Treatment equipment and treatment method for organic waste

Abstract

[Problem] To provide a processing device and a processing method for organic waste containing heavy metals, with which it is possible to further improve, as compared with the prior art, the amounts of heavy metals entrapped by tobermorite and the processing stability. [Solution] A processing method for organic waste according to the present invention is characterized by including: a step for introducing organic waste and tobermorite-forming raw material components, the step involving introducing, into the interior of an airtight container having a discharge port, which can be freely opened and closed, and a closed space, organic waste containing heavy metals and a Ca component raw material and a SiO2 component raw material that are supplied in sufficient amounts for forming 5CaO•6SiO2•5H2O crystals (tobermorite) for entrapping at least the heavy metals in 5CaO･6SiO2•5H2O crystal (tobermorite) structures while processing the organic waste; an ionizing step for ionizing the heavy metals, the Ca component, and the SiO2 component, the step involving agitating and mixing the Ca component raw material and the SiO2 component raw material, while pulverizing solids in the organic waste containing the heavy metals in the airtight container and jetting high-temperature, high-pressure steam having a temperature of 120-250°C and a pressure of 1.1-2.1 MPa onto the organic waste containing the heavy metals, the Ca component raw material, and the SiO2 component raw material that are in the process of being pulverized and mixed to perform reaction processing of said materials; a tobermorite forming step for forming tobermorite in which the heavy metals are taken into the crystal structures thereof by means of a hydrothermal reaction performed by holding the temperature in the airtight container at 120-140°C for one hour or longer after performing the ionizing step; and a cooling step for cooling steam in the airtight container to liquefy the steam.

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for treating organic waste, and more particularly, to an apparatus and a method for treating organic waste such as municipal solid waste, sewage sludge, food processing wastewater sludge or leather tanning wastewater treatment sludge containing heavy metals.

Background Art

[0002] As a method for treating organic waste, for example, a method of treating waste in high-temperature and high-pressure steam in a sealed container is known (see, for example, Japanese Patent Application Laid-Open No. 2000-33355). In the conventional method of treating waste with steam, it is said that there is almost no generation of harmful nitrogen oxides, sulfur oxides, etc. as in the case of incineration treatment, there is no problem of environmental pollution, and safe waste treatment can be expected.

[0003] However, after the treatment, the treated solid matter and liquid are in a mixed state in the container, and there is a problem that transportation, storage, etc. after taking out the treated waste are inconvenient and difficult to handle. And after the treatment, when separating the treated solid matter and liquid using a separator, the treatment process becomes complicated, a lot of labor is required, the treatment takes a long time, and a large area of land for separately installing a reaction vessel and a separator needs to be secured, etc. problems have occurred. Therefore, a treatment apparatus has been proposed that can safely treat waste using high-temperature and high-pressure steam with a single device, and continuously separate and recover the treated waste and liquid following this treatment (see Japanese Patent No. 4864884). However, this treatment apparatus requires a reactor composed of a sealed container for treating waste in high-temperature and high-pressure steam, and another sealed container for recovering the separated liquid, which is connected to the reactor composed of the sealed container. Therefore, there are problems such as high equipment costs and complicated operations.

[0004] On the other hand, sewage sludge discharged from sewage treatment plants, for example, contains pathogenic microorganisms and heavy metals. To avoid the environmental risks posed by these, it has been treated and disposed of in various ways, such as concentration, digestion, dewatering, composting, incineration, and melting. However, all of these treatment methods involve reducing volume or discarding waste, are consumption-type technologies that require large amounts of electricity and thermal energy, and have a significant environmental impact as they are sources of greenhouse gas emissions. Furthermore, they do not adhere to the principle of resource regeneration, and the high maintenance costs involved put a strain on local economies. Currently, there are problems with the accumulation of heavy metals contained in sewage sludge, as well as infection and contamination from harmful chemical substances, pathogenic microorganisms, and viruses, which have hindered the effective utilization of sewage sludge. Against this backdrop, policies for "resource utilization of sewage sludge" have recently been directed (see Non-Patent Literature 1). On the other hand, a soil remediation method has been proposed that involves treating inorganic waste under subcritical water conditions after conditioning, such as by adding lime, to solidify heavy metals (see Non-Patent Document 2). However, the introduction of resource recovery technologies that aim for the specific recycling of resources, safely process them, immobilize the heavy metals to suppress their leaching, simplify the structure of the processing equipment, and are easy to operate and low-cost has not yet been achieved.

[0005] In view of the above-mentioned conventional problems, the applicant of this application previously proposed in Japanese Patent Application No. 2014-508992 (Patent No. 6872101) an apparatus for processing organic waste containing heavy metals, which has a simple structure, is easy to operate, and is low cost, and which can safely process organic waste composed of waste containing heavy metals using high-temperature, high-pressure steam with only one device to immobilize the heavy metals and suppress their elution, and after processing, discharge a mixture containing the waste with the immobilized heavy metals and a liquid, and separate and recover the two with simple operation. The applicant of this application previously proposed an apparatus for processing organic waste containing heavy metals with the following details. In other words, the treatment device for organic waste containing heavy metals, as described in Patent No. 6872101, heavyA sealed container having a closed space for containing a slurry or solid organic waste containing metals, and a sufficient amount of Ca component raw materials and SiO2 component raw materials to form 5CaO·6SiO2·5H2O crystal (tobermorite) to encapsulate at least the heavy metals in the 5CaO·6SiO2·5H2O crystal (tobermorite) structure during the carbonization treatment of the organic waste, before record A stirring means for crushing solid matter in the machine waste while stirring and mixing it with the Ca component raw material and SiO2 component raw material, The contents are contained in a sealed container and are being crushed and mixed by the stirring means. record A steam ejection means for ejecting high-temperature, high-pressure steam to treat mechanical waste, Ca component raw materials, and SiO2 component raw materials by injecting high-temperature, high-pressure steam, thereby forming a layer of 5CaO·6SiO2·5H2O crystal (tobermorite) structure in which the heavy metals are trapped on the solid material of the organic waste, A cooling means for cooling and liquefying the vapor in the sealed container after processing, An outlet with an opening and closing mechanism is provided on the bottom side of the sealed container, A waste treatment apparatus for heavy metals comprising a discharge port for discharging a mixture of waste containing tobermorite in which the treated heavy metals are contained and a liquid containing liquefied components, and a separation and recovery means for separating the waste and the liquid from the discharged mixture, The separation and recovery means is characterized by being a separation and recovery means that collects the mixture into a recovery container and then separates the waste and the liquid, and / or a separation and recovery means that supplies the mixture to a belt conveyor device and separates the waste and the liquid while it is in motion. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2000-33355 [Patent Document 2] Patent No. 4864884 [Patent Document 3] Patent No. 6872101 [Non-patent literature]

