How to dispose of disposable diapers

Abstract

To efficiently dispose of paper diapers, especially used paper diapers, and to effectively utilize the disposed materials. [Solution] A method for processing disposable diapers, comprising a pre-treatment step of adding water to disposable diapers and crushing them; a separation step of separating the pre-treated disposable diapers into a first component mainly consisting of nonwoven fabric and film, and a second component mainly consisting of pulp and wastewater; and a methane fermentation step of adding organic waste to the second component and causing methane fermentation. A method for processing disposable diapers, comprising a pre-treatment step of adding water to disposable diapers and crushing them; a separation step of separating the pre-treated disposable diapers into a first component mainly consisting of nonwoven fabric and film, and a second component mainly consisting of pulp and wastewater; and a sewage treatment facility that nitrifies, denitrifies and performs advanced treatment of the second component with human waste or septic tank sludge.

Description

[Technical Field]

[0001] The present invention relates to a method for disposing of disposable diapers, particularly used disposable diapers. Note that in the present invention, disposable diapers include not only tape-type and pants-type disposable diapers but also urine absorption pads. [Background technology]

[0002] The commonly used tape-type or pants-type disposable diapers are equipped with a surface material, three-dimensional gathers to prevent leakage, absorbent material, waterproof material (exterior material), elastic material, etc. Tape-type diapers also have a fastening tape.

[0003] The surface material is the surface that comes into direct contact with the skin and is made of nonwoven fabric made from polyester or polyolefin. The gathers, exterior material (waterproof material), and tape are made from polyolefin film. The absorbent material is made from cotton-like pulp and polymeric absorbent material. The stretchable material is made from polyurethane.

[0004] Each part of the disposable diaper is bonded with an adhesive such as a hot melt adhesive.

[0005] As the elderly population increases, the demand for disposable diapers is increasing, and the disposal of used disposable diapers that are discarded as waste has become a serious social issue.

[0006] Conventionally, used disposable diapers have been disposed of by the following methods, but each method has the following problems. (1) A method in which used disposable diapers are crushed and then incinerated.

[0007] This method requires a large amount of heat in the incinerator to evaporate the moisture absorbed by the used disposable diapers placed in the combustion chamber, and after the moisture has evaporated, a sudden rise in combustion temperature, known as deflagration, can damage the incinerator. (2) A method of reusing used disposable diapers by crushing and heat-treating them (removing moisture and sterilizing them), then compressing and molding them, and using the crushed pulp and plastics as raw materials for fuel such as RPF (Refuse Paper & Plastic Fuel).

[0008] This method requires a large amount of heat input for water evaporation and sterilization, resulting in high fuel costs and poor business profitability.

[0009] Patent Document 1 describes a bag-breaking device that can break open bags containing used disposable diapers and crush the used disposable diapers, which has blades provided on the inner surface of the rotating drum of a drum-type washing machine. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 7359262 Summary of the Invention [Problem to be solved by the invention]

[0011] Disposable diapers are primarily composed of absorbent materials (cotton-like pulp, superabsorbent polymers), nonwoven fabric, waterproofing materials, and other tapes. While pulp is used for the cotton-like pulp absorbent material, other materials include petroleum-derived materials such as polyethylene, polypropylene, polyurethane, and the superabsorbent polymer sodium polyacrylate.

[0012] Furthermore, used disposable diapers are contaminated with feces and urine, and there is a need to develop methods for efficiently treating the wastewater containing feces and urine generated during the disposal of used disposable diapers, and for effectively utilizing the organic components in the feces and urine.

[0013] One aspect of the present invention aims to provide a method for processing disposable diapers, particularly used disposable diapers, that can generate a large amount of methane from them.

[0014] Another aspect of the present invention is to provide a method for treating disposable diapers, which can reduce the moisture content of sludge discharged from the treatment of human waste and septic tank sludge and enable it to be recycled (spontaneous combustion). [Means for solving the problem]

[0015] The present invention provides the following.

