Process for the treatment of PPK plastic composite material and plant for the production of pyrochar from PPK plastic composite material

Abstract

A process for the processing of PPK-plastic composite material, such as composite packaging, especially lightweight packaging, is described, comprising the following steps: - Sorting a primary material and providing a raw material fraction intended for further processing by pyrolysis, containing at least largely only PPK and plastic, with a higher PPK content than the plastic content, - Crushing of the raw material fraction and formation of agglomerates A, - Pyrolizing the agglomerates A to produce pyrocarbon carbon black as a pyrolysis product, whereby the pyrolysis gases generated during pyrolysis are withdrawn from the pyrolysis reactor 2 and and are burned to heat the pyrolysis reactor 2, whereby the pyrolysis gas removed from the pyrolysis reactor 2 is burned flamelessly to heat the pyrolysis reactor 2 and the heat obtained is used to indirectly heat the pyrolysis chamber 7 of the pyrolysis reactor 2. Also described is a plant for producing pyrocarbon from PPK plastic composite material.

Description

[0001] The invention relates to a method for processing PPK plastic composite material, in particular used PPK plastic composite material, and to a plant for producing pyrochar from PPK plastic composite material.

[0002] PPK (paper, cardboard, carton) plastic composite material is generated in large quantities, primarily in separately collected municipal waste (household waste, packaging waste). This type of composite material comprises a plastic component consisting of one or more types of plastic, a paper, cardboard, or carton component, and sometimes a metal component, typically aluminum. The abbreviation PPK (paper, cardboard, carton) derives from the paper, cardboard, or carton component. This type of composite material is mainly found in composite packaging, typically lightweight packaging. In these composite materials, the individual components are arranged together, typically laminated. In most cases, this fraction of municipal waste is thermally recovered as fuel, for example, by using the heat generated by combustion to feed a district heating network, as other forms of recovery are very complex and costly.The associated CO2 emissions are considered problematic in such recycling of PPK plastic composite material.

[0003] Wet chemical processes are also known for recycling such composite materials. The primary focus of these processes is to recycle the individual components of the composite. According to a previously known method, a separation liquid is used to break up the composite material after a prior comminution step, thus separating the individual components. The PPK and plastic components separated in this way can then be recycled separately. However, wet chemical processes are complex because they require chemicals and large quantities of wash water. Furthermore, the recovered material fractions must be dried before they can be recycled. One wet chemical process is known, for example, from EP 4 067 423 A1. The cellulose recovered using the wet chemical separation process can be used to produce recycled paper.PPK plastic composite material made from municipal waste is often odorous. This odor cannot be completely eliminated, or at least not entirely, through wet chemical processing of the composite material, meaning that a recycled product made from it is often not free of odors from its primary use.

[0004] German patent application DE 44 16 340 A1 proposes the pyrolytic degradation of PPK-plastic composite material to obtain activated carbon as a pyrolysis product. For this purpose, the PPK-plastic composite material is pyrolyzed, i.e., thermally treated under exclusion of oxygen or at least with a significant oxygen deficit. Subsequently, the metal fraction contained in the pyrolysis product is separated from the carbon-rich fraction, for example, by sieving. To prepare for this process, the pyrolysis material is homogenized and comminuted during the pyrolysis. The pyrolysis is carried out at temperatures of no more than 450°C, thus as a low-temperature pyrolysis process. The subsequent processing of the carbon-rich fraction as a pyrolysis product for the production of activated carbon is carried out using conventional methods.

[0005] DE 43 04 294 A1 describes a process for recovering usable materials from composite material. The composite material consists of at least one aluminum layer and one polyolefin layer. It is proposed that the composite material be placed in a reaction chamber and charred there at a temperature below the melting point of the aluminum. Subsequently, the aluminum is separated from the other components, and the charring gas is used as an energy carrier for combustion.

[0006] DE 20 2008 017 367 U1 discloses a device for preparing lignocellulose for pyrolysis. The starting material is lignocellulose or other compressible, preferably fibrous, carbon-containing substitutes or biomass, which are compressed into a biomass strand upon introduction into a pyrolysis chamber. This is considered advantageous compared to producing pellets from lignocellulose as the material to be pyrolyzed.

