Method and system for disposing of used disposable diapers

Abstract

The present invention provides a method and system for processing used disposable diapers that allows for the effective utilization of wastewater after disassembling and processing used disposable diapers and recovering recyclable resources, while also enabling the easy generation of solid raw materials from the wastewater. [Solution] The present invention provides a method for processing used disposable diapers, comprising: a separation step 2; a sorting step 4; a first pulp recovery step 7 for recovering pulp 6 from a first wastewater 5; a methane fermentation raw material recovery step 8 for recovering the first wastewater 5 for use as a raw material for methane fermentation; a dewatering step 10; a drying step 11; a solid raw material manufacturing step 12 for producing solid raw materials from solid components; and a liquid fertilizer manufacturing step 15 for producing liquid fertilizer 13, wherein the liquid fertilizer manufacturing step 15 mixes a fourth wastewater 14 with liquid components separated from a second wastewater 9 to produce liquid fertilizer 13, and the first wastewater 5, which has been processed to decompose used disposable diapers 6, is returned to the separator 1 and repeatedly used as part of the processing liquid before the pulp 6 is recovered in the first pulp recovery step 7.

Description

Technical Field

[0001] The present invention relates to a method and a system for treating used paper diapers, which produce solid raw materials for solid fertilizers or solid fuels from solid components contained in the drainage after decomposing used paper diapers, reuse the drainage after the decomposition treatment for the decomposition treatment again, or produce liquid fertilizers.

Background Art

[0002] In October 2022, in order to avoid the management pressure on farmers due to the soaring prices of chemical fertilizer raw materials and the increase in food prices, the government has put a lot of effort into the effort to utilize the sludge produced in the process of sewage treatment as fertilizer, and announced a policy to promote the domestication of chemical fertilizers. In addition, the government has compiled a policy for utilizing sewage sludge as fertilizer for agriculture, encouraged the state and local governments to use sewage sludge as fertilizer, and announced a policy to reduce the dependence on imported chemical fertilizer raw materials from foreign countries.

[0003] Furthermore, in July 2022, in order to shift the fossil fuel-centered economic, social, and industrial structure since the Industrial Revolution to a clean energy-centered one, that is, to implement GX (Green Transformation) of the entire economic and social system, necessary measures have been under consideration, and a GX implementation meeting chaired by the Prime Minister of the Cabinet has been held.

[0004] At the meeting, the roles of relevant parties and the direction of efforts for expanding the fertilizer utilization of sewage sludge resources were shown. Aiming at the domestication and stable supply of fertilizers and the construction of a resource recycling society, the Ministry of Agriculture, Forestry and Fisheries, the Ministry of Land, Infrastructure, Transport and Tourism, relevant parties in the agricultural field, and relevant parties in the sewerage field cooperate to ensure safety and quality while promoting understanding including consumers, and each relevant party is shown to make a total effort to significantly expand the fertilizer utilization of sewage sludge resources.

[0005] On the other hand, Patent Document 1 proposes a method of decomposing used disposable diapers, which have become widely used in recent years, to recover the materials that make up the diapers as recyclable resources (pulp, plastic, etc.). In addition to the materials that make up the diaper, used disposable diapers have feces and urine attached to them, and the wastewater after the used disposable diapers have been decomposed with a processing solution contains feces and urine.

[0006] Used disposable diapers are decomposed using a processing solution, and the wastewater remaining after recovering recyclable resources is treated as sewage and then discharged into the sewer system. After being treated at a sewage treatment plant, it is released into rivers, the sea, and other natural environments.

[0007] Incidentally, the wastewater remaining after decomposing used disposable diapers and recovering recyclable resources contains human waste, which is beneficial to soil nutrients (nitrogen, phosphorus, and potassium). Furthermore, the solid components (scum) extracted from the wastewater can be compressed and molded to become a raw material for solid fuel.

