Method for separating fibrous material and particulate material from used sanitary products.

Abstract

To provide a method of separating between fibrous matter and particulate matter in a used sanitary article, the method capable of enhancing a separation rate of at least one of the fibrous matter and the particulate matter to enhance the recovery rate while suppressing increase in waste-liquid treatment load and increase in environmental load.SOLUTION: A separation method comprises: a first screen step S41 of separating a dispersed liquid Q that contains fibrous matter, particulate matter, and treatment liquid disintegrated from a used sanitary article using a first screen apparatus 10 between a first accept A1 that contains a large amount of the fibrous matter and the treatment liquid and a first reject R1 that contains a large amount of the particulate matter; a first mixing step S42 of mixing a part of a treatment liquid L1 obtained by solid-liquid separating the first accept with the first reject using a first mixing apparatus 11 to generate a first mixed liquid C1; and a second screen step S43 of separating the first mixed liquid using a second screen apparatus 12 between a second accept A2 that contains a large amount of the fibrous matter and the treatment liquid and a second reject R2 that contains a large amount of particulate matter.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for separating fibrous materials and particulate materials from used sanitary products, and particularly to a method for separating fibrous materials and particulate materials from used sanitary products that is used when producing recycled materials from used sanitary products. [Background Art]

[0002] Methods for separating fibrous materials and particulate materials from used sanitary products are known. For example, Patent Document 1 discloses a method for treating used sanitary products. This treatment method includes at least a step of disintegrating sanitary products and dispersing them in water, and a step of separating and recovering fibers (fibrous materials) and SAP (particulate materials) contained in the sanitary products. In the step of disintegrating the sanitary products and dispersing them in water, a crosslinking agent and an acidic substance are added to the water.

[0003] Specifically, in Patent Document 1, first, as the step of disintegrating sanitary products and dispersing them in water, used paper diapers as a raw material are charged into a pulper and dispersed in water. Thereafter, as the step of separating and recovering fibers and SAP contained in the paper diapers, the dispersion liquid is treated using a screen or the like, and the SAP component is recovered first. Subsequently, the fiber-containing dispersion liquid is washed and dehydrated by a dehydrator or the like. Here, the dehydrated water can be returned to the process and reused. Further, the fiber-containing dispersion liquid is treated by a high concentration apparatus. Then, if necessary, washing, dehydration and screen treatment are performed to recover the fiber component. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 2013-150976 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] Patent Document 1 describes a separation process using a separation device such as a screen, in which hygienic products are disintegrated and dispersed in water, and then fibrous and particulate materials of the hygienic products are separated from the resulting dispersion. However, since both fibrous and particulate materials are fine, it is not easy to sufficiently separate and recover them in a single separation process.

[0006] Therefore, in order to increase the separation rate and recovery rate of at least one of the fibrous material and particulate material, it is conceivable to perform multiple separation steps for each.

[0007] In each separation step, the accept sample contains both solids (e.g., fibrous material) and water (liquid) (low solid content). On the other hand, the reject sample contains solids (e.g., particulate material) but not much water (liquid) (high solid content). In other words, the proportion of water (liquid) is high in the accept sample, but tends to be low in the reject sample, making it easy for the balance of water (liquid) between the accept and reject samples to become uneven.

[0008] Therefore, when accepting samples are processed again in the separation process, it is relatively easy to adjust the concentration of solids in the water (liquid) to the required range by partially removing water. However, when rejecting samples are processed again in the separation process, it becomes necessary to add more water (liquid) to adjust the concentration of solids in the water (liquid) to the required range. This would increase the amount of wastewater after the separation process, potentially leading to increased wastewater treatment burdens and environmental impacts.

[0009] The object of the present invention is to provide a separation method for used sanitary products that can increase the separation rate of at least one of the fibrous material and particulate material, thereby improving the recovery rate, while suppressing an increase in the burden of wastewater treatment and an increase in environmental impact. [Means for solving the problem]

[0010] One aspect of the present invention is a separation method for separating fibrous material and particulate material from used sanitary products, comprising: a first screening step in which a dispersion containing fibrous material, particulate material and processing liquid dissected from the used sanitary products is separated by a first screen device into a first accept containing a large amount of the fibrous material and processing liquid and a first reject containing a large amount of the particulate material; a first solid-liquid separation step in which the first accept obtained in the first screening step is separated into fibrous material and processing liquid; a first mixing step in which a portion of the processing liquid obtained in the first solid-liquid separation step is mixed with the first reject to produce a first mixed liquid; and a second screening step in which the first mixed liquid is separated by a second screen device into a second accept containing a large amount of the fibrous material and processing liquid and a second reject containing a large amount of the particulate material.

[0011] Another aspect of the present invention is a separation method for separating fibrous material and particulate material from used sanitary products, comprising: a first screening step of separating a dispersion containing fibrous material, particulate material and processing liquid dissected from the used sanitary products into a first accept containing a large amount of the particulate material and processing liquid and a first reject containing a large amount of the fibrous material using a first screening device; a first solid-liquid separation step of solid-liquid separating the first accept obtained in the first screening step into particulate material and processing liquid; a first mixing step of mixing a portion of the processing liquid obtained in the first solid-liquid separation step with the first reject to produce a first mixed liquid; and a second screening step of separating the first mixed liquid into a second accept containing a large amount of the particulate material and processing liquid and a second reject containing a large amount of the fibrous material using a second screening device. [Effects of the Invention]

[0012] According to the present invention, in a method for separating fibrous material and particulate material from used sanitary products, it is possible to provide a separation method that can increase the separation rate of at least one of the fibrous material and particulate material and improve the recovery rate, while suppressing an increase in the burden of wastewater treatment and an increase in environmental impact. [Brief explanation of the drawing]

[0013] [Figure 1] This is a block diagram showing an example of the configuration of a system used in a method for separating the constituent materials of used sanitary products according to the embodiment. [Figure 2] This is a flowchart illustrating an example of a method for separating the constituent materials of used sanitary products according to the embodiment. [Figure 3] This block diagram shows an example of the configuration of an apparatus used in a method for separating fibrous material and particulate material from used sanitary products according to the embodiment. [Figure 4] This is a flowchart illustrating an example of a method for separating fibrous material and particulate material from used sanitary products according to the embodiment. [Modes for carrying out the invention]

[0014] This embodiment relates to the following aspects. [Aspect 1] A separation method for separating fibrous material and particulate material from used sanitary products, comprising: a first screening step in which a dispersion containing fibrous material, particulate material and processing liquid dissected from the used sanitary products is separated by a first screen device into a first accept containing a large amount of the fibrous material and processing liquid and a first reject containing a large amount of the particulate material; a first solid-liquid separation step in which the first accept obtained in the first screening step is separated into fibrous material and processing liquid; a first mixing step in which a portion of the processing liquid obtained in the first solid-liquid separation step is mixed with the first reject to produce a first mixed liquid; and a second screening step in which the first mixed liquid is separated by a second screen device into a second accept containing a large amount of the fibrous material and processing liquid and a second reject containing a large amount of the particulate material.

[0015] In this method, first, a first screening step is performed on the dispersion to generate a first reject (mainly particulate matter and treated water; high solid content) and a first accept (mainly fibrous matter and treated water; low solid content). Next, the first reject is mixed with the treated liquid obtained by solid-liquid separation of the first accept to create a first mixed liquid with a diluted concentration. Then, a second screening step is performed on the first mixed liquid to obtain a second reject (mainly particulate matter). Here, when performing the second screening step on the first reject, the concentration is diluted to an appropriate concentration favorable for the screening step by mixing the first reject with the treated liquid obtained by solid-liquid separation of the first accept to create the first mixed liquid, thus enabling the second screening step to be carried out properly. At that time, particulate matter that remained in the treated liquid due to not being completely separated can also be included in the first mixed liquid when performing the second screening step. As a result, the separation rate of particulate matter can be increased, and the recovery rate can be improved. In this process, since the treatment liquid obtained by solid-liquid separation of the first acceptor is used in the second screening step, there is no need to add any additional liquid (e.g., water, treatment liquid). This helps to suppress an increase in the burden of wastewater treatment and an increase in environmental impact.

[0016] [Aspect 2] The separation method according to embodiment 1, further comprising a second mixing step of mixing the second accept obtained in the second screening step with the first accept obtained in the first screening step to produce a second mixed liquid, wherein the first solid-liquid separation step includes a step of solid-liquid separation of the second mixed liquid into the fibrous material and the processing liquid.

[0017] In this method, the first solid-liquid separation step is performed on a second mixed solution, which is a mixture of the second accept (mainly fibrous material and treatment liquid) and the first accept (mainly fibrous material and treatment water). Compared to the case where the first solid-liquid separation step is performed only on the first accept, a larger amount of fibrous material can be obtained. This increases the separation rate of fibrous material, and consequently, improves the recovery rate.