[0007] [Non-Patent Document 1] "Resource Recovery of Inorganic Waste by Hydrothermal Treatment," Takahiro Hirano (http: / / www.pref.iwate.jp / ~kiri / infor / theme / 2004 / pdf / H16-32water.pdf) [Non-Patent Document 2] "Toward the Realization of Resource Paths" Report (Draft), Resource Paths Committee Document 2, March 2007 (http: / / www.mlit.go.jp / crd / city / sewerage / gyosei / sigen7th / 02.pdf) [Disclosure of the Invention] [Problems that the invention aims to solve]

[0008] While the treatment apparatus for organic waste containing heavy metals described in the above-mentioned Patent No. 6872101 encapsulates heavy metals to levels that conform to various standards, the present invention provides a treatment apparatus and treatment method for organic waste containing heavy metals that can further improve the amount of heavy metals encapsulated by tobermorite. [Means for solving the problem]

[0009] The above problems are solved by an organic waste treatment device and treatment method having the configurations (1) to (18) below. (1) A sealed container having a closed space for containing organic waste containing heavy metals, and a sufficient amount of Ca component raw materials and SiO2 component raw materials to form 5CaO·6SiO2·5H2O crystal (tobermorite) to encapsulate at least the heavy metals in the 5CaO·6SiO2·5H2O crystal (tobermorite) structure during the processing of the organic waste, A stirring means for stirring and mixing the solid matter in the organic waste with the Ca component raw material and the SiO2 component raw material while crushing it, A steam ejection means that ionizes the heavy metals, Ca components, and SiO2 components by injecting high-temperature, high-pressure steam at a temperature of 120-250°C and a pressure of 1.1-2.1 MPa into the organic waste containing heavy metals and Ca component raw materials and SiO2 component raw materials contained in the sealed container and being crushed and mixed by the stirring means, A means for controlling the temperature inside a sealed container, which maintains the temperature inside the sealed container at 120-140°C for more than one hour after processing to form tobermorite in which the heavy metal is incorporated into the crystal structure by a hydrothermal reaction, A cooling means for cooling and liquefying the water vapor in the sealed container, An outlet with an opening and closing mechanism is provided on the bottom side of the sealed container. A treatment device for organic waste containing heavy metals, equipped with [a specific feature / equipment]. (2) The organic waste treatment apparatus according to (1), further comprising a separation and recovery means for discharging a mixture of a solid containing tobermorite in which the treated heavy metals are contained and a liquid containing liquefied components from the discharge port, and separating the solid and the liquid from the discharged mixture. (3) The organic waste treatment apparatus of (2), wherein the separation and recovery means is a separation and recovery means that recovers the mixture into a recovery container and then separates the organic waste and the liquid, and / or a separation and recovery means that supplies the mixture to a belt conveyor device and separates the solid matter and the liquid while it is in motion. (4) An organic waste treatment apparatus according to any of (1) to (3) above, wherein the heavy metals are at least one selected from chromium, lead, cadmium, arsenic, mercury, zinc, copper, and nickel. (5) An organic waste treatment device according to any of the above (1) to (4), wherein the organic waste is urban food waste, sewage sludge, food processing wastewater sludge, or tanning wastewater treatment sludge. (6) An organic waste containing heavy metals and a Ca component raw material and a SiO2 component raw material in an amount sufficient to form 5CaO·6SiO2·5H2O crystals (tobermorite) for confining at least the heavy metals in the 5CaO·6SiO2·5H2O crystal (tobermorite) structure are introduced into a sealed container having an opening and closing discharge port and a closed space. This is an organic waste and tobermorite-forming raw material component input step. While pulverizing the solid matter in the organic waste containing heavy metals contained in the sealed container, it is stirred and mixed with the Ca component raw material and the SiO2 component raw material. High-temperature and high-pressure steam with a temperature of 120 to 250 °C and a pressure of 1.1 to 2.1 MPa is injected into the organic waste containing heavy metals, the Ca component raw material, and the SiO2 component raw material that are being pulverized and mixed, and the reaction treatment is carried out to ionize the heavy metals, the Ca component, and the SiO2 component. This is an ionization step. After this ionization step, the inside of the sealed container is held at a temperature of 120 to 140 °C for 1 hour or more, and tobermorite incorporating the heavy metals into the crystal structure is formed by a hydrothermal reaction. This is a tobermorite formation step. A cooling step for cooling and liquefying the steam in the sealed container. A method for treating organic waste containing heavy metals, characterized by comprising the above steps. (7) The method for treating organic waste according to (6) above, further comprising a step of separating and recovering the liquid obtained in the cooling step and the solid matter in the treated organic waste containing tobermorite in which the heavy metals are confined. (8) The method for treating organic waste according to (6) or (7) above, wherein at least a part of the SiO2 component raw material accommodated in the sealed container for forming tobermorite is obtained by introducing rice husks of gramineous plants into the sealed container and using the SiO2 component contained in the rice husks. (9) The method for treating organic waste according to any one of (6) to (8) above, wherein the heavy metals are at least one selected from chromium, lead, cadmium, arsenic, mercury, zinc, copper, and nickel. (10) A method for treating any of the organic wastes described in (6) to (9) above, wherein the organic waste is urban food waste, sewage sludge, food processing wastewater sludge, or leather tanning wastewater treatment sludge. (11) A method for treating organic waste according to any of (6) to (10) above, wherein the amount of Ca component (A-1) and SiO component (A-2) already contained in organic waste containing heavy metals is determined by analysis, and the amount of Ca component (B-1) and SiO component (B-2) sufficient to form 5CaO·6SiO2·5H2O crystals (tobermorite) to encapsulate at least the heavy metals in the 5CaO·6SiO2·5H2O crystal (tobermorite) structure during treatment is calculated, the amount of Ca component raw material to be added (C-1) and the amount of SiO2 component raw material to be added (C-2) to the organic waste containing heavy metals is determined by the following formulas (1) and (2), and the Ca component raw material (C-1) and SiO2 component raw material (C-2) are added to the organic waste containing heavy metals to perform the treatment. [(B-1)-(A-1)]=(C-1)...Equation (1) [(B-2)-(A-2)]=(C-2) Formula (2) (12) The method for treating organic waste according to claim 11, wherein at least a part of (C-2) is the SiO component of rice husks of grasses. (13) A method for treating organic waste according to any of (6) to (12) above, wherein the heavy metals are at least one selected from chromium, lead, cadmium, arsenic, mercury, zinc, copper, and nickel, and the heavy metals are encapsulated in the 5CaO·6SiO2·5H2O crystal (tobermorite) structure in the organic waste after treatment, so that the organic waste after treatment satisfies at least one selected from water environmental standards, soil environmental standards, special fertilizer standards, and food safety standards. (14) If the organic waste contains PCBs, the method for treating organic waste according to any of (6) to (13) above, wherein the treatment decomposes the PCBs. (15) A method for treating organic waste according to any of the above (6) to (14), wherein the treatment temperature in the ionization step is 120 to 200°C, and the organic matter in the organic waste is converted into solid matter that can be used as a raw material for fertilizer. (16) A method for treating organic waste according to any of the above (6) to (15), wherein the treatment temperature in the ionization step is 120 to 200°C, and amino acids, fatty acids, or various organic acids are produced from organic matter in the organic waste by hydrolysis. (17) A method for treating organic waste according to any of the above (6) to (14), wherein the treatment temperature in the ionization step is 200 to 250°C, and the organic matter in the organic waste is carbonized to obtain carbonized material and wood acetic acid. (18) A method for treating organic waste according to any of (6) to (18) above, wherein the organic waste to be treated is a mixture of food waste and / or sewage sludge and rice husks of grasses, and the amount of SiO2 component in the organic waste is calculated taking into account the amount of SiO2 component contained in the rice husks. [Effects of the Invention]

