Recycling system comprising resource treatment facility and used absorbent article recycling facility and used absorbent article recycling method using same

Abstract

Provided is a recycling method that uses a recycling system that comprises a resource treatment facility and a used absorbent article recycling facility, the method making it possible to further improve treatment efficiency. This recycling method is a used absorbent article recycling method that uses a recycling system (A) that comprises a resource treatment facility (2) and a used absorbent article recycling facility (1). The recycling method includes a dehydration washing step (S12) for dehydrating and washing used absorbent articles with a treatment liquid that includes a dehydrating agent at a recycling facility, a separation step (S13) for separating the treatment liquid from the constituent components of the used absorbent articles at the recycling facility, a treatment liquid usage step (S24) for using a portion of the treatment liquid separated at the separation step at a resource treatment facility, and a waste heat usage step (S14) for using a portion of the waste heat generated at the resource treatment facility at the recycling facility.

Description

Recycling system including a resource recovery facility and a recycling facility for used absorbent goods, and a method for recycling used absorbent goods using the same

[0001] The present invention relates to a recycling system including a resource recovery facility and a recycling facility for used absorbent articles, and a method for recycling used absorbent articles using the same.

[0002] There is a known technology for reusing materials generated at recycling facilities for used absorbent articles in resource recovery facilities such as incineration facilities. For example, Patent Document 1 discloses a recycling system for used disposable diapers. This recycling system includes at least a processing device that uses used disposable diapers as raw materials and generates recycled material that contains a predetermined amount of moisture and is reduced in volume to a predetermined volume, and a recycling facility that recycles the used disposable diapers by burning the recycled material as fuel and extracting thermal energy. The recycling facility may be a combustion facility that is installed in the same facility as the processing device and burns the recycled material as fuel in its original state.

[0003] WO 2006 / 134941

[0004] In Patent Document 1, disposable diapers are reduced in volume at a recycling facility and then incinerated at an incineration facility, which is a type of resource recovery facility. However, from the perspective of reducing the environmental impact and ensuring a sustainable consumption and production pattern, it is preferable that the pulp fibers, superabsorbent polymers, plastic materials, etc. of the disposable diapers are recycled as materials at the recycling facility, rather than recycling the disposable diapers as fuel.

[0005] However, in this case, the recycling facility generates waste such as used treatment liquid (which may contain excrement), exhaust gas, wastewater, etc., which may reduce the processing efficiency of the recycling facility. On the other hand, resource recovery facilities such as incineration facilities have the potential to effectively utilize materials generated at recycling facilities in addition to incinerating disposable diapers.

[0006] Therefore, an object of the present invention is to provide a recycling system that includes a resource recovery facility and a recycling facility for used absorbent articles, and a recycling method using the same, which can further improve processing efficiency.

[0007] The present invention is a method for recycling used absorbent goods using a recycling system comprising a resource recovery facility and a recycling facility for used absorbent goods, the recycling method comprising: a dehydration and washing process at the recycling facility in which the used absorbent goods are dehydrated and washed with a treatment liquid containing a dehydrating agent; a separation process at the recycling facility in which components of the used absorbent goods are separated from the treatment liquid; a treatment liquid utilization process at the resource recovery facility in which a portion of the treatment liquid separated in the separation process is utilized; and a waste heat utilization process at the recycling facility in which a portion of the waste heat generated at the resource recovery facility is utilized.

[0008] According to the present invention, it is possible to provide a recycling system that includes a resource recovery facility and a recycling facility for used absorbent articles, and a recycling method using the same, which can further improve processing efficiency.

[0009] Fig. 1 is a block diagram showing an example of the configuration of a recycling system according to a first embodiment; Fig. 2 is a flow diagram showing an example of a recycling method using the recycling system according to the first embodiment; Fig. 3 is a block diagram showing an example of the configuration of a recycling system according to a second embodiment; Fig. 4 is a flow diagram showing an example of a recycling method using the recycling system according to the second embodiment;

[0010] The present embodiment relates to the following aspects.

[0011] [Mode 1] A method for recycling used absorbent goods using a recycling system comprising a resource recovery facility and a recycling facility for used absorbent goods, the method comprising: a dehydration and washing process at the recycling facility in which the used absorbent goods are dehydrated and washed with a treatment liquid containing a dehydrating agent; a separation process at the recycling facility in which components of the used absorbent goods are separated from the treatment liquid; a treatment liquid utilization process at the resource recovery facility in which a portion of the treatment liquid separated in the separation process is utilized; and a waste heat utilization process at the recycling facility in which a portion of the waste heat generated at the resource recovery facility is utilized.

[0012] In this recycling method, by effectively utilizing a portion of waste generated at a recycling facility, such as used treatment liquid (which may contain excrement), in a resource recovery facility, it is possible to reduce the waste disposal process and equipment required at the recycling facility. In addition, by effectively utilizing a portion of the exhaust heat generated at the resource recovery facility, it is possible to cover at least a portion of the thermal energy required at the recycling facility, thereby reducing the thermal energy supply process and equipment. As a result, this recycling method makes it possible to further improve the processing efficiency at both the recycling facility and the resource recovery facility.

[0013] However, a resource recycling facility is a facility that recycles waste, biomass resources, etc. Resource recycling of waste, biomass resources, etc. means making waste, biomass resources, etc. into some kind of reusable state. Examples of such resource recycling include using waste, biomass resources, etc. as raw materials or fuel, producing materials or fuel (including gas) from waste, biomass resources, etc., and generating energy (including heat and electricity) from waste, biomass resources, etc. Examples of resource recycling facilities include incineration facilities for waste, etc. and methane fermentation facilities for biomass resources, etc.

[0014] [Aspect 2] The recycling method according to aspect 1, wherein the treatment liquid further contains an oxidizing agent.

[0015] In this recycling method, by effectively utilizing the treatment liquid containing the used dehydrating agent and oxidizing agent generated at the recycling facility in the resource recovery facility, it is possible to reduce the processes and equipment required for the disposal of the dehydrating agent and oxidizing agent at the recycling facility. In addition, by effectively utilizing a portion of the exhaust heat generated by the utilization of the used dehydrating agent and oxidizing agent at the resource recovery facility in the recycling facility, it is possible to cover a portion of the thermal energy required at the recycling facility, thereby reducing the processes and equipment required for supplying thermal energy. As a result, this recycling method makes it possible to further improve the processing efficiency at both the recycling facility and the resource recovery facility.

[0016] [Aspect 3] The recycling method according to Aspect 1 or 2, wherein the treatment liquid in the dehydration and cleaning step contains an organic solvent as the dehydrating agent, the exhaust heat utilization step includes a distillation step in which a portion of the exhaust heat from the resource recovery facility is used to distill the organic solvent contained in the treatment liquid separated in the separation step, and the recycling method further includes a solvent supply step in which the organic solvent distilled in the distillation step is supplied to the dehydration and cleaning step.

[0017] In this recycling method, used organic solvent, which is one of the waste products generated in the separation process, is distilled in the distillation process using a portion of the exhaust heat from the resource recovery facility. The distilled organic solvent is then supplied to the dehydration and cleaning process in the solvent supply process for reuse. In this way, by using an organic solvent as part or all of the treatment liquid, treating used absorbent articles with the organic solvent at an appropriate location, and distilling and reusing the used organic solvent, the amount of waste liquid (treatment liquid) discharged in the recycling process can be reduced (compared to treating used absorbent articles with an aqueous solution). If the amount of waste liquid is large, it may be difficult to process it at the resource recovery facility, requiring a waste liquid disposal process. However, as described above, this recycling method reduces the amount of waste liquid. This reduces the steps and equipment required for organic solvent disposal at the recycling facility and the amount of organic solvent used. Furthermore, at least a portion of the heat energy required for the distillation process at the recycling facility can be provided by exhaust heat, thereby reducing the heat energy supply steps and equipment. This recycling method thereby improves the processing efficiency of both the recycling facility and the resource recovery facility.

[0018] [Aspect 4] The recycling method described in any one of Aspects 1 to 3 further comprises: a pretreatment step in the recycling facility, prior to the dehydration and cleaning step, in which moisture absorbed by the used absorbent articles is reduced using a pretreatment liquid; and a cooling step in the resource recovery facility, in which the pretreatment liquid used in the pretreatment step is used as cooling water.

[0019] In this recycling method, used absorbent articles are dehydrated with a pretreatment liquid in the pretreatment step, reducing the dehydration load in the dehydration washing step, and the used pretreatment liquid, which is one of the waste products generated in the pretreatment step, is used as cooling water at a resource recovery facility in the cooling step. This reduces the waste treatment process and equipment required for the pretreatment liquid at the recycling facility. In addition, at least a portion of the cooling water required at the resource recovery facility can be provided by the pretreatment liquid, reducing the cooling process and equipment required for the cooling water. This recycling method makes it possible to further improve the treatment efficiency at both the recycling facility and the resource recovery facility.

[0020] [Aspect 5] A recycling method as described in any one of aspects 1 to 4, further comprising a pre-treatment process in which the recycling facility heats and evaporates the moisture absorbed by the used absorbent articles to reduce the moisture before the dehydration and cleaning process, and the pre-treatment process includes a process of using a portion of the exhaust heat from the resource recycling facility to heat the moisture as the exhaust heat utilization process.

[0021] In this recycling method, before the dehydration and washing process, the moisture absorbed by used absorbent articles is reduced by heating and evaporating it, i.e., dehydration (pretreatment process). This reduces the dehydration burden in the dehydration and washing process. Furthermore, during this process, part of the waste heat from the resource recovery facility is used to heat the moisture (waste heat utilization process). This allows at least part of the thermal energy required for the pretreatment process at the recycling facility to be covered by the waste heat, reducing the number of thermal energy supply processes and equipment. Therefore, this recycling method makes it possible to further improve the processing efficiency at both the recycling facility and the resource recovery facility.

[0022] [Aspect 6] The recycling method according to any one of aspects 1 to 5, wherein the treatment liquid utilization step includes a methane fermentation step in which methane fermentation is performed using excrement contained in a portion of the treatment liquid separated in the separation step.

[0023] In this recycling method, the treated liquid utilization step at the resource recovery treatment facility includes a methane fermentation step in which methane fermentation is performed using excrement contained in part of the treated liquid separated in the separation step at the recycling facility. This allows at least part of the biomass resources required at the methane fermentation facility to be supplied by excrement, thereby reducing the biomass resource supply steps and equipment. Therefore, this recycling method makes it possible to further improve the treatment efficiency at both the recycling facility and the resource recovery treatment facility.

[0024] [Aspect 7] The recycling method according to Aspect 6, wherein in the waste heat utilization step, part of the waste heat generated in the resource recovery facility includes waste heat generated in the methane fermentation step.

[0025] In this recycling method, a portion of the waste heat generated in the resource recovery facility and used in the waste heat utilization process at the recycling facility includes waste heat generated in the methane fermentation process at the resource recovery facility. This reduces the number of steps and equipment required to supply thermal energy for the waste heat utilization process at the recycling facility. Therefore, this recycling method can further improve the processing efficiency of both the recycling facility and the resource recovery facility.

[0026] [Aspect 8] The recycling method according to Aspect 2, wherein the dehydration and cleaning step includes an application step of applying an ozone-containing gas as the oxidizing agent to the treatment liquid, and the recycling method further includes a gas treatment step of treating the ozone-containing gas used in the dehydration and cleaning step at the resource recovery treatment facility.

[0027] In this recycling method, in the dehydration and washing step, used absorbent articles are dehydrated and washed with a treatment liquid containing ozone-containing gas, making it easier to reuse the waste at a resource treatment facility, and the used ozone-containing gas, which is one of the waste products generated in the dehydration and washing step, is treated at the resource treatment facility. This reduces the steps and equipment required at the recycling facility for disposing of the used ozone-containing gas. As a result, this recycling method makes it possible to further improve the treatment efficiency at both the recycling facility and the resource treatment facility.

[0028] [Aspect 9] The recycling method according to any one of aspects 1 to 8, further comprising an odor treatment step in which odors generated in the dehydration and cleaning step are treated in the resource treatment facility.

