Methods for thermally decomposing plastics

Abstract

The present invention relates to a method for pyrolysis of plastics, particularly waste plastics, comprising the steps of (a) pyrolysis of the plastic in a first pyrolysis reactor to obtain a first pyrolysis product, (b) separation of the pyrolysis residue from the first pyrolysis product in a first separation unit, (c) separation of the pyrolysis residue into a low-solid fraction and a high-solid fraction in a second separation unit, and (d) pyrolysis of the high-solid fraction in a second pyrolysis reactor to obtain a second pyrolysis product. The present invention further relates to a device for pyrolysis of plastics using the method.

Description

Technical Field

[0001] The present invention relates to a method and a device for the pyrolysis of plastics, particularly waste plastics.

Background Art

[0002] Methods for pyrolyzing starting materials, particularly plastics, are known in the prior art. Here, the focus is on the separation of the gaseous fraction from the pyrolysis products, but the residue of the pyrolysis products, particularly the high solid fraction, is typically used for energy purposes.

[0003] For example, EP1154007A1 discloses a method for the pyrolysis of waste plastics. In this case, the waste plastics are pyrolyzed in a first pyrolysis reactor at a first temperature, and a first pyrolysis product containing a first gaseous fraction and a first pyrolysis residue is obtained. The first pyrolysis residue is then pyrolyzed in a second pyrolysis reactor at a second temperature higher than the first temperature, and a second pyrolysis product containing a second gaseous fraction and a second pyrolysis residue is obtained. The second pyrolysis residue is subjected to a magnetic separation method to obtain inorganic fillers and scrap metal.

[0004] A further method for the pyrolysis of waste plastics is described in WO2016 / 116114A1. Such waste plastics are converted in a pyrolysis reactor into a pyrolysis product containing a gaseous fraction and a solid pyrolysis residue. Such pyrolysis residue is then separated in a separation unit, for example in a cyclone, into a low solid fraction and a high solid fraction. The low solid fraction is returned to the pyrolysis reactor for new pyrolysis. The high solid fraction is separated in a settling tank based on its density. The first part of the lower density high solid fraction is returned to the pyrolysis reactor together with the low solid fraction, but the second part of the higher density high solid fraction can be used as a high energy fuel.

[0005] Further methods for thermally decomposing the starting materials are known from WO2017 / 168163A1, US2022 / 340819A1, US2012 / 117860A1 and EP4151702A1. [Overview of the project]

[0006] It is certainly true that pyrolysis products can be recycled, at least partially, by some of these methods. However, there is a need for methods that reduce the CO2 footprint and make a greater contribution to the circular economy and sustainability. The objective of this invention is to recycle a larger portion of the pyrolysis residue compared to known methods.

[0007] The method according to the present invention for thermally decomposing plastics is (a) A step of obtaining a first pyrolysis product by pyrolyzing the plastic in a first pyrolysis reactor, (b) A step of separating the thermal decomposition residue from the first thermal decomposition product in the first separation unit, (c) A step of separating the pyrolysis residue into a low solid fraction and a high solid fraction in a second separation unit, and (d) A step of obtaining a second pyrolysis product by pyrolyzing the high-solid fraction in a second pyrolysis reactor. Includes.

[0008] The present invention relates to a device for thermally decomposing plastics, particularly waste plastics, using the method according to the present invention. A first pyrolysis reactor for thermally decomposing the aforementioned plastic, A first separation unit for separating the thermal decomposition residue from the first thermal decomposition product, A second separation unit for separating the pyrolysis residue into the low-solid fraction and the high-solid fraction, A second pyrolysis reactor for pyrolyzing the aforementioned high-solid fraction. The devices further include those mentioned above. [Brief explanation of the drawing]

[0009] [Figure 1]Figure 1 shows a flowchart of the method for thermal decomposition of plastics. [Modes for carrying out the invention]

[0010] By carrying out two pyrolysis steps in two different pyrolysis reactors and separating the pyrolysis residue into a low-solid fraction and a high-solid fraction between the two pyrolysis steps, the method and device enable particularly good processing and separation of the first or second pyrolysis product into its individual components, thereby achieving a high degree of recyclability. The method thus can save the environment by reducing greenhouse gas emissions and waste volume. Overall, this also brings economic benefits by significantly reducing resource consumption and strengthening the circular economy.