[0010] According to the organic waste treatment apparatus of the present invention, after the step of ionizing heavy metals, Ca components, and SiO2 components, a step of maintaining the inside of a sealed container at a temperature of 120 to 140°C for one hour or more is provided, thereby enabling the formation of tobermorite in which the heavy metals are incorporated into the crystal structure with a higher incorporation rate by hydrothermal reaction. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a cross-sectional diagram illustrating an example of a treatment apparatus for treating organic waste containing heavy metals with subcritical water according to an embodiment of the present invention. [Figure 2] Figure 2 is an enlarged partial cross-sectional diagram illustrating the area around the discharge port of the organic waste treatment device containing heavy metals shown in Figure 1. [Figure 3] Figure 3 is a schematic diagram illustrating the layered crystal structure of the formed tobermorite. [Figure 4] Figure 4 is an explanatory diagram illustrating how chromium, lead, arsenic, and mercury ions are incorporated into and encapsulated within the layered crystalline structure of tobermorite. [Figure 5] Figure 5 is an explanatory diagram illustrating the reaction region when carrying out a subcritical water reaction. [Modes for carrying out the invention]

[0012] The following describes, with reference to the drawings, an example of an apparatus for treating organic waste containing heavy metals using subcritical water and an example of a method for treating waste containing heavy metals according to the present invention. Figures 1 and 2 show embodiments of the apparatus for treating organic waste containing heavy metals with subcritical water according to the present invention (hereinafter also simply referred to as the "apparatus" or "subcritical water apparatus"). As shown in Figure 1, the apparatus 10 according to this embodiment comprises a sealed container 12 for containing organic waste containing heavy metals, a steam ejection means 14 for ejecting high-temperature, high-pressure steam into the sealed container 12, a discharge port 16 provided on the bottom side of the sealed container 12, and a separation and recovery means 18 for separating and recovering the treated organic waste and liquid.

[0013] As shown in Figure 1, the sealed container 12 is a sealed container having a closed space S1 that contains organic waste to be processed, and is a container that processes organic waste under high temperature and high pressure within the closed space S1.

[0014] The sealed container 12 is supported by support legs 13 so as to be positioned at a predetermined height from the ground. The sealed container 12 is formed in a horizontal barrel shape, with its diameter gradually decreasing from the center in the left-right direction towards the end walls 12a on both sides. The sealed container 12 is formed, for example, by processing a metal plate to have heat resistance and pressure resistance, and is used to hold organic waste in a container approximately 2 m³ 3 It is provided in a size that is sufficient to accommodate it. The sealed container 12 has an input section 20 at the top of the central part and a discharge section 22 at the bottom of the central part, and these are provided to be opened and closed by opening and closing mechanisms 24 and 26, respectively.

[0015] Within the enclosed space S1 of the sealed container 12, a steam ejection pipe 28 constituting a steam ejection means 14 and a stirring means 30 for stirring organic waste are arranged. The sealed container 12 is also equipped with a safety valve 32, for example, which can adjust the set pressure, to release internal steam when the internal pressure exceeds a set value. Furthermore, a sound-dampening, deodorizing, and heavy metal recovery device 34 is provided in the middle of the exhaust pipe connected to the safety valve 32. The steam exhausted through the safety valve 32 is sound-dampened and deodorized, heavy metals and heavy metal compounds are recovered, and the steam is discharged to the outside air.

[0016] In this embodiment, as shown in Figures 1 and 2, the discharge port 16 is located on the bottom side of the left and right center of the sealed container 12, and is positioned so that the treated organic waste is discharged downwards. In this embodiment, the diameter of the discharge port 16 is set to, for example, about 300 mm. A discharge pipe 36, which protrudes downward, is connected to the discharge port 16 to form a discharge route R1 for the processed organic waste, and an opening / closing mechanism 26 is provided in the middle of the discharge route R1 to open and close the discharge port 16.