[0008] Patent Document 2 discloses a method in which used disposable diapers are finely crushed in a crusher, then mixed with water in a mixing tank, and the suspended solids in the sedimentation tank are used as a soil conditioner, fertilizer, etc. The aqueous solution, from which the suspended solids have been removed, is then treated as wastewater and discharged into the sewer system. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2021-121699 [Patent Document 2] Japanese Patent Publication No. 2004-25574 [Overview of the project] [Problems that the invention aims to solve]

[0010] However, the inventions described in Patent Documents 1 and 2 have the problem that although the wastewater after decomposing used disposable diapers (wastewater after recovering recyclable resources) contains nutrients beneficial to the soil, this wastewater is treated and wasted by being discharged into the sewer system, and is not effectively utilized.

[0011] Furthermore, wastewater discharged into sewers and sent to sewage treatment plants mixes with other sewage sludge to form sewage sludge. When this sewage sludge is used as fertilizer, it contains substances other than human waste, so it needs to be disinfected or sterilized to remove bacteria and other contaminants. For this reason, using sewage sludge as fertilizer requires disinfection and sterilization processes, which presents a challenge in that it cannot be easily manufactured.

[0012] Therefore, the present invention aims to provide a method and system for processing used disposable diapers that allows for the effective utilization of wastewater after the decomposition of used disposable diapers and the recovery of recyclable resources, and also allows for the easy generation of solid raw materials from the wastewater. [Means for solving the problem]

[0013] To solve the above-mentioned problems and achieve the objective, the first aspect of the present invention includes a separation step of disposing of used disposable diapers into components constituting disposable diapers by stirring them with a processing liquid in a separator without crushing them; a sorting step of sorting the solid components of pulp and plastic separated in the separation step using a sorting machine; a first pulp recovery step of recovering pulp from a first wastewater which is the liquid component separated in the separation step; a methane fermentation raw material recovery step of recovering the first wastewater for use as a raw material for methane fermentation; a dewatering step of separating the solid components and liquid components in a second wastewater after the pulp has been recovered in the first pulp recovery step; and in the dewatering step The apparatus comprises: a drying step for drying the solid components separated from the wastewater; a solid raw material manufacturing step for producing solid raw materials from the solid components dried in the drying step; and a liquid fertilizer manufacturing step for producing liquid fertilizer from the liquid components separated from the second wastewater in the dewatering step, and mixing the fourth wastewater, separated from the solid sludge components in the drying step, with the liquid components separated from the second wastewater to produce liquid fertilizer, wherein the first wastewater from which the used disposable diapers have been decomposed is returned to the separator and repeatedly used as part of the processing liquid, after which the pulp is recovered in the first pulp recovery step.

[0014] A second aspect of the present invention is characterized in that the second wastewater, after the pulp has been recovered in the first pulp recovery step, is returned to the separator together with the first wastewater and repeatedly used as part of the processing liquid.

[0015] A third aspect of the present invention is characterized in that the third wastewater, after separating the solid components of pulp and plastic separated in the separation step by a sorting machine in the sorting step, is returned to the separator together with the first wastewater and repeatedly used as part of the processing liquid.

[0016] A fourth aspect of the present invention is characterized in that the first wastewater obtained by decomposing the used disposable diapers is returned to the separator and repeatedly used as part of the processing liquid, after which a portion is recovered in the methane fermentation raw material recovery step and pulp is recovered from the remainder in the first pulp recovery step.

