Method and apparatus for disposing of disposable diapers

Abstract

The objective of this method and apparatus for separating and recovering plastic film from used disposable diapers is to reduce the amount of water used in the processing. [Solution] A method for processing disposable diapers, comprising a separation step of crushing and washing used disposable diapers using a separation device to separate them into a plastic fraction and pulp-containing wastewater, and a return step of dewatering the pulp-containing wastewater generated in the separation step and returning a portion of the dewatered filtrate to the separation step. The separation device comprises a water tank for storing water, a bottomed cylindrical rotating tank rotatably supported within the water tank with its rotation axis approximately horizontal, a bag-breaking blade provided on the inner surface of the rotating tank, and a motor for rotating the rotating tank.

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for treating paper diapers, particularly used paper diapers and the like. In the present invention, paper diapers include not only tape-type and pants-type paper diapers but also urine pads.

Background Art

[0002] Generally used tape-type or pants-type paper diapers include a surface material, a three-dimensional gather for leakage prevention, a water-absorbing material, a waterproof material (outer packaging material), an elastic material, and the like. In the case of the tape type, it further includes a fastening tape.

[0003] The surface material is provided on the surface that directly touches the skin and is made of a non-woven fabric made of polyester or polyolefin. The gather, the outer packaging material (waterproof material), and the tape are made of a polyolefin film. The water-absorbing material is composed of cotton-like pulp and a high-molecular water-absorbing material. The elastic material is made of polyurethane.

[0004] In Patent Document 1, as a method for treating used paper diapers, it rotates at a predetermined rotational speed with respect to the amount of used sanitary products put into a separation tank. The treatment liquid consists of a predetermined amount of calcium compound with respect to the weight of the used sanitary products put into the separation tank, hypochlorous acid added so that the free residual chlorine is at a predetermined concentration or higher, and a predetermined amount of hot water heated to a predetermined temperature with respect to the weight of the used sanitary products put into the separation tank. Hot air at a predetermined temperature is blown onto the pulp and plastic among the decomposed materials to sterilize the decomposed materials. A method for treating used sanitary products is described.

[0005] In Patent Document 2, as a bag-breaking device that can break a bag containing used paper diapers and crush the used paper diapers, a device having blades provided on the inner peripheral surface of a rotating tank is described.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-99884 [Patent Document 2] Japanese Patent Publication No. 2024-15809 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] One aspect of the present invention relates to a method and apparatus for separating and recovering plastic film from used disposable diapers, with the objective of reducing the amount of water used in the processing.

[0008] Furthermore, one aspect of the present invention aims to reduce the amount of energy required for this process. [Means for solving the problem]

[0009] The gist of this invention is as follows:

[0010] [1] A method for processing disposable diapers, comprising a separation step of crushing and washing used disposable diapers using a separation device to separate them into a plastic fraction and pulp-containing wastewater, and a return step of dewatering the pulp-containing wastewater generated in the separation step and returning a portion of the dewatered filtrate to the separation step.

[0011] [2] The method for processing disposable diapers according to [1], wherein the dewatered filtrate is subjected to a sedimentation process and the supernatant water is returned to the separation process.

[0012] [3] The method for processing disposable diapers according to [1] or [2], wherein used disposable diapers, water and chemicals are supplied to the sorting device to perform the sorting process.

[0013] [4] The diaper disposal method of [3], wherein in the sorting step, steam is supplied into the sorting device to raise the temperature inside the sorting device to 70-90°C.

[0014] [5] The agent is a diaper disposal method of [3] comprising slaked lime and calcium hypochlorite.

[0015] [6] The separating device a water tank for storing water, a bottomed cylindrical rotating tank rotatably supported in the water tank with its rotation axis substantially horizontal, a blade for bag breaking provided on the inner peripheral surface of the rotating tank, a motor for rotating the rotating tank and has a method for treating the disposable diaper of [1] or [2].

[0016] [7] A separating device that shreds and washes used disposable diapers and separates them into a plastic fraction and pulp-containing drainage, a dehydrator that dehydrates the pulp-containing drainage from the separating device, a sedimentation tank that performs sedimentation treatment on the dehydrated filtrate from the dehydrator, a return means for returning at least a part of the supernatant water of the sedimentation tank to the separating device and has a used disposable diaper treatment device. [Advantages of the Invention]

[0017] According to one aspect of the present invention, since a part of the dehydrated filtrate obtained by dehydrating the pulp-containing drainage from the separating device is returned to the separating device for reuse, the amount of water required for treatment is reduced.

