Patent Application
20210146578
The subject of the invention is a method for processing and monetizing the waste which is created after paper from used beverage cartons has been recycled and a processing line for implementing this method.
Beverage cartons are made from layers of paper, a few layers of polyethylene and, for aseptic cartons, a layer of aluminium. The paper fibres, which make up most of the packaging material, are recycled in paper mills. During the recycling of the paper fibres, a waste mixture is created consisting of a) multi-layered foils containing a few layers of polyethylene and a layer of aluminium (PE+AL foil), b) polyethylene foil (PE foil), c) non-foil plastics (e.g., lids and screw caps, mostly made of high density polyethylene, HDPE), d) paper fibres (paper recycling is not perfect) and e) other contaminants, e.g. metal (e.g. aluminium cans), plastics (e.g. PET bottles, polystyrene foam) and textiles.
Currently, the level of using waste from recycling paper from beverage cartons is very low the waste is mostly incinerated or landfilled. The methods for, using it can be separated into three groups; processing using heat, mechanical processing and separating the PE+AL foil and recycling: them using chemicals.
The most common method for processing the waste from recycling paper from used beverage cartons is to use it as fuel. Other heat processing methods are pyrolysis or gasification.
During mechanical processing, the waste is agglomerated and then made into mostly lower quality plastic products (e.g. roof tiles or drain covers). The waste (or the entire beverage carton, including the paper) can also be compacted and building materials (panels) made from it.
It is also possible to separate the PE+AL foil from the waste and recycle it using chemicals. PE+AL foil can be broken down into their components by dissolving the polyethylene or separating the layers of polyethylene from the aluminium layer. There are a number of known methods for this type of recycling from the current technology available.
Recycling packaging materials based on separating the different layers is known, for example from: document WO2015169801, The recycling described in this document involves a separating vat containing a swelling agent and carboxylic acid for separating the metals, plastics and other items. Other steps include filtration and pelletization.
Document CN101891903 describes a method of processing waste packaging from paper, plastic and aluminium foil during which the aluminium is separated from the plastic by soaking the waste in a formic acid solution of concentration 3-5 mol/l for a period of 30-40 minutes at a temperature of 40-60° C.
The method of recycling layered material comprising combinations of layers of various plastics and aluminium foils described in document CN103328105, involves a reaction with a formic or acetic acid, separating the different layers and washing the waste a number of times. The washing process is performed to separate the different types of material based on their different densities.
Document WO9427818 describes a method of treating laminates containing aluminium foils with layers of organic materials to enable the aluminium to be melted together with aluminium from drinks cans.
The disadvantage of the above solutions is that they do not provide a method for separating out the large amounts of contaminates found in the input material. Also, they require a high level of financial costs and in many cases place a similarly large burden on the environment due to the large amount of chemicals they require.
During the processing of the waste created by recycling cellulose from used beverage cartons the flake size of the input material is initially reduced at the preparation and sorting phase and the rough waste comprising heavy material and waste dust is removed with the remaining input material being separated into a fraction comprising mainly non-foil plastics, and a fraction comprising mainly polyethylene foil (PE foil) and foil of at least one layer of polyethylene and one layer of aluminium (PE+AL foil), and during the phase in which the PE+AL foil is separated into polyethylene and aluminium and their sorting, the fraction comprising PE+AL foil undergoes washing in a water-based formic acid solution and is separated into a fraction comprising mainly polyethylene and a fraction comprising mainly aluminium. A fraction comprising mainly PE foil and PE+AL foil is preferably separated into a fraction comprising mainly PE foil and a fraction comprising mainly PE+AL foil.
The method according to the invention preferably also includes:
The method according to the invention is characterized by a new use, combination and ordering of the machinery, particularly in the first and second phases. In the first phase, this involves ordering recognised machinery in such a way that the sorting of the input material into individual fractions is achieved in a sufficient quality for their further processing, and preferably also using recognised air separating machines for separating PE foil and PE+AL foil before the chemical separation, which significantly reduces the overall costs of recycling the waste and the burden on the environment. Intermediate containers, normally silos, are also placed before certain machines to ensure a regular flow of material which ensures the quality of the subsequent sorted material. The main principle of the second phase is the use of a set of machinery for hot washing, which is similar to the existing machinery used, for example, for washing recycled PET bottles, for separating the PE+AL foil using formic acid.