[0017] A fifth aspect of the present invention is a separator that disassembles and processes used disposable diapers into components constituting disposable diapers by stirring them with a processing liquid without crushing them; a sorting machine that separates the solid components of pulp and plastic separated by the separator; a first pulp recovery device that recovers pulp from a first wastewater which is the liquid component separated by the separator; a methane fermentation raw material recovery device that recovers the first wastewater for use as a raw material for methane fermentation; a dewatering device that separates the solid components and liquid components in a second wastewater after the pulp has been recovered by the pulp recovery device; and the solid components separated from the second wastewater by the dewatering device. The apparatus comprises a drying device for drying, a solid raw material manufacturing device for producing solid raw materials from the solid components dried by the drying device, and a liquid fertilizer manufacturing device that produces liquid fertilizer from liquid components separated from the second wastewater by the dewatering device, and mixes the fourth wastewater separated from the solid sludge components in the drying process with the liquid components separated from the second wastewater to produce liquid fertilizer, wherein the first wastewater from which the used disposable diapers have been decomposed is returned to the separator and repeatedly used as part of the processing liquid, after which the pulp is recovered by the first pulp recovery device. [Effects of the Invention]

[0018] According to the present invention, used disposable diapers are decomposed in a separation step, the solid components of pulp and plastic separated in the separation step are separated in a sorting step, pulp is recovered from the wastewater, which is the liquid component separated in the separation step, in a first pulp recovery step, the solid and liquid components in the wastewater after the pulp has been recovered in the first pulp recovery step are separated in a dehydration step, and the solid components separated from the wastewater in the dehydration step are dried in a drying step to produce solid raw materials. Thus, used disposable diapers are decomposed, the wastewater after the recovery of recyclable resources can be effectively utilized, and solid raw materials can be easily produced from the wastewater.

[0019] In addition, the first drainage liquid obtained by decomposing used paper diapers is returned to the separator and repeatedly used as part of the treatment liquid, so that the amount of pulp contained in the first drainage liquid can be increased, the amount of pulp recovered in one recovery process in the first pulp recovery step can be increased, and the recycled resources can be efficiently recovered.

[0020] Furthermore, the first drainage liquid obtained by decomposing used paper diapers is returned to the separator and repeatedly used as part of the treatment liquid, so that the amount of the treatment liquid used for decomposing used paper diapers can be reduced.

[0021] In addition, by repeatedly using the first drainage liquid obtained by decomposing used paper diapers as part of the treatment liquid, the concentration of the sludge portion contained in the first drainage liquid becomes high, which becomes a high-quality methane fermentation raw material.

Brief Description of the Drawings

[0022] [Figure 1] FIG. 1 is a block diagram showing the steps of a method for treating used paper diapers according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the apparatus used in each step of a method for treating used paper diapers according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0023] Hereinafter, a method for treating used paper diapers according to an embodiment of the present invention will be described with reference to the drawings. The used paper diapers in this embodiment are recyclable materials and include a liquid-permeable top sheet, a liquid-impermeable back sheet, an absorber disposed between the top sheet and the back sheet, and a plurality of elastic members that impart elasticity.

[0024] The multiple elastic members, i.e., the rubber that provides elasticity to the gathered portion, consist of multiple short elastic members, each with a length of 10 mm to 200 mm in its non-stretched state. These elastic members are solid components separated in separation step 2, described later, and become solid raw materials after being recovered together with the solid components of pulp and plastic.

[0025] Furthermore, the hot melt adhesive used in the used diapers in this embodiment includes a hot melt adhesive with a softening point of 60°C to 90°C. In addition, the absorbent material used in the used diapers in this embodiment includes a biodegradable superabsorbent polymer.

[0026] The following describes a method and system for processing used disposable diapers according to the present invention. As shown in Figures 1 and 2, the method for processing used disposable diapers according to this embodiment includes a separation step 2 in which the used disposable diaper is mixed with a processing liquid in a separator 1 without being crushed to decompose and process into components that make up the disposable diaper, and a sorting step 4 in which the solid components of pulp and plastic separated in the separation step 2 are sorted in a sorting machine 3.

[0027] Furthermore, the method for processing used disposable diapers according to this embodiment includes a first pulp recovery step 7 for recovering pulp 6 from the first wastewater 5, which is the liquid component separated in the separation step 2; a methane fermentation raw material recovery step 8 for recovering the first wastewater 5 for use as a raw material for methane fermentation; a dewatering step 10 for separating the solid component and liquid component from the second wastewater 9 after the pulp 6 has been recovered in the first pulp recovery step 7; and a drying step 11 for drying the solid component separated from the second wastewater 9 in the dewatering step 10.