[0018] According to one aspect of the present invention, the amount of steam supplied to the separating device can be reduced. [Brief Description of the Drawings]

[0019] [Figure 1] It is a flowchart showing an example of the method of the present invention. [Figure 2] It is a cross-sectional view showing an example of the bag-breaking device. [Figure 3] It is a perspective view showing the structure of the blade part of the bag-breaking device. [Embodiments for Carrying Out the Invention]

[0020] 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.

[0021] In this invention, disposable diapers are first crushed and washed using a sorting device. Preferably, the bag-breaking device described in Patent Document 2 is used as the sorting device to crush, wash, and dewater the diapers, and to separate the plastic fraction.

[0022] The bag-breaking device described in Patent Document 2 is a bag-breaking device having a water tank for storing water, a bottomed cylindrical rotating tank rotatably supported within the water tank with its rotation axis approximately horizontal, and a motor for rotating the rotating tank, characterized in that a bag-breaking blade is provided on the inner circumferential surface of the rotating tank.

[0023] Figure 2 is a longitudinal cross-sectional view of a sorting device 1 consisting of a bag-breaking device as described in Patent Document 2.

[0024] In Figure 2, a water tank 2 is installed inside the housing 1a, and a cylindrical rotating tank 3 with a closed bottom is placed inside the water tank 2. The circumferential surface of the rotating tank 3 is provided with numerous dewatering holes (not shown). In addition, a mesh-like ventilation section is provided on the bottom surface (back wall) of the rotating tank 3.

[0025] The water tank 2 and the rotating tank 3 are supported with their open ends facing the front of the housing 1a and their bottoms facing the rear of the housing 1a, so that they are tilted downward from horizontal from the front to the rear (although not shown in the figure, the water tank 2 and the rotating tank 3 may be supported so that they are approximately horizontal from the front to the rear). The rotating tank 3 is rotated by a motor 5 via a shaft 4.

[0026] A door 6 is provided on the housing 1a, facing the open end of the rotating tank 3. By opening the door 6, waste collection bags can be inserted into and removed from the rotating tank 3. A bellows 7, made of a flexible elastic material, is arranged around the inlet 2a of the water tank 2. When the door 6 is closed, one end of the bellows 7 is pressed against the inner surface, preventing water from splashing out of the water tank 2.

[0027] Multiple (for example, 3 to 6) protrusions 11 are provided on the inner circumferential wall of the rotating tank 3. By rotating the rotating tank 3 at a low speed, the waste containment bags and the waste pulled out from them can be hooked onto the protrusions 11 and lifted upward.

[0028] The projection 11 is provided as a convex ridge extending parallel to the rotation axis of the rotating tank 3. A blade 12 for tearing bags is provided on this projection 11.

[0029] As shown in Figure 3, the projection 11 has a roughly triangular cross-section in the circumferential direction of the rotating tank 3. More specifically, it is a roughly triangular shape that becomes narrower as it rises from the inner circumferential surface of the rotating tank 3.

[0030] The blade 12 is provided so as to rise from the top of the projection 11 toward the axial center of the rotating drum 3. The base end 12a of the blade 12 is fixed to the projection 11 by fixing means 13 such as bolts or rivets. Alternatively, the blade 12 may be made flat and attached to the projection 11 by a separate mounting member (for example, a pair of plates).

[0031] The tip of the blade 12 in the upward direction is a serrated blade 12b. However, the shape of the blade may be other than serrated, for example, it may be claw-shaped, needle-shaped, etc.

[0032] In Figure 2, multiple blades 12 are attached to a single projection 11 at intervals, but a single long blade may also be attached.

[0033] The blade 12 is preferably made of a highly corrosion-resistant metal such as stainless steel, titanium, or titanium alloy.

[0034] A water inlet 14, a water supply valve 15, a first water supply route 16, a chemical additive section 17, and a second water supply route 18 are provided as water supply routes for supplying water into the water tank 2.

[0035] One end of a drainage path 8, which drains water from the tank 2, is connected to the lower end of the tank 2. The other end of the drainage path 8 extends to the outside of the housing 1a. A drain valve 9 is provided in the middle of the drainage path 8 to open and close the path. By closing the drain valve 9, the rotating tank 3 can store water, chemicals, etc., in the tank 2.