During the first phase—preparing and sorting the input material—the flake size of input material is reduced in a shredder, after which the heavy contaminantes (e.g. metal, stones and glass) are removed in the air separator, then most of the paper fibre and dust contamination is removed and the moisture of the material is reduced by dry cleaning, which can be performed by a centrifuge drum, for example, after which, non-foil plastic (e.g. lids or caps) are separated from the foil (PE+AL and PE foil) during the air separation step and the material is cut in a cutting mill. Plastics other than foil may be separated before cutting and/or after cutting in the mill. In the next air separation step, the remaining other plastic is separated from the foil (a mixture of PE and PE+AL foil) and in another air separation step the PE foil can be preferably separated from the PE+AL foil.
The result of the first phase processing of the input material is output mixtures: heavy material, the waste from the dry cleaning (comprising mainly paper fibres, various plastics and aluminium dust), a mixture comprising non-foil plastics (mostly high density polyethylene HDPE) contaminated with e.g. other plastics and textiles, and a mixture comprising PE and PE+AL foil.
During the second phase, the phase for separating the PE+AL foil into polyethylene and aluminium and its sorting, the PE+AL foil is processed in a set of machinery for hot washing, a similar set of machinery usually used for hot washing plastics (mainly PET bottles), using a working solution of a water-based formic acid solution for separating the polyethylene layers from the aluminium.
In the advantageous design of the invention, the working solution is a 15-30% by weight water-based solution of formic acid (15-30% HCOOH and 70-85% water, by weight). As opposed to processing PE+AL foil using the prior art technology, it was ascertained that when processing the PE+AL foil adjusted in the first phase of the invention it is advantageous if the amount of working solution is at least ten times the bulk volume of the PE+AL foil. It is beneficial if the ratio of bulk volume PE+AL to working solution is from 1:100 to 1:10. The material from the PE+AL foil is intensively stirred in the working solution for a period of between 5 to 30 minutes, with an advantage of 7 to 15 minutes with a working solution temperature of up to 80° C., with an advantage of 40° C. to 70° C.
The main factors influencing the quality of separation of the PE+AL foil into polyethylene and aluminium during the second phase are the concentration of HCOOH, the temperature of the working solution, the duration of the process and the ratio of material to working solution. The required quality of separated PE+AL foil can be achieved with various combinations of the above mentioned parameters, where it mainly applies that the necessary process duration is shorter the higher the temperature and/or HCOOH concentration of the working solution. The HCOOH concentration in the water solution can be 15-90% by weight. A lower concentration is more favourable because the working solution is then cheaper and the vapour contains a lower amount of HCOOH. Furthermore, when a concentration of cca 30% HCOOH is exceeded, the working solution becomes explosive and all machinery must be designed to comply with work in an explosive environment (which significantly increases its cost and standard plastics processing machinery is not manufactured to this specification). The process period must be longer than about 5 minutes. The maximum ratio of material to working solution is influenced by the method and quality of stirring. It is very difficult to achieve a ratio of PE+AL foil to working solution of more than 1:10, and conversely when this ratio is lower than 1:50 the operation of the machinery ceases to be optimal.
The machinery through which the processed material passes in phase II includes a mixing screw, a reaction tank, a dewatering screw, a friction washing machine, a centrifuge and machinery for hot air drying. The PE+AL foil is soaked and sprayed in the mixing screw with the working solution which is heated to the working temperature. This step heats the foil, so that the temperature doesn't drop in the reaction tanks, and makes the foil easier to process and transport. The material is intensively mixed in the working solution in the reaction tank at a given temperature and for a given period such that the PE+AL foil is separated into PE and aluminium flakes and dust. The dewatering screw removes part of the working solution from the processed material. The working solution is then further removed mechanically in the friction washing machine and the centrifuge. At the same time, aluminium flakes and dust are removed from the PE foil in these machines. The aluminium continues to the screw press and is then processed at phase—processing aluminium. The polyethylene flakes are dried by air. This occurs initially at the ambient temperature in the centrifuge, and then with hot air in a separate section of the line. With certain designs of the invention the air used for drying doesn't need to be cleaned. In another version this air is runoff for cleaning. A water or bio filter is used to capture the HCOOH content of the air. With another version of the invention it is possible to clean the remnants of the working solution from polyethylene after the mechanical drying stage by rinsing with water (instead of the step involving hot air drying).