[0011] The plastic preferably comprises polyolefin and / or polystyrene (PS), and the polyolefin may also comprise polyethylene (PE) and / or polypropylene (PP). The plastic contains the polyolefin and / or polystyrene in an amount of preferably 65% ​​by weight or more, more preferably 70% by weight or more, and particularly 90% by weight or more, based on the total weight of the plastic. As a result, a pyrolysis residue containing a significant proportion of aliphatic hydrocarbons (or a mixture of multiple aliphatic hydrocarbons) can be obtained.

[0012] The plastic preferably contains 20% by weight or more, more preferably 50% by weight or more, even more preferably 70% by weight or more, and particularly 90% by weight or more of the polyolefin, based on the total weight of the plastic. As the proportion of polyolefin increases, the amount of wax obtained by the method according to the present invention may increase, and the cost-effectiveness of the method can be improved. The plastic may contain thermoplastics, duromers and / or elastomers, in particular further polymers from the group consisting of acrylonitrile-butadiene-styrene copolymer (ABS), polyvinyl chloride (PVC), polyamide (PA), and / or polyester.

[0013] Prior to step (a) of the method described above, the plastic may be plasticized, for example, in a mixer, particularly in an extruder. For plasticization, the plastic is preferably heated to a temperature of 120°C or higher, more preferably 200-500°C, and even more preferably 400-470°C. Subsequent thermal decomposition can then be carried out more energy-efficiently and in a shorter time.

[0014] In the extruder, the plastic can also be degassed to produce a gas-free, homogeneous mass, which in turn can be obtained by subsequent thermal decomposition as a homogeneous pyrolysis product.

[0015] Prior to step (a) of the method described above, a viscosity-reducing diluent may be added to the plastic, particularly the plasticized plastic. For this purpose, the device may have an introduction device configured to add the viscosity-reducing diluent to the plastic before the pyrolysis in the first pyrolysis reactor. The diluent is added to the plastic in an amount of preferably 5% by weight or more, more preferably 9% by weight or more, based on the total weight of the plastic. The ratio of plastic to diluent is preferably 1:4 or more, more preferably 1:9 or more. By adding the diluent to the plastic, the mobility of the polymer chains can be increased at a given temperature, and as a result, the heat injection into the plastic can be improved during pyrolysis. Furthermore, the risk of the plastic overheating in the wall region of the pyrolysis reactor can be reduced due to the viscosity reduction, because such plastic is usually heated by a heating device located near the outer wall of the pyrolysis reactor. The risk of the plastic caulking during pyrolysis can also be reduced by reducing the viscosity.

[0016] By adding the diluent to the plastic, its viscosity can be reduced by preferably 30% or more, more preferably 50% or more, and especially preferably 80% or more, based on the viscosity of the plastic without the diluent, under the same measurement conditions, particularly at temperatures in the range of 180 to 240°C. This can improve the pumping capacity of the plastic, thereby facilitating its processing.

[0017] When the diluent is added, the plastic is preferably at a temperature of 120°C or higher, more preferably 150-300°C, and particularly 200-300°C. Alternatively or additionally, the diluent may be heated to a temperature of preferably 120°C or higher, more preferably 150°C or higher, and particularly 200-300°C, before being added to the plastic. By increasing the temperature of the plastic and / or the diluent, the diluent can be mixed with the plastic more quickly and efficiently. Subsequent thermal decomposition can also be carried out more energy-efficiently and faster.