[0029] In this recycling method, odors, which are one of the waste products generated in the dehydration and cleaning process, are treated at a resource treatment facility. This reduces the odor treatment process and equipment required at the recycling facility. This makes it possible to further improve the treatment efficiency at both the recycling facility and the resource treatment facility.

[0030] [Aspect 10] A recycling method described in any one of aspects 1 to 9, wherein the exhaust heat utilization process includes a drying process in which a portion of the exhaust heat from the resource recovery treatment facility is used to dry the components separated in the separation process.

[0031] In this recycling method, at least a portion of the heat energy required to dry the components in the drying process can be supplied by exhaust heat, and the process and equipment for supplying the heat energy used for drying can be reduced, thereby making it possible to further improve the processing efficiency at both recycling facilities and resource recovery facilities.

[0032] [Mode 11] A method for recycling used absorbent goods using a recycling facility for used absorbent goods, comprising: a dehydration and washing process for dehydrating and washing used absorbent goods with a treatment liquid containing a dehydrating agent; a separation process for separating the constituent components of the used absorbent goods from the treatment liquid; a treatment liquid supply process for supplying a portion of the treatment liquid separated in the separation process to a combustible waste recycling facility; and an exhaust heat utilization process for utilizing a portion of the exhaust heat generated at the recycling facility within the recycling facility.

[0033] In this recycling method, by supplying a portion of waste generated at a recycling facility, such as used treatment liquid (which may contain excrement), to a resource recovery facility, it is possible to reduce the waste disposal process and equipment required at the recycling facility. In addition, by effectively utilizing a portion of the exhaust heat generated at the resource recovery facility, it is possible to cover at least a portion of the thermal energy required at the recycling facility, thereby reducing the thermal energy supply process and equipment. As a result, this recycling method makes it possible to further improve the processing efficiency at both the recycling facility and the resource recovery facility.

[0034] [Mode 12] A recycling system comprising a resource recovery facility and a recycling facility for used absorbent goods, wherein the recycling facility comprises a dehydration and washing section that dehydrates and washes used absorbent goods with a treatment liquid containing a dehydrating agent, and a separation section that separates the constituent components of the used absorbent goods from the treatment liquid, the resource recovery facility comprises a treatment liquid utilization section that utilizes a portion of the treatment liquid separated in the separation section, and the recycling facility further comprises an exhaust heat utilization section that utilizes a portion of the exhaust heat generated at the resource recovery facility.

[0035] In this recycling system, by effectively utilizing a portion of the waste generated at the recycling facility, such as used treatment liquid (which may contain excrement), in the resource recovery facility, it is possible to reduce the waste disposal process and equipment required at the recycling facility. In addition, by effectively utilizing a portion of the exhaust heat generated at the resource recovery facility, it is possible to cover at least a portion of the thermal energy required at the recycling facility, thereby reducing the thermal energy supply process and equipment. As a result, this recycling system makes it possible to further improve the processing efficiency at both the recycling facility and the resource recovery facility.

[0036] [Aspect 13] A recycling system having a recycling facility for used absorbent goods, the recycling facility comprising: a dehydration and washing section that dehydrates and washes used absorbent goods with a treatment liquid containing a dehydrating agent; a separation section that separates the constituent components of the used absorbent goods from the treatment liquid; a treatment liquid supply section that supplies a portion of the treatment liquid separated in the separation section to a combustible material recycling facility; and an exhaust heat utilization section that utilizes a portion of the exhaust heat generated at the recycling facility within the recycling facility.

[0037] In this recycling system, by supplying a portion of waste generated at the recycling facility, such as used treatment liquid (which may contain excrement), to a resource recovery facility, it is possible to reduce the waste disposal process and equipment required at the recycling facility. In addition, by effectively utilizing a portion of the exhaust heat generated at the resource recovery facility, it is possible to cover at least a portion of the thermal energy required at the recycling facility, thereby reducing the thermal energy supply process and equipment. As a result, this recycling method makes it possible to further improve the processing efficiency at both the recycling facility and the resource recovery facility.

[0038] Hereinafter, a recycling system including a resource recovery facility and a recycling facility for used absorbent articles according to an embodiment, and a method for recycling used absorbent articles using the same will be described.

[0039] (First Embodiment) However, used absorbent articles include absorbent articles that have been used, such as those containing excrement and those not containing excrement, as well as unused but discarded absorbent articles, such as those that have been transferred but not used, and those that have been manufactured or stored but discarded (factory loss, storage loss, etc.). Absorbent articles include those containing superabsorbent polymers and pulp fibers as absorbent materials, such as disposable diapers, urine absorption pads, sanitary napkins, bed sheets, and pet sheets. Note that recycled superabsorbent polymers refer to superabsorbent polymers derived from used absorbent articles and recovered and regenerated from used absorbent articles. Recycled pulp fibers refer to pulp fibers derived from used absorbent articles and recovered and regenerated from used absorbent articles. Used absorbent articles contain contaminants. Examples of such contaminants include excrement, sebum, bacteria, odorous substances, and coloring substances derived from these substances, machine oil from manufacturing equipment, and various organic substances.

[0040] An example of the configuration of an absorbent article will be described. The absorbent article comprises a top sheet, a back sheet, and an absorbent body disposed between the top sheet and the back sheet. An example of the size of the absorbent article is a length of approximately 15 to 100 cm and a width of 5 to 100 cm. The absorbent article may further comprise other components that are typically included in absorbent articles, such as a diffusion sheet, a leak-proof wall, a side sheet, and an exterior sheet.

[0041] The material for the top sheet is not particularly limited as long as it can be used in absorbent articles, and examples thereof include liquid-permeable nonwoven fabrics, synthetic resin films with liquid-permeable holes, and composite sheets thereof. The material for the back sheet is not particularly limited as long as it can be used in absorbent articles, and examples thereof include liquid-impermeable nonwoven fabrics, liquid-impermeable synthetic resin films, and composite sheets thereof. The material for the diffusion sheet is not particularly limited as long as it can be used in absorbent articles, and examples thereof include liquid-permeable nonwoven fabrics. The materials for the leak barrier, side sheets, and exterior sheets are not particularly limited as long as they can be used in absorbent articles, and examples thereof include liquid-impermeable nonwoven fabrics. The materials for the nonwoven fabrics and synthetic resin films are not particularly limited as long as they can be used in absorbent articles, and examples thereof include synthetic resins. Examples of synthetic resins include olefin-based resins such as polyethylene and polypropylene, polyamide-based resins such as 6-nylon and 6,6-nylon, and polyester-based resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). The nonwoven fabric may be made of natural fibers such as cotton, rayon, etc. In this embodiment, at least the nonwoven fabric and the synthetic resin film are referred to as plastic materials.

[0042] Examples of absorbent materials include absorbent materials, namely, pulp fibers and superabsorbent polymers. Pulp fibers are not particularly limited as long as they can be used in absorbent articles, and examples include cellulosic fibers. Cellulosic fibers include, for example, wood pulp, crosslinked pulp, non-wood pulp, regenerated cellulose, and semi-synthetic cellulose. Pulp fiber size includes an average fiber length of, for example, several tens of microns, preferably 20 to 40 microns, and an average fiber length of, for example, several millimeters, preferably 2 to 5 mm. Superabsorbent polymers (SAPs) are not particularly limited as long as they are usable in absorbent articles and contain acid groups, and examples include those containing carboxyl groups, sulfo groups, etc., with those containing carboxyl groups being preferred. Examples include absorbent polymers based on polyacrylates (containing carboxyl groups), polysulfonates (containing sulfo groups, etc.), and polymaleic anhydrides (containing carboxyl groups). The size of the superabsorbent polymer (when dry) can be, for example, an average particle size of several hundred μm, preferably 200 to 500 μm. The absorbent body may include a core wrap sheet formed of a liquid-permeable sheet such as tissue, which encloses the absorbent material.

[0043] One side and the other side of the absorbent body are bonded to the top sheet and the back sheet, respectively, via an adhesive. In a plan view, the portion (peripheral portion) of the top sheet that extends outward from the absorbent body so as to surround the absorbent body is bonded via an adhesive to the portion (peripheral portion) of the back sheet that extends outward from the absorbent body so as to surround the absorbent body. Therefore, the absorbent body is enclosed within the bonded body of the top sheet and the back sheet. If the absorbent body has a core wrap sheet, the absorbent material is bonded to the core wrap sheet via an adhesive. The diffusion sheet, leak-proof wall, side sheet, and exterior sheet are also each bonded to other components with an adhesive. The adhesive is not particularly limited as long as it can be used in absorbent articles, and examples thereof include hot-melt adhesives. Examples of hot-melt adhesives include pressure-sensitive adhesives or heat-sensitive adhesives that are primarily rubber-based, such as styrene-ethylene-butadiene-styrene, styrene-butadiene-styrene, and styrene-isoprene-styrene, or olefin-based, such as polyethylene.

[0044] As described above, an absorbent article having the above-mentioned configuration contains some or all of the above-mentioned contaminants at the stage of a used absorbent article.

[0045] Next, a recycling system including a resource recovery facility and a recycling facility for used absorbent articles according to this embodiment, and a recycling method using the same will be described. In this embodiment, a waste incineration facility will be described as an example of the resource recovery facility.

[0046] FIG. 1 is a block diagram showing an example of the configuration of a recycling system A according to this embodiment. The recycling system A includes a recycling facility 1 for used absorbent goods and a waste incineration facility 2 (resource treatment facility). The recycling facility 1 and the incineration facility 2 may be integrated, adjacent, or co-located. Furthermore, both facilities may be located on the same site or on separate sites. The recycling facility 1 separates and recovers some or all of the components of used absorbent goods so that they can be reused as materials for various products (including absorbent goods). The incineration facility 2 is a facility that incinerates waste such as garbage and is exemplified by a garbage incineration plant (a waste disposal plant). The incineration facility 2 may include a device that utilizes thermal energy generated by incineration. By treating waste (e.g., effluent and exhaust gas) generated at the recycling facility 1 at the incineration facility 2 and utilizing the energy (e.g., heat and electricity) generated at the incineration facility 2 at the recycling facility 1, the processing efficiency of both facilities can be further improved.

[0047] FIG. 2 is a flow diagram showing an example of a recycling method using the recycling system A according to this embodiment. The recycling method includes a step S1 for treating used absorbent articles, which is carried out at a recycling facility 1, and a step S2 for treating waste, which is carried out at an incineration facility 2. Step S1 is a step for separating and recovering some or all of the components of used absorbent articles so that they can be reused as materials for various products (including absorbent articles). Step S2 is a step for incinerating the waste, which may include a step for utilizing the generated thermal energy, etc. By treating the waste generated in step S1 in step S2 and utilizing the energy (e.g., heat, electricity) generated in step S2 in step S1, the processing efficiency at both facilities can be further improved.

[0048] The recycling system A and the recycling method using the same will be described below.

[0049] First, we will explain step S1 of the recycling method, which is carried out at the recycling facility 1. Step S1 includes a dehydration and washing step S12 and a separation step S13. Step S1 may further include at least one of a crushing step S10, a pretreatment step S11, a waste heat utilization step S14 (a drying step S14a and a distillation step S14b), and a solvent supply step S15.

[0050] The recycling facility 1 includes a dehydration and washing device 12 (dehydration and washing section) and a separation device 13 (separation section). The recycling facility 1 may further include at least one of a crushing device 10 (crushing section), a pretreatment device 11 (pretreatment section), a drying device 14a (drying section), a distillation device 14b (distillation section), and a solvent supplying device 15 (solvent supplying section).

[0051] The dehydration and washing step S12 and the separation step S13 are respectively performed by the dehydration and washing device 12 and the separation device 13. The crushing step S10, the pretreatment step S11, the drying step S14a, the distillation step S14b, and the solvent supplying step S15 are respectively performed by the crushing device 10, the pretreatment device 11, the drying device 14a, the distillation device 14b, and the solvent supplying device 15. Each step will be specifically described below.

