DE19821473A1 - Recycling soiled sanitary materials - Google Patents

Abstract

To recover useful material from used sanitary products, they are initially broken down mechanically to separate the absorbent layers from the backing and/or top sheet layers, in a dry process. To recover useful material from used sanitary products, they are initially broken down mechanically to separate the absorbent layers from the backing and/or top sheet layers, in a dry process. The fragments are fed to at least one washing and separating stage to separate the matter into film, super absorbent polymers (SAP), cellulose and the soiling. The gel formed by the super-absorbent polymer, swollen by a high water content, is compressed into a specific density of \-1 g/cm<3> in an insoluble condition. The precipitated SAP is separated from the floating cellulose fibers and dirt particles, and from the washing fluid. The cellulose fibers are cleaned, disinfected, dried and prepared, and the film material is also cleaned and prepared. The mechanical grinding of the materials mechanically separates the plastics film materials from the remainder, and the separated film matter and the cellulose/SAP fractions are fed to separate washing stages (8a,8b), where they are washed. The cellulose and SAP are separated by gel contraction and precipitation in a continuous water separation stage. The three washed fractions of film and cellulose and SAP are recovered and prepared as required. The cellulose absorbent layer is torn from the plastics film, and the torn film sections retain their dimensions. The gel contraction is through the addition of soluble alkaline earth salts, hydroxides or oxides of calcium chloride, magnesium chloride and magnesium sulfate. The additives bring the washing fluid to a pH 6-14 and pref. pH 6.5-8.0 at a temp. of 18-30 deg C. The gel contraction is in a reaction time of 10 secs. to 20 mins., and pref. 3-5 mins. The separation and precipitation is in a gravity field by flotation of the cellulose fibers and film scraps through blown-in air, with precipitation of the contracted SAP. The washing water, soiled by the extracted impurities, is filtered, enriched with nitrogen, and cleaned by reverse osmosis for further use. An Independent claim is included for an apparatus with two washing stages (8a,8b) to take the separated film and cellulose/SAP fractions. Preferred Features: A precipitation bath is at one washing stage (8b) for the separation of the cellulose and SAP, with an outlet for the removal of the contracted SAP. The mechanical dry grinding action on the start materials is through a disk mill (4) with a cyclone separator (5). A ladle or curved sieve separates the cellulose fraction from the precipitated SAP, which is emptied in the screw press (12) for water extraction.

Description

The invention relates to a method for treating Hygienic products made of absorbent composites, the latter contain a cellulose-containing absorption layer Superabsorbent polymers and one on the absorption layer attached back and / or top sheet made of plastic film.

A method is known from US Pat. No. 5,322,225 for obtaining valuable materials from soiled hygiene products which are usually to be disposed of, the following method steps being used:

• - Mechanical shredding of the dirty disposable items detached one attached to the absorption layer ten back and / or top sheets made of film material,
• - Transfer the shredded disposable items into a washing and separating liquor and separation of the groups of substances
  • - foils
  • - Super absorber polymers
  • - cellulose (cellulose) parts,
  • - pollutants
• - Cleaning, disinfecting, drying and preparation of the gerei made cellulose parts,
• - Cleaning and preparation of the film parts.

Furthermore, US Pat. No. 5,558,745 describes a method for loading are about hygiene products that contain superabsorbents (superab sorbing polymers, SAP), known, in which the ver dirty and crushed hygiene products in a water be treated bad and the soluble parts in this Water bath can be solved. The superabsorbents are used to to allow separation to be treated with a means which causes the so-called gel collapse, so that the Superabsorbent from the swollen into a contracted one State changes in which a specific density is greater than Water enters and the superabsorbent in granular Consistency drops.

Inducing gel collapse with the help of alkaline earth salt, especially calcium chloride, magnesium chloride and Manganese chloride, is known from J. Chem. Phys. 1982, p. 5725 ff.

The method known from US Pat. No. 5,558,745 works in essentially discontinuous and in batches, being very many individual stations have to be covered. At this method is therefore both a rough application various washing containers as well as a relatively large one Energy and water expenditure required. The separation of the three groups of substances, namely foil, SAP and pulp, is in several steps, with the separation steps the individual groups can interfere and that make physical separation difficult.