[0028] Furthermore, the method for processing used disposable diapers according to this embodiment includes a solid raw material manufacturing step 12 for producing solid raw materials from solid components dried in a drying step 11, and a liquid fertilizer manufacturing step 15 for producing liquid fertilizer 13 from liquid components separated from the second wastewater 9 in a dewatering step 10, and mixing the fourth wastewater 14 separated from the solid sludge components in the drying step 11 with the liquid components separated from the second wastewater 9 to produce liquid fertilizer.

[0029] The first wastewater 5, obtained by decomposing used disposable diapers, is returned to the separator 1 and reused as part of the processing liquid before the pulp 6 is recovered in the first pulp recovery process 7. The second wastewater 9, obtained after the pulp 6 has been recovered in the first pulp recovery process 7, is returned to the separator 1 along with the first wastewater 5 and reused as part of the processing liquid. Furthermore, the third wastewater 16, obtained after the solid components of pulp and plastic separated in the separation process 2 are separated by the sorting machine 3 in the sorting process 4, is returned to the separator 1 along with the first wastewater 5 and reused as part of the processing liquid.

[0030] The separator 1 used in separation step 2 consists of an outer separator tank fixed to a housing and an inner separator tank with numerous small holes formed on its outer surface, which is rotatably supported within the outer separator tank. Used diapers and processing liquid are introduced into the inner separator tank, and the used diapers are agitated together with the processing liquid by the rotation of the inner separator tank, causing them to decompose and be processed into the materials that make up the diapers. The used diapers are decomposed and processed into pulp, plastic, and other materials within the inner separator tank, with most of the pulp remaining mixed in the processing liquid.

[0031] When the decomposition process of used disposable diapers is complete and the processing liquid is discharged from the inner cylinder separation tank, the inner cylinder separation tank remains as solid material: plastic 17, a small amount of pulp attached to the plastic 17 (plastic pulp 18), and other materials. The processing liquid (first wastewater 5) discharged from the inner cylinder separation tank is used to recover pulp 6 by the first pulp recovery device 19.

[0032] The pulp 6 recovered by the first pulp recovery device 19 in the first pulp recovery process 7 contains a large amount of moisture. This pulp 6, which contains a large amount of moisture, can be used as a raw material for recycled paper, cardboard, and disposable diapers. When using the moisture-containing pulp 6 as a raw material for recycled paper, cardboard, or disposable diapers, the moisture can be removed as needed using a dewatering device or drying device.

[0033] Furthermore, the first wastewater 5 discharged from the inner cylinder separation tank is used to recover pulp 6 by the first pulp recovery device 19, and, if necessary, is recovered by the methane fermentation raw material recovery device 20 in the methane fermentation raw material recovery process 8 and used as a methane fermentation raw material. The first wastewater 5 discharged from the inner cylinder separation tank can be returned to the inner cylinder separation tank and used again as part of the processing liquid for used disposable diapers.

[0034] In this case, the first wastewater 5 discharged from the inner cylinder separation tank can be selected by a switching valve or the like to be recovered as methane fermentation raw material in the methane fermentation raw material recovery device 20, recovered as pulp in the first pulp recovery device 19, or returned to the inner cylinder separation tank of the separator 1 and used as part of the treatment liquid. If methane fermentation raw material is needed, the first wastewater 5 is sent to the methane fermentation raw material recovery device 20; if methane fermentation raw material is not needed, it is sent to the first pulp recovery device 19 and the pulp is recovered. When a certain amount of used disposable diapers are decomposed in the separator 1 and then another certain amount of used disposable diapers are decomposed in the separator 1, the first wastewater 5 is returned to the inner cylinder separation tank of the separator 1 and used as part of the treatment liquid. By repeatedly using the first wastewater 5 as part of the treatment liquid, the concentration of sludge components contained in the first wastewater 5 increases.