[0016] [1] A method for treating disposable diapers, comprising: a pre-treatment step of adding water to disposable diapers to disintegrate them; a separation step of separating the pre-treated disposable diapers into a first component mainly consisting of nonwoven fabric and film, and a second component mainly consisting of pulp and wastewater; and a methane fermentation step of adding organic waste to the second component to cause methane fermentation.

[0017] [2] The method for treating disposable diapers according to [1], further comprising a step of molding the first component for use as fuel.

[0018] [3] The method for disposing of disposable diapers according to [1], wherein the organic waste is food waste or livestock manure.

[0019] [4] A pre-treatment process in which water is added to disposable diapers to disintegrate them; A separation step of separating the pretreated disposable diaper into a first component mainly composed of nonwoven fabric and film and a second component mainly composed of pulp and wastewater; A method for treating disposable diapers, comprising the steps of mixing sewage or septic tank sludge, subjecting the sludge to advanced treatment consisting of nitrification, denitrification, coagulation sedimentation, and activated carbon, and then mixing the second component with excess sludge discharged from the sewage treatment facility and dehydrating the mixture. [5] A pre-treatment process in which water is added to disposable diapers to disintegrate them; A step of separating the pretreated disposable diaper into a first component mainly consisting of nonwoven fabric and film and a second component mainly consisting of pulp and wastewater; a step of mixing the second component with sewage or septic tank sludge and flocculating and dewatering the mixture; A method for disposing of disposable diapers comprising the steps of:

[0020] [6] A method for processing disposable diapers according to [4] or [5], further comprising a step of using the dewatered sludge after the dewatering step as a combustion aid.

[0021] [7] The method for processing disposable diapers as described in [4], wherein the nitrification, denitrification, and advanced treatment processes are carried out in a newly constructed or existing sewage treatment facility.

[0022] [8] A method of performing the pretreatment step using a bag breaking device, The bag-breaking device includes a water tank for storing water, a cylindrical rotating tank with a bottom that is rotatably supported in the water tank with its rotation axis approximately horizontal and that stores disposable diapers and water, a motor that rotates the rotating tank, and a bag-breaking blade that is provided on the inner peripheral surface of the rotating tank. A method for processing disposable diapers according to any one of [1] to [7], wherein disposable diapers, chemicals, and water are placed in the rotating tank and the rotating tank is rotated to crush the disposable diapers.

[0023] [9] The method for disposing of disposable diapers according to [8], wherein the chemical comprises at least slaked lime.

[0024]

[10] The rotating tank has a number of small holes on its circumferential surface, The method for treating disposable diapers according to [8] or [9], wherein after the disposable diapers are crushed, the rotary drum is rotated, the second component is discharged through the small holes, and the first component remaining in the rotary drum is removed. [Effects of the Invention]

[0025] According to the first aspect of the present invention, nonwoven fabrics and films separated from disposable diapers can be used as fuel. Also, pulp and wastewater can be subjected to methane fermentation to extract methane, which can be used as fuel.

[0026] Methane is produced not only from the pulp but also from the excrement and urine attached to the disposable diapers, resulting in a large amount of methane production. Furthermore, by mixing the second component containing pulp with organic waste, the C / N ratio (carbon / nitrogen ratio) during methane fermentation can be adjusted, improving the efficiency of methane fermentation.

[0027] According to the first to third inventions, nonwoven fabrics and films separated from disposable diapers can be used as fuel. Also, according to the second invention, pulp functions as a flocculation aid and dehydration aid, so dehydrated sludge with a low moisture content can be obtained from a human waste treatment facility that consists of nitrification, denitrification, and advanced treatment processes.

[0028] In one embodiment of the first and second inventions, when the separated wastewater is treated in an existing wastewater treatment facility, the operating rate of the existing wastewater treatment facility can be improved. [Brief explanation of the drawings]