It is therefore the task of specifying a method that can be carried out continuously, that one has less effort in stations and with one moderate energy and water requirements.

This object is achieved with a method of the type mentioned at the outset, which works with the following method steps:

• - Mechanical crushing of the composites without Adding liquid,
• - mechanical separation of the plastic film from the cellulose-containing absorption layer with the Superabsorbents,
• - Transfer the plastic film fraction and the cellulose and absorber-containing fraction in separate washing liquors,
• - washing the fractions,
• - Separation in an aqueous to be operated continuously Separation section of cellulose and superabsorbents, the latter after gel contraction and failures,
• - winning and, if necessary, further processing of the three washed fractions plastic film, cellulose and Superabsorbents.

In particular through the upstream dry separation of Foil and pulp / SAP fraction and dividing into two separate washing lines for plastic and pulp / SAP Frak tion can be a considerable amount of equipment and also save energy and water. The Ver Soiling the plastic film is relatively easy to brush during cleaning of the soiled pulp with the adhering SAP particles is considerably more complex. It also prevents the aqueous liquors from interfering with the substances to be washed influence each other. The after washing the pulp superabsorbent fraction he required separation is possible continuously.

In particular, the cellulose-containing absorption layer dry from the existing back and / or top sheets sen, so that the present sections of the used Plastic film essentially maintain its size and thus also easier mechanically from the other fractions are separable.

The gel contraction of the SAP is preferably done by adding  a soluble alkaline earth metal salt to the aqueous separation bath; in particular calcium chloride is used. So that can a washing section can be worked continuously by the components are stirred and mixed and then eating pulp and collapsed SAP be separated from each other. As a driving force for this Flow serves the flow energy of the water flowing in the Circuit flows. With the help of special agitator shafts with kinked blades result in mechanical impact, that improve pulp cleaning. Here too a propulsion that generates the pulp, its density is slightly higher than that of water. By appropriately setting the flow rate and the The duration of the SAP backflow can be coordinated in this way be that everything in the area of separation SAP back len is.

As is known, the superabsorbents are acrylic polymers which can absorb many times their own weight in water (cf. information in US Pat. No. 5,558,745). While the SAP have a specific weight in the swollen state very close to 1 g / cm ³ and are therefore practically difficult to separate from the surrounding water, in the contracted state they are much heavier than water, sink and can be separated relatively easily.

A calcium chloride solution is suitable here, which is kept in the neutral range, i.e. at a pH between 6.5 and 8.0, and which can be used at room temperature, i.e. in the range from 18 ° to 30 ° C. The dissolved amount of calcium chloride can be kept at 10 ^-6 to 10 ^-4 mol / l. Depending on the degree of soiling, type of superabsorbent and similar technological parameters, it is also possible to deviate from the above values.

The separation and failure occurs in the gravity field by flotation of the cellulose suspension using air  blow and lower the contracted SAP, which on Reason can be deducted via funnel or the like.

The invention further includes a device for through implementation of the method, whereby for the separation of film and Celulose / SAP fraction a fiberizing machine, for example a corrugated mill is provided.

Furthermore, a washing section for separating the Cellulose / SAP fraction provided at least one Has sink. Each of the wash troughs has a bottom area or is ver with a separate sedimentation basin bound, which is provided with a discharge opening, from which the deposited contracted superabsorbent polymers are laxable.

In addition, the washing section becomes a ladle screen, which is preferred as a curved sieve is connected. The ladle screens can be emptied into a drainage screw that sieves the pulp and removes the unwanted water pulls.

Smaller shreds of film still present in the plastic Laundry is picked up on a conveyor belt.

It can be used with those selected for the present procedure Components carried out a continuous process become.

Use embodiments of the process flow Individual parts are shown using the drawing. The Figures of the drawing show:

Figure 1 is a schematic view of the device as a whole with different individual parts.

Fig. 1a and 1b detailed solutions of the water treatment;

Fig. 2 dry separation of the plastic fraction;

Fig. 3 is a washtub for washing liquor with an acrylate deduction;

Fig. 4 representation of the shape of the agitator shafts in the pulp washing;

Fig. 5 shows the shape of the film Transportvorrich lines in the film washing of the plastic fraction.