[0018] The diluent may be added to the plastic using a supply device. The supply device may have a metering device such as a metering pump. For example, the plastic, in particular the plasticized plastic, may be supplied to a mixer, such as a static mixer, where it may be mixed with the diluent. When the plastic is plasticized in an extruder, the diluent may be added directly to the extruder. For this purpose, the supply device may be located in, for example, the compression zone or mixing zone of the extruder.

[0019] The diluent may contain hydrocarbons selected from alkanes, cycloalkanes, and / or aromatics. As a result of the pyrolysis, such diluent may be converted into gaseous and / or liquid products and can be at least partially separated from the pyrolysis residue and reused. In particular, the diluent may contain a fraction obtained from crude oil, preferably heavy fuel oil. The heavy fuel oil may be oil obtained from petroleum in petroleum refining, for example, residue from a pyrolysis system. The heavy fuel oil preferably contains aromatic hydrocarbons in a proportion of 25% by weight or more based on the total weight of the heavy fuel oil.

[0020] Alternatively or additionally, the diluent may comprise a portion of the liquid fraction and / or a portion of the low solids fraction of the first pyrolysis product. This may enable reuse of the liquid fraction and the low solids fraction. The diluent preferably consists of at least a portion of the liquid fraction and / or at least a portion of the low solids fraction of the first pyrolysis product. And a high degree of recycling can be achieved.

[0021] The diluent preferably has a boiling point (or the lower end of the boiling range) of 300 °C or higher, particularly 350 °C or higher. As a result, evaporation of the diluent can be prevented immediately after the mixture of plastic and diluent is introduced into the pyrolysis reactor, but evaporation, cracking and / or depolymerization of the diluent can only occur by the progress of the residence time of the mixture in the pyrolysis reactor and the associated heating of the mixture. As a result, a homogeneous pyrolysis product can be obtained.

[0022] In step (a) of the method, the plastic is pyrolyzed in a first pyrolysis reactor. The first pyrolysis reactor may be a screw reactor, a fluidized bed reactor, a rotary tube reactor, or a coker, preferably a coker.

[0023] In step (a) of the method, the temperature in the first pyrolysis reactor is preferably in the range of 300 - 800 °C, more preferably 350 - 700 °C. The pressure in the first pyrolysis reactor in step (a) is preferably in the range of 1 - 30 bar, more preferably 5 - 30 bar, even more preferably 10 - 25 bar. Further, the pyrolysis is preferably carried out in step (a) over a period of 0.3 minutes, more preferably over a period of 1 - 10 minutes, particularly over a period of 1.5 - 5 minutes. As a result, a good balance between cost effectiveness and method efficiency can be achieved.

[0024] The thermal decomposition in step (a) may be thermal decomposition (i.e., thermal cracking without catalyst addition) and / or catalytic decomposition (i.e., catalytic cracking). Thermal decomposition is preferred in order to avoid contamination of either wax or solids caused by the catalyst component.

[0025] The thermal decomposition in step (a) can be carried out in the absence of oxygen, particularly in an inert atmosphere, for example, under nitrogen. The absence or removal of oxygen can prevent complete combustion, and the polymer contained in the plastic may be cleaved or depolymerized.

[0026] The first pyrolysis product includes a pyrolysis residue. Furthermore, the first pyrolysis product includes a liquid fraction and / or a gaseous fraction. In step (b) of the method, the pyrolysis residue is separated from the first pyrolysis product in a first separation unit. The separation can be carried out by evaporation and / or centrifugation (i.e., centrifugation), preferably by centrifugation. Therefore, the first separation unit may include an evaporator, a cyclone, and / or a hydrocyclone, and in particular includes a hydrocyclone.

[0027] The temperature in the first separation unit in step (b) is preferably in the range of 300 to 700°C, more preferably in the range of 330 to 420°C. The pressure in the first separation unit in step (b) is preferably in the range of 1 to 15 bar, more preferably in the range of 2 to 8 bar. Efficient and good separation of the pyrolysis residue can be achieved by these method parameters.