[0018] [Aspect 3] a third mixing step of mixing another part of the treatment liquid obtained in the first solid-liquid separation step with the second reject obtained in the second screening step to produce a third mixed liquid; and a second solid-liquid separation step of solid-liquid separating the third mixed liquid into the particulate matter and the treatment liquid, the separation method according to aspect 1 or 2, further comprising the above steps.

[0019] In the present method, the second reject (mainly particulate matter) is mixed with the treatment liquid obtained by solid-liquid separation of the first accept to obtain the third mixed liquid having a reduced concentration, and the second solid-liquid separation step is performed on the third mixed liquid, thereby obtaining particulate matter. Here, when performing the second solid-liquid separation step on the second reject, by mixing the treatment liquid obtained by solid-liquid separation of the first accept into the second reject, the concentration of the mixture is diluted to an appropriate concentration required for the solid-liquid separation step, so that the second solid-liquid separation step can be appropriately performed. At this time, the particulate matter remaining in the treatment liquid that has not been completely separated in the first solid-liquid separation step can also be included in the third mixed liquid to perform the second solid-liquid separation step. Thereby, the separation rate of the particulate matter can be further increased, and thus the recovery rate can be further improved.

[0020] [Aspect 4] The separation method according to aspect 3, further comprising: before the first screening step, a disintegration step of disintegrating fibrous matter and particulate matter of the used sanitary products in the treatment liquid to produce the dispersion liquid; and a returning step of returning a part of the treatment liquid obtained in the second solid-liquid separation step back to the disintegration step.

[0021] In the present method, since a part of the treatment liquid obtained in the second solid-liquid separation step is returned to the disintegration step, the amount of newly added liquid (e.g., water, treatment liquid) can be suppressed compared to the case where there is no returning step. Thereby, an increase in waste liquid treatment load and an increase in environmental load can be suppressed.

[0022] [Aspect 5] The separation method according to any one of embodiments 1 to 4, further comprising a third solid-liquid separation step of compressing the fibrous material separated in the first solid-liquid separation step to separate the fibrous material from the processing liquid, wherein the first mixing step includes a step of mixing a portion of the processing liquid obtained in the third solid-liquid separation step with the first mixed liquid.

[0023] In this method, in the third solid-liquid separation step, the fibrous material (aggregate thereof) separated in the first solid-liquid separation step is compressed to extract the processing liquid contained in the fibrous material (aggregate thereof), and the extracted processing liquid is mixed with the first mixed liquid. As a result, when performing the second screening step, particulate matter remaining in the processing liquid that could not be separated in the first and third solid-liquid separation steps can also be included in the first mixed liquid when performing the second screening step. This allows for a higher separation rate of particulate matter and an improved recovery rate.

[0024] [Aspect 6] The separation method according to embodiment 3, further comprising a third solid-liquid separation step of compressing the fibrous material separated in the first solid-liquid separation step to separate the fibrous material from the processing liquid, wherein the third mixing step includes mixing a portion of the processing liquid obtained in the third solid-liquid separation step with the third mixed liquid.

[0025] In this method, in the third solid-liquid separation step, the fibrous material (aggregate thereof) separated in the first solid-liquid separation step is compressed to extract the processing liquid contained in the fibrous material (aggregate thereof), and the extracted processing liquid is mixed with the third mixed liquid. As a result, when performing the second solid-liquid separation step, particulate matter that remained in the processing liquid because it could not be completely separated in the first and third solid-liquid separation steps can also be included in the third mixed liquid when performing the second solid-liquid separation step. This makes it possible to further increase the separation rate of particulate matter and improve the recovery rate.

[0026] [Aspect 7] The separation method according to embodiment 1 or 2, wherein the particulate matter is a superabsorbent polymer, and the treatment solution is an aqueous solution containing an inactivating agent for inactivating the superabsorbent polymer.

[0027] In this method, the treatment solution is an aqueous solution containing an inactivating agent that deactivates the superabsorbent polymer, thus suppressing the swelling of the superabsorbent polymer and making it difficult to separate at each step. As a result, the separation rate of the superabsorbent polymer, i.e., particulate matter, can be increased, and the recovery rate can be improved. In this case, using an aqueous solution containing an inactivating agent tends to increase the burden of wastewater treatment and the environmental impact compared to using ordinary water, but this method can suppress these issues.

[0028] [Aspect 8] The separation method according to embodiment 7, wherein the inactivator comprises an inorganic acid or an organic acid.

[0029] In this method, the inactivator contains an inorganic or organic acid. Therefore, the superabsorbent polymer can be properly inactivated, and swelling of the superabsorbent polymer, which makes it difficult to separate, can be further suppressed in each step.

[0030] [Aspect 9] A separation method for separating fibrous material and particulate material from used sanitary products, comprising: a first screening step in which a dispersion containing fibrous material, particulate material and processing liquid dissected from the used sanitary products is separated by a first screen device into a first accept containing a large amount of the particulate material and processing liquid and a first reject containing a large amount of the fibrous material; a first solid-liquid separation step in which the first accept obtained in the first screening step is separated into particulate material and processing liquid; a first mixing step in which a portion of the processing liquid obtained in the first solid-liquid separation step is mixed with the first reject to produce a first mixed liquid; and a second screening step in which the first mixed liquid is separated by a second screen device into a second accept containing a large amount of the particulate material and processing liquid and a second reject containing a large amount of the fibrous material.

[0031] In this method, first, a first screening step is performed on the dispersion to generate a first reject (mainly fibrous material; high solid content) and a first accept (mainly particulate material and treated water; low solid content). Next, the first reject is mixed with the treated liquid obtained by solid-liquid separation of the first accept to create a first mixed liquid with a diluted concentration. Then, a second screening step is performed on the first mixed liquid to obtain a second reject (mainly fibrous material). Here, when performing the second screening step on the first reject, the concentration is diluted to the appropriate concentration required for the screening step by mixing the first reject with the treated liquid obtained by solid-liquid separation of the first accept to create the first mixed liquid, thus enabling the second screening step to be carried out properly. At that time, any fibrous material that remained in the treated liquid due to not being completely separated can also be included in the first mixed liquid when performing the second screening step. As a result, the separation rate of fibrous material can be increased, and the recovery rate can be improved. In this process, since the treatment liquid obtained by solid-liquid separation of the first acceptor is used in the second screening step, there is no need to add any additional liquid (e.g., water, treatment liquid). This helps to suppress an increase in the burden of wastewater treatment and an increase in environmental impact.

[0032] The following describes a method for separating fibrous material and particulate material from used sanitary products according to this embodiment.

[0033] However, used sanitary products are sanitary products that have been used by a user, but may also include unused sanitary products. Examples of sanitary products include absorbent items such as disposable diapers, urine pads, incontinence pads, sanitary napkins, disposable underwear, bed sheets, and pet sheets. Used sanitary products may or may not have absorbed or retained the user's excrement (e.g., urine, feces, menstrual blood).

[0034] First, an example of the configuration of the sanitary product to be addressed in the embodiment will be described. The sanitary product comprises a surface sheet, a back sheet, and an absorbent material placed between the surface sheet and the back sheet. The size of the sanitary product may be, for example, about 15 to 100 cm in length and 5 to 100 cm in width, but is not limited to this example. In addition, the sanitary product may further include other components that are generally found in sanitary products, such as a diffusion sheet, a leak-proof wall, a side sheet, an outer sheet, an elastic member, etc.

[0035] Examples of components for the surface sheet include liquid-permeable nonwoven fabrics, synthetic resin films with liquid-permeable pores, and composite sheets thereof. Examples of components for the back sheet include liquid-impermeable nonwoven fabrics, liquid-impermeable synthetic resin films, and composite sheets thereof. Examples of components for the diffusion sheet include liquid-permeable nonwoven fabrics. Examples of components for the leak-proof wall and side sheets include water-repellent nonwoven fabrics, and the leak-proof wall may include an elastic member such as rubber. Examples of components for the outer sheet include liquid-impermeable and breathable nonwoven fabrics, liquid-impermeable and breathable synthetic resin films, and composite sheets thereof. Examples of components for the elastic member include rubber-based synthetic resins. There are no particular restrictions on the type of nonwoven fabric, and examples include meltblown nonwoven fabrics, spunbond nonwoven fabrics, airlaid nonwoven fabrics, and air-through nonwoven fabrics. There are no particular restrictions on the type of synthetic resin film, and known film materials can be used. There are no particular restrictions on the materials used for nonwoven fabrics and synthetic resin films, as long as they can be used for sanitary products. Examples include olefin resins such as polyethylene and polypropylene, polyamide resins such as 6-nylon and 6,6-nylon, and polyester resins such as polyethylene terephthalate and polybutylene terephthalate. These nonwoven fabrics and synthetic resin films are synthetic resins and can be called plastic materials. In this embodiment, the back sheet is made of a synthetic resin film, and the front sheet is made of a nonwoven fabric.