[0017] In other words, the discharge section 22 is configured to include a discharge port 16, a discharge cylinder 36, and an opening / closing mechanism 26. The opening / closing mechanism 26 consists of an opening / closing valve such as a ball valve, which opens and closes the discharge path R1 by rotating a spherical valve body 38, which has a through hole 37 in its center that communicates with the discharge path R1, around a rotating shaft 40 that is provided perpendicular to the discharge path.

[0018] Since the sealed container 12 is formed in a horizontal barrel shape, gravity easily causes the organic waste inside to collect towards the central part where the discharge port 16 is located, and the processed organic waste can be easily discharged from the discharge port 16 simply by opening the opening / closing mechanism 26.

[0019] The input section 20 has an input port 42 opening on the upper side of the sealed container 12, and an input cylinder 43 that protrudes upward is attached to the input port 42, and an opening / closing mechanism 24, such as a ball valve, is provided to open and close the input cylinder 43.

[0020] The opening can be opened via the opening / closing mechanism 24 to allow organic waste containing heavy metals and the Ca component raw materials and SiO2 component raw materials to be put into the sealed container 12, and during processing, it is closed to maintain the sealed state of the closed space S1 inside the sealed container 12.

[0021] The steam ejection means 14 ejects high-temperature, high-pressure steam into the sealed container 12, creating a high-temperature, high-pressure environment inside the sealed container 12, and processes the organic waste through the steam.

[0022] As shown in Figure 1, the steam ejection means 14 includes a steam ejection tube 28, which is a hollow tube disposed inside the sealed container 12 and has numerous steam ejection holes 44 formed on its circumferential side; a steam generator 46 such as a boiler; and a steam supply pipe 47 that supplies steam from the steam generator 46 into the steam ejection tube 28. The steam ejected from the steam ejection means 14 into the sealed container 12 ionizes the heavy metals and the Ca and SiO2 components for tobermorite formation during processing inside the sealed container 12. To efficiently promote this ionization, for example, the steam ejected from the steam outlet pipe 28 is preferably at a temperature of 120-250°C and a pressure of 1.1-2.1 MPa. The inside of the sealed container 12 is maintained at a temperature of 120-250°C and a pressure of approximately 1.1-2 MPa.

[0023] A metal chamber is provided surrounding the sealed container 12, and its interior is a heat transfer medium / refrigerant circulation space 70. The processing device 10 is equipped with a sealed container temperature adjustment means 80 to maintain the temperature inside the sealed container 12 at 120-140°C. This sealed container temperature adjustment means 80 includes a heat transfer medium supply source 82 for supplying heat transfer medium to the heat transfer medium / refrigerant circulation space 70, a refrigerant supply source 84 for supplying refrigerant to the heat transfer medium / refrigerant circulation space 70, an operation control means 86 for controlling the operation of these supply sources 82 and 84, and a temperature measuring means 88 for measuring (or estimating) the temperature inside the sealed container 12. The temperature measuring means 88 measures (or estimates) the temperature inside the sealed container 12, while the operation control means 86 controls the operation of the temperature adjustment means 80 inside the sealed container, supplying a refrigerant or heat transfer medium as necessary to adjust the temperature inside the sealed container 12 to a predetermined temperature range.

[0024] The steam ejection pipe 28 is positioned horizontally and elongated at approximately the center of the sealed container 12 in the vertical direction, and is rotatably supported via bearings 45 provided on both end walls 12a of the sealed container 12. In other words, the steam ejection pipe 28 rotates around a horizontal axis, ejecting steam radially and directing the steam directly onto the organic waste.

[0025] The steam ejection tube 28 rotates by obtaining rotational driving force from a rotary drive device 51 such as a motor via a chain or the like. A stirring blade 48 is further attached to the steam ejection tube 28, and the steam ejection tube 28 also serves as the rotating shaft 49 of the stirring means. In other words, the steam ejection means 14 includes a rotating shaft / steam ejection tube 28 which is constructed by making the rotating shaft 49 of the stirring means 30 a hollow tube and forming a plurality of steam ejection holes 44 on the circumferential surface of the hollow tube.

[0026] The steam ejection means 14 is not limited to the configuration of this embodiment, but may also be configured in any other way, such as a configuration in which steam is ejected from the tip of a tube inserted into the sealed container 12, or a configuration in which multiple steam ejection tubes are arranged.

[0027] The stirring means 30 is a means for stirring the organic waste being processed in the sealed container 12, and can process the organic waste evenly, uniformly, and quickly. The stirring means 30 includes a rotating shaft 49 consisting of the steam ejection pipe 28 described above, and stirring blades 48 attached to the rotating shaft 49 and having a portion that extends in the circumferential direction of the rotating shaft. In this embodiment, the stirring blades 48 are formed of a right-handed spiral blade 48a and a left-handed spiral blade 48b, which are arranged in opposite directions to each other at approximately the axial center position of the rotating shaft 49.

[0028] The stirring blades 48 are designed so that the length from the rotating shaft 49 to the tip of the blade gradually decreases in diameter from the left and right center towards both ends. This ensures that organic waste is reliably stirred in accordance with the horizontal barrel shape of the sealed container 12. Furthermore, the blades are designed to form a certain gap H between the tip of the blade and the inner wall of the sealed container 12.

[0029] The spiral blades 48a and 48b transport the organic waste from the central part toward the walls at both ends, while simultaneously crushing the solid organic waste and agitating it. In this embodiment, the agitation means 30 is designed to ultimately crush the organic waste to, for example, about 0.3 to 0.8 mm.

[0030] The organic waste conveyed to the end wall 12a side by the stirring blade 48 is pushed along by the organic waste conveyed later on the end wall 12a side, and is conveyed along the inner wall of the sealed container 12, passing through the gap H, and returning to the center.

[0031] The stirring means 30 is not limited to that of this embodiment, and may be configured in any way, such as a configuration in which stirring is performed using multiple plate-shaped or blade-shaped stirring blades or rods attached to the rotating shaft 49, or a configuration in which stirring is performed using a pressurized fluid such as steam. The size of the crushed organic waste may also be set arbitrarily.

[0032] When waste is treated by ejecting high-temperature, high-pressure steam as described above, most heavy metals are incorporated into and encapsulated within the layered crystalline structure of tobermorite as described above. However, if, for example, chloride ions, silicate ions, carbonate ions, sulfate ions, phosphate ions, etc., are present as anions in the waste, they may dissolve in the steam-hot water according to the cation-anion solubility balance.