[0007] DE 20 2004 019 735 U1 discloses a waste processing plant. This processing plant includes a device for separating the waste according to its size in order to sort it into at least two different waste fractions. Subsequently, the waste fractions containing the larger particles are shredded.

[0008] DE 33 30 577 A1 discloses a process for the thermal treatment of waste with further utilization of the resulting residue. The waste materials are thermally treated in order to separate fractions lower in carbon and higher in minerals from the resulting dry residue. Based on the prior art discussed above, the invention aims to propose a method for utilizing primarily discarded PPK-plastic composite material, the properties of which of the resulting product are better suited to an intended use. The invention further aims to propose the use of granular pyrochar, as well as a system for producing pyrochar from PPK-plastic composite material.

[0009] The process-related task is solved by a procedure for handling discarded PPK plastic composite material with the following steps: - Sorting a primary material and providing a raw material fraction intended for further processing by pyrolysis, containing at least largely only PPK and plastic, with a higher PPK content than the plastic content, - Crushing the raw material fraction and forming agglomerates, - Pyrolizing the agglomerates to produce pyrocarbon (carbon black) as a pyrolysis product, wherein the pyrolysis gases produced during pyrolysis are extracted from the pyrolysis reactor and burned to heat the pyrolysis reactor, wherein the pyrolysis gas removed from the pyrolysis reactor is burned flamelessly to heat the pyrolysis reactor and the heat obtained is used to indirectly heat the pyrolysis chamber of the pyrolysis reactor.

[0010] In this process, the product – pyrochar (coke) – is preconditioned by forming the raw material fraction to be fed into the pyrolysis process. This is achieved by ensuring that the raw material fraction consists primarily of PPK (paper, cardboard, and plastic) and plastic as a PPK-plastic composite material, which is crushed and homogenized before its thermal treatment. If granular pyrochar is to be produced, the raw material fraction is formed into agglomerates after homogenization, or concurrently with this process, which can also involve crushing. Homogenizing the raw material fraction ensures a uniform distribution of the plastic particles within the PPK fraction. When agglomerates are formed, they also contain plastic particles. During pyrolysis, these particles are decomposed, creating additional voids within the pyrochar.

[0011] The pyrolysis gas produced during pyrolysis is used to heat the pyrolysis reactor, allowing it to operate autothermally after initial heating with an external gas. Since the pyrolysis gas yield from the plastic particles is higher than from the PPK fraction, the plastic content in the raw material fraction is significant for heating the pyrolysis reactor. With the exception of the metal components, the non-gasifying components of the raw material fraction are converted to pyrocarbon (carbon black) by pyrolysis. Pyrolysis proceeds in the absence of oxygen, or at least with a significant oxygen deficit. The pyrolysis process is typically carried out in such a way that the agglomerates within the pyrolysis reactor do not disintegrate. Therefore, the size of the pyrocarbon aggregates is determined by the size of the previously formed raw material fraction agglomerates.Thus, the size of the raw material fraction agglomerates influences the size of the pyrochar particles. Such granular, especially coarse-grained, pyrochar is suitable as a carbon sink due to its properties, including its high porosity resulting from the incorporation of plastic particles into the raw material fraction agglomerates, specifically for use as a construction aggregate. The carbon is permanently stored in such a product. When used as a construction aggregate, this material is permanently removed from the carbon cycle. Good experiences have been gained with the use of granular pyrochar produced according to the aforementioned process in asphalt mixtures, particularly cold asphalt mixtures, as well as in concrete mixtures.

[0012] Using structures or structural components, be it a road (in the case of incorporating pyrochar into an asphalt mix) or a building or structural element, to store carbon significantly improves the product's CO2 footprint. In addition to using such a structure as a carbon sink, its properties are also enhanced by this type of aggregate. When used as an aggregate for asphalt, particularly cold asphalt, its durability is improved, especially with regard to thermally induced stresses. Using approximately 2% pyrochar in cold asphalt already makes its production climate-neutral. To produce concrete in a climate-neutral manner, a pyrochar aggregate of 4 to 5% is considered sufficient for such a structure or concrete component to be described as "climate-neutrally produced."