[0029] [Figure 1] This is a diagram illustrating an example of an embodiment of the disposable diaper disposal method of the first invention. [Figure 2] This is a diagram illustrating an example of an embodiment of the disposable diaper disposal method of the second invention. [Figure 3] This is a diagram illustrating an example of a conventional standard denitrification system for sewage treatment. [Figure 4] This is a diagram illustrating an example of an embodiment of the disposable diaper disposal method (standard denitrification system) of the second invention. [Figure 5] This is a diagram illustrating an example of a conventional direct dewatering system for human waste treatment (discharge into rivers). [Figure 6] This is a diagram illustrating an example of an embodiment of the disposable diaper disposal method (direct dewatering system; river discharge) of the third invention. [Figure 7] This is a system diagram showing an example of a conventional direct dewatering system (discharge into the sewage system). [Figure 8] This is a diagram illustrating an example of an embodiment of the disposable diaper disposal method (direct dewatering system; discharge into the sewage system) of the third invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] The following describes in detail an embodiment of the present invention regarding the processing method for disposable diapers with reference to the drawings. The disposable diapers processed in this invention are typically used diapers contaminated with feces and urine, but are not limited to used diapers. Unused diapers, defective diapers discharged from factories, or diapers that have absorbed water or mud due to disasters, etc., may also be used.

[0031] [Embodiment of the First Invention] In the first invention, disposable diapers are first pretreated (pretreatment step). A suitable method for pretreating disposable diapers is to add water and then shred the disposable diapers. Preferably, shredding is performed using the bag-breaking device described in Patent Document 1.

[0032] The bag-breaking device described in Patent Document 1 is a bag-breaking device for breaking waste container bags, and is a drum-type washing machine having a water tank for storing washing water, a bottomed cylindrical rotating tub for storing laundry and supported rotatably within the water tank with its rotation axis approximately horizontal, and a motor for rotating the rotating tub, wherein a bag-breaking blade is provided on the inner circumferential surface of the rotating tub. Preferably, a projection extending in a direction parallel to the axis of the rotating tub is provided on the inner circumferential surface of the rotating tub, and the blade is attached to the projection. Preferably, the blade is plate-shaped, with a sawtooth-shaped cutting edge along one side, and the other side is attached to the projection. Preferably, the blade is made of a highly corrosion-resistant metal such as stainless steel, titanium, or titanium alloy.

[0033] The rotating tank preferably has a diameter of 100 to 300 cm and a length of 100 to 300 cm, and has a large number of small holes with a diameter of 5 to 15 mm on the circumferential surface (approximately 10 to 30% opening rate on the circumferential surface).

[0034] In this pretreatment, in order to promote the disintegration of the disposable diapers, heating and / or the addition of chemicals such as alkali may be performed while stirring and mixing, or heating and / or the addition of chemicals may be performed while stirring and mixing. The heating means is preferably a means for heating to 80°C or higher by blowing in steam.

[0035] The chemical preferably contains a component that removes moisture (dehydrates) from the absorbent polymer (SAP) contained in the disposable diaper. Suitable chemicals include slaked lime and calcium chloride, but other chemicals such as sodium salts, magnesium salts, organic acids (citric acid, oxalic acid), and inorganic acids (nitric acid, sulfuric acid, hydrochloric acid) may also be used.

[0036] The chemicals may contain a disinfectant component for sterilization. There are no particular restrictions on the disinfectant component, but an inexpensive one is calcium hypochlorite (bleaching powder).

[0037] To facilitate the decomposition and cleaning of disposable diapers, surfactants may be used as part of the chemicals. Suitable surfactants include linear alkylbenzenes, higher alcohols, α-olefins, quaternary ammoniums, fatty acids, and alpha-sulfo fatty acids. It is preferable to use 0.1 to 100 parts by weight, particularly 1 to 10 parts by weight, of surfactant per 100 parts by weight of used disposable diapers.

[0038] In one embodiment of the present invention, the chemical is composed of slaked lime and calcium hypochlorite, with a mixing ratio of 80-98% slaked lime and 20-2% calcium hypochlorite. When the chemical is composed of slaked lime and calcium hypochlorite, it is preferable to use 0.1-20 parts by weight, particularly 1-10 parts by weight, of slaked lime and calcium hypochlorite, and 50-1000 parts by weight, particularly 100-500 parts by weight, of water per 100 parts by weight of used disposable diapers.

[0039] The disposable diapers decomposed by the pretreatment are then separated into a first component (plastic component) mainly consisting of nonwoven fabric and film, and a second component mainly consisting of pulp and wastewater containing feces and urine (separation step).