[0036] The absorbent material can be composed of at least one of the following: an absorbent material, such as pulp fibers, which are fibrous materials, and a superabsorbent polymer, which is a particulate material. Examples of pulp fibers, such as fibrous materials, include cellulose fibers. Examples of cellulose fibers include wood pulp, cross-linked pulp, non-wood pulp, regenerated cellulose, and semi-synthetic cellulose. The size of the pulp fibers can be such that the average major diameter of the fibers is several tens of μm, preferably 20 to 40 μm, and the average fiber length can be such that several millimeters, preferably 2 to 5 mm. Examples of superabsorbent polymers (SAP), which are particulate materials, include polyacrylate-based, polysulfonate-based, and maleate anhydride-based superabsorbent polymers. The size of the superabsorbent polymer (when dry) can be such that the average particle size is such that several hundred μm, preferably 200 to 500 μm. The absorbent material may include a core wrap formed of a liquid-permeable sheet. In this embodiment, the absorbent material is composed of pulp fibers, which are fibrous materials, and a superabsorbent polymer, which is a particulate material, wrapped in a core wrap.

[0037] One side and the other side of the absorbent are joined to the surface sheet and the back sheet, respectively, via adhesive. In a plan view, the portion of the surface sheet that extends outward from the absorbent, surrounding it (peripheral portion), is joined to the portion of the back sheet that extends outward from the absorbent, surrounding it (peripheral portion), via adhesive. Therefore, the absorbent is enclosed within the joint of the surface sheet and the back sheet. There are no particular restrictions on the adhesive, but examples include hot-melt adhesives. Examples of hot-melt adhesives include rubber-based adhesives such as styrene-ethylene-butadiene-styrene, styrene-butadiene-styrene, and styrene-isoprene-styrene, or olefin-based adhesives such as polyethylene, which are pressure-sensitive or heat-sensitive adhesives.

[0038] Next, a method for separating fibrous material and particulate material from used sanitary products according to this embodiment will be described in detail. Here, as an example to which this method for separating fibrous material and particulate material from used sanitary products is applied, a method for separating the constituent materials of used sanitary products (examples: plastic material, pulp fiber, and superabsorbent polymer) will be described. In this embodiment, the sanitary product is an absorbent article (disposable diaper).

[0039] Figure 1 is a block diagram showing an example of the configuration of System 1 used in a method for separating the constituent materials of used sanitary products according to the embodiment. Figure 2 is a flowchart showing an example of a method for separating the constituent materials of used sanitary products according to the embodiment. The method in Figure 2 is carried out using System 1 in Figure 1, and separates used sanitary products contained in a collection bag into plastic material, superabsorbent polymer (SAP) which is a particulate matter, and pulp fiber which is a fibrous matter. A detailed explanation follows below.

[0040] As shown in Figure 2, the method for separating the constituent materials of used sanitary products comprises a crushing step S1, a first separation step S2, a dust removal step S3, a second separation step S4, a third separation step S5, an oxidizing agent treatment step S6, and a fourth separation step S7.

[0041] In this embodiment, used sanitary products are collected from an external source for reuse (recycling). Multiple used sanitary products are sealed in a collection bag to prevent leakage of excrement, bacteria, and odors. Each used sanitary product within the collection bag is collected in a rolled or folded state, for example, with the surface sheet containing the excrement facing inward, to prevent excrement and bacteria from being exposed on the outside and odors from spreading to the surroundings. Note that used sanitary products do not necessarily have to be sealed in a collection bag or rolled up.

[0042] The crushing step S1 is a step in which used sanitary products are crushed together with an inactivating aqueous solution containing an inactivating agent that inactivates superabsorbent polymers. The crushing step S1 is carried out by a crushing device 3 (examples: a twin-shaft rotary crusher, a twin-shaft differential crusher, a twin-shaft shear crusher, etc.). Crushing together with the inactivating aqueous solution includes cases where used sanitary products are supplied to the crushing device 3 together with the inactivating aqueous solution and crushed, or cases where used sanitary products are placed in the inactivating aqueous solution stored in the crushing device 3 and crushed. In this embodiment, the former case is used.

[0043] In this embodiment, in the crushing step S1, collection bags 91 containing used sanitary products are supplied to a receiving device 2 (example: receiving tank, receiving container) and moved to a crushing device 3 connected to the bottom of the receiving device 2. At the same time, an inactivated aqueous solution (example: acidic aqueous solution (acid-containing aqueous solution)) is supplied to the crushing device 3 via the receiving device 2. The collection bags 91 are crushed together with the inactivated aqueous solution by the crushing device 3. As a result, the used sanitary products inside the collection bags 91 are crushed together with the collection bags 91 in the inactivated aqueous solution, and crushed material is generated. At this time, the superabsorbent polymer is inactivated by the inactivated aqueous solution. The crushed material, together with the inactivated aqueous solution, is sent to the first separation step S2 as a mixture 92. Note that the inactivated aqueous solution may be stored in advance in the crushing device 3 before receiving the collection bags 91. Note that the mixture may be not only a solid, but also a slurry or a liquid, and the same applies hereinafter.

[0044] In the crushing step S1, it is preferable that the used sanitary products are crushed so that the size of the crushed material is approximately 1 to 150 mm, preferably 5 to 100 mm. If the size is 1 mm or larger, other materials (e.g., film, nonwoven fabric, elastic material, etc.) other than pulp fibers and superabsorbent polymers are cut into large pieces, making it easier to separate these materials from the pulp fibers and superabsorbent polymers in subsequent steps. If the size is 150 mm or smaller, the materials of the used sanitary products are less likely to entangle with each other, making it easier for larger materials to separate, and also making it easier to separate the pulp fibers and superabsorbent polymers that are sandwiched between these materials.

[0045] When used sanitary products are pulverized with an inactivating aqueous solution, the superabsorbent polymer contained in the used sanitary products is inactivated, dehydrated, and reduced to a small particle size. This makes it easier to handle (separate and recover) the superabsorbent polymer in subsequent processes, improving the efficiency of the process. As the inactivating agent, it is preferable to use an aqueous solution of an inorganic acid or an organic acid, i.e., an acidic aqueous solution. Using an acidic aqueous solution makes it less likely for ash and chlorine to remain on plastic materials, superabsorbent polymers, and pulp fibers compared to using aqueous solutions of lime or calcium chloride, and makes it easier to adjust the degree of inactivation (particle size and specific gravity) by pH. In addition, the inactivating aqueous solution may be an aqueous solution containing a known polyvalent metal ion source capable of supplying polyvalent metal ions.

[0046] Examples of organic acids include citric acid, tartaric acid, glycolic acid, malic acid, succinic acid, acetic acid, and ascorbic acid, with citric acid being preferred. Citric acid can trap and remove metal ions and other substances in excrement through its chelating effect, and can also remove dirt components through its cleaning effect. On the other hand, examples of inorganic acids include sulfuric acid, hydrochloric acid, and nitric acid, with sulfuric acid being preferred. Sulfuric acid does not contain chlorine, and therefore chlorine is less likely to remain on plastic materials, resulting in lower costs.

[0047] The pH of the acidic aqueous solution is preferably between 1.0 and 4.0. A pH of 1.0 or higher reduces equipment corrosion and the amount of alkaline chemicals required for neutralization during wastewater treatment. A pH of 4.0 or lower allows for sufficiently small superabsorbent polymers, thereby enhancing sterilization capabilities. Since pH changes with water temperature, the pH in this invention refers to the pH measured at an aqueous solution temperature of 20°C.

[0048] The concentration of the organic acid in the aqueous solution of the organic acid is not particularly limited, but if the organic acid is citric acid, it is preferably 0.5% by mass or more and 4% by mass or less. The concentration of the inorganic acid in the aqueous solution of the inorganic acid is not particularly limited, but if the inorganic acid is sulfuric acid, it is preferably 0.1% by mass or more and 2.0% by mass or less. In this embodiment, the case in which an aqueous solution of sulfuric acid (dilute sulfuric acid), i.e., an acidic aqueous solution (acid-containing aqueous solution), is used as the inactivating aqueous solution will be described.

[0049] The crushing step S1 in the crushing device 3 does not necessarily have to be carried out with an inactivating aqueous solution such as an acidic aqueous solution; for example, it may be carried out in air. In that case, at least the subsequent steps, the first separation step S2 and / or the second separation step S4, are carried out with the inactivating aqueous solution.

[0050] Thus, in the crushing process S1, each component of the used sanitary product is crushed to approximately a predetermined size. At that time, the heat generated during crushing and / or the heat of the acidic aqueous solution can reduce the bonding strength of the adhesive (e.g., hot melt adhesive) between each component, making it possible to easily separate the components from one another.