[0033] To this end, the present invention involves treating the waste in a sealed container 12 by ejecting high-temperature, high-pressure steam and maintaining the temperature, and then cooling the sealed container 12 with a refrigerant to liquefy the water vapor in the closed space S1, resulting in a treated liquid containing water-soluble compounds of the heavy metals. This liquid is then separated from the treated waste containing tobermorite in which the heavy metals are contained, and recovered.

[0034] The cooling means for cooling the sealed container 12 may also be the same as the temperature adjustment means 80 inside the sealed container. That is, the temperature adjustment means 80 inside the sealed container flows a refrigerant (cooling water) into the heat transfer medium / refrigerant flow space 70, thereby cooling the inside of the closed space S1. As the refrigerant, water or oil with controlled temperature, or gases such as air or nitrogen, can be used as needed.

[0035] As a means of forming the heat transfer medium / refrigerant flow space 70, an example of a metal chamber integrally covering the sealed container 12 was shown, but the means is not limited to this example. It may also be a structure in which a large portion of the outer surface of the sealed container 12 is covered with multiple metal chambers, or in the form of a metal pipe running around the outer circumference of the sealed container 12. Two or more of these can also be used in combination.

[0036] Next, the separation and recovery means 18 will be described. An example of the separation and recovery means 18 is shown in Figure 1, as described above. The mixture of organic waste and liquid processed near the discharge port 16 is temporarily collected in a collection container 50-1. The liquid is separated by a stainless steel mesh 56 that prevents the organic waste from passing through but allows the liquid to pass through, and is collected in another collection container 50-3 located below the collection container 50-1.

[0037] The organic waste remains separated on the stainless steel mesh 56 of the collection container 50-1, with the liquid separated. To remove it, a controlled drive device (not shown) is used to rotate one side of the stainless steel mesh 56 downwards around a rotation axis, opening it and allowing gravity to drop the organic waste into the collection container (not shown). The system has a simple configuration, is easy to operate, has a low-cost structure, and can effectively separate and recover the processed organic waste and liquid.

[0038] The present invention relates to a waste treatment device for heavy metals, which treats medical waste such as synthetic resin syringes, blood-stained gauze, disposable diapers, surgical organs, etc., discarded from medical institutions, household waste such as food waste, plastic and other synthetic resin containers, food processing waste, agricultural and fishery waste, various industrial product waste, industrial waste such as sewage sludge, and soil formed by landfilling these materials, using high-temperature, high-pressure steam. Furthermore, the device is capable of effectively separating the soil containing tobermorite with encapsulated heavy metals obtained from the treatment from the liquefied liquid in the manner described above, with simple operation, and recovering the waste and liquid separately.

[0039] Next, we will describe a treatment method using the heavy metal-containing organic waste treatment device described above. In the following explanation, sewage sludge will be used as an example of organic waste containing heavy metals.

[0040] Preparation process for the processing device Prepare a processing device 10 having the structure described above.

[0041] Process for inputting organic waste containing heavy metals and raw material components for tobermorite formation. Organic waste containing heavy metals, and sufficient amounts of Ca and SiO2 raw materials to form 5CaO·6SiO2·5H2O crystals (tobermorite) to encapsulate at least the heavy metals within the 5CaO·6SiO2·5H2O crystal (tobermorite) structure during the processing of the organic waste are placed inside the sealed container 12 and contained therein. At this time, for the efficiency of processing and for later purposes, rice husks from grasses can be mixed into the organic waste. The rice husks contain approximately 20% by mass of SiO2.

[0042] The sufficient amounts of the Ca component raw material and the SiO2 component raw material can be calculated as follows. Before this calculation, the amount of Ca (A-1) and SiO (A-2) components already present in the organic waste containing heavy metals to be processed should be analyzed and determined. In this case, if the organic waste is mixed with rice husks, the amount of SiO component derived from the rice husks should be given due consideration. Then, the amounts of Ca component (B-1) and SiO2 component (B-2) sufficient to form 5CaO·6SiO2·5H2O crystals (tobermorite) for encapsulating at least the heavy metals within the 5CaO·6SiO2·5H2O crystal (tobermorite) structure during processing are calculated, and the amounts of Ca component raw material (C-1) and SiO2 component raw material (C-2) to be added to the organic waste containing heavy metals are determined using the following formulas (1) and (2). [(B-1)-(A-1)]=(C-1)...Equation (1) [(B-2)-(A-2)]=(C-2) Formula (2)

[0043] Above, rice husks were described as part of organic waste, but rice husks from grasses may also be added as at least a part of (C-2) above, that is, as a source of raw material components for tobermorite formation, and their SiO components may be used.

[0044] Ionization process (subcritical water treatment process) The solid matter in the organic waste containing heavy metals contained in the sealed container 12 is crushed and mixed with the amounts of Ca component raw material and SiO2 component raw material calculated in the previous step. High-temperature, high-pressure steam at a temperature of 120-250°C and a pressure of 2.1 MPa is then injected into the organic waste containing heavy metals, the Ca component raw material, and the SiO2 component raw material as they are being crushed and mixed. As a result, the released steam creates a high-temperature, high-pressure environment inside the sealed container 12, for example, at around 120-250°C and 1.1-2.1 MPa. In a sealed container 12, under high temperature and high pressure conditions, the organic waste is processed for 15 minutes to 1 hour while being stirred and crushed by a rotating stirring blade 48. As described above, when treated with high-temperature, high-pressure steam (120-250°C, 1.1-2.1 MPa for 15 minutes to 1 hour), heavy metals are converted into metal ions, CaO already present in the organic waste and newly added CaO become calcium ions, and SiO2 components already present in the organic waste and newly added SiO2 components become silicon oxide ions. If the temperature and pressure are below the lower limit, there is a risk that the ionization of heavy metals and the Ca and Si oxide components necessary for tobermorite crystal formation will not be sufficient. If they exceed the upper limit, there will be no problem with the ionization of heavy metals and tobermorite-forming additives, but the hydrolysis of organic matter that occurs simultaneously will proceed and the carbonization reaction will not start. If the processing time is below the lower limit, the ionization of heavy metals and the Ca and Si oxide components necessary for tobermorite crystal formation may not be sufficient, resulting in insufficient tobermorite production. There is no upper limit, but excessively long processing times are uneconomical.