[0013] In a preferred embodiment of the process, the raw material fraction is supplied with respect to its PPK (paper, cardboard, and plastic) content such that the amount of pyrolysis gas obtained through pyrolysis is sufficient to heat the pyrolysis reactor, but not so much pyrolysis gas is generated that the amount of heat produced by burning the pyrolysis gas significantly exceeds the amount of heat required to heat the pyrolysis reactor. The residual or excess heat obtained from burning the pyrolysis gases and not used to heat the pyrolysis reactor is preferably supplied to a heat sink located downstream of the pyrolysis reactor. This heat sink can be other heat-consuming equipment, possibly related to the processing of the delivered municipal waste. This residual or excess heat can also be used for heating purposes, such as for heating buildings.This residual or excess heat can be used effectively via one or more heat exchangers, through which the heat from the heating gas is transferred to the other usable medium.

[0014] The plastic content in the raw material fraction is preferably less than 30%, and particularly less than 20%. Typically, a plastic content of 5 to 15% is sufficient to operate the pyrolysis reactor autothermally. To start up the pyrolysis reactor, the burner is initially operated with an external fuel gas, such as natural gas, but only until sufficient pyrolysis gas can be drawn from the pyrolysis reactor to operate the burner. Higher plastic content leads to a higher pyrolysis gas yield and thus to a greater amount of heat that is not required for the pyrolysis process.

[0015] The pyrolysis reactor itself is preferably designed as a continuous flow reactor, for example, operated with one or more screw conveyors to transport the raw material fraction. The shredded raw material fraction, typically formed into agglomerates, is introduced via a cell airlock to minimize oxygen input into the pyrolysis reactor. The pyrolysis reactor is typically indirectly heated. This means that the pyrolysis reactor has a double wall, with the heating gas being directed into the space between an outer jacket and the inner jacket, which encloses the pyrolysis chamber. Pyrolysis can also be carried out in batches.

[0016] The composition of the raw material fraction can be influenced by removing any plastic particles it may contain that are not integrated with the PPK material. If the plastic content in the raw material fraction is too low to generate the amount of pyrolysis gas required to heat the pyrolysis reactor, additional plastic parts or particles can be introduced into the raw material fraction. The same can be achieved by varying the PPK content.

[0017] The comminution and homogenization of the raw material fraction preferably takes place in a cutting mill, also known as a shredder. In such a shredder, the raw material fraction is not only reduced to the desired particle size by cutting, but the comminution is also simultaneously formed into agglomerates. These agglomerates are not excessively compacted, but can exist more as a loose aggregate of comminution. For the purposes of this process, they have an average size of 5 mm to 40 mm, particularly between 15 mm and 30 mm. A size that is too small is considered less suitable for using the pyrolysis particles as a construction aggregate. Providing larger raw material fraction agglomerates will generally require additional process steps that cannot be readily achieved with conventional shredders.The agglomerate size in the raw material fraction generally exhibits a narrow size range to ensure that the pyrolysis time for the agglomerates in the raw material fraction is as uniform as possible. The aforementioned size specification refers to the edge length of the agglomerates produced in such a shredder.

[0018] The pyrolysis gas is combusted (oxidized) without a flame. A FLOX burner is used for this purpose. This type of thermal utilization of the pyrolysis gases has the advantage of minimizing nitrogen oxide emissions. Furthermore, the achievable temperatures are lower than in a combustion process with a flame. This flameless burner cleverly exploits the fact that the high temperatures of a combustion process with a flame are not required to heat the pyrolysis reactor. The pyrolysis process is preferably carried out as medium-temperature pyrolysis with a temperature between 500°C and 700°C. Within this temperature range, at the desired throughput, carbonization to a C / H ratio of less than 0.3 is achieved. Such a degree of carbonization is desirable for the further use of the pyrocarbon.This material then possesses the hardness and desired surface area required for the exemplary use as a construction aggregate mentioned above. The duration of the pyrolysis process, that is, the residence time of the raw material fraction in the pyrolysis reactor, is typically 3 to 6 hours for the raw material fraction agglomerate size specified above.