[0036] When the drain valve 9 is opened, the water stored in the water tank 2 can be drained through the drainage path 8. When the rotating tank 3 is rotated at high speed, the contents are pressed against the side of the rotating tank 3 by centrifugal force. At this time, the moisture contained in the contents escapes between the water tank 2 and the rotating tank 3 through multiple dewatering holes provided on the side of the rotating tank 3 and is drained through the drainage path 8. In this way, the rotating tank 3 also functions as a dewatering chamber.

[0037] Furthermore, the rotating tank 3 is structured in such a way that warm air is circulated through an air passage consisting of an inlet 19, an air passage 20, a heater 21, an air blowing means 22, an air passage 23, and an air outlet 24 provided in the water tank 2. When warm air is being blown, the rotating tank 3 also functions as a drying chamber.

[0038] The rotating tank 3 preferably has a diameter of 100 to 300 cm and a length of 100 to 300 cm, and has numerous small holes with a diameter of 5 to 15 mm on its circumferential surface (resulting in an opening ratio of approximately 10 to 30% of the circumferential surface).

[0039] To process the disposable diapers contained in the waste collection bag using this bag-breaking device 1, the door 4 is opened and the waste collection bag is placed into the rotating tank 3. After closing the door 4, the rotating tank 3 is rotated by the motor 5. In this case, the rotating tank 3 may rotate in one direction or it may reciprocate in forward and reverse directions.

[0040] When the rotating tank 3 is rotated, the blades 12 tear open the bags, and the waste contained inside is released from the bags. By rotating it back and forth, the bags can be torn open efficiently.

[0041] To promote the crushing of disposable diapers, it is preferable to pour water into the rotating tank 3, heat it and / or add chemicals such as alkali, and then stir and mix it, or to heat it and / or add chemicals while stirring and mixing. A heating method of 80°C or higher by blowing in steam is preferred.

[0042] Watering or adding chemicals can be done at the beginning, or after the waste bag has burst.

[0043] Since the bag breaking and diaper crushing are carried out in a completely sealed state, no odors or waste are released to the outside.

[0044] The chemical preferably contains a component that removes moisture (dehydrates) from the superabsorbent polymer (SAP) contained in the disposable diaper. Slaked lime and calcium chloride are preferred chemicals, but sodium salts, magnesium salts, organic acids (citric acid, oxalic acid), inorganic acids (nitric acid, sulfuric acid, hydrochloric acid), etc. may also be used.

[0045] The chemical may contain a disinfectant component to kill germs. There are no particular restrictions on the disinfectant component, but inexpensive options include calcium hypochlorite (bleaching powder).

[0046] 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.

[0047] In one embodiment of the present invention, the agent is composed of slaked lime and calcium hypochlorite, with a mixing ratio of 80-98% slaked lime and 20-2% calcium hypochlorite. When the agent 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.

[0048] After the bag-breaking and crushing processes described above, the rotary tank 3 is rotated at high speed. As a result, a plastic fraction consisting mainly of film and nonwoven fabric, with pulp and superabsorbent polymer attached, remains in the rotary tank 3. The pulp and wastewater containing feces and urine are discharged outside the bag-breaking device through small holes and sent to the wastewater treatment process. 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 rotary tank along with the plastic fraction.

[0049] Afterward, water is poured into the water tank 2 from the water inlet 14 to rinse out any residue in the rotating tank 3. This rinsing may be done by pouring water in or by rinsing water in a reservoir. The water poured in may be hot water or room temperature water.

[0050] After rinsing is complete, the rotating tank 3 is rotated at high speed to perform dewatering. The dewatered plastic fraction is removed from the rotating tank 3 by opening the door 4. The moisture content of this plastic fraction is 20-70%, particularly 45-60%. After dewatering, when the dewatered material is dried with hot air in the bag-breaking device 1, the moisture content of the plastic fraction is 20-50%, particularly 30-40%.

[0051] The pulp content of this plastic fraction is typically around 15% to 40% by dry weight.

[0052] Figure 1 is a flowchart showing the method for processing used disposable diapers using this sorting device 1.

[0053] The wastewater from the drainage path 8 of the bag-breaking device 1 is introduced into the drainage tank 31, and from the drainage tank 31 into the slurry tank 32. The liquid in the slurry tank 32 is introduced into the dewatering machine 33 and dewatered. Suitable dewatering machines 33 include screw presses, centrifugal dewatering machines, and belt presses, with screw presses being particularly preferred.