The formic acid contained in the water in the water filters or rinsing water is treated in a waste water treatment plant or is regenerated by distillation or electro-dialysis, or can be neutralized into sodium formate using sodium hydroxide or sodium bicarbonate. With an advantageous design the sodium formate can be sold as a by-product.
The result of processing the PE+AL foil in the second phase is two fractions, one containing mainly, polyethylene (polyethylene flakes contaminated with aluminium and other plastics) and the other containing mainly aluminium (aluminium contaminated with paper fibres and plastics).
In phase III—aluminium processing—the fraction containing mainly aluminium can be processed chemically or by smelting. The input material is the fraction containing mainly aluminium (contaminated with paper fibres and plastics) which is the result of processing the PE+AL foil in phase II. The aluminium processing stage with advantage involves smelting in a protected environment. The advantageous processing of aluminium by smelting involves two steps—drying the material, e.g. in a rotating kiln (under ambient conditions) and melting down the aluminium and burning off the contaminants, e.g. in a batch oven under protected atmospheric conditions. The protected atmospheric conditions in the second step may be created by nitrogen, for example.
Phase IV of the process—polyethylene processing—is performed using polyethylene re-granulation machinery that allows processing material with high amounts of contaminants.
Phase V—processing non-foil plastics which are separated from the foil by air separation, is performed by regular machinery used for recycling plastics contaminated with other materials. The input material at this phase is cleaned of any admixture and processed into regrind or granules.
The final products from processing waste according to the invention are polyethylene granules, non-foil plastic regrind (or granules) containing mainly HDPE and aluminium.
The processing line for performing the method of processing waste from recycling paper from used beverage cartons, especially the processing line performing the method described above, includes phase I machinery—for preparing and sorting the input material and phase II machinery—for separating PE+AL foil into polyethylene and aluminium and their sorting.
The machinery for phase I—preparing and sorting the input material—includes a shredder, the first air separator for eliminating rough waste, dry cleaning machinery, with the advantage a centrifuge for eliminating paper fibre and dust contamination and for reducing the moisture of the material, and in the advantageous design a second air separator for separating non-foil plastic from the foil, a cutting mill for cutting the foil, a third air separator for separating the remaining other plastic from the foil and preferably a fourth air separator for separating the mainly PE foil fraction and the fraction containing mainly PE+AL foil.
The machinery for Phase II—separating PE+AL foil into polyethylene and aluminium and their sorting—includes stirring machinery for performing the reaction between the material and formic acid solution, a set of machinery for mechanically drying the material, with the advantage a draining screw, friction washing machine and centrifuge for reducing the moisture and separating the mainly polyethylene and mainly aluminium fractions, machinery for hot air drying and a set of machinery for preparing and regenerating the formic acid working solution.
The set of machinery for preparing and regenerating the formic acid working solution in Phase II, includes dosing device, collection tanks, a decanter centrifuge, a heat exchanger for heating the working solution and the respective pipe connections for circulating the solution. The working solution which is removed from material with draining screw, friction washing machine and centrifuge is gathered in a collection tank, from which preferably part of it is fed to a decanter centrifuge and part to a second collection tank. The decanter removes any mechanical contaminants (mainly aluminium dust and flakes) which can then be processed in Phase III—aluminium processing. The treated working solution is gathered in a collection tank into which fresh working solution is simultaneously added by a dosing device. The solution is then heated in the tank to the working temperature and fed to the mixing screw and reaction tank.
The attached drawings include:
Paper mill waste created after recycling paper fibres from used beverage cartons was processed using the invention method in five phases, on a processing line designed according to the invention in the following manner:
Phase I—preparing and sorting the input material—is set out in the schematic diagram in
The result of Phase I waste processing was 5 output fractions (denoted by the Roman numeral I, a hyphen and letters B to F), whose properties are set out in the next table.