[0051] Furthermore, by heating an acidic aqueous solution (temperature: 70-95°C), the adhesive used to join the components of used sanitary products (e.g., hot melt adhesive) can be softened, reducing the adhesive's bonding strength. This allows the components to be easily separated naturally or with a small impact. It also makes it possible to sterilize (disinfect) used sanitary products more effectively.

[0052] If the crushing step S1 is not used, for example, the used sanitary products may be immersed in heated water or an aqueous solution (example: an inactivated aqueous solution such as an oxidizing agent aqueous solution), and the bonding strength of the adhesives between the components may be reduced by physical impact such as stirring, thereby separating the components from each other. If an aqueous solution that does not contain an inactivating agent, such as water, is used, at least the subsequent first separation step S2 and / or second separation step S4 shall be carried out together with the inactivated aqueous solution.

[0053] The first separation step S2 is a step of separating used sanitary products into a first fraction containing plastic material and a second fraction containing excrement, inactivated superabsorbent polymer, and pulp fibers. In other words, in the first separation step S2, the mixture of plastic material, excrement, inactivated superabsorbent polymer, and pulp fibers obtained by decomposing used sanitary products is separated into a first fraction containing plastic material and a second fraction containing excrement, superabsorbent polymer, and pulp fibers. The first separation step S2 is carried out by a first separation device 4 (examples: pulper separator, screen separator).

[0054] In this embodiment, in the first separation step S2, a mixture 92 of crushed material produced in the crushing step S1 and an acidic aqueous solution which is an inactivated aqueous solution is supplied to the pulper separator, which is the first separation device 4. The pulper separator is equipped with a stirring separation tank that has the functions of both a washing tank for washing the mixture and a sieving tank for separating the mixture. In addition, a different acidic aqueous solution not used in the crushing step S1 may be supplied as the acidic aqueous solution in the first separation step S2.

[0055] Mixture 92 is stirred by a pulper separator and washed to remove impurities from the crushed material. It is then separated by a screen into a first fraction containing collection bags, film, nonwoven fabric, etc., and a second fraction containing pulp fibers, inactivated superabsorbent polymer, excrement, and acidic aqueous solution. That is, the pulp fibers, superabsorbent polymer, excrement, and acidic aqueous solution (the second fraction) pass through the screen and are separated from mixture 92, being sent out of the pulper separator as mixture 93. Meanwhile, other materials such as collection bags, film, and nonwoven fabric (the first fraction) that could not pass through the screen remain in the pulper separator. At this time, some of the pulp fibers, superabsorbent polymer, excrement, and acidic aqueous solution may not pass through the screen and remain on the screen along with the other materials. Also, some of the other materials may pass through the screen.

[0056] Furthermore, as in this embodiment, if the superabsorbent polymer is inactivated and granulated before the first separation step S2 (e.g., in the crushing step S1) to suppress its water absorption capacity, then in the steps after the first separation step S2, the inactivation aqueous solution (acidic aqueous solution) may not be used. Instead, the inactivation aqueous solution may be largely removed, and then water (aqueous solution) without an inactivating agent may be used. In that case, water (aqueous solution) without an inactivating agent may be used from any step after the first separation step S2. This reduces the amount of inactivation aqueous solution (and inactivating agent) used, thereby reducing the burden on wastewater treatment.

[0057] Furthermore, if the superabsorbent polymer is not inactivated beforehand (e.g., in the crushing step S1) prior to the first separation step S2, the first separation step S2 may include a step of first treating the used sanitary products with an inactivating aqueous solution (acidic aqueous solution), that is, a step of inactivating the superabsorbent polymer. In that case, possible treatment methods include, for example, immersing the used sanitary products in an inactivating aqueous solution (acidic aqueous solution) or spraying the used sanitary products with an inactivating aqueous solution (acidic aqueous solution). The acidic aqueous solution is as previously described. After the first separation step S2, a step of separating the used sanitary products into a first fraction and a second fraction is carried out. In this case as well, as described above, water (aqueous solution) without an inactivating agent may be used from any step after the first separation step S2.

[0058] However, other materials such as collection bags, films, and nonwoven fabrics are made of synthetic resins and can be considered plastic materials. Therefore, in the first separation step S2, the plastic materials and a small amount of residue (pulp fibers, superabsorbent polymer, excrement, and acidic aqueous solution) become the residue on the screen (reject), and the separated pulp fibers, superabsorbent polymer, excrement, and acidic aqueous solution become the material that passes through the screen (accept), forming a mixture 93.

[0059] In this embodiment, the first separation step S2 is performed on one of two first separation devices connected in parallel. For example, two pulper separators are connected in parallel, and when one pulper separator is running and maintenance is required for that pulper separator, that pulper separator is stopped and the other pulper separator is started. This allows the first separation step S2 to be performed continuously. Note that three or more first separation devices may be connected in parallel.

[0060] In this embodiment, in the first separation step S2, the pH of the acidic aqueous solution is adjusted to be maintained within a predetermined range. The predetermined range of pH is defined as a range where the pH fluctuation is within ±1.0. This ensures that the difference between the specific gravity and size of the superabsorbent polymer and the specific gravity and size of the pulp fibers is within a predetermined range. In this case, the difference being within a predetermined range means, for example, that one is within a range of 0.2 to 5 times that of the other. This ensures that the difference between the pulp fibers and the superabsorbent polymer is that the specific gravity is within a predetermined range and the size is within a predetermined range. As a result, the pulp fibers and superabsorbent polymer can be easily separated from other materials (mainly plastic materials) in used sanitary products, excluding the pulp fibers and superabsorbent polymer, by utilizing the differences in size and specific gravity. pH adjustment can be performed using an acidic aqueous solution or an alkaline aqueous solution based on the pH value measured by a pH sensor. Note that in the second separation step S4 and the third separation step S5, the pH may also be adjusted in the same manner as in the first separation step S2.

[0061] Furthermore, if an inactivating aqueous solution (acidic aqueous solution) is used in the crushing step S1, the pH of the acidic aqueous solution may be adjusted in the same manner as in the first separation step S2.

[0062] In the first fraction (including the plastic material) of the first separation step S2, the following treatments are performed as needed: separation (screen separation of the plastic material from the remaining excrement, superabsorbent polymer, and pulp fibers that could not be separated in the first separation step S2 by physical impact in an acidic aqueous solution), washing and sterilization (e.g., ozonated water treatment), dewatering and drying, and the plastic material is recovered.

[0063] The dust removal process S3 is a process of removing foreign matter (dust removal) from the mixture 93 containing pulp fibers, superabsorbent polymer, excrement, and acidic aqueous solution separated in the first separation process S2. The dust removal process S3 is carried out by a dust removal device 5 (examples: screen separator, cyclone separator).

[0064] In this embodiment, the dust removal step S3 uses a dust removal device 5 to separate foreign matter (such as collection bags, films, nonwoven fabrics, and elastic materials) that could not be separated from the mixture 93 supplied from the first separation step S2. The dust removal device 5 consists of, for example, a screen separator (with a relatively large mesh opening), a screen separator (with a relatively small mesh opening), and a cyclone separator arranged in this order, and foreign matter is sequentially separated from the mixture 93. As a result, a mixture 94 of pulp fibers and superabsorbent polymer with few foreign matter and an acidic aqueous solution (containing excrement) is obtained. The mixture 94 is supplied to the second separation step S4. Note that if it is not necessary to separate foreign matter in the mixture 93 (for example, if there is little foreign matter, or if foreign matter will be separated in a later step), the dust removal step S3 can be omitted.

[0065] The second separation step S4 is a step of separating the superabsorbent polymer from the mixture 94 (or mixture 93) supplied from the dust removal step S3 (or the first separation step S2). Here, the mixture 94 (or mixture 93) contains pulp fibers, superabsorbent polymer, and an acidic aqueous solution (including excrement) dissected from used sanitary products. Therefore, the mixture 94 can be described as a dispersion containing fibrous material (pulp fibers), particulate material (superabsorbent polymer), and processing liquid (acidic aqueous solution) dissected from used sanitary products. The second separation step S4 is carried out by a second separation device 6 (examples: screen separator, drum screen separator, or a combination thereof).

[0066] In this embodiment, in the second separation step S4, the superabsorbent polymer and acidic aqueous solution are separated from the mixture 94 by a plurality of screen separators and a drum screen separator, and the pulp fibers (with the superabsorbent polymer remaining on the surface, etc.) and acidic aqueous solution are separated. This yields a mixture 95 containing the superabsorbent polymer and a mixture 96 containing pulp fibers (with the superabsorbent polymer remaining) and acidic aqueous solution. The acidic aqueous solution is then removed from the mixture 95, and if necessary, it is sterilized, washed, dried, etc., and recovered as the superabsorbent polymer. The superabsorbent polymer (SAP) separated and recovered in this way becomes so-called recycled superabsorbent polymer. Meanwhile, the mixture 96 is supplied to the third separation step S5. Details of the second separation step S4 will be described later.