[0054] The wastewater discharged from the sorting device 1 contains pulp and superabsorbent polymers. This wastewater has a high pulp concentration of 2-5 wt%, and if left standing, the pulp settles, making transport difficult. Therefore, the wastewater from the sorting device 1 is received in the wastewater tank 31, and once the water level in the wastewater tank 31 rises, it is sent to the slurry tank 32, and then to the dewatering machine 33.

[0055] Furthermore, if the residence time in the drainage tank 31 or slurry tank 32 is prolonged, pulp will adhere to the tanks, pipes, and various equipment, forming clumps. To prevent such transfer problems caused by pulp, it is preferable to minimize the residence time in the drainage tank 31. In addition, it is preferable to agitate the slurry tank 32 with an agitator (not shown) to prevent sedimentation.

[0056] The solids obtained by dewatering in the dewatering machine 33 are mainly pulp and are therefore sent to the recycling process.

[0057] The dewatered filtrate from the dewatering machine 33 is introduced into the sedimentation tank 34 and subjected to sedimentation treatment. At least a portion of the supernatant water from the sedimentation tank 34 is supplied to the water supply tank 36 for the separation device 1 via a pump (not shown) and piping 35.

[0058] The water supply tank 36 also receives relatively clean water, such as well water, tap water, and industrial water (hereinafter referred to as clean water).

[0059] Alternatively, the water supply tank 36 may be omitted, and purified water or the return supernatant water from the piping 35 may be supplied directly to the separation device 1.

[0060] The highly concentrated dewatered filtrate removed from the bottom of the sedimentation tank 34 is introduced into the neutralization tank 37, where sulfuric acid and other substances are added to neutralize it, and then it is discharged through the discharge tank 38.

[0061] In this embodiment, at least a portion of the supernatant water obtained by settling the dewatered filtrate in the sedimentation tank 34 is reused in the separation device 1, thus reducing the amount of clean water used. In addition, the amount of liquid sent to the neutralization tank 37 is reduced, so the discharge volume from the discharge tank 38 is also reduced.

[0062] The supernatant water in the sedimentation tank 34 is at a temperature of approximately 30-40°C, which is higher than clean water such as well water, city water, and industrial water. By reusing this high-temperature supernatant water, the amount of clean water used is reduced, and therefore the amount of steam blown into the separation device 1 is also reduced. [Examples]

[0063] [Example 1] [Disposal of used diapers for the first time] Used disposable diapers were processed using the sorting device 1 shown in Figures 2 and 3, following the flow chart in Figure 1, which included crushing, rinsing, and dewatering steps.

[0064] The dimensions of the rotating tank in sorting device 1 are as follows:

[0065] Rotating tank diameter: 180 cm Rotating tank depth: 120cm <Operating conditions for the crushing process> Rotation speed: 30 rpm Crushing time: 60 min Used diaper capacity: 200 kg Chemicals used: 12 kg slaked lime, 0.4 kg calcium hypochlorite Input water: Well water (water temperature 20℃) 800L The water temperature in the rotating tank was raised to 80°C by blowing in 83 kg of steam. <Dehydration process before rinsing> After crushing, the rotary tank was rotated at a high speed of 700 rpm for 5 minutes to dewater the material and discharge the wastewater into the drainage tank 31, leaving the plastic fraction, mainly consisting of film, nonwoven fabric, and pulp, in the rotary tank.

[0066] <Rinsing and dewatering process> Next, 1000L of well water (water temperature 20℃) was supplied, and the rotating tank was rotated for 20 minutes in the same manner as above to perform rinsing. After that, dewatering was performed in the same manner as above, and the dewatered wastewater was discharged into the drainage tank 31.

[0067] The properties of the residue (plastic fraction) in the rotating tank after dewatering were as follows:

[0068] Moisture content: 57% Film ratio in solid content: 69% Ratio of pulp and superabsorbent polymer in solid content: 31% Film composition: PP, PE, PET Superabsorbent polymer composition: Polyacrylate Film length in the longitudinal direction: 15-450mm Polymer water absorbing material diameter: 1~2mm Pulp fiber length: 2-5 mm

[0069] This plastic fraction was removed from the rotating tank 3 and supplied to the recycling process.

