatment facility) 51B Off-site water treatment facility (off-site water treatment facility) 52A On-site dehydrated cake 52B Off-site dehydrated cake 55 Feeding section S (S １ , S ２ ) High temperature steam S １ High temperature first steam S ２ High temperature secondary steam W １ Organic waste W １１ Digested sludge W １２Ｂ Thermal modification L １ Introduction line L ２ Discharge line L ３ Digested sludge circulation line L ４ Dehydrated cake discharge line L ５ Drainage line L ６ Off-site dewatered cake feeding line (feeding line) L ７ Dehydrated cake introduction line L １１ Steam introduction line L １２ Thermal reformate introduction line L １３ Gas Exhaust Line

Claims

1. An organic waste treatment system comprising: a digestion tank for digesting organic waste from within a water treatment facility; a digested sludge circulation line for circulating a portion of the digested sludge treated in the digestion tank as circulated digested sludge back to the digestion tank; a thermal reforming unit for introducing dehydrated cake from an outside water treatment facility outside the water treatment facility and for thermally reforming the cake; a control unit for controlling the operating conditions of the thermal reforming unit; and a thermally reformed product introduction line for introducing the thermally reformed product reformed in the thermal reforming unit into the digestion tank, wherein the control unit controls the pressure in the thermal reforming tank of the thermal reforming unit to maintain it at or above the saturated water vapor pressure.

2. The organic waste treatment system according to claim 1, further comprising: a sludge dehydrator that dehydrates a portion of the digested sludge to produce on-site dehydrated cake; and a dehydrated cake introduction line that introduces the on-site dehydrated cake from the sludge dehydrator into the thermal reforming device, wherein the on-site dehydrated cake from the on-site and the off-site dehydrated cake from the off-site are thermally reformed in the thermal reforming device.

3. An organic waste treatment system as described in claim 1 or 2, characterized in that the thermal reforming conditions of the thermal reforming device are 120 to 150°C, and the digestion conditions of the digester are 30 to 60°C.

4. The organic waste treatment system described in claim 1 or 2, characterized in that the thermal reforming device comprises: a thermal reforming tank that performs thermal reforming treatment on sludge; a steam supply device that supplies steam to the sludge in the thermal reforming tank; a gas discharge line that discharges gas in the thermal reforming tank into the solubilized sludge discharged from the thermal reforming tank; a pressure sensor that measures the pressure in the thermal reforming tank; a pressure control valve that opens and closes the gas discharge pipe; and a pressure control means that adjusts the opening of the pressure control valve so that the measurement value of the pressure sensor becomes a target value.

5. The organic waste treatment system according to claim 4, further comprising an outlet pipe for discharging the solubilized sludge from the thermal reforming tank, and the gas discharge pipe is connected to the outlet pipe.

6. An organic waste treatment system as described in claim 4, characterized in that it is provided with an outlet pipe for discharging the solubilized sludge from the thermal reforming tank, and the outlet pipe has its inlet inserted inside the thermal reforming tank.

7. The organic waste treatment system according to claim 6, wherein the pipe inlet is disposed so as to face the bottom of the thermal reforming tank.

8. An organic waste treatment system as described in claim 4, characterized in that it comprises a liquid level sensor that measures a physical quantity correlated with the liquid level height of the sludge in the thermal reforming tank, a liquid level adjustment valve that opens and closes the outlet pipe, and a liquid level control means that adjusts the opening of the liquid level adjustment valve so that the measurement value of the liquid level sensor becomes a target value.

9. A method for treating organic waste, comprising: a digestion process for digesting first organic waste, which is sludge within a water treatment facility; a sludge circulation process for discharging digested sludge treated in the digestion process and circulating a portion of the digested sludge to the digestion tank as circulated sludge; a thermal reforming process for thermally reforming off-site dehydrated cake from the water treatment facility outside the water treatment facility; a steam supply process for introducing the thermally reformed product reformed in the thermal reforming device into the digestion tank for digestion, and further supplying steam as a heat source into a thermal reforming tank for thermally reforming the sludge; a measurement process for measuring the pressure within the thermal reforming tank; and a pressure control process for releasing gas within the thermal reforming tank into an outlet pipe through which solubilized sludge discharged from the thermal reforming tank flows by opening and closing a pressure regulating valve.

10. A method for treating organic waste as described in claim 9, characterized in that it includes a sludge dehydration process in which a portion of the digested sludge is dehydrated to produce on-site dehydrated cake, and in the thermal modification process, the on-site dehydrated cake and the off-site dehydrated cake are thermally modified.

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