[0028] The first separation unit preferably includes a hydrocyclone, which allows the gaseous fraction, the liquid fraction, and the pyrolysis residue to be separated from each other in a single method step. Such a hydrocyclone is described in application WO2023 / 036751A1. By introducing the first pyrolysis product through an inlet located in the upper region of the hydrocyclone shell, a vortex flow may be generated in the hydrocyclone, as a result of which the gaseous fraction can be separated from the first pyrolysis product and discharged through an outlet located in the upper region of the hydrocyclone (e.g., on the ceiling). The residue of the first pyrolysis product can then be discharged by gravity toward the bottom of the hydrocyclone, where the tangential velocity of the vortex flow being formed can increase continuously. As a result, at least a portion of the pyrolysis residue can be discharged through an outlet located at the bottom of the hydrocyclone, while at least a portion of the liquid fraction of the first pyrolysis product can pass through an internal container located in the hydrocyclone and discharge from there through an outlet. This portion of the liquid fraction can then be used as a diluent for reducing the viscosity of the plastic before step (a) of the method. The pyrolysis residue discharged through the outlet located at the bottom of the hydrocyclone can then be used in step (c) of the method. The hydrocyclone is operated at a temperature preferably in the range of 300 to 450°C, more preferably 320 to 420°C, and particularly preferably 360 to 400°C.

[0029] The pyrolysis residue separated in step (b) of the above method preferably has a boiling point (or lower end of the boiling point range) of 250°C or higher, more preferably 300°C or higher, even more preferably 330°C or higher, and particularly preferably 350°C or higher. The boiling point (or boiling point range) of the pyrolysis residue can be determined by ASTM standard D7500-15:2019 (preferably when the pyrolysis residue has a boiling point or boiling point range of 100 to 850°C, particularly 100 to 735°C) or by ASTM standard D2887-22:2022 (preferably when the pyrolysis residue has a boiling point or boiling point range of 55 to 538°C).

[0030] The pyrolysis residue separated in step (b) of the above method preferably contains carbon atoms having 14 or more carbon atoms per molecule, more preferably 16 or more carbon atoms per molecule, and particularly preferably 18 or more carbon atoms per molecule. The pyrolysis residue can then be well separated in the following step (c) of the above method.

[0031] In step (c) of the above method, the pyrolysis residue is separated into a low solid fraction and a high solid fraction in a second separation unit. The low solid fraction preferably has a liquid content of more than 70% by weight, more preferably more than 80% by weight, more preferably more than 85% by weight, more preferably more than 90% by weight, more preferably more than 95% by weight, more preferably more than 98% by weight, and more preferably more than 99% by weight. The low solid fraction preferably has a liquid content in the range of 80 to 100% by weight, more preferably 90 to 99.9% by weight, based on the total weight of the low solid fraction. The low solid fraction preferably has a liquid content of 0.600 to 1.100 g / cm³ at 20°C and 101325 Pa. 3 More preferably 0.750 to 0.990 g / cm³ 3 It has a density within the range.

[0032] The high-solids fraction preferably has a liquid content of less than 95% by weight, more preferably less than 90% by weight, more preferably less than 85% by weight, more preferably less than 80% by weight, more preferably less than 75% by weight, and more preferably less than 70% by weight. The high-solids fraction preferably has a liquid content in the range of 50 to 95% by weight, more preferably 70 to 90% by weight, based on the total weight of the high-solids fraction. The high-solids fraction preferably has a liquid content of 0.650 to 1.300 g / cm³ at 20°C and 101325 Pa. 3 , more preferably 0.800 to 1.150 g / cm³ 3 It has a density within the range of [value]. Preferably, the high-solid fraction has a lower liquid proportion than the low-solid fraction. Preferably, the high-solid fraction has a higher density than the low-solid fraction at 20°C and 101325 Pa.