[0019] PPK-plastic composite material is present in considerable quantities in separately collected municipal waste. Therefore, municipal waste (household waste, packaging waste) is a preferred primary material for carrying out the process. During processing and primary sorting, components that are not PPK-plastic composite materials are removed from this material as far as possible. These are sorted out from the material stream and then sent for their own recycling or further processing. Since such sorting, which is preferably carried out mechanically and thus fully automatically, also contains plastic parts not part of a composite material in the sorted PPK-plastic composite material fraction, these plastic components can be used to adjust the desired PPK-plastic ratio in the raw material fraction for pyrolysis by removing a proportion of these plastic particles.As a rule, the proportion of plastic in the sorted material fraction will be too high, so that the desired PPK-plastic ratio can be adjusted by subsequently sorting out (secondary sorting) non-composite plastic components.

[0020] The invention is described below with reference to an exemplary embodiment and the accompanying figures. These show: Fig. 1: A flowchart to explain the manufacturing process according to the invention for producing granular pyrocarbon from PPK plastic composite material, Fig. 2: a photograph of the raw material fraction produced by shredding with its agglomerates, from which the pyrocarbon is produced by pyrolysis, and Fig. 3: a line drawing of the photograph of Fig. 2 agglomerates shown.

[0021] To produce granular pyrochar, a PPK plastic composite material serves as the starting material to be pyrolyzed, in the illustrated embodiment of which are discarded PPK plastic packagings that have been sorted out from separately collected municipal waste through several process steps.

[0022] To provide the raw material fraction for pyrolysis, which largely consists only of paper, cardboard, and plastic as composite materials, the municipal waste generated during household waste collection is processed and sorted in several stages to separate the desired paper, cardboard, and plastic packaging (typically lightweight packaging) from other materials contained in the waste. In a first processing step, the separately collected municipal waste is screened to remove larger components, such as films, as well as fine-grained material from the material stream. For this purpose, the delivered waste is subjected to appropriate screening, so that, in the illustrated embodiment, the material stream intended for further sorting has an average particle size of approximately 50 mm to 300 mm.

[0023] The delivered municipal waste is also processed by removing unwanted materials. Lightweight materials, such as polystyrene, are vacuumed off; ferrous metals are magnetically removed from the material stream. In a next step, beverage composites, for example, are removed from the material stream using a near-infrared separator (NIR separator). Non-ferrous metals are also typically removed from the material stream using eddy current separators. From the material stream purified of these substances, polymeric plastic materials are then sorted out using another near-infrared separator. PE, PP, PET, and PS are typically removed from the material stream in this way. These materials, separated by type, are then sent for further recycling.

[0024] Once the material stream has passed through this processing stage, the PPK plastic packaging is separated from the remaining material, typically also using a near-infrared separator. This step is referred to as primary sorting in this context. Due to the nature of the process, it is almost unavoidable that plastic components not bonded to PPK will also be sorted into the target fraction during this sorting stage. In principle, this material stream could also be subjected to the subsequent process steps without further sorting – a so-called secondary sorting stage.However, if the aim is to maintain consistent quality in the continuous production of granular pyrocarbon, secondary sorting is carried out to adjust the plastic content in the raw material fraction to be supplied in subsequent process steps, typically by removing unbonded plastic particles from the material stream. At the same time, potential contaminants can be removed through secondary sorting.

[0025] The primary purpose of secondary sorting is to adjust the PPK-plastic ratio in the raw material fraction. In the illustrated embodiment, the raw material fraction, which is subjected to further processing steps, contains less than 15% plastic. Secondary sorting is performed in this embodiment to obtain a plastic content of 10 to 12% in the raw material fraction. The raw material fraction provided in this way is then shredded in a shredder 1. The shredder 1 is a cutting mill in which the fed material – the raw material fraction – is reduced in size by cutting. The shredder 1 can have one or two rotors. This shredding step also homogenizes the raw material fraction and causes agglomerates to form. The size of the agglomerates in the illustrated embodiment is approximately 22 to 26 mm.This refers to the average edge length of the agglomerates formed by shredding. Fig. Figure 2 shows a pictorial representation of agglomerates of the raw material fraction. In the Fig. 3 are the outlines of the agglomerates of the raw material fraction of the Fig.Figure 2 shows the agglomerates and is labeled "A". The size of the agglomerates A determines the size of the granular pyrocarbon formed in the subsequent pyrolysis step. The coarser the agglomerates A, the coarser the resulting pyrocarbon. The grain size of the pyrocarbon can be adjusted by varying the size of the agglomerates A, depending on the intended use. In the embodiment shown in the figures, the pyrocarbon produced by this process serves as a construction aggregate. For this purpose, an average grain size of approximately 18 mm to 23 mm is the target for the granular pyrocarbon in the illustrated embodiment.