[0052] The shredding step S10 is a step of shredding used absorbent articles. The shredding device 10 used in the shredding step S10 is not particularly limited as long as it can expose the internal superabsorbent polymer and pulp fibers, and examples thereof include a biaxial shredder (e.g., a biaxial rotary shredder, a biaxial differential shredder, or a biaxial shear shredder). As a result, a portion or all of the used absorbent article is shredded to generate multiple small pieces containing one or more component parts. The size of the small pieces is not particularly limited as long as they can be handled in the subsequent steps, and examples include squares with sides of 1 to 10 cm in a plan view or equivalent sizes (approximately the same area). Here, shredding also refers to the case where the sheets (e.g., top sheet, back sheet, and exterior sheet) constituting the outer surface of the used absorbent article are torn, thereby releasing the internal superabsorbent polymer and pulp fibers to the outside. In this case, the plurality of small pieces may include one or more pieces of a torn sheet, or one or more lumps containing discharged superabsorbent polymer or pulp fibers.

[0053] The crushing step S10 may be carried out in air or in a liquid. When the crushing step S10 is carried out in a liquid, examples of the liquid include water and the aqueous solutions used in the pretreatment step S11, i.e., an acidic aqueous solution (described below) and a polyvalent metal salt aqueous solution (described below). Therefore, when an acidic aqueous solution or a polyvalent metal salt aqueous solution is used as the liquid, the crushing step S10 and the pretreatment step S11 can be said to be carried out simultaneously.

[0054] The crushing step S10 is mainly performed to facilitate separation of one or more components of the used absorbent article from the other components in the separation step S13, and therefore may be performed before the separation step S13. Therefore, the crushing step S10 may be performed before the separation step S13, and either before the dehydration washing step S12, during the dehydration washing step S12, or after the dehydration washing step S12. However, "before the dehydration washing step S12" means either before the pretreatment step S11, during the pretreatment step S11, or after the pretreatment step S11.

[0055] If the crushing step S10 is not performed and uncrushed used absorbent articles are used as they are in the dehydration and cleaning step S12 (they may or may not have undergone the pre-treatment step S11), for example, by using an organic solvent (described below) as a dehydrating agent, the adhesive of the used absorbent articles can be dissolved in the organic solvent, allowing the used absorbent articles to be disassembled into their individual component parts.

[0056] The pretreatment step S11 is a step of reducing the moisture absorbed by used absorbent articles (particularly superabsorbent polymers) that have been crushed through the crushing step S10 or have not been crushed, i.e., a step of dehydrating the used absorbent articles. However, because the pretreatment step S11 is a step carried out before the dehydration and washing step S12, it is sufficient that the used absorbent articles or their crushed counterparts are dehydrated to a certain extent, and complete dehydration is not necessarily required. The proportion of moisture to be dehydrated can be, for example, 10 to 90% by mass of the moisture absorbed in the used absorbent articles.

[0057] Specifically, the pretreatment step S11 is a step in which a used absorbent article is subjected to at least one of an acidic aqueous solution treatment, a polyvalent metal salt treatment, a high-pressure steam treatment, a freeze-drying treatment, and an organic solvent treatment as a pretreatment. These treatments are treatments for dehydrating a superabsorbent polymer. The acidic aqueous solution treatment is a treatment in which a superabsorbent polymer is brought into contact with an acidic aqueous solution. The polyvalent metal salt treatment is a treatment in which a superabsorbent polymer is brought into contact with an aqueous solution containing a polyvalent metal salt. The high-pressure steam treatment is a treatment in which a superabsorbent polymer is brought into contact with high-pressure steam. The freeze-drying treatment is a treatment in which a superabsorbent polymer is exposed to a low-temperature dry atmosphere. The organic solvent treatment is a treatment in which a high molecular weight absorbent polymer is brought into contact with a hydrophilic organic solvent. Although known methods can be used for each of these treatments, the acidic aqueous solution treatment and the polyvalent metal salt treatment in particular are as follows.

[0058] The acidic aqueous solution treatment as the pretreatment step S11 is a step of inactivating the superabsorbent polymer of a used absorbent article with an acidic aqueous solution. For example, the acidic aqueous solution treatment is a step of inactivating the superabsorbent polymer by immersing a used absorbent article (which may or may not have been crushed in the crushing step S10) in an acidic aqueous solution. The acidic aqueous solution treatment is preferable to the polyvalent metal salt treatment in that it is less likely to leave ash residue.

[0059] The acid (inactivator) in the acidic aqueous solution is not particularly limited, and examples thereof include acidic substances such as inorganic acids and organic acids. Examples of inorganic acids include sulfuric acid, hydrochloric acid, and nitric acid, with sulfuric acid being preferred from the viewpoints of not containing chlorine and cost. Examples of organic acids include carboxylic acids having multiple carboxyl groups (e.g., citric acid), carboxylic acids having one carboxyl group (e.g., acetic acid), and sulfonic acids (e.g., methanesulfonic acid). Organic acids are preferably those having multiple carboxyl groups, and more preferably citric acid, because they readily form chelate complexes with divalent or higher metals (e.g., calcium) contained in excrement and are less likely to leave ash residue in the superabsorbent polymer and pulp fibers. The acid concentration of the acidic aqueous solution is not particularly limited as long as it can perform the dehydration function, and examples thereof include 0.1 to 30% by mass. Furthermore, the acid (inactivator) is preferably an acid dissociation constant (pK ａ , in water) ａ , in water).

[0060] The acidic aqueous solution preferably has a pH within a predetermined range. The upper limit of the pH is preferably 6.0, more preferably 5.0. A pH of 6.0 or less can facilitate dehydration of the superabsorbent polymer. The lower limit of the pH is preferably 0.5, more preferably 1.0. A pH of 0.5 or more can prevent damage to the pulp fibers, which are another target for recovery. However, the pH is measured at 25°C using, for example, a twin pH meter AS-711 manufactured by Horiba, Ltd.

[0061] The pretreatment device 11 for performing the acidic aqueous solution treatment is not particularly limited in its specific configuration as long as it can immerse a superabsorbent polymer in an acidic aqueous solution. The pretreatment device 11 has, for example, a tank in which used absorbent articles (or crushed products thereof) containing a superabsorbent polymer can be placed and in which an acidic aqueous solution can be stored, a supply means for supplying the acidic aqueous solution into the tank, and a stirring means for stirring the acidic aqueous solution in the tank.

[0062] In the acidic aqueous solution treatment, the temperature of the acidic aqueous solution is not particularly limited, and may be, for example, room temperature (25° C.). To accelerate the reaction rate, the acidic aqueous solution may be heated to a temperature range lower than 100° C. The treatment time is not particularly limited, and may be, for example, about 5 to 60 minutes.

[0063] When an acidic aqueous solution treatment is performed in the pretreatment step S11, some or all of the pretreatment liquid, which is the used acidic aqueous solution, may be supplied to the incineration facility 2. That is, the used pretreatment liquid containing used absorbent articles (or a plurality of small pieces) is filtered using a screen or the like to separate the used pretreatment liquid from the used absorbent articles, and then supplied to the incineration facility 2. In this case, the pretreatment liquid supplied to the incineration facility 2 can be used, for example, as cooling water for the equipment in the incineration facility 2 (e.g., the incineration apparatus 21, the methane fermentation apparatus 22, the power generation apparatus 23). The pretreatment liquid used as cooling water may be mixed with another cooling water before use. This allows the recycling facility 1 to eliminate the acidic aqueous solution wastewater treatment process and wastewater treatment equipment, and the incineration facility 2 to reduce the amount of new cooling water supplied.

[0064] Although not shown, when an acidic aqueous solution treatment step is performed as the pretreatment step S11, a reactivation treatment step is then performed in which the superabsorbent polymer inactivated by the acidic aqueous solution treatment is activated using alkali metal ions supplied from an alkali metal ion source. The reactivation treatment step may be performed before the dehydration and cleaning step S12. Alternatively, the reactivation treatment step may be included in the dehydration and cleaning step S12 and performed during the dehydration and cleaning step S12. In this case, an aqueous solution containing an alkali metal ion source is added to the solution used in the dehydration and cleaning step S12. Alternatively, the reactivation treatment step may be performed after the dehydration and cleaning step S12.

[0065] Specifically, the reactivation treatment involves reactivating the inactivated superabsorbent polymer with alkali metal ions in an alkaline aqueous solution, which is an aqueous solution containing an alkali metal ion source. At this time, the H ions in the inactivated superabsorbent polymer are replaced with alkali metal ions, neutralizing the polymer and turning it into a reactivated superabsorbent polymer. In other words, the water absorption capacity of the superabsorbent polymer is restored. Note that if the reactivation treatment is performed during the dehydration and washing step S12, the reactivated superabsorbent polymer will not absorb water because a dehydrating agent is present around it.

[0066] Examples of alkali metal ions include lithium ions, sodium ions, and potassium ions, as well as any combination thereof. The alkali metal ion source is not particularly limited as long as it can supply these alkali metal ions, and examples include alkali metal hydroxides and salts of alkali metal hydroxides with acids having a larger acid dissociation constant than the acid groups of the superabsorbent polymer. Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, and potassium hydroxide, as well as any combination thereof. Examples of salts include lithium carbonate, sodium carbonate, potassium carbonate, lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, lithium chloride, sodium chloride, and potassium chloride. The aqueous solution containing the alkali metal ion source is preferably neutral or alkaline, and more preferably alkaline. The concentration of the alkali metal ion source in the alkaline aqueous solution is not particularly limited as long as it reactivates the superabsorbent polymer. When an alkali metal hydroxide is used as the alkali metal ion source, the concentration may be, for example, 0.5 to 50% by mass.

[0067] The specific configuration of the device for carrying out the reactivation treatment is not particularly limited as long as it can immerse the inactivated superabsorbent polymer in the alkaline aqueous solution. The device may, for example, have a tank in which used absorbent articles containing a superabsorbent polymer (or crushed products thereof) can be placed and in which the alkaline aqueous solution can be stored, a supply means for supplying the alkaline aqueous solution into the tank, and a stirring means for stirring the alkaline aqueous solution in the tank.

[0068] In the reactivation treatment, the temperature of the alkaline aqueous solution is not particularly limited and may be, for example, room temperature (25° C.). To accelerate the reaction rate, the alkaline aqueous solution may be heated to a temperature lower than 100° C. The treatment time is not particularly limited and may be, for example, about 5 to 60 minutes.

[0069] When a reactivation treatment step is performed in which the superabsorbent polymer inactivated with an acidic aqueous solution is reactivated with alkali metal ions in an alkaline aqueous solution, some or all of the used alkaline aqueous solution may be supplied to the incineration facility 2. That is, the used alkaline aqueous solution containing the used absorbent articles (or a plurality of small pieces) is filtered with a screen or the like to separate the used alkaline aqueous solution from the used absorbent articles, and then supplied to the incineration facility 2. In this case, the alkaline aqueous solution supplied to the incineration facility 2 can be used, for example, as cooling water for the equipment in the incineration facility 2 (e.g., the incineration apparatus 21, the methane fermentation apparatus 22, the power generation apparatus 23). The alkaline aqueous solution used as cooling water may be mixed with another cooling water before use. This allows the recycling facility 1 to eliminate the alkaline aqueous solution wastewater treatment step and wastewater treatment equipment, and the incineration facility 2 to reduce the amount of new cooling water supplied.

[0070] When both the used acidic aqueous solution and the used alkaline aqueous solution are supplied to the incineration facility 2, they may be mixed and supplied. In this case, the mixed solution of the acidic aqueous solution and the alkaline aqueous solution is neutralized to become a neutral or nearly neutral aqueous solution. As a result, when the mixed solution is used as cooling water for the equipment in the incineration facility 2 (e.g., the incineration device 21, the methane fermentation device 22, and the power generation device 23), the occurrence of effects on the equipment (e.g., corrosion) can be suppressed.

[0071] The polyvalent metal salt treatment as the pretreatment step S11 is a step of inactivating the superabsorbent polymer of a used absorbent article with polyvalent metal ions supplied from the polyvalent metal salt. For example, the used absorbent article (which may or may not have been crushed in the crushing step S10) is immersed in an aqueous solution of the polyvalent metal salt to bring the superabsorbent polymer into contact with the polyvalent metal ions and inactivate it. The polyvalent metal salt treatment is preferable to the acidic aqueous solution treatment in that dehydration is more easily promoted.