[0040] This separation step is preferably carried out using the bag-breaking device disclosed in Patent Document 1.

[0041] In other words, the rotating tank of the bag-breaking device described in Patent Document 1 has numerous small holes formed on its circumferential surface. Therefore, after the above pretreatment, when the rotating tank is rotated at high speed, the plastic components remain in the rotating tank, while the pulp and wastewater containing feces and urine are discharged outside the bag-breaking device through the small holes. The superabsorbent polymer is finely crushed within the bag-breaking device, so most of it is discharged together with the pulp and wastewater, but some remains in the rotating tank along with the plastic components.

[0042] The plastic component is removed from the rotary tub, dried and compression molded as necessary, and then used as fuel, for example, in a sludge incinerator.

[0043] Organic waste such as food waste and livestock manure is added to the pulp- and manure-containing wastewater (pulp slurry) discharged from the bag-breaking device. At this time, it is preferable that the C / N ratio (carbon / nitrogen ratio) in the liquid (total of pulp slurry and organic waste) after addition is 10 to 300, particularly 20 to 100.

[0044] This liquid is introduced into a methane fermentation tank and subjected to methane fermentation treatment.

[0045] The pulp slurry flowing out from the bag breaking device may be filtered through a screen to separate and recover part of the pulp, and the organic waste may be added to the remaining wastewater.

[0046] The recovered pulp can be used as a raw material for recycled waste paper after being dewatered or dried, or can be used as a dewatering aid, for example, to reduce the moisture content of dewatered cake discharged from wastewater treatment facilities.

[0047] According to this embodiment of the first invention, the nonwoven fabric and film separated from disposable diapers can be used as fuel. Also, pulp and wastewater can be subjected to methane fermentation to extract methane, which can be used as fuel.

[0048] In this embodiment, methane is produced not only from pulp but also from feces and urine attached to disposable diapers, resulting in a large amount of methane production. Furthermore, by mixing the second component, which is mainly composed of pulp and feces-containing wastewater, with organic waste, it is possible to adjust the C / N ratio (carbon / nitrogen ratio) during methane fermentation and improve the efficiency of methane fermentation.

[0049] [Embodiments of the Second and Third Inventions] An embodiment of the second invention will be described below with reference to FIGS.

[0050] In the second and third inventions, the disposable diapers are first pretreated (pretreatment step). A suitable method for pretreating the disposable diapers is to add water and then crush the disposable diapers. Preferably, the bag-breaking device described in Patent Document 110 is used.

[0051] As in the first invention, in order to accelerate this disintegration treatment, heating and / or the addition of chemicals such as alkali may be performed while stirring and mixing, or heating and / or the addition of chemicals may be performed while stirring and mixing.

[0052] The heating means is preferably a means for heating by blowing in steam to a temperature of 80° C. or higher. The chemicals used are the same as those in the first invention.

[0053] The disposable diapers decomposed by the pretreatment are then separated into a first component (plastic component) mainly consisting of nonwoven fabric and film, and a second component mainly consisting of pulp and wastewater containing feces and urine (separation step).

[0054] As the separation means employed in this separation step, it is preferable to use the bag breaking device disclosed in Patent Document 1.

[0055] As mentioned above, the rotating tub of the bag-breaking device in Patent Document 1 has many small holes formed on its circumferential surface, so when the rotating tub is rotated at high speed after the above pretreatment, the plastic components remain in the rotating tub, while the pulp and wastewater containing feces and urine are discharged outside the bag-breaking device through the small holes. Because the polymer absorbent material is finely crushed in the bag-breaking device, most of it is discharged together with the pulp and wastewater, but some remains in the rotating tub together with the nonwoven fabric and film.

[0056] The plastic component is removed from the rotary tub, dried and compression molded as required, and then used as fuel, for example, in a sludge incinerator.

[0057] In the second invention, the second component discharged from the bag-breaking device is mixed with excess sludge discharged from a normal night soil treatment facility (standard denitrification system), dehydrated, and then supplied to a nitrification / denitrification treatment facility. In the third invention, the second component discharged from the bag-breaking device is mixed with night soil or septic tank sludge, and directly coagulated and dehydrated (direct dehydration system), and the resulting dehydrated cake with a low moisture content is used as a combustion improver, etc.