[0067] The third separation step S5 is a step of separating pulp fibers from the mixture 96 supplied from the second separation step S4. The third separation step S5 is carried out by a third separation device 7 (examples: drum screen separator, screw press separator, or a combination thereof).

[0068] In this embodiment, in the third separation step S5, a drum screen device and a screw press device separate the pulp fibers (with superabsorbent polymer remaining on the surface, etc.) and the acidic aqueous solution from the mixture 96. As a result, the mixture 97, which consists of pulp fibers (with superabsorbent polymer remaining on the surface, etc.), and the acidic aqueous solution (not shown) are obtained. The mixture 97 is supplied to the oxidizing agent treatment step S6. Details of the third separation step S5 will be described later.

[0069] The oxidizing agent treatment step S6 is a step in which the superabsorbent polymer in the mixture 97 (including pulp fibers and superabsorbent polymer remaining on the surface of pulp fibers, etc.) supplied from the third separation step S5 is oxidized and decomposed with an aqueous oxidizing agent solution, solubilized, and removed from the pulp fibers. The oxidizing agent treatment step S6 is carried out by an oxidizing agent treatment device 8 (example: a treatment tank for storing an aqueous oxidizing agent solution).

[0070] In this embodiment, in the oxidizing agent treatment step S6, a mixture 97 (containing pulp fibers having a superabsorbent polymer) is introduced into a treatment tank that stores an aqueous solution of an oxidizing agent containing ozone as the oxidizing agent. The superabsorbent polymer in the pulp fibers is oxidatively decomposed and solubilized, resulting in pulp fibers with very few impurities. The pulp fibers with few impurities (including the superabsorbent polymer) are supplied to the fourth separation step S7 as a mixture 98 together with the aqueous solution of the oxidizing agent.

[0071] Regarding the type of oxidizing agent in the oxidizing agent treatment step S6, for example, at least one of ozone and hydrogen peroxide can be used, but in this embodiment, ozone is used from the viewpoint of oxidizing power, bactericidal power and bleaching power. The ozone concentration in the aqueous oxidizing agent solution is not particularly limited as long as it is a concentration that can decompose the superabsorbent polymer, but for example, it is 10 to 50 ppm by mass. The concentration is not too low so that the superabsorbent polymer can be completely solubilized, and the concentration is not too high so that the pulp fibers are not damaged. The treatment time in the aqueous oxidizing agent solution is not particularly limited as long as it is a time that can decompose the superabsorbent polymer, but it is shorter if the ozone concentration in the aqueous oxidizing agent solution is high and longer if the ozone concentration is low, and is typically 5 to 300 minutes. The product of the ozone concentration in the aqueous oxidizing agent solution (ppm) and the treatment time (minutes) of the treatment step (hereinafter also referred to as the "CT value") is preferably 100 to 15000 ppm·minute. If the CT value is too low, the superabsorbent polymer may not be completely solubilized, potentially leaving residue in the pulp fibers. If the CT value is too high, it may damage the pulp fibers.

[0072] The fourth separation step S7 is a step of separating pulp fibers from the mixture 98 supplied from the oxidizing agent treatment step S6. The fourth separation step S7 is carried out by a fourth separation apparatus 9 (examples: drum screen apparatus, screw press apparatus, or a combination thereof).

[0073] In this embodiment, in the fourth separation step S7, pulp fibers and an aqueous oxidizing agent solution are separated from the mixture 96 by a drum screen device and a screw press device. As a result, pulp fibers and an aqueous oxidizing agent solution (not shown) are extracted. The pulp fibers are recovered after being sterilized, washed, dried, etc., as necessary. The pulp fibers separated and recovered in this way become so-called recycled pulp fibers.

[0074] Next, a method for separating fibrous material and particulate material from used sanitary products will be described. In this embodiment, the method for separating fibrous material and particulate material from used sanitary products will be described in the case where it is applied to the method for separating the constituent materials of used sanitary products. In this case, the method for separating fibrous material and particulate material from used sanitary products corresponds to at least the second separation step S4 and the third separation step S5 described above. However, the method for separating fibrous material and particulate material from used sanitary products is not limited to this example.

[0075] Figure 3 is a block diagram showing an example of the configuration of an apparatus used in the method for separating fibrous and particulate matter from used sanitary products according to the embodiment, applied to System 1 in Figure 1. Figure 4 is a flow chart showing an example of the method for separating fibrous and particulate matter from used sanitary products according to the embodiment, applied to the separation method in Figure 2. The method in Figure 4 is carried out using the apparatus in Figure 3, and separates a dispersion containing fibrous matter, particulate matter, and processing liquid dissected from used sanitary products into particulate matter (and a portion of the processing liquid) and fibrous matter (and a portion of the processing liquid). A detailed explanation follows below.

[0076] As shown in Figure 4, the method for separating fibrous material and particulate material from used sanitary products comprises a first screen step S41, a first mixing step S42, a second screen step S43, and a first solid-liquid separation step S52. In this embodiment, the separation method further comprises a third mixing step S44, a second solid-liquid separation step S45, a second mixing step S51, and a third solid-liquid separation step S53.

[0077] In this embodiment, the first screening step S41, the first mixing step S42, the second screening step S43, the third mixing step S44, and the second solid-liquid separation step S45 of this separation method are included in the second separation step S4, and therefore can be said to be steps applied to the second separation step S4. On the other hand, the second mixing step S51, the first solid-liquid separation step S52, and the third solid-liquid separation step S53 are included in the third separation step S5, and therefore can be said to be steps applied to the third separation step S5.

[0078] In accordance with this separation method, as shown in Figure 3, the apparatus used for separating fibrous material and particulate material from used sanitary products comprises a first screen device 10, a first mixing device 11, a second screen device 12, and a first solid-liquid separator 16. In this embodiment, the apparatus used for this separation method further comprises a third mixing device 13, a second solid-liquid separator 14, a second mixing device 15, and a third solid-liquid separator 17.

[0079] Of the devices used in this separation method, the first screen device 10, the first mixing device 11, the second screen device 12, the third mixing device 13, and the second solid-liquid separation device 14 are included in the second separation device 6, and therefore can be said to be devices applied to the second separation device 6. On the other hand, the second mixing device 15, the first solid-liquid separation device 16, and the third solid-liquid separation device 17 are included in the third separation device 7, and therefore can be said to be devices applied to the third separation device 7.

[0080] In the following description, in this embodiment, the screens of each screening device are preferably screens through which fibrous material can pass more easily than particulate material. The hole shape of the screen is preferably a slit shape with a width smaller than the particle size of the particulate material, larger than the fiber diameter of the fibrous material, and longer than the fiber length of the fibrous material. This makes it easier for fibrous material to pass through the screen and difficult for particulate material to pass through the screen. On the other hand, the screens of each solid-liquid separation device (excluding the second solid-liquid separation device 14) are preferably screens through which particulate material can pass more easily than fibrous material. The hole shape of the screen is preferably a round hole shape with a diameter larger than the particle size of the particulate material and smaller than the fiber length of the fibrous material. This makes it easier for particulate material to pass through the screen and difficult for fibrous material to pass through the screen.

[0081] First, let's explain the second separation process S4.

[0082] First, the first screening step S41 is a step in which a dispersion Q containing fibrous material, particulate matter, and processing liquid separated from used sanitary products is separated into a first accept A1 which contains a large amount of fibrous material (example: pulp fibers) and processing liquid, and a first reject R1 which contains a large amount of particulate matter (example: superabsorbent polymer). The first screening step S41 is carried out by a first screening device 10 (example: screen separator).

[0083] In this embodiment, in the first screening step S41, first, the mixture 94 is supplied to the first screening device 10 via piping 21-1 from the dust removal step S3 (or the first separation step S2). The mixture 94 is a dispersion Q containing fibrous material (example: pulp fibers), particulate material (example: superabsorbent polymer), and processing liquid (example: acidic aqueous solution) separated from used sanitary products. The dispersion Q is then separated by the first screening device 10 into a first accept A1 containing a large amount of fibrous material and processing liquid, and a first reject R1 containing a large amount of particulate material but a small amount of processing liquid. The first accept A1 is then supplied to the first solid-liquid separation step S52. On the other hand, the first reject R1 is supplied to the first mixing step S42.

[0084] The proportion of processing solution in the first accept A1 is greater than the proportion of processing solution in the first reject R1. In other words, the solid content concentration in the first accept A1 is lower than that of the first reject R1. For example, the solid content concentration in the first accept A1 is 0.01 to 1% by mass, while the solid content concentration in the first reject R1 is 0.1 to 3% by mass. Furthermore, the first accept A1 contains a relatively large amount of fibrous material, which is the main component, but also contains particulate material. The first reject R1 contains a relatively large amount of particulate material, which is the main component, but also contains fibrous material.