[0072] The polyvalent metal salt in the polyvalent metal salt aqueous solution is not particularly limited, and examples thereof include alkaline earth metal salts and transition metal salts. Examples of alkaline earth metal salts include salts of beryllium, magnesium, calcium, strontium, and barium, with calcium chloride, calcium nitrate, magnesium chloride, and magnesium nitrate being preferred, and calcium chloride being more preferred. Examples of transition metal salts include salts of iron, cobalt, nickel, copper, and aluminum, with their inorganic or organic acid salts being preferred. Examples of inorganic acid salts include iron chloride, iron sulfate, iron phosphate, iron nitrate, cobalt chloride, cobalt sulfate, cobalt phosphate, cobalt nitrate, nickel chloride, nickel sulfate, copper chloride, copper sulfate, and aluminum sulfate. Examples of organic acid salts include iron lactate, cobalt acetate, cobalt stearate, nickel acetate, and copper acetate. The concentration of the polyvalent metal salt in the aqueous polyvalent metal salt solution is not particularly limited as long as it can perform the dehydrating function, and when an alkaline earth metal salt is used as the polyvalent metal, the concentration is, for example, 0.1 to 10 mass %.

[0073] The pretreatment device 11 for carrying out the polyvalent metal salt treatment is not particularly limited in its specific configuration as long as it can immerse a superabsorbent polymer in an aqueous solution of a polyvalent metal salt. The pretreatment device 11 has, for example, a tank in which a used absorbent article (or a disassembled product thereof) containing a superabsorbent polymer can be placed and in which an aqueous solution of a polyvalent metal salt can be stored, a supply means for supplying the aqueous solution of a polyvalent metal salt into the tank, and a stirring means for stirring the aqueous solution of a polyvalent metal salt in the tank.

[0074] In the polyvalent metal salt treatment, the temperature of the polyvalent metal salt aqueous solution is not particularly limited and may be, for example, room temperature (25°C). To increase the reaction rate, the polyvalent metal salt aqueous solution may be heated to a temperature range lower than 100°C. The treatment time is not particularly limited and may be, for example, about 10 to 120 minutes. The pH of the polyvalent metal salt aqueous solution is not particularly limited and may be, for example, 11 or less. When an alkaline compound is used, the pH of the aqueous solution is preferably greater than 7 and less than or equal to 11.

[0075] When polyvalent metal salt treatment is performed in the pretreatment step S11, some or all of the pretreatment liquid, which is the used polyvalent metal salt aqueous solution, may be supplied to the incineration facility 2. That is, the used pretreatment liquid containing used absorbent articles (or a plurality of small pieces) is filtered using a screen or the like to separate the used pretreatment liquid from the used absorbent articles, and then supplied to the incineration facility 2. In this case, the pretreatment liquid supplied to the incineration facility 2 can be used, for example, as cooling water for the equipment in the incineration facility 2 (e.g., the incineration device 21, the methane fermentation device 22, the power generation device 23). The pretreatment liquid used as cooling water may be mixed with another cooling water before use. This allows the recycling facility 1 to eliminate the need for a wastewater treatment process and wastewater treatment equipment for the polyvalent metal salt aqueous solution, and the incineration facility 2 to reduce the amount of new cooling water supplied.

[0076] When polyvalent metal salt treatment is performed as the pretreatment step S11, the superabsorbent polymer inactivated by the polyvalent metal salt treatment is subsequently subjected to a step of substituting polyvalent metal ions with an acidic substance (acidic aqueous solution) (acidic substance substitution treatment), followed by a step of neutralizing the superabsorbent polymer in which the polyvalent metal ions have been substituted with the acidic substance using an alkaline substance (alkaline aqueous solution) containing sodium (alkaline substance neutralization treatment). The step of substituting polyvalent metal ions with an acidic substance is performed before the dehydration and cleaning step S12 or during the dehydration and cleaning step S12. If performed during the dehydration and cleaning step S12, an aqueous solution containing an acidic substance is added to the solution used in the dehydration and cleaning step S12. On the other hand, the step of neutralizing the superabsorbent polymer with an alkaline substance is performed after the step of substituting polyvalent metal ions with an acidic substance, during the dehydration and cleaning step or after the dehydration and cleaning step S12. When the dehydration and cleaning step S12 is performed during the dehydration and cleaning step S12, an aqueous solution containing an alkaline substance having sodium is added to the solution in the dehydration and cleaning step S12.

[0077] The step of substituting the polyvalent metal ions of the superabsorbent polymer inactivated by the polyvalent metal salt treatment with an acidic substance (acidic substance substitution treatment) is substantially the same as the acidic aqueous solution treatment described above. However, the acid in the acidic aqueous solution is preferably a strongly acidic inorganic acid. Examples of such inorganic acids include sulfuric acid, hydrochloric acid, and nitric acid, but sulfuric acid is preferred from the viewpoints of not containing chlorine and cost.

[0078] The above-mentioned step of neutralizing the superabsorbent polymer in which polyvalent metal ions have been substituted with an acidic substance using an alkaline substance (alkaline substance neutralization treatment) is substantially the same as the above-mentioned reactivation treatment, except that the alkali metal ion source is an alkaline substance containing sodium, such as sodium hydroxide, and the alkali metal ions in the alkaline aqueous solution, which is an aqueous solution containing the alkali metal ion source, are sodium ions.

[0079] In the pretreatment step S11, the proportion of used absorbent articles (or a plurality of small pieces) in the aqueous solution used in the various treatments is not particularly limited, as long as the various treatments can be carried out. Examples of the proportion include 0.1 to 50% by mass, and preferably 1 to 40% by mass. A proportion of 0.1% by mass or more allows the treatments to proceed efficiently. A proportion of 50% by mass or less allows the various treatments to proceed more easily.

[0080] When a superabsorbent polymer inactivated with a polyvalent metal salt aqueous solution is subjected to an acidic substance substitution treatment with an acidic aqueous solution, a portion or all of the used acidic aqueous solution may be supplied to the incineration facility 2. Furthermore, when a superabsorbent polymer subjected to an acidic substance substitution treatment with an acidic aqueous solution is subjected to an alkaline substance neutralization treatment with an alkaline aqueous solution, a portion or all of the used alkaline aqueous solution may be supplied to the incineration facility 2. In this case, examples of uses of the acidic aqueous solution and the alkaline aqueous solution supplied to the incineration facility 2 include cooling water for equipment within the incineration facility 2 (e.g., the incineration apparatus 21, the methane fermentation apparatus 22, and the power generation apparatus 23). The acidic aqueous solution and the alkaline aqueous solution used as cooling water may be mixed with other cooling water and used. This can eliminate the need for an acidic aqueous solution effluent treatment process and effluent treatment equipment in the recycling facility 1, and can reduce the amount of new cooling water supplied to the incineration facility 2. Furthermore, when both the acidic aqueous solution and the alkaline aqueous solution are supplied to the incineration facility 2, they may be mixed and supplied. In this case, the mixture of the acidic aqueous solution and the alkaline aqueous solution can be neutralized to become a neutral or nearly neutral aqueous solution, so that when used as cooling water for equipment within the incineration facility 2 (e.g., incineration apparatus 21), the impact on the equipment can be reduced.

[0081] Preferably, the pretreatment step S11 includes a step of separating and removing the water generated in the pretreatment step S11 before the dehydration and washing step S12. For example, the water solution containing the used absorbent articles (or a plurality of small pieces) in the pretreatment step S11 is filtered through a screen or the like to separate and remove the water generated in the pretreatment step S11. By removing the water once before the dehydration and washing step S12 in this way, the solution containing the dehydrating agent (which may further contain an oxidizing agent: as described below) in the dehydration and washing step S12 can be treated at the desired concentration without being diluted.

[0082] An apparatus that supplies a part or all of the effluent from the pretreatment step S11 (acidic aqueous solution, alkaline aqueous solution, polyvalent metal salt aqueous solution) to the incineration facility 2 can be called an effluent supply apparatus (effluent supply unit: not shown). An example of such an apparatus is a liquid feed pump (not shown) attached to the pretreatment device 11.

[0083] The dehydration and washing step S12 is a step of dehydrating and washing the used absorbent article with a treatment liquid containing a dehydrating agent. In the present embodiment, as a preferred aspect, the dehydration and washing step S12 is a step of dehydrating and washing a mixture containing a superabsorbent polymer having acid groups, which is a component of the used absorbent article, and pulp fibers, with a solution containing a dehydrating agent (which may further contain an oxidizing agent) that can dehydrate the superabsorbent polymer and pulp fibers.

[0084] The mixture containing the superabsorbent polymer and pulp fibers, which are components of the absorbent article, is not particularly limited as long as it contains the superabsorbent polymer and pulp fibers of a used absorbent article. For example, the mixture may be a used absorbent article that has not undergone either the shredding step S10 or the pretreatment step S11. If the used absorbent article has undergone the shredding step S10, the mixture is a plurality of small pieces formed by shredding the used absorbent article, and contains the superabsorbent polymer and pulp fibers, but the superabsorbent polymer and pulp fibers have not been individually separated. If the used absorbent article has undergone the pretreatment step S11, the mixture is a pretreated used absorbent article, and contains the superabsorbent polymer and pulp fibers that have been dehydrated to a certain extent, but the superabsorbent polymer and pulp fibers have not been individually separated. When used absorbent articles have been subjected to both the shredding step S10 and the pre-treatment step S11, the mixture is a plurality of small pieces that have been pre-treated and contain superabsorbent polymer and pulp fibers that have been dehydrated to a certain extent, but the superabsorbent polymer and pulp fibers have not been separated individually. Alternatively, the mixture may be a mixture containing superabsorbent polymer and pulp fibers that has been prepared separately in advance, regardless of the shredding step S10 or the pre-treatment step S11.

[0085] The mixture may further contain a plastic material that is a component of used absorbent articles. In this case, the dehydration and washing step S12 is a step of dehydrating and washing the mixture containing the superabsorbent polymer, pulp fiber, and plastic material that are components of used absorbent articles with a solution containing a dehydrating agent and an oxidizing agent. The mixture containing the superabsorbent polymer, pulp fiber, and plastic material that are components of used absorbent articles is not particularly limited as long as it contains the superabsorbent polymer, pulp fiber, and plastic material of the used absorbent article, and may or may not have been subjected to the crushing step S10 and / or pretreatment step S11, as in the case of the mixture containing the superabsorbent polymer and pulp fiber described above.

[0086] The solution containing a dehydrating agent, preferably an oxidizing agent, may be a solution composed of only the dehydrating agent, or only the dehydrating agent and the oxidizing agent, or may contain other solvents, such as organic solvents or water, as long as they do not affect dehydration or dehydration and oxidation. The total proportion of the dehydrating agent or the dehydrating agent and the oxidizing agent in the solution is, for example, 50% by mass or more, and preferably higher from the viewpoint of the effect of dehydration or dehydration and oxidation. Therefore, it is preferably 70% by mass or less, more preferably 80% by mass or less, and even more preferably 90% by mass or less. However, when water is contained as another solvent, the proportion of water is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% or less.

[0087] When used in combination with an oxidizing agent, the dehydrating agent is not particularly limited as long as it is not easily oxidized by the oxidizing agent and is capable of dehydrating the superabsorbent polymer and pulp fibers contained in the used absorbent article. The dehydrating agent is, for example, a liquid, and is thought to be able to dissolve and dehydrate the moisture contained in the components and also dissolve and remove contaminants, but is not limited to this mechanism.

[0088] The dehydrating agent is not particularly limited as long as it has a dehydrating effect and preferably can remove contaminants, and examples thereof include organic solvents. Examples of organic solvents include hydrophilic organic solvents and polar organic solvents. Examples of organic solvents that belong to at least one of these groups include ketone-based organic solvents and alcohol-based organic solvents. Other organic solvents include fluorine-based organic solvents. Examples of ketone-based organic solvents include acetone. Acetone dissolves water well, is resistant to oxidation by oxidizing agents, and has the property of protecting functional groups. Therefore, acetone can dehydrate superabsorbent polymers and pulp fibers while suppressing the decomposition (dissolution) of components, particularly easily decomposed superabsorbent polymers, and can remove some or all of the contaminants contained in these components. Furthermore, when the dehydrating agent is an organic solvent, it can dissolve the adhesive that bonds the components of used absorbent articles, making it easier to separate the components from each other. Examples of alcohol-based organic solvents include ethanol and methanol. Examples of the fluorine-based organic solvent include 1-chloro-2,3,3-trifluoropropene and 1,1,1,3,3-pentafluorobutane.