[0035] The wastewater (second wastewater 9) remaining after the pulp 6 has been recovered from the first wastewater 5 contains sludge components. This second wastewater 9 is dewatered by the dewatering device 21 in the dewatering process 10, separating it into solid sludge components (scum) and liquid components. The liquid components separated from the second wastewater 9 by the dewatering device 21 become liquid fertilizer 13 in the liquid fertilizer manufacturing process 15, and the solid sludge components are dried by the drying device 22 in the drying process 11. In this case, even after dewatering by the dewatering device 21, the solid sludge components still contain some moisture, and the drying device 22 reduces the amount of moisture contained as much as possible.

[0036] The drying apparatus 22 can utilize vacuum drying, freeze-vacuum drying, freeze-drying, heating drying with a heater, etc. From the solid sludge components (scum) dried by this drying apparatus 22, solid raw material 23 is produced in the solid raw material manufacturing process 12. This solid raw material 23 is then crushed into a powder by the solid fertilizer manufacturing apparatus 24 to produce powdered fertilizer 25, and then formed into granules to produce granular fertilizer 26. These powdered fertilizers 25 and granular fertilizers 26 are sludge recovered from used disposable diapers, are organic matter excreted from the human body, and contain nitrogen, phosphorus, potassium, etc., which are beneficial nutrients for the soil. Furthermore, harmful fungi are killed because the used disposable diapers are sterilized and disinfected during the decomposition process.

[0037] Furthermore, the solid raw material 23 produced by the drying device 22 is mixed with pulp recovered by the first pulp recovery device 19, etc., by the solid fuel manufacturing device 27 and compressed and molded to produce solid fuel 28. In addition, the water separated from the solid sludge components by the drying device 22 is mixed with the water dewatered by the dewatering device 21 to become the raw material for liquid fertilizer 13.

[0038] The solid material remaining in the inner cylinder separation tank of separator 1, namely plastic 17, plastic pulp 18 (plastic 17 with a small amount of pulp attached), and other materials are sent to the sorting machine 3 in sorting process 4. The sorting machine 3 consists of an outer cylinder sorting tank fixed to the housing and an inner cylinder sorting tank with numerous small holes formed on its outer surface, which is rotatably supported within the outer cylinder sorting tank. The solid components remaining in the inner cylinder separation tank, namely pulp 6, plastic 17, plastic pulp 18 (plastic pulp 6 with a small amount of pulp attached), and other materials are fed into the inner cylinder sorting tank.

[0039] Dry air is supplied into the outer drum sorting tank, and the air blows onto the pulp 6, plastic 17, plastic pulp 18 with a small amount of pulp 6 attached, and other materials in the inner drum sorting tank that rotates within the outer drum sorting tank, separating them into pulp 6, plastic 17, plastic pulp 18, and other materials. Pulp 6 is mixed in the dry air, and in the second pulp recovery process 31, the pulp 6 is captured and recovered by a filter or the like in the second pulp recovery device 30. In addition, the plastic pulp 18 in the inner drum sorting machine is recovered in the plastic pulp recovery process 32. Furthermore, the plastic 17 remaining in the outer drum sorting tank is recovered in the plastic recovery process 29.

[0040] Furthermore, the drying air that is blown into the outer shell sorting tank, along with the pulp 6, plastic 17, plastic pulp 18 with a small amount of pulp 6 attached, and other materials, contains moisture. The third wastewater 16, which is recovered by cooling, is mixed with the first wastewater 5 and reused as the first wastewater 5.

[0041] Furthermore, the plastic 17 and plastic pulp 18 remaining in the separator 1 have some moisture attached to them. These plastics 17 and 18 with some moisture attached can be reused as recycled plastic without being sorted (dried) in sorting step 4. When using the plastics 17 and plastic pulp 18 with some moisture attached as recycled plastic, the moisture may be removed using a dewatering device or drying device as needed. In addition, plastic pulp 18 with a small amount of pulp attached to the surface of the plastic may have the attached pulp removed by washing with a washing solution.