[0070] <Treatment of wastewater from the crushing and rinsing processes> The wastewater introduced from the drainage tank 31 into the slurry tank 32 was supplied to the screw press dewatering machine 33 for dewatering treatment, separating it into a dewatered material mainly consisting of pulp and a dewatered filtrate.

[0071] The dewatered filtrate was introduced into the sedimentation tank 34 for sedimentation. The temperature of the supernatant water was 38°C. 540 L of this supernatant water was returned to the feed tank 36 and stored there.

[0072] [Disposal of used diapers, second time] In the crushing process, the processing of new used diapers was carried out under the same conditions as the first time, except that 540 L of the returned supernatant water from the sedimentation tank 34 and 260 L of well water (water temperature 20°C) (total 800 L) were supplied to the separation device 1.

[0073] This second round of disposal of used diapers was carried out immediately after the completion of the first round.

[0074] [Disposal of used diapers from the 3rd to 5th rounds] Immediately after completing the second batch of used diapers, processing of new used diapers began. (Third processing batch)

[0075] Furthermore, immediately after the completion of the third batch of used diapers, the processing of new used diapers was carried out. (Fourth batch of processing)

[0076] Furthermore, immediately after the completion of the fourth batch of used diapers, a new batch of used diapers was processed (fifth batch).

[0077] The conditions for the 3rd through 5th processing steps are the same as for the 2nd step.

[0078] [Disposal of used diapers from the 6th to 9th batches] After completing the disposal of the fifth batch of used diapers, I finished work for the day.

[0079] The following day, the disposal of the 6th through 9th batches of used diapers was carried out using the same procedure as the disposal of the 1st through 5th batches.

[0080] <Results / Discussion> In the second through fifth treatment cycles, the total amount of water used was reduced by 30% compared to the first treatment cycle.

[0081] Furthermore, the second through fifth treatments were carried out immediately after the completion of the previous treatment. As a result, the water temperature in the sedimentation tank 34 gradually increased with each treatment, and the amount of steam blown into the rotating tank decreased accordingly. Specifically, the water temperature in the sedimentation tank and the amount of steam blown into each treatment at the start of each treatment were as follows.

[0082] [Table 1]

[0083] The 6th through 9th tests were conducted the day after the 1st through 5th tests, and similarly, the water temperature in the sedimentation tank 34 increased with each subsequent test. Consequently, the amount of steam used also decreased. [Explanation of symbols]

[0084] 1 Sorting device 1a Enclosure 2 Aquariums 3 Rotating tank 4 Door Body 5 Motors 9. Drain valve 11 Protrusion 12 blades 14 Water inlet 17. Drug Additive Section 19 Inlet 20,23 Airflow path 21 Heater 22 Blower means 24 Air outlet 31 Drain tank 32 Slurry Tanks 33 Dehydrator 34 Sedimentation tank 36 Water tank 37 Neutralization tank 38 Outlet tank

Claims

1. A sorting process involves crushing and washing used disposable diapers using a sorting device, and then separating them into a plastic fraction and pulp-containing wastewater. A method for processing disposable diapers, comprising a dewatering step for the pulp-containing wastewater generated in the sorting step, and a return step for returning a portion of the dewatered filtrate to the sorting step.

2. The disposable diaper processing method according to claim 1, wherein the dewatered filtrate is subjected to a sedimentation process and the supernatant water is returned to the separation process.

3. The disposable diaper processing method according to claim 1 or 2, wherein used disposable diapers, water, and chemicals are supplied to the sorting device to perform the sorting process.

4. The disposable diaper processing method according to claim 3, wherein in the sorting step, steam is supplied into the sorting device to raise the temperature inside the sorting device to 70 to 90°C.

5. The method for disposable diapers according to claim 3, wherein the aforementioned agent comprises slaked lime and calcium hypochlorite.

6. The sorting device is A water tank for storing water, A bottomed cylindrical rotating tank is supported within the water tank so as to be rotatable with its rotation axis approximately horizontal, A blade for breaking bags is provided on the inner surface of the rotating tank, A motor that rotates the rotating tank and A method for disposing of disposable diapers according to claim 1 or 2, having the following:

7. A sorting device that crushes and washes used disposable diapers and separates them into a plastic fraction and pulp-containing wastewater, A dewatering machine for dewatering pulp-containing wastewater from the sorting device, A sedimentation tank for settling the dewatered filtrate from the dewatering machine, A return means for returning at least a portion of the supernatant water from the sedimentation tank to the separation device. A used disposable diaper processing device having

Images