[0089] The proportion of the dehydrating agent in the solution is, for example, 50% by mass or more. From the viewpoint of the effects of dehydration and removal of contaminants, the proportion of the dehydrating agent in the solution is preferably higher, and when the oxidizing agent is a gas, the proportion is preferably 70% by mass or more, and more preferably 90% by mass or more.

[0090] There are no particular limitations on the oxidizing agent, as long as it can remove contaminants contained in used absorbent articles while suppressing their impact on the constituent components (e.g., oxidative decomposition of superabsorbent polymers, damage to pulp fibers). The oxidizing agent is, for example, a liquid or a gas mixed with a liquid, and is thought to reduce contaminants by oxidatively decomposing the contaminants, reducing their molecular weight and making them more soluble in the solution, but is not limited to this mechanism.

[0091] Examples of oxidizing agents include ozone, hydrogen peroxide, and chlorine-based substances (e.g., chlorine), or a combination of two or more thereof. These oxidizing agents have relatively high oxidizing power and are therefore likely to reduce contaminants contained in components of used absorbent articles, such as superabsorbent polymers, pulp fibers, and plastic materials. This makes it possible to remove bacteria and reduce odorous and discoloring substances, thereby sterilizing, deodorizing, and decolorizing (bleaching) the components. Note that when acetone is used as a dehydrating agent, hydrogen peroxide is not used as an oxidizing agent.

[0092] The oxidizing agent may be mixed into the liquid dehydrating agent, or may be mixed into another solvent (e.g., organic solvent, water) and then mixed into the dehydrating agent.

[0093] Ozone is preferably used as the oxidizing agent. In this case, the dehydrating and cleaning step S12 includes an applying step S12a of applying an ozone-containing gas to the treatment liquid, which is a solution containing a dehydrating agent. The ozone-containing gas may be, for example, a mixed gas of ozone with air or nitrogen.

[0094] In the application step S12a, when ozone (ozone-containing gas) is supplied to the dehydrating agent to form a solution containing a dehydrating agent and an oxidizing agent, the ozone concentration in the solution is not particularly limited as long as it is a concentration that can reduce contaminants contained in the components. The ozone concentration is, for example, 0.2 to 2 mass ppm, preferably 0.4 to 1.5 mass ppm. A concentration of 0.2 mass ppm or more facilitates the reduction of contaminants, while a concentration of 2 mass ppm or less can suppress oxidative decomposition of the superabsorbent polymer and damage to pulp fibers. The contact time between the ozone-containing solution and the components is not particularly limited as long as it is a time that can reduce contaminants contained in the components. Generally, the contact time is shorter when the ozone concentration is high and longer when the ozone concentration is low. The contact time is, for example, 1 to 200 minutes, preferably 2 to 60 minutes. The product of the ozone concentration (ppm by mass) and the contact time (minutes) (hereinafter also referred to as the "CT value") is preferably 0.2 to 40 ppm by mass min, more preferably 0.5 to 20 ppm by mass min. A CT value of 0.2 ppm by mass min or more can easily reduce contaminants, while a CT value of 40 ppm by mass min or less can suppress oxidative decomposition of components, particularly easily decomposed superabsorbent polymers. Treatment with ozone can reduce contaminants contained in components, for example, remove bacteria and reduce odorous and colored substances, and can sterilize, deodorize, and decolorize (bleach) the components. Examples of ozone generators that supply gaseous ozone (ozone-containing gas) into a dehydrating agent include the ED-OWX-2 Ozone Water Exposure Tester manufactured by Ecodesign Co., Ltd., the OS-25V Ozone Generator manufactured by Mitsubishi Electric Corporation, and the REX MC Ozonizer MC-985S manufactured by a subsidiary of Rex Industrial Co., Ltd.

[0095] When a gas (e.g., ozone) is used as the oxidizing agent, the oxidizing agent may be supplied to the dehydrating agent by, for example, the following method. This method involves generating a predetermined amount of oxidizing agent in an oxidizing agent generator, continuously supplying the oxidizing agent to the dehydrating agent in the treatment tank at a predetermined airflow rate, while continuously discharging (discharging) the same amount of waste oxidizing agent (used oxidizing agent) outside the treatment tank. In this case, a flow of oxidizing agent is easily generated, making it easier for new oxidizing agent to be continuously supplied to the surface of the component, and making it easier for reactants to be continuously discharged from the surface. This allows the oxidation reaction on the surface of the component to proceed more reliably.

[0096] Alternatively, the oxidizing agent may include either an activated species generated by irradiating another oxidizing agent contained in the solution with ultraviolet light, or an activated species generated by irradiating water and / or another oxidizing agent contained in the solution with ultraviolet light when the solution contains water. For example, when the wavelength of ultraviolet light is 253.7 nm, the activated species generated by the reaction of ultraviolet light with an oxidizing agent (ozone + water, hydrogen peroxide), i.e., hydroxyl radicals, can decompose at least a portion of the pollutants (organic matter). Furthermore, when the wavelength of ultraviolet light is 184.9 nm, the activated species generated by the reaction of ultraviolet light with water, i.e., hydroxyl radicals, can decompose at least a portion of the pollutants (organic matter).

[0097] The proportion of used absorbent articles (or a plurality of small pieces) in the solution is not particularly limited as long as the dehydration and washing step S12 can be carried out. Examples of the proportion include 0.1 to 20% by mass, and preferably 1 to 10% by mass. A proportion of 0.1% by mass or more allows the process to proceed efficiently. A proportion of 20% by mass or less allows the dehydration and washing to proceed more easily.

[0098] Contaminants such as excrement, sebum, bacteria, odorous substances, and coloring substances derived from them, machine oils in manufacturing equipment, and various organic substances are believed to be reduced as follows. Specifically, dehydration using a dehydrating agent primarily involves expelling contaminants absorbed inside the components to the outside along with moisture. Contaminants attached to the components are then expelled (eluted) and removed along with the released moisture. When an oxidizing agent is included, oxidation also primarily involves oxidative decomposition of contaminants attached to the components (including those expelled from the inside and attached to the components), resulting in lower molecular weights, solubilization, and removal. This also enables sterilization, deodorization, and bleaching of the components. However, the reduction of contaminants in the above-mentioned components is not limited to this mechanism.

[0099] In the dehydration and washing step S12, the temperature for the dehydration and washing is not particularly limited as long as the dehydration and washing treatment can be performed, but is at least performed at a temperature lower than the boiling point of the dehydrating agent. Examples of the temperature for the dehydration and washing include room temperature (e.g., 25°C) to 50°C, with 30 to 40°C being preferred. A temperature above room temperature makes it easier to shorten the time required for dehydration and washing. A temperature of 50°C or less makes it easier to suppress evaporation (boiling) of the dehydrating agent, for example, an organic solvent, and suppresses dehydration condensation of the acid groups of the superabsorbent polymer, thereby making it easier to suppress a decrease in its water absorbency. The time for the dehydration and washing is not particularly limited as long as the dehydration and washing treatment can be performed, and may be, for example, 1 to 200 minutes.

[0100] When ozone (ozone-containing gas) is used as the oxidizing agent, the ozone-containing gas is supplied to a treatment liquid, which is a solution containing a dehydrating agent, and then a portion of the ozone-containing gas is released from the treatment liquid. Therefore, a portion or all of the released used ozone-containing gas may be supplied to the incineration facility 2. In this case, the ozone-containing gas is supplied, for example, to an incineration device 21 (e.g., an incinerator) in the incineration facility 2. The ozone-containing gas is decomposed by the heat of the incineration device 21 into oxygen, which can contribute to the combustion of waste. As a result, the recycling facility 1 can omit an exhaust gas treatment process and exhaust gas treatment equipment for the ozone-containing gas, and the incineration facility 2 can improve the combustion efficiency of waste.

[0101] Alternatively, the ozone-containing gas may be supplied to, for example, a methane fermentation device 22 (not shown) in the incineration facility 2. In this case, if the ozone-containing gas is passed through a biomass resource that serves as a raw material for methane fermentation in advance to decompose and solubilize the organic matter that constitutes the biomass resource, methane fermentation of the biomass resource can be promoted, and the yield of methane gas can be increased.

[0102] The dehydrating and cleaning apparatus 12 that performs the dehydrating and cleaning step S12 is not particularly limited in its specific configuration, as long as it can bring into contact (or immerse) a mixture containing components of used absorbent articles (e.g., superabsorbent polymer, pulp fiber, plastic material) with a solution containing a dehydrating agent and an oxidizing agent. The dehydrating and cleaning apparatus 12, for example, has a tank in which used absorbent articles (or crushed articles) can be placed and in which a solution containing a dehydrating agent and an oxidizing agent can be stored, a supply means for supplying the dehydrating agent and the oxidizing agent into the tank, and a stirring means for stirring the solution in the tank. When ozone is used as the oxidizing agent, the dehydrating and cleaning apparatus 12 may include an ozone generator.

[0103] However, in this method, when an acidic aqueous solution treatment is performed as the pretreatment step S11 and a reactivation treatment is performed during the dehydration washing step S12, it is preferable that the solution containing an oxidizing agent and a dehydrating agent in the dehydration washing step S12 contains as little unnecessary moisture as possible (except for the moisture discharged from used absorbent articles). An aqueous solution containing an alkali metal ion source is supplied to the solution separately from the oxidizing agent and the dehydrating agent. This allows the reactivation treatment to be performed while the dehydration washing step S12 is being performed. In this case, the aqueous solution containing the alkali metal ion source may be supplied to the solution containing the oxidizing agent and the dehydrating agent, and then used absorbent articles (or crushed articles thereof) may be supplied. Alternatively, used absorbent articles may be supplied to the solution containing the oxidizing agent and the dehydrating agent, and after a predetermined time has elapsed, the aqueous solution containing the alkali metal ion source may be supplied.

[0104] However, in this method, when polyvalent metal salt treatment is performed as the pretreatment step S11 and the acidic substance substitution treatment is performed during the dehydration and washing step S12, it is preferable that the solution containing an oxidizing agent and a dehydrating agent in the dehydration and washing step S12 contains as little moisture as possible (except for the moisture discharged from used absorbent articles). An aqueous solution containing an acidic substance is supplied to the solution separately from the oxidizing agent and the dehydrating agent. Thus, the acidic substance substitution treatment is performed while the dehydration and washing step S12 is being performed. In this case, the aqueous solution containing the acidic substance may be supplied to the solution containing the oxidizing agent and the dehydrating agent, and then used absorbent articles (or crushed articles thereof) may be supplied. Alternatively, used absorbent articles may be supplied to the solution containing the oxidizing agent and the dehydrating agent, and then, after a predetermined time, the aqueous solution containing the acidic substance may be supplied.

[0105] Furthermore, when polyvalent metal salt treatment is performed as the pretreatment step S11, and an alkaline substance neutralization treatment is performed during the dehydration and washing step S12 after the acidic substance substitution treatment, it is preferable that the solution containing an oxidizing agent and a dehydrating agent used in the dehydration and washing step S12 contains as little unnecessary moisture as possible (except for the moisture discharged from used absorbent articles). An aqueous solution containing an alkaline substance containing sodium is supplied to the solution separately from the oxidizing agent and the dehydrating agent. This allows the alkaline substance neutralization treatment to be performed while the dehydration and washing step S12 is being performed. In this case, the aqueous solution containing an alkaline substance containing sodium may be supplied to the solution containing the oxidizing agent and the dehydrating agent, and then used absorbent articles (or crushed articles thereof) may be supplied. Alternatively, used absorbent articles may be supplied to the solution containing the oxidizing agent and the dehydrating agent, and after a predetermined time has elapsed, the aqueous solution containing an alkaline substance containing sodium may be supplied.