[0085] Next, the first mixing step S42 is a step in which a portion of the processed liquid L1 obtained in the first solid-liquid separation step S52 is mixed with the first reject R1 to produce the first mixed liquid C1. The first mixing step S42 is carried out in the first mixing apparatus 11 (example: container or tank and a stirrer). However, the first solid-liquid separation step S52 will be described later. Furthermore, in the first mixing step S42, a portion of the processed liquid L3 obtained in the third solid-liquid separation step S53 after the first solid-liquid separation step S52 may be mixed with the first reject R1. However, the third solid-liquid separation step S53 will be described later.

[0086] In this embodiment, in the first mixing step S42, at least a portion of the processing liquid L1 obtained in the first solid-liquid separation step S52 is first supplied to the first mixing device 11 via piping 24-1 and 24-2. The processing liquid L1 is obtained by solid-liquid separation from the first accept A1. The processing liquid L1 is mixed with the first accept A1 without being separated into the first reject R1 and contains particulate matter separated on the processing liquid L1 side during solid-liquid separation. Meanwhile, the first reject R1 obtained in the first screening step S41 is supplied to the first mixing device 11 via piping 22-1. At least a portion of the processing liquid L1 and the first reject R1 are then mixed in the first mixing device 11 to produce the first mixed liquid C1. The first mixed liquid C1 is supplied to the second screening step S43.

[0087] The first mixed solution C1 includes particulate matter supplied from the processing solution L1 and the first reject R1, and may contain fibrous material. Since the solid content concentration of the processing solution L1 is lower than that of the first reject R1, the solid content concentration of the first mixed solution C1 is lower than that of the first reject R1. For example, the solid content concentration in the first mixed solution C1 is 0.01 to 1% by mass.

[0088] Next, the second screening step S43 is a step in which the first mixed liquid C1 is separated into a second accept A2 which contains a large amount of fibrous material and processing liquid, and a second reject R2 which contains a large amount of particulate material. The second screening step S43 is carried out by a second screening device 12 (example: screen separator).

[0089] In this embodiment, in the second screening step S43, first, the first mixed liquid C1 is supplied from the first mixing step S42 to the second screening device 12 via piping 22-2. The first mixed liquid C1 is a mixture of particulate matter, fibrous matter, and processing liquid. The first mixed liquid C1 is then separated by the second screening device 12 into a second accept A2 containing a large amount of fibrous matter and processing liquid, and a second reject R2 containing a large amount of particulate matter but a small amount of processing liquid. The second accept A2 is then supplied to the second mixing step S51. On the other hand, the second reject R2 is supplied to the third mixing step S44.

[0090] The proportion of processing solution in Accept A2 is greater than the proportion of processing solution in Reject R2. In other words, the solid content concentration in Accept A2 is lower than that of Reject R2. For example, the solid content concentration in Accept A2 is 0.01 to 1% by mass, while the solid content concentration in Reject R2 is 0.1 to 3% by mass. Furthermore, Accept A2 contains a relatively large amount of fibrous material, which is the main component, but may also contain particulate material. Reject R2 contains a relatively large amount of particulate material, which is the main component, but may also contain fibrous material.

[0091] Next, the third mixing step S44 is a step in which a portion of the processed liquid L1 obtained in the first solid-liquid separation step S52 is mixed with the second reject R2 to produce a third mixed liquid C3. The third mixing step S44 is carried out in a third mixing apparatus 13 (example: a container or tank and a stirrer). In addition, in the third mixing step S44, a portion of the processed liquid L3 obtained in the third solid-liquid separation step S53 after the first solid-liquid separation step S52 may be further mixed with the second reject R2. However, the third solid-liquid separation step S53 will be described later.

[0092] In this embodiment, in the third mixing step S44, first, at least a portion of the processing liquid L1 obtained in the first solid-liquid separation step S52 is supplied to the third mixing device 13 via piping 24-1. The processing liquid L1 contains particulate matter as described above. Meanwhile, the second reject R2 obtained in the second screening step S43 is supplied to the third mixing device 13 via piping 22-3. At least a portion of the processing liquid L1 and the second reject R2 are mixed in the third mixing device 13 to produce the third mixed liquid C3. However, the solid content concentration of the processing liquid L1 is lower than the solid content concentration of the second reject R2. The third mixed liquid C3 is supplied to the second solid-liquid separation step S45.

[0093] The third mixed solution C3 contains particulate matter supplied from the processing solution L1 and the second reject R2, and may contain fibrous material. Since the solid content concentration of the processing solution L1 is lower than that of the second reject R2, the solid content concentration of the third mixed solution C3 is lower than that of the second reject R2. For example, the solid content concentration in the third mixed solution C3 is 0.01 to 1% by mass.

[0094] The third mixing step S44 may be omitted. In that case, the second reject R2 is sterilized, washed, dehydrated, dried, etc. as necessary, and removed to the outside as particulate matter (superabsorbent polymer) for reuse, or supplied to the second solid-liquid separation step S45.

[0095] Next, the second solid-liquid separation step S45 is a process of solid-liquid separation of the third mixed liquid C3 obtained in the third mixing step S44 into particulate matter P1 as a solid and a processing liquid L2 containing fibrous material as a liquid. The second solid-liquid separation step S45 is carried out in the second solid-liquid separation apparatus 14 (example: drum screen separator).

[0096] In this embodiment, in the second solid-liquid separation step S45, first, the third mixed liquid C3 from the third mixing step S44 is supplied to the second solid-liquid separation device 14 via the piping 22-4. The third mixed liquid C3 is a mixture of particulate matter and a processing liquid, and may contain fibrous material. The third mixed liquid C3 is then separated by the second solid-liquid separation device 14 into solid particulate matter P1 and liquid processing liquid L2 containing fibrous material. The particulate matter P1 is then recovered after being sterilized, washed, dehydrated, dried, etc., as necessary. If the separated and recovered particulate matter P1 is a superabsorbent polymer (SAP), it is reactivated after recovery (for example, by contacting it with an alkali metal ion source capable of supplying known alkali metal ions) to become a so-called recycled superabsorbent polymer with excellent water absorption performance.

[0097] On the other hand, the processing liquid L2 containing fibrous material is returned to at least one of the processes prior to the second separation process S4: the crushing process S1, the first separation process S2, and the dust removal process S3, and reused as processing liquid (acidic aqueous solution). For example, the solid content concentration in the processing liquid L2 is 0.01 to 1% by mass. The crushing process S1, the first separation process S2, and the dust removal process S3 can be described as disintegration processes that disintegrate fibrous and particulate matter of used sanitary products in the processing liquid to produce a dispersion. In this case, if the processing liquid contains fibrous material, it can be returned to the disintegration process to separate and recover the fibrous material in the processing liquid. This increases the recovery rate of fibrous material.

[0098] Furthermore, for the second solid-liquid separation device 14, a screen is preferable in which fibrous material can pass through more easily than particulate material. The hole shape of the screen is preferably a slit shape that is smaller than the particle size of the particulate material, wider than the fiber diameter of the fibrous material, and longer than the fiber length of the fibrous material. As a result, fibrous material can easily pass through the screen, allowing the processing liquid L2 containing fibrous material to be discharged as a liquid, while particulate material has difficulty passing through the screen, and particulate material P1 can be recovered as a solid.

[0099] Next, the third separation step S5 will be explained.

[0100] First, the second mixing step S51 is a step in which the second accept A2 obtained in the second screening step S43 is mixed with the first accept A1 obtained in the first screening step S41 to produce a second mixed liquid C2. The second mixing step S51 is carried out in a second mixing apparatus 15 (example: container or tank and a stirrer).

[0101] In this embodiment, in the second mixing step S51, first, the first accept A1 obtained in the first screening step S41 is supplied to the second mixing device 15 via piping 21-2. The first accept A1 is a processed liquid containing a relatively large amount of fibrous material and a small amount of particulate material. Meanwhile, the second accept A2 obtained in the second screening step S43 is supplied to the second mixing device 15 via piping 23. The second accept A2 is a processed liquid containing a relatively large amount of fibrous material and a small amount of particulate material. The first accept A1 and the second accept A2 are then mixed in the second mixing device 15 to produce the second mixed liquid C2. The second mixed liquid C2 is supplied to the first solid-liquid separation step S52.

[0102] The second mixture C2 contains fibrous material supplied from the first accept A1 and the second accept A2, a processing solution, and a small amount of particulate matter. Because the solid content concentration of the second accept A2 tends to be lower than that of the first accept A1, the solid content concentration of the second mixture C2 also tends to be lower than that of the first accept A1. For example, the solid content concentration in the second mixture C2 is 0.01 to 1% by mass.

[0103] The second mixing step S51 may be omitted. In that case, the first accept A1 is supplied to the first solid-liquid separation step S52.