[0042] Next, we will explain the analysis results of the powdered fertilizer 25 and granular fertilizer 26 produced from solid raw materials manufactured by the used disposable diaper processing method according to this embodiment. [Table 1] As shown in Table 1 of TIFF2026079080000002.tif69144, the powdered fertilizer 25 and granular fertilizer 26 produced from the solid raw materials of this embodiment contain lime, zinc, and copper in addition to nitrogen, phosphorus, and potassium. The lime is contained in the processing liquid used when processing used disposable diapers.

[0043] Furthermore, the levels of harmful substances such as arsenic, cadmium, nickel, chromium, mercury, and lead are below the levels stipulated by the Fertilizer Control Law, and are at levels that do not pose a problem when applied to fields as fertilizer and released into the natural environment.

[0044] Furthermore, powdered and granular fertilizers manufactured from solid raw materials contain lime and are therefore strongly alkaline, but this can be neutralized by mixing them with a neutralizing agent. Additionally, because powdered and granular fertilizers manufactured from solid raw materials contain lime, they can also be used as soil conditioners to neutralize acidic soil.

[0045] Next, a used diaper processing system according to this embodiment will be described. As shown in Figure 2, the used diaper processing system according to this embodiment includes a separator 1 that disassembles and processes used diapers into components that make up the diaper by stirring them with a processing liquid without crushing them, a sorting machine 3 that separates the solid components of pulp and plastic separated by the separator 1, a pulp recovery device 19 that recovers pulp 6 from the first wastewater 5 which is the liquid component separated by the separator 1, and a methane fermentation raw material recovery device 20 that recovers the first wastewater 5 for use as a raw material for methane fermentation.

[0046] Furthermore, the used diaper processing system according to this embodiment includes a dewatering device 21 that separates solid and liquid components from the second wastewater 9 after the pulp has been recovered by the pulp recovery device 19; a drying device 22 that dries the solid components separated from the second wastewater 9 by the dewatering device 21; a solid raw material manufacturing device 33 that produces solid raw materials from the solid components dried by the drying device 22; and a liquid fertilizer manufacturing device 34 that produces liquid fertilizer from the liquid components separated from the second wastewater 9 by the dewatering device 21 and mixes the fourth wastewater 14, which has been separated from the solid sludge components by the drying device 22, with the liquid components separated from the second wastewater 9 to produce liquid fertilizer.

[0047] In this embodiment of the used diaper processing system, the first wastewater 5 obtained by disassembling the used diapers is returned to the separator 1 and reused as part of the processing liquid, after which the pulp 6 is recovered in the pulp recovery device 19.

[0048] As described above, according to the used diaper processing method and processing system of this embodiment, the first wastewater 5 obtained by disassembling the used diapers is returned to the separator 1 and reused as part of the processing liquid, thereby increasing the amount of pulp contained in the first wastewater 5. This makes it possible to increase the amount recovered in a single step in the first pulp recovery step 7, and to efficiently recover recyclable resources.

[0049] Furthermore, the first wastewater 5 obtained by decomposing used disposable diapers is returned to the separator 1 and reused as part of the processing liquid, thereby reducing the amount of processing liquid used for decomposing used disposable diapers.

[0050] Furthermore, since the second wastewater 9, which remains after the dismantling and processing of used disposable diapers and the recovery of recyclable resources, is not discharged into sewage systems, the second wastewater 9 can be effectively utilized, and solid raw materials 23 can be easily produced from the wastewater that was previously discarded. On the other hand, since lime is strongly alkaline, it can also be used after being neutralized by mixing it with a neutralizing agent.