Phase II—separating PE+AL foil into polyethylene and aluminium and their sorting—is schematically set out in
The set of hot washing machines, set 21, used in this example is regularly used for washing soiled plastics (mainly PET bottles) in lye. Set 21 was made up of two parts; 1) machinery which processed the material (fraction I-F containing mainly PE+AL foil, and 2) machinery which prepared and regenerated the working solution. These two parts of set 21 are described in more detail in the following table.
The machinery used for processing fraction I-F:
Machinery for preparing and regenerating the working solution:
The set of hot washing machinery, set 21, used the following method for processing fraction I-F:
The working solution was a 20% formic acid water solution (20% HCOOH and 80% water by weight). The volume ratio of fraction I-F to the working solution was 1:20. Fraction I-F was intensively stirred for 15 minutes at solution temperature of 50° C.
The following table sets out the characteristics of the main flow of the material which was the result of processing fraction I-F during Phase II.
Fraction II-B containing mainly aluminium was saved for further processing. Fraction containing mainly polyethylene (e.g. in flake form) was processed in Phase IV in re-granulation machinery which contained special filters enabling material with large amounts of contaminants to be processed, in the case of this example this was up to 5% of the weight. Fraction I-D containing mainly non-foil plastics sorted from the foils in air separators was processed in Phase V, where this processing was performed in a regular manner on regular machinery used for recycling plastics contaminated with other material. At this step of the process the input material was cleaned of any admixture and processed into regrind.
Waste from the recycling of paper fibres from used beverage cartons from the Papierfabrik Niderauer Mühle GmbH paper mill was processed on a line designed to perform the invention method in the same way as Example. No. 1, where in this case 896 kg of I-A input material with 24% moisture by weight, i.e. 680 kg of dry state material was processed in Phase I—preparation and sorting of input material. Shredder 11, air separator 12, dry cleaning machinery 13, first silo 18, air separator 14, cutting mill 15, second silo 18, and air separators 16 and 17 were used in the Phase I processing.
From processing the I-A input material, 5 kg of rough waste I-B, a mix of heavy materials, e.g. metals, stone and glass was produced. 168 kg of dust waste I-C, a mixture from the dry cleaning made up of mostly paper fibres, a mix of various plastics and aluminium dust was also obtained. The moisture of the I-C waste was measured at 42-43% by weight, thus the dry weight of the waste was 97 kg. 128 kg of fraction I-D containing mostly non-foil plastic in the form of pieces, a mixture of mainly HDPE contaminated with e.g., foil and textiles was also obtained. 278 kg of fraction I-E was obtained which contained mainly PE foil, a mixture of PE foil contaminated with aluminium and other plastics. The moisture was measured at 3% weight, thus the dry material was 269 kg. There was also 126 kg of fraction I-F obtained containing mainly PE+AL foil made of polyethylene and aluminium. The moisture here was measured at 2-3%, therefore the dry material weight was 122 kg.
The next step involved processing fraction I-F containing mainly PE+AL foil in Phase II—separating PE+AL foil into polyethylene and aluminium and their sorting. The separation was performed using a formic acid (HCOOH) water solution with a 20% concentration by weight, at 50° C., for 15 minutes, where the bulk volume of the flake form fraction I-F before processing was 5% of the total volume of flakes and liquid. The quality of fraction II-A containing mainly polyethylene was sufficient for processing in Phase IV. and the quality of fraction II-B containing mainly aluminium contaminated with paper fibres and plastic was sufficient for Phase III processing by smelting aluminium in a protected atmosphere.
The invention method is applicable in the waste recycling industry for processing waste from paper mills which recycle used beverage cartons. Processing and making value from waste and using the processing lines with this method, according to the invention, makes it possible to monetize waste and further use it whilst maintaining low costs.
| Number | Date | Country | Kind |
|---|---|---|---|
| PV 2017-446 | Aug 2017 | CZ | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CZ2018/000034 | 7/19/2018 | WO | 00 |