[0045] If the processing temperature in the ionization process is set to 120-200°C, the organic matter in organic waste can be converted into solid material that can be used as raw material for fertilizer and animal feed while maintaining its organic properties. In this case, depending on the type of organic waste, amino acids, fatty acids, or various organic acids can be produced from the organic matter within it through hydrolysis. On the other hand, when the processing temperature in the ionization process is set to 200-250°C, the organic matter in the organic waste can be carbonized to obtain carbonized material and wood acetic acid. This carbonized material can be used as a raw material for fertilizers, soil conditioners, and deodorizers.

[0046] Tobermorite formation process After the ionization step, the supply of high-temperature, high-pressure steam in the ionization step is stopped, and the temperature inside the sealed container 12 is maintained within the range of 120 to 140°C for at least one hour using the sealed container temperature adjustment means 80, allowing the metal ions, calcium ions, and silica ions derived from the heavy metal to undergo a sufficient hydrothermal reaction for a relatively long period of time according to the following formula (3), thereby forming crystals of a mineral called stable calcium silicate (tobermorite: 5CaO·6SiO2·5H2O). At this time, it is not necessary to adjust the pressure inside the sealed container 12, nor is stirring particularly necessary. There is no particular upper limit on the processing time in this step, but for economic reasons it is about 2 hours. In this process, if the processing temperature is below the above range, the inter-elemental bonding of heavy metals and the Ca and Si components necessary for tobermorite crystal formation may not be sufficiently established, and there is a risk that tobermorite incorporating sufficient heavy metals will not be formed. If the temperature exceeds the above range, the molecular motion is too active, and tobermorite crystallization will not begin.

[0047] In other words, in the ionization step, when treated with high-temperature, high-pressure steam (120-250°C, 1.1-2.1 MPa for 15 minutes to 1 hour), heavy metals are converted into metal ions (Figure 4 shows the case where heavy metals such as chromium, lead, arsenic, and mercury are contained in the organic waste, and these become chromium ions, lead ions, arsenic ions, and mercury ions), as shown in Figure 4. In addition, the Ca component already present in the organic waste and newly added CaO become calcium ions, and the SiO2 component already present in the organic waste and newly added SiO2 component become silica ions. Then, in the subsequent tobermorite formation step, these ions migrate to the surface reaction layer 81 of the soil particles 80 and undergo a hydrothermal reaction, forming a tobermorite layered crystalline layer 82 on the surface of the soil particles 80. During the formation of this layered crystal structure, heavy metal ions (chromium ions, lead ions, arsenic ions, and mercury ions) are incorporated into the layered crystal structure of tobermorite by replacing calcium ions through ion exchange reactions.

[0048] 6SO2+5CaO+5H2O→5CaO 6SiO2 5H2O...Formula (3) As schematically shown in Figure 3, tobermorite crystals have a layered structure in which Si-O tetrahedron layers, Ca-O octahedron layers, and Si-O tetrahedron layers are repeated, with calcium ions intercalated between the Si-O tetrahedron layers.

[0049] During the formation of this layered crystal structure, heavy metals are incorporated into the layered crystal structure and encapsulated by ion exchange reactions with calcium ions, thereby replacing the calcium ions (see Figure 4). The heavy metals are incorporated into and encapsulated within the layered crystal structure of tobermorite, and as a result, their elution is suppressed.

[0050] According to equation (3) above, the molar ratio of Ca / Si (theoretical value) is approximately 0.8. However, when the aforementioned hydrothermal reaction is carried out, some of the SiO2 component dissolves in water to form silicate ions, and in some cases, this SiO2 component does not contribute to the formation of tobermorite layered crystals. Therefore, it is preferable to pre-add an amount of the SiO2 component that satisfies formula (3) to compensate for this.

[0051] However, if too much is added, the silicate ion concentration will increase, and as will be explained later, heavy metals will no longer be trapped in the tobermorite layered crystal structure.

[0052] Furthermore, by increasing the amount of SiO2 component so that the molar ratio of Ca / Si is in the range of 0.6 to 0.8, and by blending the SiO2 component and Ca component, it is possible to maintain a high confinement rate of heavy metals in the tobermorite layered crystal.

[0053] In this way, heavy metals can be trapped within the robust tobermorite crystals, making it possible to suppress the leaching of heavy metals such as chromium, lead, cadmium, arsenic, mercury, zinc, copper, and nickel, which were previously difficult to treat. In this way, 5CaO·6SiO2·5H2O crystals (tobermorite) can be efficiently produced, and the heavy metals can be securely encapsulated within their crystal structure.

[0054] cooling process In this process, the water vapor inside the sealed container 12 is cooled and liquefied. As described above, when waste is treated in a sealed container 12 while ejecting high-temperature, high-pressure steam, most heavy metals are incorporated into the layered crystalline structure of tobermorite and contained as described above. However, if, for example, chloride ions, carbonate ions, sulfate ions, phosphate ions, nitrate ions, etc., are present as anions in the waste, those that bind with cations other than coexisting heavy metals will form particles, while the remaining anions, whose ion balance is disrupted, may exist as a solution bound to sodium or potassium. Therefore, in this invention, after the tobermorite formation step, the sealed container 12 is cooled with a refrigerant to liquefy the water vapor in the closed space S1, resulting in a treated liquid containing the water-soluble compounds of the heavy metals.

[0055] Separation and recovery process The liquid obtained in the cooling step and the solid matter in the treated organic waste containing tobermorite in which the heavy metals are encapsulated are separated and recovered. This separation and recovery step is carried out by the separation and recovery means 18. This allows for the processing of organic waste and the separation and recovery of the organic waste from the liquid using only one device. Furthermore, there is no need to transport the difficult-to-handle organic waste mixed with the liquid outside, and the organic waste can be separated and recovered directly from the sealed container with simple operation, immediately following the processing. The separation and recovery configuration is also simple and can be manufactured at low cost. Each opening and closing mechanism may be configured to be opened and closed manually, or to be opened and closed mechanically using electricity or other means. The solid material recovered at this time mainly consists of fertilizer raw materials, animal feed, and charcoal (activated carbon) while retaining their organic properties, depending on the processing temperature in the ionization process. As mentioned above, when rice husks are used as organic waste or as a raw material component for SiC, they themselves become part of fertilizer or activated carbon (charcoal), making them a useful recycling technology.