[0026] The pyrolysis of the raw material fraction agglomerates A is carried out in a pyrolysis reactor 2. Pyrolysis reactor 2 operates in a continuous flow, so that the raw material fraction agglomerates A are continuously fed into pyrolysis reactor 2 and removed from it once the desired degree of coalification has been reached. Pyrolysis reactor 2 has one or more screw conveyors 3, which convey the raw material fraction agglomerates A through it. Pyrolysis reactor 2 is connected to the outlet of shredder 1. A rotary valve 4 integrated into the agglomerate feed ensures that only a minimum of oxygen enters the interior of the pyrolysis reactor – its pyrolysis chamber – when the raw material fraction agglomerates are introduced. The thermal treatment of the raw material fraction agglomerates takes place in the pyrolysis reactor without oxygen, or at least with a significant oxygen deficit.The inlet opening for the feed of the raw material fraction agglomerates A is indicated by reference numeral 5 in the figure. The pyrolyzed raw material fraction agglomerates are extracted as pyrochar via an outlet opening 6 and fed to the intended further use. In the illustrated embodiment, where the pyrochar is used as a construction aggregate, it is packaged in bags after being extracted from the pyrolysis reactor 2 and, if necessary, temporarily stored.

[0027] Pyrolysis is carried out as an autothermal process. The pyrolysis reactor 2 is designed with two walls, with the pyrolysis chamber 7 being the cavity in which at least one screw conveyor 3 is located. The inner housing 8 enclosing the pyrolysis chamber 7 is itself enclosed by an outer housing 9, leaving a passage between the two housings 8 and 9 through which hot gas is passed to indirectly heat the pyrolysis chamber 7. A burner 10 is used to generate the heating gas required for heating the pyrolysis chamber 7. Once the pyrolysis reactor 2 has reached its operating temperature, the burner 10 is operated exclusively with pyrolysis gas discharged from the pyrolysis chamber 7 through an exhaust port 11. Even at relatively low temperatures, flammable pyrolysis gases escape from the plastic components of the raw material fraction.The heat generated by the operation of burner 10 during the combustion of the pyrolysis gases drawn from pyrolysis chamber 7 is sufficient, often significantly more than is required to heat pyrolysis chamber 7. Therefore, the operation of pyrolysis reactor 2 can be described as autothermal. Fuel gas is supplied via a fuel gas supply 12 solely for starting up pyrolysis reactor 2, until the pyrolysis gas flow drawn from pyrolysis chamber 7 via a pyrolysis gas line 13 is sufficient to operate burner 10. A cleaning device, for example a filter, can be integrated into the pyrolysis gas line 13 to clean the drawn-off pyrolysis gas. The hot exhaust gas from burner 10 is introduced via a heating line 14 into the jacket 15 surrounding the inner housing 8. The hot gas flow, along with the residual heat it contains, exits the jacket 15 via an outlet 16.The heat still contained within can be used for another purpose. For example, it can be transferred to another medium via a heat exchanger.

[0028] In the illustrated embodiment, the pyrolysis of the raw material fraction is carried out at a temperature of 600°C ± 10°C. Good conversion rates can be achieved at this temperature. Therefore, in the illustrated embodiment, the pyrolysis reactor 2, or rather its pyrolysis chamber 7, is maintained at a temperature of approximately 600°C. To ensure consistent quality of the pyrochar, the temperature in the pyrolysis chamber 7 is kept as constant as possible.

[0029] Given that the temperature required for pyrolysis is not excessively high, the burner 10 in the illustrated embodiment is a so-called flameless burner. It therefore operates according to the FLOX process. While the temperature achievable with this burner is lower than that produced by a flame burner, such high temperatures are not necessary for pyrolysis. Furthermore, with a flameless burner, nitrogen oxide emissions are reduced to an absolute minimum.

[0030] The granular pyrochar produced from municipal waste in the illustrated embodiment is used as a construction aggregate, particularly in cold asphalt mixtures or in concrete components or structures. This allows carbon to be stored and permanently removed from the cycle, which has a positive effect on the CO2 footprint of the structure.