[0106] When both the acidic substance replacement treatment and the alkaline substance neutralization treatment are performed in the dehydration and washing step S12, first, used absorbent articles (or crushed absorbent articles) are supplied to a solution containing a dehydrating agent (preferably further containing an oxidizing agent), and the dehydration and washing treatment is performed for a predetermined time (e.g., 1 to 30 minutes). Next, an aqueous solution containing an acidic substance is supplied to the solution, and the acidic substance replacement treatment is performed for a predetermined time (e.g., 1 to 30 minutes). Next, an aqueous solution containing an alkaline substance including sodium is supplied to the solution, and the alkaline substance neutralization treatment is performed for a predetermined time (e.g., 1 to 30 minutes).

[0107] In the dehydration and cleaning process S12, gases containing various components may be generated by the process, in addition to the ozone-containing gas when ozone is used as the oxidizing agent. Therefore, gases containing various components generated by the process may be present in the tank storing the solution containing the dehydrating agent (preferably also containing an oxidizing agent). These gases may include harmful gases, such as odors containing malodorous components (e.g., nitrogen compounds, sulfur compounds). Therefore, some or all of the harmful gases (e.g., odors) may be supplied to the incineration facility 2. In this case, the harmful gases are supplied, for example, to the incineration device 21 or the methane fermentation device 22 within the incineration facility 2. The harmful gases are decomposed and rendered harmless (e.g., deodorized) by the heat of the incineration device 21, or are subjected to methane fermentation in the methane fermentation device 22. This allows the recycling facility 1 to eliminate odorous exhaust gas treatment processes and equipment. The incineration facility 2 can secure combustion gas for the power generation device 23 and raw materials for methane fermentation. In addition, by combining the ozone-containing gas with the gas containing various components generated by the treatment and supplying them to the incineration device 21 in the incineration facility 2, the supply can be carried out efficiently.

[0108] An apparatus that supplies part or all of the exhaust gas (ozone-containing gas, odor) from the dehydration and cleaning step S12 to the incineration facility 2 can be called an exhaust gas supply apparatus (exhaust gas supply unit: not shown). An example of such an apparatus is an air pump (not shown) attached to the dehydration and cleaning apparatus 12.

[0109] The separation step S13 is a step of separating at least the superabsorbent polymer and the pulp fibers from the solution containing the mixture of the superabsorbent polymer and the pulp fibers. In this separation step S13, the solution containing the mixture of the superabsorbent polymer and the pulp fibers is separated into the pulp fibers and the superabsorbent polymer and a solution containing contaminants and other materials. As a result, the pulp fibers and the superabsorbent polymer that have been dehydrated and washed and have had the contaminants and other materials reduced are separated and recovered, for example, together.

[0110] The separation device 13 that performs the separation step S13 is not particularly limited in its specific configuration, as long as it can separate a solution containing a mixture of superabsorbent polymer and pulp fiber into a solution containing pulp fiber and superabsorbent polymer and contaminants and other materials. Examples of the separation device 13 include a device having a screen that does not allow the superabsorbent polymer and pulp fiber to pass through, but allows the solution (including contaminants and other materials (small foreign matter)) to pass through. If the mixture contains other materials (large foreign matter) larger than the superabsorbent polymer and pulp fiber, the device may further have a screen that allows the superabsorbent polymer and pulp fiber to pass through but does not allow the other materials (large foreign matter) to pass through.

[0111] When the pulp fibers and the superabsorbent polymer are separated and recovered together, they can be easily reused together as materials for a single product. Such products include absorbent sheets, absorbents, cat litter, sandbag modifiers, and solid fuels. The superabsorbent polymer and pulp fibers that have been separated together may be further separated from each other using a screen or the like.

[0112] The solution may further contain plastic materials that are components of used absorbent articles. In this case, the separation step S13 is a step of separating the superabsorbent polymer, pulp fibers, and plastic materials from the solution containing a mixture of the superabsorbent polymer, pulp fibers, and plastic materials that are components of used absorbent articles. As a result, the pulp fibers, superabsorbent polymer, and plastic materials that have been dehydrated and washed and have reduced contaminants and other materials are separated and recovered, for example, together. An example of an apparatus for achieving this is an apparatus having one or more screens as described above.

[0113] When the pulp fibers, superabsorbent polymers, and plastic materials are separated and collected together, they can easily be reused together as materials for a single product. Examples of such products include cat litter, building materials (including sound-absorbing materials and cement), injection-molded products, and solid fuels. The plastic materials may be further separated from the separated pulp fibers, superabsorbent polymers, and plastic materials using a screen or other device. This allows the plastic materials to be used in individual applications (e.g., bags made by the inflation method).

[0114] In the separation step S13, gases containing various components may be generated from the treatment liquid, which is a solution containing pollutants and other materials. Therefore, gases containing various components generated by the treatment may be present in the separation device 13. These gases may include, for example, harmful gases, such as odors containing malodorous components. Therefore, some or all of the harmful gases may be supplied to the incineration facility 2. In this case, the harmful gases are supplied, for example, to the incineration device 21 or the methane fermentation device 22 within the incineration facility 2. The harmful gases are decomposed and rendered harmless by the heat of the incineration device 21, or are subjected to methane fermentation in the methane fermentation device 22. This allows the recycling facility 1 to reduce odor treatment steps and equipment. The incineration facility 2 can secure combustion gas for the power generation device 23 and raw materials for methane fermentation.

[0115] The device that supplies part or all of the exhaust gas (odor) from the separation step S13 to the incineration facility 2 can be called an exhaust gas supply device (exhaust gas supply unit: not shown). An example of such a device is an air pump (not shown) attached to the separation device 13.

[0116] The exhaust heat utilization step S14 is a step in the recycling facility 1 that utilizes a portion of the exhaust heat generated in the incineration facility 2 (e.g., incineration equipment 21). The exhaust heat utilization step S14 includes at least one of a drying step S14a and a distillation step S14b. However, either the drying step S14a or the distillation step S14b may be performed in the incineration facility 2. Furthermore, the exhaust heat utilization step S14 is not limited to the drying step S14a and the distillation step S14b, and may be used as a heat source required for other devices in the recycling facility 1. Note that the exhaust heat utilization step S14 may utilize a portion of the exhaust heat generated in the methane fermentation device 22 or the power generation device 23 of the incineration facility 2 in the recycling facility 1.

[0117] The pulp fiber and superabsorbent polymer, or the superabsorbent polymer, pulp fiber, and plastic separated in the separation step S13, is supplied to the drying step S14a (drying device 14a) of the exhaust heat utilization step S14. On the other hand, the treatment liquid, which is a solution containing contaminants and other materials separated in the separation step S13, is supplied to the distillation step S14b (distillation device 14b) of the exhaust heat utilization step S14.

[0118] In the drying step S14a, a portion of the exhaust heat generated in the incineration facility 2 (e.g., incineration equipment 21) is used to heat (and reduce pressure) the supplied pulp fibers and superabsorbent polymer, or components such as superabsorbent polymer, pulp fibers, and plastic, to dry them. If necessary, washing with water or a solvent may be performed once before drying. Note that the drying step S14a may also use a portion of the exhaust heat generated in the methane fermentation device 22 or power generation device 23 of the incineration facility 2.

[0119] The drying step S14a is carried out by placing the components in a dry atmosphere at a temperature higher than room temperature or by blowing dry air at a temperature higher than room temperature onto the components. The drying temperature is, for example, 40 to 110°C, and preferably 50 to 100°C. A drying temperature of 40°C or higher can shorten the drying time. A drying temperature of 110°C or lower can suppress sticking of the components to each other and deterioration of the components due to heat. The drying time can be, for example, 30 to 300 minutes. The drying step S14a may be carried out under reduced pressure, for example, at 0.1 to 100 kPa, in order to accelerate drying. The drying device 14a is not particularly limited as long as it can dry the components.

[0120] The drying step S14a is performed at least one of after the dehydration and cleaning step S12 and before the separation step S13, and after the separation step S13. However, in cases where the components are more easily dried by using a dehydrating agent in the dehydration and cleaning step S12, the drying step S14a can be omitted.

[0121] The drying step S14a may include a step of recovering a dehydrating agent (e.g., an organic solvent) as a processing liquid by cooling the vapor generated when drying the supplied components. In this case, the recovered dehydrating agent is supplied to the solvent supplying step S15.

[0122] In the distillation process S14b, a portion of the exhaust heat generated in the incineration facility 2 (e.g., incineration equipment 21) is used to heat the supplied treatment liquid, thereby boiling and evaporating the dehydrating agent contained in the treatment liquid. The vapor is then cooled to recover the dehydrating agent. That is, the dehydrating agent is separated and recovered by distillation. The recovered dehydrating agent has reduced contaminants. On the other hand, the treatment liquid that remains undistilled contains contaminants and other materials. The distillation device 14b is not particularly limited as long as it can distill the treatment liquid. Note that the distillation process S14b may also utilize a portion of the exhaust heat generated in the methane fermentation device 22 or the power generation device 23 of the incineration facility 2.

[0123] In the distillation step S14b, a part or all of the treated liquid that remains undistilled may be supplied to the incineration facility 2. In this case, contaminants in the treated liquid, such as various organic substances such as excrement, sebum, and other materials, are incinerated in the incineration device 21 in the incineration facility 2, or are subjected to methane fermentation in the methane fermentation device 22 in the incineration facility 2. This allows the recycling facility 1 to reduce the waste disposal process and waste disposal equipment for the contaminants in the treated liquid, and the incineration facility 2 can secure combustion gas for the power generation device 23 and raw materials for methane fermentation.

[0124] The step of supplying a part or all of the treated liquid remaining without distillation in the distillation step S14b to the incineration facility 2 can be referred to as a treated liquid supply step (not shown). In this case, the device that supplies a part or all of the treated liquid remaining without distillation in the distillation device 14b to the incineration facility 2 can be referred to as a treated liquid supply device (treated liquid supply unit: not shown). An example of such a device is a liquid transfer pump (not shown) attached to the distillation device 14b.

[0125] Note that a part or all of the treated liquid, which is a solution containing contaminants and other materials separated in the separation step S13, may be supplied to the incineration facility 2 without going through the distillation step S14b (distillation apparatus 14b). The step of supplying a part or all of such treated liquid to the incineration facility 2 can also be referred to as a treated liquid supply step (not shown). In this case, the contaminants in the treated liquid, such as various organic substances such as excrement, sebum, and other materials, may be incinerated in the incineration apparatus 21 within the incineration facility 2, or may be subjected to methane fermentation in the methane fermentation apparatus 22 within the incineration facility 2. In this case, the device that supplies a part or all of the treated liquid to the incineration facility 2 can also be referred to as a treated liquid supply device (treated liquid supply unit: not shown). An example of such a device is a liquid feed pump.

[0126] At least one of the drying device 14a and the distillation device 14b utilizes the exhaust heat from the incineration facility 2 to perform the exhaust heat utilization process S14, i.e., at least one of the drying process S14a and the distillation process S14b, and can therefore be called an exhaust heat utilization section.

[0127] The solvent supply step S15 is a step of supplying the dehydrating agent (e.g., organic solvent), which is the treatment liquid distilled, separated, and recovered in the distillation step S14b, to the dehydration and cleaning step S12. The solvent supply device 15 that performs the solvent supply step S15 is not particularly limited as long as it can transfer the treatment liquid from the distillation device 14b to the dehydration and cleaning device 12. An example of such a device is a liquid transfer pump.

[0128] In addition, if a dehydrating agent (e.g., an organic solvent) which is the processing liquid is recovered in the drying step S14a, the solvent supply step S15 may also be a step of supplying the recovered dehydrating agent to the dehydration cleaning step S12.

[0129] Although not shown, waste generated from the processing of used absorbent goods at the recycling facility 1 may be supplied to the incineration device 21 of the incineration facility 2 for incineration. This allows the recycling facility 1 to reduce the waste disposal process and waste disposal equipment, and the incineration facility 2 can secure combustion gas for the power generation device 23 and raw materials for methane fermentation.

[0130] Next, step S2 performed in the incineration facility 2 in the recycling method will be described. Step S2 includes a treatment liquid utilization step S24. Step S2 may further include at least one of a cooling step S21, a gas treatment step S22, and an odor treatment step S23. Step S2 may also include an exhaust heat supply step (not shown). These steps are not performed sequentially, but are performed as needed.