[0051] Furthermore, the solid raw material 23 produced by the used diaper processing method and processing system according to this embodiment is sterilized and disinfected during the decomposition process of the used diapers, so it does not contain bacteria harmful to the human body and can be used as a raw material in good hygienic condition.

[0052] Furthermore, the solid raw material 23 according to this embodiment is sludge attached to used disposable diapers and is excreted from the human body, so it does not contain any other sludge (such as livestock manure or other substances). As a result, the powdered fertilizer 25, granular fertilizer 26, and solid fuel 28 produced from this solid raw material 23 are hygienic and do not harm the human body or the environment. In addition, burning it as solid fuel does not have an adverse effect on the environment.

[0053] Furthermore, according to the used diaper processing method and system of this embodiment, in addition to decomposing the used diapers and recovering the recyclable resources of pulp 6, plastic 17, and plastic pulp 18, the second wastewater 9 obtained from processing the used diapers is also separated into solid and liquid components. The liquid component is used as liquid fertilizer 13, and the solid component is used as solid raw material 23 for powdered fertilizer 25, granular fertilizer 26, and solid raw material 23. Thus, it becomes possible to recycle used diapers almost completely (perfect recycling).

[0054] As a result, there is nothing released into the natural environment after processing used disposable diapers, thus there is no adverse impact on the natural environment. In particular, in this embodiment of the used disposable diaper processing method, the used disposable diapers are not crushed, so no small pieces of plastic (microplastics) are generated. Moreover, since the first wastewater 5, second wastewater 9, third wastewater 16, and fourth wastewater 14 are reused, they are not discharged into sewers or the ground, and therefore microplastics are not released into the ocean.

[0055] Furthermore, according to this embodiment, by returning the first wastewater 5 to the inner cylinder separation tank and using it again as part of the processing liquid for processing used disposable diapers, it can be used as a good raw material for methane fermentation. In this case, by repeatedly using the first wastewater 5 as the processing liquid for processing used disposable diapers, the amount of pulp contained in the first wastewater 5 also increases, so that a larger amount of pulp can be recovered by the first pulp recovery device 19 in the first pulp recovery step 7.

[0056] Furthermore, by repeatedly using the first wastewater 5, which is obtained by decomposing used disposable diapers, as part of the processing liquid, the concentration of sludge contained in the first wastewater 5 increases, resulting in a high-quality raw material for methane fermentation.

[0057] Furthermore, according to this embodiment, the used disposable diapers processed by the separator 1 are made by using short elastic members (rubber) with a length of 10 mm to 200 mm for the gather portion, using a hot melt adhesive with a softening point of 60°C to 90°C for the hot melt adhesive, and using a biodegradable superabsorbent polymer for the absorbent material, which makes them easier to decompose and enables material recycling.

[0058] In the above embodiment, the material was decomposed by the separator 1, and the solid material remaining in the inner cylinder separation tank was separated into plastic 17, plastic pulp 18, and pulp 6 by the sorting machine 3 in the sorting step 4, and the plastic 17, plastic pulp 18, and pulp 6 were recovered. However, the material may also be decomposed by the separator 1, and the solid material remaining in the inner cylinder separation tank may not be sorted by the sorting machine 3, and the plastic 17 and plastic pulp 18 may be used as recycled plastic as is.

[0059] As described above, embodiments of the present invention have been disclosed, but it will be apparent to those skilled in the art that modifications can be made without departing from the scope of the invention. All such modifications and equivalents are intended to be included in the claims. [Industrial applicability]

[0060] The method and system for processing used disposable diapers according to the present invention are not limited to a method for producing solid raw materials from used disposable diapers, but can also be used to decompose urine pads and other sanitary products and produce solid raw materials from these urine pads and other sanitary products. [Explanation of Symbols]

[0061] 1 Separator 2 Separation process 3. Sorting machine 4. Sorting process 5. First drainage 6. Pulp 7. First Pulp Recovery Process 8. Methane fermentation raw material recovery process 9. Second drainage 10 Dehydration process 11 Drying process 12 Solid raw material manufacturing process 13 Liquid fertilizer 14. Fourth drainage 15 Liquid fertilizer manufacturing process