The diagram shown in FIG. 1 shows the details of a device as it is used for a method for treating hygiene products made of absorbent composites and for extracting valuable materials.

In hospitals, retirement homes and private households, incontinence articles and baby diapers are produced that are contaminated with faeces and urine. These articles are collected in hermetically sealed lid bags, which are brought together in containers. Shortly before processing, the closed lid sacks are fed to an automatic opening device 2 , opened and opened with a conveyor belt 30 . On a sorting table 3 , any contaminants are removed manually or using manipulators, for example plastic parts, such as syringes, or similar foreign bodies. Metal parts are separated out via metal detectors and manipulators.

About another conveyor belt 31 then get the preparatory disposable article to a disc or corrugated mill 4 , in which the disposable items are torn into small pieces when not wetted, the back and / or top sheet attached to the absorption layer depending on the function of the disc mill Plastic film is undamaged and largely torn free of cellulose. The plastic film usually consists of polyethylene or polypropylene, although other film materials, for example starch derivatives, are also known.

The shredded and cracked material is then sent over a cyclone 5 to Chen cellulose fines and dust, which arise in the disc shredder, to separate and remove from the outset.

The material coming from the cyclone separator 5 remains unwetted and not watered and is guided over a conveyor section 6 . Then it arrives in the dry separating section 7 (see FIG. 2). As can be seen in detail from FIG. 2, continuously moving rod rakes 40 take up the vertically falling material stream 41 and collect the plastic fraction 42 . The separated plastic fraction 42 is transferred to a conveyor belt 33 by lowering the bars 43 from the bar rake 40 . The pulp fraction 44, on the other hand, falls through the rods 43 onto the conveyor belt 34 and is continuously processed separately.

After separation, the plastic fraction 42 passes into a film wash 8 a, the remaining fractions (cellulose and SAP) into a cellulose wash 8 b.

A washing liquor is present in the washing tub of the cellulose wash 8 b. The temperature of the aqueous washing liquor is about 20 ° C. The liquor calcium chloride is used in an amount which induces the gel collapse of the SAP, namely about 10 ^-5 to 10 ^-6 mol / l. The swollen superabsorbent polymer is converted by the dissolved alkaline earth salt into a water-insoluble, white and elastic, but no longer flowable gel with a specific weight sufficiently greater than 1 g / cm ³ .

The washing liquor from the cellulose washing is transferred to one or more further basins, stirred and circulated, so that the mass is washed and rinsed. Faeces are discharged through the wash liquor 9 .

Flotation is then carried out in a separate settling tank 9 (see FIG. 3). The sedimentation basin 9 is provided with discharge funnels 32 on its pool bottom, in which the sunken and contracted amounts of gel are collected and kept ready for removal. Incoming air ensures that the cellulose fibers are kept in suspension and rise to the top so that they cannot escape with the contracted SAP particles. Furthermore, residues of plastic films are carried to the surface.

Fig. 3 shows the settling tank 9 in a somewhat more detailed representation. The cellulose components are swirled and carried upwards by air flowing in from the side, which has a floating effect in the water, and form a middle layer. In the uppermost part of the sedimentation tank, lighter plastic parts are collected which can be fished out or removed in other ways.

At the bottom of the settling basin 9 , collapsed SAP particles collect, which are suctioned off via a periodically acting suction device 35 .

After the superabsorbents are removed, the liberated wash liquor is introduced into a separating tank 10 where the cellulosic fibers are fed via a curved screen 11 is removed from the basin 10 and into a dewatering screw 12th The water is extracted from them by means of the drainage screw 12 . The water that is pressed out is drained into a pump sump and fed back into the washing and treatment section after cleaning.

The cellulose fibers removed are washed again in a post-wash in a container 13 . The cellulose fibers are then fed via a curved screen to a so-called omni-sorter system 14 ( FIG. 1a), as is known per se to the person skilled in the art. Here, residual foreign bodies are removed from the cellulose fibers and the last remaining scraps of polyethylene and polypropylene film are screened out.