[0033] The separation in the second separation unit may include, and preferably includes, separation by gravity, filtration, and / or centrifugation. Gravimetric separation may include sedimentation and / or decantation. Therefore, the second separation unit may include a gravity separation device, a filter, a centrifuge, and / or a hydrocyclone, and preferably a hydrocyclone. The gravity separation device may include a sedimentation system and / or a decanter. When the second separation unit includes a hydrocyclone, it may be constructed and operated in the same or similar manner as the hydrocyclone of the first separation unit, as described above.

[0034] Preferably, the separation in the second separation unit in step (c) includes separation by centrifugal force in combination with filtration or gravity separation. The separation by centrifugal force may be performed before the filtration or gravity separation. Thus, the second separation unit may include the hydrocyclone in combination with the filter or gravity separation device. The hydrocyclone may be located upstream of the filter or gravity separation device. In this way, sharp separation into the low-solids fraction and the high-solids fraction can be achieved.

[0035] The temperature in the second separation unit in step (c) is preferably in the range of 100 to 700°C, more preferably 100 to 350°C, and even more preferably 100 to 200°C. During gravity separation or filtration, the temperature is preferably in the range of 180 to 700°C. During centrifugation, the temperature is preferably 200°C or less, more preferably in the range of 100 to 180°C. During separation by centrifugation, the temperature is preferably in the range of 200 to 700°C. When the temperature is selected as shown according to the method, separation into low-solids and high-solids can be efficiently performed.

[0036] In step (d) of the above method, the high-solid fraction is thermally decomposed in a second thermal decomposition reactor to obtain a second thermal decomposition product. The second thermal decomposition reactor may be a screw reactor, a fluidized bed reactor, a rotary tube reactor, or a coker, and is preferably a coker. The temperature in the second thermal decomposition reactor is preferably in the range of 400 to 800°C, more preferably in the range of 500 to 700°C. This efficiently thermally decomposes the high-solid fraction.

[0037] The temperature during pyrolysis in the second pyrolysis reactor in step (d) may be higher than the temperature during pyrolysis in the first pyrolysis reactor in step (a). The temperature in the second pyrolysis reactor is preferably 50°C or higher, more preferably 80°C or higher, even more preferably 100°C or higher, even more preferably 150°C or higher, and particularly 200°C or higher, than the temperature in the first pyrolysis reactor.

[0038] The pressure in the second pyrolysis reactor is preferably in the range of 1 to 20 bar, more preferably 2 to 12 bar, and particularly in the range of 2 to 8 bar. In the second pyrolysis reactor, pyrolysis is preferably carried out for a period of 1 to 90 minutes, particularly 1.5 to 5 minutes. As a result, a good balance between cost-effectiveness and method efficiency can be achieved.

[0039] The ratio of the volumes of the first pyrolysis reactor and the second pyrolysis reactor is at most 10:3, more preferably at most 10:2, and more preferably in the range of 10:0.2 to 10:2, in particular 10:1 to 10:2. The said volume is understood to be the maximum possible packing level of each of the said pyrolysis reactors.

[0040] The second thermal decomposition product may include a solid, a gas, and / or a liquid.

[0041] The amount of gas is preferably 10% by weight or more, more preferably 20% by weight or more, and even more preferably 40% by weight or more, based on the total weight of the second pyrolysis product. The gas contains carbon in a proportion of preferably 5% by weight or more, more preferably 15% by weight or more, even more preferably 20% by weight or more, and particularly 40% by weight or more, based on the total weight of the gas. The carbon in the gas preferably includes methane, ethane, ethene, propane, propene, butane, butene, butadiene, or a mixture of these components. These components of the gas can be separated from each other, for example, by fractional distillation, for further use, for example, to supply them to other systems of a smelter.

[0042] The liquid preferably contains oil, which may include light oil and heavy oil. The light oil may contain 3 to 14 carbon atoms per molecule, and the heavy oil may contain 11 to 50 carbon atoms per molecule. The separation of the individual components of the oil from each other, in particular the separation of the individual components of the carbon atoms from each other, can be carried out, for example, by fractional distillation, enabling further subsequent use, for example, as fuel. The separation of the gas and the liquid from each other and the separation of the gas and / or the liquid into individual components can be carried out in the same distillation apparatus.