[0056] [Examples] The heavy metal solidification characteristics of dewatered sewage sludge containing heavy metals were tested using the above-mentioned treatment apparatus 10 with subcritical water. The test conditions described below were substantially the same as those described in the example in the aforementioned Japanese Patent Publication No. 4864884. (1) Test apparatus: The structure is as shown in Figure 1, with a reaction volume (closed space S1) of 2 m³. 3 A batch-processing type subcritical water treatment system was used. The boiler capacity is 500 kg / h. (2) Test conditions: Ionization process Set temperature within enclosed space S1: Rise to a maximum temperature of 185°C and maintain a constant temperature. Pressure inside enclosed space S1: Maintained up to 1.6 MPa. Processing time: 1.5 hours When considering the use of the processed solid material as fertilizer or animal feed, higher temperature and pressure conditions tend to lead to over-decomposition and loss of nutrients from the organic matter. Tobermorite formation process Set temperature in closed space S1: 120°C Pressure inside enclosed space S1: 1.1 MPa (3) Test procedure: Dewatered sewage sludge (water content approximately 78% by mass) (collected at Sewage Treatment Plant A in Kanagawa Prefecture), which was known to have low levels of Ca and SiO2 components, was treated in the subcritical water treatment apparatus. A sufficient amount of Ca component raw material [CaO)] 10 kg and SiO2 component raw material [silica (SiO2)] 13 kg (of which 5 kg was to be from rice husks, so 25 kg of dry weight of rice husks was used) was added to the sludge, and the Ca component raw material and SiO2 component raw material were thoroughly mixed with the dewatered sewage sludge. After adding and mixing the raw materials, steam was injected into a sealed container until the subcritical water reaction conditions for the ionization process were met. While maintaining these predetermined conditions, the mixture was stirred and subcritical water treatment was performed for the required time to hydrolyze the organic matter and ionize the heavy metals and tobermorite-forming component raw materials. The reaction time ranges from 30 minutes to 1 hour. Subsequently, the sealed container temperature control means 80 was used to treat the enclosed space at a predetermined temperature and pressure of 1.1 MPa and time for the tobermorite formation process, thereby forming tobermorite. After the reaction was complete, the mixture was cooled to room temperature, degassed, and returned to atmospheric pressure. Then, 10 kg of liquid containing the liquefied components was separated, followed by the separation and removal of approximately 300 kg of sludge containing tobermorite in which the heavy metals were contained (the weight increased slightly due to the hydration reaction of saturated steam).

[0057] For a total of 30 samples, including dewatered sewage sludge, liquids containing liquefied components, and sludge containing tobermorite with the aforementioned heavy metals encapsulated, physicochemical analysis of general organic components, including fertilizer components, heavy metals, and trace chemical substances was performed using the analytical methods described below. This physicochemical analysis was conducted in accordance with the "Guidelines for the Management of Heavy Metals in Sludge Fertilizer (Revised 1st Edition)" published by the Ministry of Agriculture, Forestry and Fisheries in March 2015. The permissible limits for heavy metals in sludge fertilizer were also those listed in these guidelines.

[0058] Regarding the treated sludge, the results were compiled, and the solidification rate by subcritical water treatment (the ratio of the reduction in the concentration of heavy metals in the treated sludge to the concentration of heavy metals in the raw wastewater dewatered sludge) was calculated. Two examples of the analysis results of sludge containing tobermorite in which the aforementioned heavy metals are encapsulated are shown in Table 1 as Example 1 and Example 2. The same table also includes Comparative Examples 1 and 2, which are based on the examples described in Japanese Patent Publication No. 4864884. [Table 1]

[0059] Table 1 shows that this treatment process reduces the amount of heavy metals leached out to a level that fully satisfies the permissible limits for heavy metals in sludge fertilizer as stated in the above-mentioned manual. Furthermore, it can be seen that the reduction in the amount of heavy metals eluted and the increase in the immobilization rate after treatment by the present invention are significantly lower than those of Comparative Examples 1 and 2. Furthermore, it is noteworthy that, for example, in terms of the immobilization rate of Cr, there is a 10% difference between Comparative Example 1 (43%) and Example 2 (53%), indicating variability in the treatment. However, in Example 1, the rate is 65%, and in Example 2, it is 66%, a difference of only 1%, demonstrating that a stable and consistent treatment is being performed. This trend is the same for other heavy metals as well. From the above, the effects of the present invention are clear. [Explanation of Symbols]

[0060] 10. Treatment of organic waste containing heavy metals 12. Airtight container 14. Steam ejection means 16 Outlet 18 Separation and recovery means 30 Stirring means 70 Heat transfer fluid / refrigerant flow space 80 Temperature adjustment means in closed container 82 Heat medium supply source 84 Refrigerant supply source S1 Closed space

Claims

1. Organic waste containing heavy metals, and at least the heavy metals during the treatment of the organic waste are 5CaO・6SiO ２ ・5H ２ 5CaO·6SiO for encapsulation within the O crystal (tobermorite) structure ２ ・5H ２ A sufficient amount of Ca component raw material and SiO to form O crystals (tobermorite) ２ A sealed container having a closed space for containing the raw materials, While crushing the solid matter in the aforementioned organic waste, the Ca component raw material and SiO ２ A stirring means for stirring and mixing the raw material components, The organic waste containing heavy metals, Ca component raw materials, and SiO are contained in the sealed container and being crushed and mixed by the stirring means. ２ By injecting high-temperature, high-pressure steam at a temperature of 120 to 250°C and a pressure of 1.1 to 2.1 MPa into the raw material components, a reaction treatment is performed, resulting in the formation of the heavy metals, Ca components, and SiO ２ A vapor ejection means for ionizing the components, After the ionization treatment by the steam ejection means is completed, the sealed container is maintained at a temperature of 120 to 140°C for one hour or more to form tobermorite in which the heavy metal has been incorporated into the crystal structure by a hydrothermal reaction. A cooling means for cooling and liquefying the water vapor in the sealed container, An outlet with an opening and closing mechanism is provided on the bottom side of the sealed container. A treatment device for organic waste containing heavy metals, equipped with [a specific feature / equipment].