The cellulose is pressed through a sieve by means of a rotor, whereby the shape of the rotor clears the inside of the sieve basket. At the same time, a UV disinfection section is integrated in the water circuit of the omni-sorter system 14 . Cellulose and water are disinfected here. The disinfected and cleaned cellulose can then be used for various areas of pulp production, in particular also "virgin" material can be mixed in, for example in paper production.

In the film washing section 8 a, the film pieces 42 are cleaned of faeces. Propulsion in the film washing stretch 8 a takes place via a conveyor arm arrangement 50 shown in FIG. 5. At the end of the film washing section there is a take-off bath 19 which receives the pieces of film floating on the water due to their lower density and conveys them to a collecting container (not shown). The plastic scraps from the washing section 8 b which have meanwhile been collected are also collected for recycling.

The wastewater treatment of the water to be circulated is carried out approximately every week. The water is transferred to an elevated tank 15 ( FIG. 1b), biological waste water treatment taking place over a period of three weeks. The water is nitrified, ie enriched with nitrogen gas. The water passes from the waste water elevated tank 15 into a sedimentation tank 16 , in which the sewage sludge settles and nitrification is carried out again. The pre-clarified water now goes into a reverse osmosis system with upstream ultrafiltration. The purified water after the reverse osmosis is stored in a fresh water storage container and fed into the water cycle as required.

The enriched concentrate of reverse osmosis is in one Distilled vacuum evaporator and the purified distillate also returned to the water cycle.

The concentrate of the vacuum evaporation is residual material and will disposed of as residual waste.

This results in a procedure that is under proportion The production of valuable materials from disposable is moderately low products and also recovery a large amount of valuable substances.

Claims (12)

1. A method for treating hygiene products made of absorbent composites, the latter containing a cellulose-containing absorption layer, superabsorbent polymers and a backing sheet and / or top sheet made of plastic film attached to the absorption layer, with the following process steps:

• - mechanical crushing of the composites without the addition of liquid;
• - Mechanical separation of the plastic film from the cellulose-containing absorption layer with the superabsorbents;
• - Transfer the plastic film fraction and the cellulose and absorber-containing fraction into separate washing liquors ( 8 a, 8 b),
• - washing the fractions;
• - Separation of cellulose and superabsorbents with the help of gel contraction and precipitation in a continuously operated aqueous separation section;
• - Obtaining and, if necessary, further processing of the three washed fractions of plastic film, cellulose and superabsorbent polymer (SAP).

2. The method according to claim 1, characterized in that the cellulose-containing absorption layer from the baking and / or topsheet is torn that the sections of the used plastic film essentially their Keep size. 3. The method according to claim 1, characterized in that the gel contraction of the SAP by adding a soluble one  Alkaline earth metal salt, preferably calcium chloride, for aqueous separation liquor takes place. 4. The method according to claim 1 and 3, characterized in that the aqueous solution has a pH between 6.5 and 8.0 has and at a temperature between 18 and 30 ° C. (Room temperature) is maintained. 5. The method according to any one of the preceding claims, characterized in that the separation and failures in a gravitational field by flotation of the Cellulose suspension and possibly film residues is carried out by means of air blowing and by Allowing the contracted superabsorbents to sink is carried out. 6. The method according to any one of the preceding claims, characterized in that the polluted water for Filtered recovery, enriched with nitrogen and is cleaned by reverse osmosis. 7. Device for performing the method according to claim 1 and optionally further claims 1 to 6, characterized by two washing sections ( 8 a, 8 b), in which the plastic fraction and the pulp SAP fraction are washed separately. 8. The device according to claim 7, characterized in that the washing trough ( 8 b) for separating the cellulose and SAP fraction is assigned a separate sedimentation basin, which is provided with a discharge opening from which the contracted superabsorbent polymers can be removed. 9. A device for performing the method according to claim 1, characterized in that the defibration machine is a disk mill ( 4 ). 10. The device according to claim 9, characterized in that the defibration machine ( 4 ) is followed by a cyclone separator ( 5 ). 11. Device for performing the method according to Claim 1, characterized in that for separating the Cellulose fraction from the sunken SAP a curved screen is used. 12. Device according to one of the preceding claims, characterized in that the scooping and curved screens in drainage screws ( 12 , 16 ) can be emptied.