[0031] The process described above has been presented with regard to its basic process steps. Of course, further steps, particularly for the operation of the pyrolysis reactor, may be included.

[0032] A special feature of this process is that granular pyrochar can be obtained from components found in municipal waste that are conventionally very difficult to recycle. Reference symbol list 1 shredder (cutting mill) 2 Pyrolysis reactor 3 auger 4 cell lock 5 Entrance opening 6 Exit opening 7 Pyrolysis chamber 8 cases 9 cases 10 burners 11 Pyrolysis gas opening 12 Fuel gas supply 13 Pyrolysis gas line 14 Heating cable 15 Sheath space 16 Exit A Agglomerate

Claims

[1] Process for the processing of PPK plastic composite material with the following steps: - Sorting of a primary material and providing a raw material fraction intended for further processing by pyrolysis, containing at least largely only PPC and plastic with a higher PPC content than the plastic content, - Crushing the raw material fraction and forming agglomerates (A), - Pyrolizing the agglomerates (A) to produce pyrocarbon (carbon black) as a pyrolysis product, wherein the pyrolysis gases generated during pyrolysis are withdrawn from the pyrolysis reactor (2) and burned to heat the pyrolysis reactor (2), wherein the pyrolysis gas discharged from the pyrolysis reactor (2) is burned flamelessly to heat the pyrolysis reactor (2) and the pyrolysis chamber (7) of the pyrolysis reactor (2) is indirectly heated with the heat obtained. [2] Method according to claim 1, characterized bythat the heating of the pyrolysis reactor (2) is controlled at least partly via the plastic content in the raw material fraction. [3] Method according to claim 1 or 2, characterized by that the step of providing the raw material fraction is carried out so that the raw material fraction contains a plastic content of less than 30%, in particular less than 20%. [4] Method according to claim 2 or 3, characterized by that the plastic content in the raw material fraction is adjusted by removing or adding plastic and / or PPK components from or to the sorted primary material. [5] Method according to one of claims 1 to 4, characterized by that the comminution of the raw material fraction is carried out in a shredder (1), in which comminution process a homogenization of the raw material fraction and agglomeration formation simultaneously take place. [6] Method according to claim 5, characterized bythat the crushing and agglomeration process is carried out in such a way that the average size of the agglomerates is 5 mm to 40 mm, in particular 15 mm to 25 mm. [7] Method according to one of claims 1 to 6, characterized by that the pyrolysis is carried out so that the pyrocoal as a pyrolysis product has a carbonisation degree (H / C ratio) of less than 0.3, in particular less than 0.

25. [8] Method according to one of claims 1 to 7, characterized by that the pyrolysis is carried out as medium-temperature pyrolysis at a temperature between 500 °C and 700 °C. [9] Method according to one of claims 1 to 8, characterized by that the residual or surplus heat not used to heat the pyrolysis reactor (2) is used for another purpose requiring heat. [10] Method according to one of claims 1 to 9, characterized bythat separately collected municipal waste with a proportion of used PPK plastic composite material is used as the primary material. [11] Method according to claim 10, characterized by that the PPK plastic composite material is sorted out from the municipal waste after initial processing. [12] Method according to claim 11, characterized by that the processing and sorting to obtain the primary material is carried out fully automatically. [13] Method according to one of claims 1 to 12, characterized by that the PPK plastic composite material from composite packaging is recycled. [14] Plant for producing pyrocarbon from PPK plastic composite material for carrying out the process according to one of claims 1 to 13, comprising: - a sorting plant for sorting out PPK plastic composite material primary material from separately collected municipal waste, - a shredder (1) for cutting and homogenising the raw material fraction, - an indirectly heated pyrolysis reactor (2) with a pyrolysis gas outlet, - a burner (10) operated with the pyrolysis gas generated during operation of the pyrolysis reactor (2), by means of which the pyrolysis reactor (2) is heated, wherein the burner (10) operated with the pyrolysis gas is a flameless burner, in particular a burner (10) operated according to the FLOX process, and - a heat sink downstream of the pyrolysis reactor (2) for utilising residual or surplus heat of the heating gas used to heat the pyrolysis reactor (2). [15] Plant according to claim 14, characterized by that the crusher is a shredder (1) by which the raw material fraction is crushed and formed into agglomerates (A).

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