2. The apparatus for processing organic waste according to claim 1, further comprising a separation and recovery means for discharging a mixture of a solid containing tobermorite in which the processed heavy metals are contained and a liquid containing liquefied components from the discharge port, and separating the solid and the liquid from the discharged mixture.

3. The organic waste processing apparatus according to claim 2, wherein the separation and recovery means is a separation and recovery means that recovers the mixture into a recovery container and then separates the organic waste and the liquid, and / or a separation and recovery means that supplies the mixture to a belt conveyor device and separates the solid matter and the liquid while it is in motion.

4. An organic waste treatment apparatus according to any one of claims 1 to 3, wherein the heavy metals are at least one selected from chromium, lead, cadmium, arsenic, mercury, zinc, copper, and nickel.

5. The apparatus for processing organic waste according to any one of claims 1 to 4, wherein the organic waste is urban food waste, sewage sludge, food processing wastewater sludge, or leather tanning wastewater treatment sludge.

6. Inside a sealed container having an opening / closing discharge port and a closed space, organic waste containing heavy metals and, during the treatment of the organic waste, at least the heavy metals are encapsulated in a 5CaO·6SiO ２ ·5H ２ O crystal (tobermorite) structure. A Ca component raw material and a SiO ２ ·5H ２ O crystal (tobermorite) are introduced into the organic waste and the raw material component input step for tobermorite formation by adding a sufficient amount of the raw material components ２ and the step of introducing the raw material components for forming tobermorite The solid matter in the organic waste containing heavy metals, contained in the sealed container, is crushed while the Ca component raw material and SiO ２ The raw materials are stirred and mixed with the organic waste containing heavy metals, the Ca component raw materials and SiO, which are being crushed and mixed. ２ By injecting high-temperature, high-pressure steam at a temperature of 120 to 250°C and a pressure of 1.1 to 2.1 MPa into the raw material components, a reaction treatment is performed, resulting in the formation of the heavy metals, Ca components, and SiO ２ The ionization process involves ionizing the components, A tobermorite formation step is performed in which, after the completion of the ionization step, the sealed container is kept at a temperature of 120 to 140°C for at least one hour to form tobermorite in which the heavy metal has been incorporated into the crystal structure by a hydrothermal reaction. A cooling step for cooling and liquefying the water vapor in the sealed container, A method for treating organic waste containing heavy metals, characterized by comprising the following:

7. The method for treating organic waste according to claim 6, further comprising a step of separating and recovering the liquid obtained in the cooling step from the solid matter in the treated organic waste containing tobermorite in which the heavy metals are encapsulated.

8. The SiO contained in a sealed container for tobermorite formation ２ As at least a part of the raw materials, rice husks from grasses are placed in a sealed container, and the SiO contained in the rice husks ２ A method for treating organic waste according to claim 6 or 7, using the components.

9. A method for treating organic waste according to any one of claims 6 to 8, wherein the heavy metals are at least one selected from chromium, lead, cadmium, arsenic, mercury, zinc, copper, and nickel.

10. A method for treating organic waste according to any one of claims 6 to 9, wherein the organic waste is urban food waste, sewage sludge, food processing wastewater sludge, or leather tanning wastewater treatment sludge.

11. The amount of Ca component (A-1) and SiO component (A-2) already present in organic waste containing heavy metals is determined by analysis, and at least the heavy metals are reduced to 5CaO・6SiO during processing. ２ ・5H ２ 5CaO·6SiO for encapsulation within the O crystal (tobermorite) structure ２ ・5H ２ A sufficient amount of Ca component (B-1) and SiO to form O crystals (tobermorite) ２ The amount of component (B-2) is calculated, and the amount of Ca component raw material to be added to organic waste containing heavy metals (C-1) and SiO is calculated using the following formulas (1) and (2). ２ Determine the amount of component raw materials added (C-2), and add Ca component raw materials (C-1) and SiO to organic waste containing heavy metals. ２ A method for treating organic waste according to any one of claims 6 to 10, wherein the treatment is performed by adding a component raw material (C-2). [(B-1)-(A-1)]=(C-1)...Formula (1) [(B-2)-(A-2)]=(C-2)...Formula (2)

12. The method for treating organic waste according to claim 11, wherein at least a part of (C-2) is the SiO component of rice husks of grasses.

13. The heavy metals are at least one selected from chromium, lead, cadmium, arsenic, mercury, zinc, copper, and nickel, and the heavy metals are 5CaO・6SiO in the organic waste after treatment. ２ ・5H ２ A method for treating organic waste according to any one of claims 6 to 12, wherein the organic waste after treatment satisfies at least one selected from water environmental standards, soil environmental standards, special fertilizer standards, and food safety standards, because it is encapsulated in an O-crystal (tobermorite) structure.

14. A method for treating organic waste according to any one of claims 6 to 13, wherein if the organic waste contains PCBs, the treatment is performed to decompose the PCBs.

15. A method for treating organic waste according to any one of claims 6 to 14, wherein the treatment temperature in the ionization step is 120 to 200°C, and the organic matter in the organic waste is converted into solid matter that can be used as a raw material for fertilizer.

16. A method for treating organic waste according to any one of claims 6 to 15, wherein the treatment temperature in the ionization step is 120 to 200°C, and amino acids, fatty acids, or various organic acids are produced from organic matter in the organic waste by hydrolysis.

17. A method for treating organic waste according to any one of claims 6 to 14, wherein the treatment temperature in the ionization step is 200 to 250°C, and the organic matter in the organic waste is carbonized to obtain carbonized material and wood acetic acid.

18. The organic waste to be processed is a mixture of food waste and / or sewage sludge and rice husks from grasses, and the SiO in the organic waste ２ The amount of the component is the amount of SiO contained in the rice husk. ２ A method for treating organic waste according to any one of claims 6 to 16, calculated taking into account the amount of each component.

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