[0043] The amount of the solid is preferably 70% by weight or less, more preferably 55% by weight or less, and even more preferably 30% by weight or less, based on the total weight of the second pyrolysis product. The solid may contain inorganic salts, ceramic raw materials, asphaltenes, tar, and / or coke. In particular, the solid may contain talc, iron oxide (e.g., ferric oxide), aluminum oxide, titanium dioxide, magnesium oxide, and / or calcium carbonate. When the imparted pyrolysis residue is obtained by pyrolysis of a plastic, the solid may contain additives contained in the plastic. For example, the additives may include fillers, coloring pigments, and / or other additives. Experts know which additives are used depending on the respective plastic and application field.

[0044] The method may further include step (e): separating at least a portion of the solid from the second pyrolysis product. For this purpose, the device may have a solid-to-separation device.

[0045] The separation of the solid from the second pyrolysis product may include separation by gravity, filtration, and / or centrifugation, preferably by filtration. Gravity separation may include sedimentation and / or decantation. When the separation includes filtration, it may be carried out by a filter medium which may contain activated carbon or bleached earth. As a result, any polar components (e.g., tar or polyphenols) dissolved in the solvent together with the wax can be separated and adsorbed by the filter medium. During filtration, particles with an average particle size (D50) of less than 100 μm, and especially less than 50 μm, can also be easily removed (determined by laser diffraction).

[0046] The separation of the solid from the second pyrolysis product may be carried out directly in the second pyrolysis reactor. For these purposes, the second pyrolysis reactor is preferably a screw reactor. The solid may be discharged directly from the extruder using a discharge device.

[0047] The solid, after being separated from the second pyrolysis product, i.e., after step (e) of the method, can be dried, for example, in an oven. As a result, the solid may become free-flowing and therefore easier to process. The solid is dried at a temperature preferably in the range of 50 to 250°C, more preferably 100 to 200°C, and even more preferably 130 to 160°C. The drying time is preferably 120 minutes or less, particularly 5 to 60 minutes. One or more components can be separated from the solid, particularly from the dried solid, and then reused, for example, as an additive for plastics.

[0048] The present invention relates in particular to the following embodiments: 1. A method for thermally decomposing plastics, particularly waste plastics, (a) A step of obtaining a first pyrolysis product by pyrolyzing the plastic in a first pyrolysis reactor, (b) A step of separating the thermal decomposition residue from the first thermal decomposition product in the first separation unit, (c) A step of separating the pyrolysis residue into a low solid fraction and a high solid fraction in a second separation unit, and (d) The method comprising the step of thermally decomposing the high-solid fraction in a second thermal decomposition reactor to obtain a second thermal decomposition product.

[0049] 2. The method according to Embodiment 1, wherein the plastic comprises polyolefin and / or polystyrene (PS), and the polyolefin preferably comprises polyethylene (PE) and / or polypropylene (PP).

[0050] 3. The method according to Embodiment 2, wherein the plastic contains the polyolefin and / or polystyrene in an amount of 65% by weight or more, more preferably 70% by weight or more, and particularly 90% by weight or more, based on the total weight of the plastic.

[0051] 4. The method according to Embodiment 2 or Embodiment 3, wherein the plastic contains 20% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, and particularly 90% by weight or more, of polyolefin based on the total weight of the plastic.

[0052] 5. The method according to any one of the above embodiments, wherein the plastic is heated to a temperature of 120°C or higher, preferably 200-500°C, more preferably 400-470°C, before step (a).

[0053] 6. The method according to any one of the above embodiments, wherein the viscosity-reducing diluent is added to the plastic before step (a).

[0054] 7. The method according to Embodiment 6, wherein the diluent is added to the plastic in an amount of 5% by weight or more, more preferably 9% by weight or more, based on the total weight of the plastic.