[0058] <Nitrification / denitrification / advanced treatment process> In the nitrification, denitrification, and advanced treatment processes of sewage treatment facilities, the excess sludge (organic and inorganic sludge) discharged from the standard denitrification system is mixed with the second component and then dewatered, as shown in Figure 4. Advanced treatment consists of coagulation sedimentation (COD and color removal) and activated carbon (COD removal) treatment. As shown in Figure 4, it is also possible to add filtration (SS removal) between the coagulation sedimentation and activated carbon treatments.

[0059] The liquid in the night soil receiving tank is introduced into a storage tank after impurities (screen residue removal) are removed by an impurity removal device. The liquid in the storage tank is then introduced into a denitrification tank. Dilution water is supplied to the denitrification tank from a dilution water source, as well as a portion of the nitrified liquid from the nitrification tank (described below), a portion of the settled sludge from the settling tank, diluted liquid from the sludge thickener, and dehydrated filtrate from the dehydration equipment, and denitrification treatment is carried out by the action of denitrifying bacteria.

[0060] The liquid in the denitrification tank is transferred to the nitrification tank, where it is aerated and nitrification is carried out by nitrifying bacteria. Part of the nitrified liquid from the nitrification tank is returned to the denitrification tank, and the remainder is sent to the secondary denitrification tank where it is denitrified by the action of denitrifying bacteria.

[0061] The liquid in the secondary denitrification tank is transferred to the reaeration tank, where it is aerated, nitrified, and aerobicly treated for organic matter, before being introduced into the settling tank for solid-liquid separation. The supernatant water is introduced into the coagulation tank via the mixing tank, where a coagulant is added, and then introduced into the coagulation and settling tank.

[0062] The supernatant water from the coagulation sedimentation tank is further treated in advanced treatment facilities before being discharged. Advanced treatment includes, for example, filtration and the removal of color and COD using activated carbon towers.

[0063] The sludge that has settled and separated in the settling tank and coagulation settling tank is introduced into a sludge thickening device such as a thickener, where it is separated into a dilute liquid with a low solids concentration and a concentrated liquid with a high solids concentration, and then dehydrated using a general dehydrator (filter press, centrifugal dehydrator, screw press, etc.) (standard denitrification system).

[0064] The direct dewatering system solves the problem of high moisture content in dewatered sludge of conventional direct dewatering systems by directly flocculating and concentrating (granulation concentrating technology) the sludge without removing excrement and sediment, and dewatering it in a highly efficient dewatering machine (for example, a screw press), thereby achieving a low moisture content, or in other words, converting the sludge into a combustion improver. In standard denitrification systems, the wastewater is discharged into the river, whereas in direct dehydration systems (discharge to sewer), the wastewater is diluted with dilution water and then discharged into the sewer.

[0065] Organic and inorganic excess sludge discharged from sewage treatment facilities (standard denitrification systems) is mixed with a second component derived from disposable diapers and dehydrated in a dehydration treatment facility. As a result, the second component improves the overall dehydration property, resulting in a low moisture content of the dehydrated sludge, for example, below 70%. This means that the dehydrated sludge can be used directly as a combustion improver.

[0066] Many existing wastewater treatment facilities in sewage treatment plants and agricultural and community settings have excess treatment capacity. Treating wastewater from the pretreatment process of disposable diapers at these existing facilities can increase the operating rate of the existing facilities and reduce overall costs (including equipment costs, maintenance costs, and labor costs).

[0067] Furthermore, in the third invention, as shown in the direct dewatering system in Figures 6 and 8, human waste or septic tank sludge may be mixed with a second component (pulp derived from disposable diapers), then subjected to coagulation and separation treatment, and finally dewatered.