[0131] The incineration facility 2 includes an incineration device 21 (incineration unit) that incinerates waste. The incineration facility 2 may further include at least one of a methane fermentation device 22 (methane fermentation unit) that produces methane gas by methane fermentation using organic matter in the waste, and a power generation device 23 (power generation unit) that generates power using high-temperature exhaust gas from the incineration device 21 and / or methane gas from the methane fermentation device 22.

[0132] The cooling step S21, gas treatment step S22, odor treatment step S23, and treated liquid utilization step S24 in step S2 are respectively carried out by the incineration apparatus 21, the incineration apparatus 21, the incineration apparatus 21 and methane fermentation apparatus 22, and the incineration apparatus 21 and methane fermentation apparatus 22 of the incineration facility 2. Each step will be described in detail below. When step S2 includes an exhaust heat supply step (not shown), the step is carried out by the incineration apparatus 21 and methane fermentation apparatus 22.

[0133] The cooling step S21 is a step of cooling with cooling water parts of the incineration apparatus 21, the methane fermentation apparatus 22, the power generation apparatus 23, or peripheral equipment of any of these apparatuses that require cooling. Cooling is performed, for example, by circulating cooling water through a predetermined cooling pipe, or by spraying cooling water or air onto the parts that require cooling. In the cooling step S21, as described above, the pretreatment liquid (acidic aqueous solution, polyvalent metal salt aqueous solution), alkaline aqueous solution, or acidic aqueous solution can be used as the cooling water.

[0134] The gas treatment step S22 is a step in which, when an ozone-containing gas is used in the dehydration and cleaning step S12, the ozone-containing gas is treated in the incineration facility 2. For example, when the incineration device 21 incinerates waste, the ozone-containing gas is supplied to the incineration device 21 and is decomposed by heat to become oxygen, which contributes to the combustion of the waste.

[0135] Furthermore, in the gas treatment step S22, the ozone-containing gas may be supplied to, for example, a methane fermentation apparatus 22 (not shown) in the incineration facility 2. In this case, if the ozone-containing gas is passed through a biomass resource that serves as a raw material for methane fermentation in advance to decompose and solubilize the organic matter that constitutes the biomass resource, methane fermentation of the biomass resource can be promoted, and the yield of methane gas can be increased.

[0136] The odor treatment step S23 is a step in which gas containing various components (e.g., odor) generated in the dehydration and cleaning step S12 and the separation step S13 is treated in the incineration facility 2. The gas containing various components is supplied to, for example, the incineration device 21 in which waste is burned, and is decomposed by heat to be rendered harmless (e.g., deodorized), or is fermented into methane in the methane fermentation device 22.

[0137] The treated liquid utilization step S24 is a step in which the treated liquid, which is a solution containing pollutants and other materials produced in the distillation step S14b (or separation step S13), is treated in an incineration device 21 or a methane fermentation device 22. The pollutants in the treated liquid, such as various organic substances such as excrement, sebum, and other materials, are incinerated in the incineration device 21 or subjected to methane fermentation in a methane fermentation device 22 within the incineration facility 2.

[0138] The exhaust heat supply process (not shown) is a process of supplying a portion of the exhaust heat generated in the incineration facility 2 (e.g., incineration equipment 21, methane fermentation device 22, power generation device 23) to the recycling facility 1. The heat is supplied using a known liquid or gas heat medium (which may belong to either the incineration facility 2 or the recycling facility 1).

[0139] The power generation device 23 generates electricity using high-temperature exhaust gas generated by the incineration device 21 burning waste and the like and / or methane gas generated by methane fermentation in the methane fermentation device 22. The generated electricity may cover part or all of the electricity required by the equipment in the incineration facility 2 (e.g., the incineration device 21, the methane fermentation device 22, and the power generation device 23), or may cover part or all of the electricity required by the equipment in the recycling facility 1 (e.g., the crushing device 10, the pretreatment device 11, the dehydration and cleaning device 12, the separation device 13, the drying device 14a, the distillation device 14b, and the solvent supply device 15).

[0140] In this way, in this recycling method, by effectively utilizing in the incineration facility 2 a portion of the waste (such as waste liquid and exhaust gas) such as the used treatment liquid (which may contain excrement) generated in the separation step S13 of the recycling facility 1, it is possible to reduce the waste disposal treatment steps and equipment required in the recycling facility 1. In addition, by effectively utilizing a portion of the exhaust heat generated in the incineration facility 2 in the exhaust heat utilization step S14 (e.g., drying step S14a, distillation step S14b) of the recycling facility 1, it is possible to cover at least a portion of the thermal energy required in the recycling facility 1, thereby reducing the thermal energy supply steps and equipment. As a result, in this recycling method, it is possible to further improve the processing efficiency of both the recycling facility 1 and the incineration facility 2.

[0141] In a preferred embodiment of this recycling method, the treatment liquid further contains an oxidizing agent in addition to a dehydrating agent. Therefore, by effectively utilizing the treatment liquid containing the used dehydrating agent and oxidizing agent generated at the recycling facility 1 in the incineration facility 2, it is possible to reduce the processes and equipment required for the disposal of the dehydrating agent and oxidizing agent at the recycling facility 1. In addition, by effectively utilizing a portion of the exhaust heat, etc. generated by the use of the used dehydrating agent and oxidizing agent at the incineration facility 2 in the recycling facility 1, it is possible to cover a portion of the thermal energy, etc. required at the recycling facility 1, thereby reducing the processes and equipment required for supplying thermal energy. As a result, in this recycling method, it is possible to further improve the processing efficiency at both the recycling facility 1 and the incineration facility 2.

[0142] In a preferred embodiment, this recycling method includes an organic solvent as a dehydrating agent. The used organic solvent, which is one of the waste products generated in the separation step S13, is distilled in the distillation step S14b using a portion of the exhaust heat from the incineration facility 2 and then supplied to the dehydration and cleaning step S12 in the solvent supply step S15 for reuse. In this way, by using an organic solvent as part or all of the treatment liquid, treating used absorbent articles with the organic solvent at an appropriate location, and distilling and reusing the used organic solvent, the amount of waste liquid (treatment liquid) discharged in the process at the recycling facility 1 can be reduced (compared to treating used absorbent articles with an aqueous solution). If the amount of waste liquid is large, it may be difficult to process it in the incineration facility 2, necessitating a waste liquid disposal process. However, as described above, the amount of waste liquid is small in this recycling method. This reduces the steps and equipment required for organic solvent disposal at the recycling facility 1, thereby reducing the amount of organic solvent used. In addition, at least a portion of the heat energy required for the distillation step S14b in the recycling facility 1 can be supplied by exhaust heat, thereby reducing the number of heat energy supply steps and equipment, thereby further improving the processing efficiency in both the recycling facility 1 and the incineration facility 2 in this recycling method.

[0143] In a preferred embodiment of this recycling method, used absorbent articles are dehydrated with a pretreatment liquid in the pretreatment step S11, reducing the dehydration load in the dehydration washing step S12, and the used pretreatment liquid, which is one of the waste products generated in the pretreatment step S11, is used as cooling water for the incineration facility 2 in the cooling step S21. This makes it possible to reduce the steps and equipment required for waste treatment of the pretreatment liquid at the recycling facility 1. In addition, at least a portion of the cooling water required at the incineration facility 2 can be provided by the pretreatment liquid, making it possible to reduce the steps and equipment required for cooling the cooling water. This makes it possible to further improve the treatment efficiency at both the recycling facility 1 and the incineration facility 2 in this recycling method.

[0144] In a preferred embodiment of this recycling method, the treatment liquid contains an ozone-containing gas as an oxidizing agent. Then, in the dehydration and washing step S12, used absorbent articles are dehydrated and washed with the treatment liquid containing the ozone-containing gas, making it easier to use the waste in an incineration facility, and the used ozone-containing gas, which is one of the waste products generated in the dehydration and washing step S12, is treated in the incineration facility 2. This makes it possible to reduce the steps and equipment required in the recycling facility 1 for disposing of the used ozone-containing gas. In addition, combustion in the incineration facility 2 can be assisted by oxygen generated by the decomposition of ozone. This makes it possible to further improve the treatment efficiency of both the recycling facility 1 and the incineration facility 2 in this recycling method.

[0145] In a preferred embodiment of this recycling method, odors, which are one type of waste generated in the dehydration and cleaning step S12, are treated in the incineration facility 2. This reduces the number of odor disposal treatment steps and equipment required in the recycling facility 1. This makes it possible to further improve the treatment efficiency in both the recycling facility 1 and the incineration facility 2.

[0146] In a preferred embodiment of this recycling method, at least a portion of the thermal energy required to dry the components in the drying step S14a can be supplied by a portion of the exhaust heat from the incineration facility 2, thereby reducing the number of steps and equipment required to supply the thermal energy used for drying. This makes it possible to further improve the processing efficiency of both the recycling facility 1 and the incineration facility 2 in this recycling method.

[0147] As described above, in a preferred embodiment of this recycling method, the dehydration and washing step S12 simultaneously uses a dehydrating agent and an oxidizing agent to simultaneously dehydrate and wash at least the superabsorbent polymer having acid groups and the pulp fibers. Therefore, the dehydrating agent can first dehydrate the water absorbed by the superabsorbent polymer and the pulp fibers, which may contain contaminants. At the same time, the oxidizing agent can reduce contaminants contained in the superabsorbent polymer and the pulp fibers (e.g., excrement, sebum, bacteria derived from them, odorous substances, coloring substances, machine oil from manufacturing equipment, various organic substances, etc.). This reduces contaminants in at least the superabsorbent polymer and the pulp fibers. Furthermore, by simultaneously performing dehydration and washing, an increase in the number of processes is suppressed, thereby suppressing increases in costs associated with these processes. Therefore, in a method for recovering components of used absorbent articles, contaminants in the components can be reduced while suppressing increases in costs.

[0148] Second Embodiment Next, a recycling system including a resource recovery facility and a recycling facility for used absorbent articles according to this embodiment, and a recycling method using the same will be described. In this embodiment, a methane fermentation facility for biomass resources will be described as an example of the resource recovery facility. Below, differences from the first embodiment will be mainly described.

[0149] FIG. 3 is a block diagram showing an example of the configuration of a recycling system B according to this embodiment. The recycling system B includes a recycling facility 3 for used absorbent goods and a methane fermentation facility 4 (resource recovery facility). The recycling facility 3 and the methane fermentation facility 4 may be integrated, adjacent, or co-located. Furthermore, both facilities may be located on the same site or on separate sites. The recycling facility 3 is essentially the same as the recycling facility 1. The methane fermentation facility 4 generates methane gas and the like by performing methane fermentation using microorganisms (e.g., methanogens, which are anaerobic bacteria) using biomass resources. It may be a standalone facility or may be combined with another facility, such as a waste treatment facility at a waste incineration plant or a sewage treatment facility at a sewage treatment plant. The methane fermentation facility 4 may include a device (e.g., a power generation device) that utilizes thermal energy generated by methane fermentation. By treating the waste generated at the recycling facility 3 (e.g., waste liquid, exhaust gas) at the methane fermentation facility 4 and utilizing the energy generated at the methane fermentation facility 4 (e.g., heat, electricity) at the recycling facility 3, the processing efficiency at both facilities can be further improved.

[0150] 4 is a flow diagram showing an example of a recycling method using the recycling system B according to this embodiment. The recycling method includes a step S3 of processing used absorbent goods carried out in a recycling facility 3, and a step S4 of processing related to methane fermentation carried out in a methane fermentation facility 4. Step S3 is substantially the same as step S1. Step S4 is a step of performing methane fermentation by microorganisms using biomass resources to produce methane gas, etc., and may include a step of utilizing the generated thermal energy, etc. By processing the waste generated in step S3 in step S4 and utilizing the energy (e.g., heat, electricity) generated in step S4 in step S3, the processing efficiency at both facilities can be further improved.

[0151] The recycling system B and the recycling method using the same will now be described.

[0152] First, step S3, which is carried out at the recycling facility 3 in the recycling method, will be described. Step S3 is substantially the same as step S1. The crushing step S30 to the solvent supplying step S35 of step S3 are substantially the same as the crushing step S10 to the solvent supplying step S15 of step S1, respectively. However, the content of the pre-treatment step S31 (S34c) differs from that of the pre-treatment step S11. The pre-treatment step S31 (S34c) will be described later.