Claims

1. A separation process (2) is performed in which used disposable diapers are mixed with a processing liquid in a separator (1) without being crushed, and are broken down and processed into components that make up the disposable diapers. A sorting step (4) is performed in which the solid components pulp (6) and plastic (17) separated in the separation step (2) are sorted using a sorting machine (3), A first pulp recovery step (7) recovers pulp (6) from the first wastewater (5), which is the liquid component separated in the separation step (2), A methane fermentation raw material recovery step (8) recovers the first wastewater (5) for use as a raw material for methane fermentation, A dewatering step (10) separates the solid and liquid components in the second wastewater (9) after the pulp (6) has been recovered in the first pulp recovery step (7), A drying step (11) is performed to dry the solid component separated from the second drained liquid (9) in the dehydration step (10), A solid raw material manufacturing process (12) for producing a solid raw material from the solid component dried in the drying process (11), The liquid fertilizer manufacturing process (15) includes generating liquid fertilizer (13) from the liquid components separated from the second wastewater (9) in the dewatering process (10), and mixing the fourth wastewater (14), separated from the solid sludge components in the drying process (11), with the liquid components separated from the second wastewater (9) to generate liquid fertilizer, A method for processing used disposable diapers, characterized in that the first wastewater (5) obtained by disassembling the used disposable diapers is returned to the separator (1) and repeatedly used as part of the processing liquid, after which the pulp (6) is recovered in the first pulp recovery step (7).

2. The method for processing used disposable diapers according to claim 1, characterized in that the second wastewater (9) after the pulp (6) has been recovered in the first pulp recovery step (7) is returned to the separator (1) together with the first wastewater (5) and repeatedly used as part of the processing liquid.

3. The method for processing used disposable diapers according to claim 1 or 2, characterized in that the third wastewater (16) after separating the solid components pulp (6) and plastic (17) separated in the separation step (2) by a sorting machine (3) in the sorting step (4) is returned to the separator (1) together with the first wastewater (5) and repeatedly used as part of the processing liquid.

4. The method for processing used disposable diapers according to claim 2, characterized in that the first wastewater (5) obtained by decomposing the used disposable diapers is returned to the separator (1) and repeatedly used as part of the processing liquid, after which a portion is recovered in the methane fermentation raw material recovery step (8) as needed, and the remainder is recovered as pulp in the first pulp recovery step (7).

5. A separator (1) that disposes of used disposable diapers into their constituent components by agitating them with a processing liquid without crushing them, A sorting machine (3) separates the solid components pulp (6) and plastic (17) separated by the separator (1), A first pulp recovery device (19) recovers pulp (6) from the first wastewater (5), which is the liquid component separated by the separator (1), A methane fermentation raw material recovery device (20) recovers the first wastewater (5) for use as a raw material for methane fermentation, A dewatering device (21) separates the solid and liquid components in the second wastewater (9) after the pulp (6) has been recovered by the first pulp recovery device (19), A drying device (22) for drying the solid components separated from the second drainage liquid (9) by the dewatering device (21), A solid raw material manufacturing apparatus (33) for producing solid raw materials from the solid components dried in the drying apparatus (22), The apparatus comprises a liquid fertilizer manufacturing apparatus (34) which produces liquid fertilizer (13) from the liquid components separated from the second wastewater (9) in the dewatering apparatus (21), and mixes the fourth wastewater (14), separated from the solid sludge components in the drying process (11), with the liquid components separated from the second wastewater (9) to produce liquid fertilizer (13), A used disposable diaper processing system characterized in that the first wastewater (5) obtained by disassembling the used disposable diapers is returned to the separator (1) and repeatedly used as part of the processing liquid, after which the pulp (6) is recovered by the first pulp recovery device (19).

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