[0068] When the coagulation and dehydration treatment is carried out, it is preferable to carry out the treatment by the method exemplified below. <Coagulation and dehydration treatment> In one example of coagulation and dehydration treatment, human waste, septic tank sludge, etc. are coagulated using an inorganic coagulant (or a cationic organic polymer coagulant) and an anionic organic polymer coagulant, and the coagulation-treated liquid is dehydrated in a dehydrator. Note that when the wastewater, human waste, septic tank sludge, and a second component (pulp derived from disposable diapers) are mixed and coagulated and dehydrated, the moisture content of the dehydrated sludge is lower than when only the wastewater is coagulated and dehydrated.

[0069] The dewatered sludge produced by dewatering is sent to a resource recovery facility. The dewatered filtrate is either sent to a nitrification-denitrification facility or a dewatering facility (standard denitrification system), or diluted with dilution water before being discharged into the sewer system.

[0070] When carrying out this flocculation and separation treatment, a polymer flocculant may be added, followed by concentration treatment in a concentrator (such as a granulation concentration tank or concentration screen) before being fed to a dehydrator. In this case, a screw press is often used as the dehydrator, but a conventional belt press type dehydrator can also be used to achieve a low moisture content, eliminating the need for major modifications to existing equipment.

[0071] Alternatively, after adding a polymer flocculant, the sludge may be concentrated using a concentration screen device, sent to a resource recovery or sludge treatment facility, subjected to secondary flocculation treatment with an inorganic flocculant, the flocculated sludge returned to the raw water, and the liquid portion sent to a nitrification-denitrification facility.

Claims

1. A pre-treatment process in which water is added to disposable diapers to disintegrate them; A separation step of separating the pretreated disposable diaper into a first component mainly composed of nonwoven fabric and film and a second component mainly composed of pulp and wastewater; a methane fermentation step of adding organic waste to the second component and performing methane fermentation; A method for disposing of disposable diapers comprising the steps of:

2. The method for treating disposable diapers according to claim 1, further comprising a step of molding the first component for use as fuel.

3. The method for disposing of disposable diapers according to claim 1, wherein the organic waste is food waste or livestock manure.

4. A pre-treatment process in which water is added to disposable diapers to disintegrate them; A separation step of separating the pretreated disposable diaper into a first component mainly composed of nonwoven fabric and film and a second component mainly composed of pulp and wastewater; A method for treating disposable diapers, comprising the steps of mixing sewage or septic tank sludge and subjecting it to advanced treatment consisting of nitrification, denitrification, coagulation sedimentation, and activated carbon, and then mixing the second component with excess sludge discharged from the sewage treatment facility and dehydrating the mixture.

5. A pre-treatment process in which water is added to disposable diapers to disintegrate them; A separation step of separating the pretreated disposable diaper into a first component mainly composed of nonwoven fabric and film and a second component mainly composed of pulp and wastewater; a step of mixing the sewage or septic tank sludge with the second component and flocculating and dewatering the mixture; A method for disposing of disposable diapers comprising the steps of:

6. 6. The method for treating disposable diapers according to claim 4, further comprising a step of utilizing the dehydrated sludge obtained after the dehydration step as a combustion improver.

7. 5. The method for treating disposable diapers according to claim 4, wherein the nitrification, denitrification and advanced treatment steps are carried out in a new or existing human waste treatment facility.

8. A method for carrying out the pretreatment step using a bag-breaking device, The bag-breaking device includes a water tank for storing water, a cylindrical rotating tank with a bottom that is rotatably supported in the water tank with its rotation axis approximately horizontal and that stores disposable diapers and water, a motor that rotates the rotating tank, and a bag-breaking blade that is provided on the inner peripheral surface of the rotating tank. The method for disposing of disposable diapers according to any one of claims 1 to 7, wherein disposable diapers, chemicals and water are placed in the rotary drum, and the rotary drum is rotated to disintegrate the disposable diapers.

9. The method for treating disposable diapers according to claim 8, wherein the chemicals include at least hydrated lime.

10. A large number of small holes are provided on the circumferential surface of the rotating tank, 10. The method for treating disposable diapers according to claim 8 or 9, wherein after the disposable diapers are disintegrated, the rotary drum is rotated, the second component is discharged through the small holes, and the first component remaining in the rotary drum is removed.

Images