[0104] Next, the first solid-liquid separation step S52 is a step in which the second mixed liquid C2 obtained in the second mixing step S51 is separated into a solid fibrous material F1 and a liquid processing liquid L1 containing particulate matter. However, if the second mixing step S51 is omitted, the first solid-liquid separation step S52 is a step in which the first accept A1 obtained in the first screening step S41 is separated into a solid fibrous material F1 and a liquid processing liquid L1 containing particulate matter. The first solid-liquid separation step S52 is carried out in the first solid-liquid separation apparatus 16 (example: drum screen separator).

[0105] In this embodiment, in the first solid-liquid separation step S52, first, the second mixed liquid C2 is supplied from the second mixing step S51 to the first solid-liquid separation device 16 via piping 21-3. The second mixed liquid C2 is a mixture of fibrous material and processing liquid, and contains a small amount of particulate matter. The second mixed liquid C2 is then separated by the first solid-liquid separation device 16 into fibrous material F1 as a solid and processing liquid L1 containing particulate matter as a liquid. However, the fibrous material F1 includes processing liquid and particulate matter that remain after solid-liquid separation. The fibrous material F1 is supplied to the third solid-liquid separation step S53. On the other hand, a portion of the processing liquid L1 containing particulate matter is supplied to the first mixing step S42 and / or the third mixing step S44.

[0106] If the second mixing step S51 is omitted, in the first solid-liquid separation step S52, the first accept A1 from the first screening step S41 is supplied to the first solid-liquid separation device 16 via piping 21-2 and 21-3, and solid-liquid separation is performed.

[0107] The third solid-liquid separation step S53 is a step in which the fibrous material F1 obtained in the first solid-liquid separation step S52 is compressed to separate it into a solid fibrous material F2 and a liquid processing liquid L3. The third solid-liquid separation step S53 is carried out using a third solid-liquid separation apparatus 17 (example: screw press separator).

[0108] In this embodiment, in the third solid-liquid separation step S53, first, fibrous material F1 is supplied from the first solid-liquid separation step S52 to the third solid-liquid separation device 17 via piping 21-4. Fibrous material F1 is a mixture of fibrous material, residual processing liquid, and particulate matter that cannot be completely separated. The fibrous material F1 is then separated into solid fibrous material F2 and liquid processing liquid L3 containing particulate matter by compression in the third solid-liquid separation device 17. However, fibrous material F2 may contain residual processing liquid and particulate matter that cannot be completely separated by solid-liquid separation. The fibrous material F2 is supplied as a mixture 97 to the oxidizing agent treatment step S6 (oxidizing agent treatment device 8). On the other hand, a portion of the processing liquid L3 containing particulate matter is supplied to the first mixing step S42 and / or the third mixing step S44.

[0109] The third solid-liquid separation step S53 may be omitted. In that case, the fibrous material F1 from the first solid-liquid separation step S52 is supplied as a mixture 97 to the oxidizing agent treatment step S6 (oxidizing agent treatment device 8). In addition, a portion of the fibrous material F1 and / or fibrous material F2 may be sterilized, washed, dried, etc., as needed, and removed as fibrous material for reuse. If the fibrous material F1 and / or fibrous material F2 separated and recovered in this way are pulp fibers, they become so-called recycled pulp fibers.

[0110] The second separation step S4 and the third separation step S5 are carried out as described above.

[0111] In this embodiment, the method for separating fibrous material and particulate material from used sanitary products is applied to S4 and S5 of the method for separating the constituent materials of used sanitary products. However, if a predetermined dispersion Q is provided, it may be carried out as a standalone separation method, or it may be carried out in addition to other pre- and post-processing steps.

[0112] In this embodiment, first, in the first screening step S41, the dispersion Q containing fibrous material, particulate material, and treatment liquid separated from used sanitary products is separated into a first reject R1 (mainly particulate material and treatment water) and a first accept A1 (mainly fibrous material and treatment water). Next, in the first mixing step S42, the first reject R1 is mixed with a portion of the treatment liquid L1 obtained by solid-liquid separation of the first accept A1 in the first solid-liquid separation step S52 to produce a first mixed liquid C1 with a diluted concentration. Next, in the second screening step S43, the first mixed liquid C1 is separated into a second accept A2 (mainly fibrous material and treatment water) and a second reject R2 (mainly particulate material).

[0113] Thus, when the second screening process S43 is performed on the first reject R1, the first reject R1 is mixed with the processing liquid L1 obtained by solid-liquid separation of the first accept A1 in the first solid-liquid separation process S52 to form the first mixed liquid C1. This allows the concentration of solids in the first reject R1 to be diluted to an appropriate concentration favorable for the screening process, thus enabling the second screening process S43 to be carried out properly. At that time, any particulate matter that remained in the processing liquid L1 due to not being completely separated can also be included in the first mixed liquid C1 and the second screening process S43 can be carried out. As a result, the separation rate of particulate matter in the second reject R2 (mainly particulate matter) can be increased, and the recovery rate of particulate matter can be improved.

[0114] In this process, a portion of the treatment liquid L1 obtained by solid-liquid separation of the first accept A1 is used to adjust the concentration of solids in the first reject R1. Therefore, since there is no need to add any new liquid (e.g., water, treatment liquid) in the second screening step S43, it is possible to suppress an increase in the burden of wastewater treatment and an increase in environmental impact.

[0115] In a preferred embodiment of this product, in the second mixing step S51, the second accept A2 (mainly fibrous material and treatment liquid) obtained in the second screening step S43 is mixed with the first accept A1 (mainly fibrous material and treatment water) to produce a second mixed liquid C2, and in the first solid-liquid separation step S52, the second mixed liquid C2 is subjected to solid-liquid separation. Therefore, compared to the case where the first solid-liquid separation step S52 is performed only on the first accept A1, more fibrous material can be obtained. This increases the separation rate of fibrous material, and thereby improves the recovery rate.

[0116] In a preferred embodiment of this product, in the third mixing step S44, a portion of the processing liquid L1 obtained by solid-liquid separation of the first accept A1 in the first solid-liquid separation step S52 is mixed with the second reject R2 (mainly particulate matter) obtained in the second screening step S43 to produce a third mixed liquid C3. In the second solid-liquid separation step S45, solid-liquid separation is performed on the third mixed liquid C3 to obtain particulate matter. When performing the second solid-liquid separation step S45 on the second reject R2, the concentration of the second reject R2 can be diluted to the appropriate concentration required for the solid-liquid separation step by mixing the processing liquid L1 obtained by solid-liquid separation of the first accept A1 with the second reject R2, thereby enabling the second solid-liquid separation step S45 to be carried out properly. At that time, particulate matter that remained in the processing liquid L1 that could not be separated in the first solid-liquid separation step S52 can also be included in the third mixed liquid C3 when performing the second solid-liquid separation step S45. This allows for a higher separation rate of particulate matter, which in turn improves the recovery rate.

[0117] In a preferred embodiment of this product, prior to the first screen step S41, the process further includes a disintegration step (at least one of S1 to S3) in which fibrous and particulate matter of used sanitary products are disintegrated in the processing liquid to generate a dispersion liquid Q, and a return step (not shown) in which a portion of the processing liquid L2 obtained in the second solid-liquid separation step S45 is returned to the disintegration step (at least one of S1 to S3). This reduces the amount of additional liquid (examples: water, processing liquid) compared to the case without the return step. This reduces the burden on wastewater treatment and the increase in environmental impact.

[0118] In a preferred embodiment of this product, in the third solid-liquid separation step S53, the fibrous material (aggregate thereof) separated in the first solid-liquid separation step S52 is compressed to extract the processing liquid L3 contained in the fibrous material F1 (aggregate thereof), and a portion of the extracted processing liquid L3 is mixed with the first mixed liquid C1. As a result, when the second screening step S43 is performed, particulate matter that was not completely separated in the first and third solid-liquid separation steps S52 and S53 and remained in the processing liquid can also be included in the first mixed liquid C1 when the second screening step S43 is performed. This makes it possible to further increase the separation rate of particulate matter and further improve the recovery rate of particulate matter.

[0119] In a preferred embodiment of this product, in the third solid-liquid separation step S53, the fibrous material (aggregate thereof) separated in the first solid-liquid separation step 52 is compressed to extract the processing liquid L3 contained in the fibrous material F1 (aggregate thereof), and the extracted processing liquid L3 is mixed with the third mixed liquid C3. As a result, when the second solid-liquid separation step S45 is performed, particulate matter that was not completely separated in the first and third solid-liquid separation steps S52 and S53 and remained in the processing liquid can also be included in the third mixed liquid C3 when the third solid-liquid separation step S53 is performed. This makes it possible to further increase the separation rate of particulate matter and further improve the recovery rate of particulate matter.

[0120] In a preferred embodiment of this product, the particulate matter is a superabsorbent polymer, and the treatment solution is an aqueous solution containing an inactivating agent that inactivates the superabsorbent polymer. Therefore, swelling of the superabsorbent polymer, which makes it difficult to separate, can be suppressed in each step using the treatment solution. As a result, the separation rate of the superabsorbent polymer, i.e., the particulate matter, can be increased, and the recovery rate can be improved. In this case, using an aqueous solution containing an inactivating agent tends to increase the burden of wastewater treatment and the environmental impact compared to using ordinary water, but these can be suppressed with this method.