[0153] The recycling facility 3 is substantially the same as the recycling facility 1. The crushing device 30 to the solvent supplying device 35 of the recycling facility 3 are substantially the same as the crushing device 10 to the solvent supplying device 15, respectively. However, the pre-treatment device 31 is different from the pre-treatment device 11. The pre-treatment device 31 will be described later.

[0154] The crushing step S30 to the solvent supplying step S35 are carried out by the crushing device 30 to the solvent supplying device 35, respectively.

[0155] The pretreatment step S31 is basically the same as the pretreatment step S11 in that it is a step of dehydrating used absorbent articles, but differs from the pretreatment step S11 in the specific pretreatment method. Specifically, the pretreatment step S31 reduces moisture absorbed by used absorbent articles (particularly superabsorbent polymers) by heating and evaporating it. In this case, the heat source for heating the moisture may be generated by the pretreatment device 11 itself, or another heat source, such as part of the exhaust heat from the methane fermentation facility 4, may be used. An example of the exhaust heat from the methane fermentation facility 4 is exhaust heat B generated by the methane fermentation device 41 (described below). When part of the exhaust heat from the methane fermentation facility 4 is used, the pretreatment step S31 can also be referred to as an exhaust heat utilization step S34c.

[0156] The specific configuration of the pretreatment device 31 that performs the heat treatment is not particularly limited as long as it can heat the superabsorbent polymer. For example, the pretreatment device 31 may be a thermostatic bath in which used absorbent articles (or crushed products thereof) containing a superabsorbent polymer can be placed and heated.

[0157] When heating is performed in the pretreatment step S31, some or all of the exhaust gas, such as water vapor generated by heating, may be supplied to the methane fermentation facility 4. In this case, the exhaust gas supplied to the methane fermentation facility 4 may be used, for example, in the methane fermentation device 41 or the power generation device 43 in the methane fermentation facility 4. In the methane fermentation device 41, for example, water for adjusting the moisture content during methane fermentation may be used, and in the power generation device 43, for example, cooling water for the device may be used. This allows the recycling facility 3 to reduce the number of exhaust gas treatment steps and equipment, and the methane fermentation facility 4 to reduce the amount of new moisture supplied.

[0158] An apparatus that supplies part or all of the exhaust gas (steam, etc.) from the pretreatment step S11 to the methane fermentation facility 4 can be referred to as an exhaust gas supply apparatus (exhaust gas supply unit: not shown). An example of such an apparatus is a gas pump (not shown) attached to the pretreatment device 31.

[0159] Next, we will explain step S4, which is carried out in the methane fermentation facility 4 in the recycling method. Step S4 is substantially the same as step S2, except that each step is carried out in the methane fermentation apparatus 41, the power generation apparatus 43, or any peripheral equipment of these apparatuses in the methane fermentation facility 4. The cooling step S41 to the treated liquid utilization step S44 and the exhaust heat supply step S45 in step S4 are substantially the same as the cooling step S21 to the treated liquid utilization step S24 and the exhaust heat supply step (not shown) in step S2.

[0160] The cooling step S41 is a step of cooling with cooling water parts of the methane fermentation apparatus 41, the power generation apparatus 43, or peripheral equipment of either of these apparatuses that require cooling. Cooling is performed, for example, by circulating cooling water through a predetermined cooling pipe or by spraying cooling water or air onto the parts that require cooling. In the cooling step S41, as described above, exhaust gas (cooled during transport) such as the steam used in the pretreatment step S31 can be used as the cooling water.

[0161] The gas treatment step S42 is a step in which exhaust gas such as the steam used in the pretreatment step S31, or an ozone-containing gas when used in the dehydration and cleaning step S32, is treated (used) in the methane fermentation facility 4. Steam can be used, for example, as moisture for adjusting the moisture content during methane fermentation. For example, when the methane fermentation device 41 performs methane fermentation, if the organic matter of the biomass resource is decomposed and solubilized with the ozone-containing gas in advance, methane fermentation of the biomass resource can be promoted and the yield of methane gas can be increased.

[0162] The odor treatment step S43 is a step in which gas containing various components (e.g., odor) generated in the dehydration and cleaning step S32 and the separation step S33 is treated in the methane fermentation facility 4. The gas containing various components is supplied to, for example, a methane fermentation device 41 performing methane fermentation, and is used for methane fermentation or is rendered harmless (e.g., deodorized).

[0163] The treated liquid utilization step S44 is a step in which the treated liquid, which is a solution containing contaminants and other materials and which is produced in the distillation step S34b (and separation step S33), is treated in the methane fermentation facility 4. Contaminants in the treated liquid, such as various organic substances such as excrement, sebum, and other materials, are supplied to a methane fermentation device 41, for example, where they are used for methane fermentation or are rendered harmless (e.g., deodorized).

[0164] The exhaust heat supply step S45 is a step of supplying a portion of the exhaust heat generated in the methane fermentation facility 4 (e.g., the methane fermentation device 41, the power generation device 43) to the recycling facility 1. The heat is supplied using a known liquid or gas heat medium (which may belong to either the incineration facility 2 or the recycling facility 1).

[0165] The power generation device 43 generates electric power using the methane gas produced by methane fermentation in the methane fermentation device 41. The generated electric power may cover part or all of the electric power required by the equipment in the methane fermentation facility 4 (e.g., the methane fermentation device 41 and the power generation device 43), or may cover part or all of the electric power required by the equipment in the recycling facility 3 (e.g., the crushing device 30, the pretreatment device 31 (34c), the dehydration and cleaning device 32, the separation device 33, the drying device 34a, the distillation device 34b, and the solvent supply device 35).

[0166] In this recycling method, before the dehydration and washing step S32, the moisture absorbed by the used absorbent goods is reduced, i.e., dehydrated, by heating and evaporating it (pretreatment step S31). This reduces the dehydration burden in the dehydration and washing step S32. Furthermore, during this process, part of the exhaust heat from the resource recovery facility is used to heat the moisture (exhaust heat utilization step S34 (34c)). This allows at least part of the thermal energy required for the pretreatment step S31 in the recycling facility 3 to be supplied by the exhaust heat, thereby reducing the number of thermal energy supply steps and equipment. Therefore, this recycling method makes it possible to further improve the processing efficiency of both the recycling facility 3 and the methane fermentation facility 4.

[0167] In this recycling method, the treated liquid utilization step S44 in the methane fermentation facility 4 includes a methane fermentation step of performing methane fermentation using excrement contained in part of the treated liquid separated in the separation step S33 in the recycling facility 3. This allows at least part of the biomass resources required in the methane fermentation facility 4 to be supplied by the excrement, thereby reducing the steps and equipment for supplying biomass resources. Therefore, in this recycling method, it is possible to further improve the processing efficiency in both the recycling facility 3 and the methane fermentation facility 4.

[0168] In this recycling method, part of the exhaust heat generated in the methane fermentation facility 4 and used in the exhaust heat utilization step S34 in the recycling facility 3 includes exhaust heat generated in the methane fermentation step in the methane fermentation facility 4. This makes it possible to reduce the number of steps and equipment for supplying thermal energy for the exhaust heat utilization step S34 required in the recycling facility 3. Therefore, in this recycling method, the processing efficiency of both the recycling facility 3 and the methane fermentation facility 4 can be further improved.

[0169] In this way, in this embodiment, the recycling method can also achieve the same effects as in the first embodiment.

[0170] The recycling method and recycling system of the present invention are not limited to the above-described embodiments, and can be appropriately combined and modified within the scope of the purpose and intent of the present invention. Note that in this specification, ordinal numbers such as "first" and "second" are used to distinguish items to which the ordinal numbers are assigned, and do not indicate the order, priority, importance, etc. of each item.

[0171] 2 Incineration facility 1 Recycling facility A Recycling system S12 Dehydration and cleaning process S13 Separation process S24 Treated liquid utilization process S14 Waste heat utilization process

Claims

1. A method for recycling used absorbent goods using a recycling system equipped with a resource recovery facility and a recycling facility for used absorbent goods, comprising: a dehydration and washing process in the recycling facility for dehydrating and washing used absorbent goods with a treatment liquid containing a dehydrating agent; a separation process in the recycling facility for separating components of the used absorbent goods from the treatment liquid; a treatment liquid utilization process in the resource recovery facility for utilizing a portion of the treatment liquid separated in the separation process; and an exhaust heat utilization process in the recycling facility for utilizing a portion of the exhaust heat generated in the resource recovery facility.

2. The recycling method according to claim 1, wherein the treatment liquid further contains an oxidizing agent.

3. The recycling method according to claim 1 or 2, wherein the treatment liquid in the dehydrating and cleaning process contains an organic solvent as the dehydrating agent, the exhaust heat utilization process includes a distillation process in which a portion of the exhaust heat from the resource recovery facility is used to distill the organic solvent contained in the treatment liquid separated in the separation process, and the recycling method further includes a solvent supply process in which the organic solvent distilled in the distillation process is supplied to the dehydrating and cleaning process.

4. The recycling method according to claim 1 or 2, further comprising: a pretreatment step in the recycling facility, prior to the dehydration and cleaning step, of reducing moisture absorbed by the used absorbent articles with a pretreatment liquid; and a cooling step in the resource recovery facility, of using the pretreatment liquid used in the pretreatment step as cooling water.

5. The recycling method according to claim 1 or 2, further comprising a pre-treatment process in which the moisture absorbed by the used absorbent articles is heated, evaporated and reduced in the recycling facility prior to the dehydration and cleaning process, and the pre-treatment process includes a process in which a portion of the exhaust heat from the resource recycling facility is used to heat the moisture as the exhaust heat utilization process.

6. The recycling method according to claim 1 or 2, wherein the treated liquid utilization step includes a methane fermentation step of carrying out methane fermentation using excrement contained in a portion of the treated liquid separated in the separation step.

7. The recycling method according to claim 6, wherein in the waste heat utilization step, part of the waste heat generated in the resource recovery facility includes waste heat generated in the methane fermentation step.

8. The recycling method according to claim 2, wherein the dehydration and cleaning step includes an application step of applying an ozone-containing gas as the oxidizing agent to the treatment liquid, and the recycling method further includes a gas treatment step of treating the ozone-containing gas used in the dehydration and cleaning step in the resource recovery facility.

9. The recycling method according to claim 1 or 2, further comprising an odor treatment step of treating odors generated in the dehydration and cleaning step in the resource recovery facility.

10. The recycling method according to claim 1 or 2, wherein the exhaust heat utilization process includes a drying process in which a portion of the exhaust heat from the resource recovery facility is used to dry the components separated in the separation process.

11. A method for recycling used absorbent goods using a recycling facility for used absorbent goods, comprising: a dehydration and washing process for dehydrating and washing used absorbent goods with a treatment liquid containing a dehydrating agent; a separation process for separating components of the used absorbent goods from the treatment liquid; a treatment liquid supply process for supplying a portion of the treatment liquid separated in the separation process to a combustible waste recycling facility; and an exhaust heat utilization process for utilizing a portion of the exhaust heat generated at the resource recycling facility within the recycling facility.

12. A recycling system comprising a resource recovery facility and a recycling facility for used absorbent goods, wherein the recycling facility comprises: a dehydration and washing section that dehydrates and washes used absorbent goods with a treatment liquid containing a dehydrating agent; and a separation section that separates components of the used absorbent goods from the treatment liquid, the resource recovery facility comprises a treatment liquid utilization section that utilizes a portion of the treatment liquid separated in the separation section, and the recycling facility further comprises an exhaust heat utilization section that utilizes a portion of the exhaust heat generated at the resource recovery facility.

13. A recycling system equipped with a recycling facility for used absorbent goods, the recycling facility comprising: a dehydration and washing section that dehydrates and washes used absorbent goods with a treatment liquid containing a dehydrating agent; a separation section that separates components of the used absorbent goods from the treatment liquid; a treatment liquid supply section that supplies a portion of the treatment liquid separated in the separation section to a combustible waste recycling facility; and an exhaust heat utilization section that utilizes a portion of the exhaust heat generated at the resource recycling facility within the recycling facility.

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