[0121] In a preferred embodiment of this product, the inactivator contains an inorganic acid or an organic acid. This allows for the proper inactivation of the superabsorbent polymer as particulate matter, and further suppresses swelling of the superabsorbent polymer, which makes it difficult to separate, in each step using the treatment solution.

[0122] Next, a separation method for separating fibrous material and particulate material from used sanitary products according to another embodiment will be described.

[0123] This alternative embodiment differs from the previously described embodiment in that, at least in the first screen apparatus 10 and the second screen apparatus 12, the accept contains a large amount of particulate matter (rather than fibrous material), and the reject contains a large amount of fibrous material (rather than particulate material).

[0124] In this alternative embodiment, the hole shape of the screen in each screen device is preferably a round hole shape with a diameter larger than the particle size of the particulate matter and smaller than the fiber length of the fibrous material. This makes it easier for particulate matter to pass through the screen and makes it difficult for fibrous material to pass through the screen. On the other hand, in a solid-liquid separation device, the hole shape of the screen is preferably a slit shape with a width smaller than the particle size of the particulate matter and larger than the fiber diameter of the fibrous material and longer than the fiber length of the fibrous material. This makes it easier for fibrous material to pass through the screen together with the processing liquid, even if fibrous material remains in the processing liquid, and makes it difficult for particulate matter to pass through the screen.

[0125] The separation method of this alternative embodiment comprises a first screening step, a first solid-liquid separation step, a first mixing step, and a second screening step. The first screening step separates a dispersion containing fibrous material, particulate matter, and processing liquid dissected from used sanitary products into a first accept containing a large amount of particulate matter and processing liquid, and a first reject containing a large amount of fibrous material, using a first screening device. The first solid-liquid separation step separates the first accept obtained in the first screening step into particulate matter and processing liquid (containing fibrous material) through solid-liquid separation. The first mixing step mixes a portion of the processing liquid (containing fibrous material) obtained in the first solid-liquid separation step with the first reject (containing a large amount of fibrous material) to produce a first mixed liquid. The second screening step separates the first mixed liquid into a second accept containing a large amount of particulate matter and processing liquid, and a second reject containing a large amount of fibrous material, using a second screening device.

[0126] In other words, in this alternative embodiment of the separation method, first, a first screening step separates the dispersion into a first reject (mainly fibrous material) and a first accept (mainly particulate material and treated water). Next, in a first mixing step, the first reject is mixed with the treated liquid (mainly fibrous material) obtained by solid-liquid separation of the first accept in the first solid-liquid separation step to produce a first mixed liquid with a diluted concentration. Next, in a second screening step, the first mixed liquid is separated into a second reject (mainly fibrous material) and a second accept (mainly particulate material and treated liquid). The second reject (mainly fibrous material) may, for example, be supplied to the oxidizing agent treatment step S6, or it may be sterilized, washed, dried, etc. as needed and removed to the outside as fibrous material (pulp fibers) for reuse. The second accept (mainly particulate material and treated liquid) may, for example, be sterilized, washed, dried, etc. as needed and removed to the outside as particulate material (superabsorbent polymer) for reuse. Furthermore, the particulate matter obtained by solid-liquid separation of the first accept in the first solid-liquid separation step may be removed as particulate matter (superabsorbent polymer) after, for example, sterilization, washing, drying, etc., as necessary, and reused.

[0127] Here, when performing the second screening process on the first reject (mainly fibrous material), the first reject is mixed with the processing liquid (mainly fibrous material) obtained by solid-liquid separation of the first accept (mainly particulate material and treated water) to form the first mixed solution. This allows the concentration of solids in the first reject to be diluted to the appropriate concentration required for the screening process, thus enabling the second screening process to be carried out properly. At the same time, any fibrous material that remained in the processing liquid due to not being completely separated can also be included in the first mixed solution for the second screening process. As a result, the separation rate of fibrous material in the second reject R2 (mainly fibrous material) can be increased, and the recovery rate can be improved.

[0128] In this process, the treatment liquid obtained by solid-liquid separation of the first accept is used to adjust the concentration of solids in the first reject R1. Therefore, since there is no need to add new liquid (e.g., water, treatment liquid) in the second screening process, it is possible to suppress an increase in the burden of wastewater treatment and an increase in environmental impact.

[0129] In a preferred embodiment of this alternative model, the process may further include a second mixing step in which the second accept (mainly particulate matter and treatment liquid) obtained in the second screening step is mixed with the first accept (mainly particulate matter and treatment water) obtained in the first screening step to produce a second mixed liquid. In this case, the first solid-liquid separation step may include a step of solid-liquid separation of the second mixed liquid into particulate matter and treatment liquid.

[0130] Since the first solid-liquid separation process is performed on a second mixed solution, which is a mixture of the second accept (mainly particulate matter and treatment liquid) and the first accept (mainly particulate matter and treatment water), more particulate matter can be obtained compared to when the first solid-liquid separation process is performed only on the first accept. This increases the separation rate of particulate matter and improves its recovery rate.

[0131] The sanitary products of the present invention are not limited to the embodiments described above, and can be appropriately combined or modified without departing from the purpose and spirit of the present invention. [Explanation of Symbols]

[0132] 10. First Screen Device 11 1st mixing device 12. Second Screen Device Q dispersion A1 First Acceptance R1 First rejection L1 Treatment solution C1 1st mixed liquid A2 Second Acceptance R2 Second rejection S41 First Screening Process S42 1st mixing process S43 Second Screening Process

Claims

1. A separation method for separating fibrous material and particulate material from used sanitary products, A first screening step involves separating a dispersion containing fibrous material, particulate material, and processing liquid separated from the aforementioned used sanitary product into a first accept containing a large amount of the fibrous material and processing liquid, and a first reject containing a large amount of the particulate material, using a first screening device. A first solid-liquid separation step is performed to separate the first accept obtained in the first screening step into the fibrous material and the processing liquid, A first mixing step involves mixing a portion of the processing liquid obtained in the first solid-liquid separation step with the first reject to produce a first mixed liquid, A second screening step is performed in which the first mixture is separated by a second screening device into a second accept containing a large amount of the fibrous material and the processing liquid, and a second reject containing a large amount of the particulate material. A separation method comprising:

2. The process further comprises a second mixing step in which the second accept obtained in the second screening step is mixed with the first accept obtained in the first screening step to produce a second mixed solution. The first solid-liquid separation step includes a step of separating the second mixture into the fibrous material and the processing liquid. The separation method according to claim 1.

3. A third mixing step is performed in which a portion of the processing liquid obtained in the first solid-liquid separation step is mixed with the second reject obtained in the second screening step to produce a third mixed liquid, A second solid-liquid separation step is performed to separate the third mixture into particulate matter and the processing liquid, It also has, The separation method according to claim 1 or 2.

4. Prior to the first screening step, a disintegration step is performed in which the fibrous and particulate materials of the used sanitary products are disintegrated in the processing liquid to produce the dispersion, A return step in which a portion of the processing liquid obtained in the second solid-liquid separation step is returned to the disintegration step, It also has, The separation method according to claim 3.

5. The system further comprises a third solid-liquid separation step, in which the fibrous material separated in the first solid-liquid separation step is compressed to separate the fibrous material from the processing liquid. The first mixing step includes mixing a portion of the processing liquid obtained in the third solid-liquid separation step with the first mixed liquid. The separation method according to claim 1 or 2.

6. The system further comprises a third solid-liquid separation step, in which the fibrous material separated in the first solid-liquid separation step is compressed to separate the fibrous material from the processing liquid. The third mixing step includes mixing a portion of the processing liquid obtained in the third solid-liquid separation step with the third mixed liquid. The separation method according to claim 3.

7. The particulate matter is a superabsorbent polymer, The treatment solution is an aqueous solution containing an inactivator that inactivates the superabsorbent polymer. The separation method according to claim 1 or 2.

8. The inactivator includes an inorganic acid or an organic acid. The separation method according to claim 7.

9. A separation method for separating fibrous material and particulate material from used sanitary products, A first screening step involves separating a dispersion containing fibrous material, particulate material, and processing liquid separated from the used sanitary product into a first accept containing a large amount of the particulate material and processing liquid, and a first reject containing a large amount of the fibrous material, using a first screening device. A first solid-liquid separation step is performed to separate the first accept obtained in the first screening step into particulate matter and the processing liquid, A first mixing step involves mixing a portion of the processing liquid obtained in the first solid-liquid separation step with the first reject to produce a first mixed liquid, A second screening step is performed in which the first mixture is separated by a second screening device into a second accept containing a large amount of the particulate matter and the processing liquid, and a second reject containing a large amount of the fibrous material. A separation method comprising:

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