[0055] 8. The method according to Embodiment 6 or Embodiment 7, wherein the ratio of plastic to diluent is 1:4 or higher, preferably 1:9 or higher.

[0056] 9. The method according to any one of Embodiments 6 to 8, wherein the diluent comprises a hydrocarbon selected from alkanes, cycloalkanes, and / or aromatics.

[0057] 10. The method according to any one of Embodiments 6 to 9, wherein the diluent includes crude oil, preferably heavy oil, and in particular a fraction obtained from heavy oil having an aromatic hydrocarbon content of 25% by weight or more based on the total weight of the heavy oil.

[0058] 11. The method according to any one of Embodiments 6 to 10, wherein the diluent comprises the liquid fraction portion and / or the low solid fraction portion of the first thermal decomposition product.

[0059] 12. The method according to any one of Embodiments 6 to 11, wherein the diluent has a boiling point of 300°C or higher, preferably 350°C or higher.

[0060] 13. The method according to any one of Embodiments 6 to 12, wherein the diluent and / or the plastic is heated to a temperature of 120°C or higher, preferably 150°C or higher, preferably in the range of 150 to 300°C, more preferably 200 to 300°C, before the diluent is added to the plastic.

[0061] 14. The method according to any one of the above embodiments, wherein the temperature in the first pyrolysis reactor in step (a) is in the range of 300 to 800°C, preferably 350 to 700°C.

[0062] 15. The method according to any one of the above embodiments, wherein the pressure in the first pyrolysis reactor in step (a) is in the range of 1 to 30 bar, preferably 5 to 30 bar, and more preferably 10 to 25 bar.

[0063] 16. The method according to any one of the above embodiments, wherein the thermal decomposition is carried out in step (a) over a period of 0.3 minutes or more, preferably 1 to 10 minutes, and particularly over a period of 1.5 to 5 minutes.

[0064] 17. The method according to any one of the above embodiments, wherein the separation in the first separation unit in step (b) includes separation by evaporation and / or centrifugation, preferably by centrifugation.

[0065] 18. The method according to any one of the above embodiments, wherein the temperature in the first separation unit in step (b) is in the range of 300 to 700°C, preferably 330 to 420°C.

[0066] 19. The method according to any one of the above embodiments, wherein the pressure in the first separation unit in step (b) is in the range of 1 to 15 bar, preferably 2 to 8 bar.

[0067] 20. The method according to any one of the above embodiments, wherein the pyrolysis residue separated in step (b) has a boiling point of 250°C or higher, preferably 300°C or higher, more preferably 330°C or higher, and most preferably 350°C or higher.

[0068] 21. The method according to any one of the above embodiments, wherein the pyrolysis residue separated in step (b) contains carbon atoms having 14 or more carbon atoms per molecule, preferably 16 or more carbon atoms per molecule, more preferably 18 or more carbon atoms per molecule.

[0069] 22. The method according to any one of the above embodiments, wherein the low solid fraction has a liquid content of more than 70% by weight, preferably more than 80% by weight, more preferably more than 85% by weight, more preferably more than 90% by weight, more preferably more than 95% by weight, more preferably more than 98% by weight, and more preferably more than 99% by weight.

[0070] 23. The method according to any one of the above embodiments, wherein the high-solid fraction has a liquid content of less than 95% by weight, preferably less than 90% by weight, more preferably less than 85% by weight, more preferably less than 80% by weight, more preferably less than 75% by weight, and more preferably less than 70% by weight.

[0071] 24. The method according to any one of the above embodiments, wherein the low solid fraction has a liquid content in the range of 80 to 100% by weight, preferably 90 to 99.9% by weight, based on the total weight of the low solid fraction, and / or the high solid fraction has a liquid content in the range of 50 to 95% by weight, preferably 70 to 90% by weight, based on the total weight of the high solid fraction.

[0072] 25. The low-solid fraction has a concentration of 0.600 to 1.100 g / cm³ at 20°C and 101325 Pa, based on the total weight of the low-solid fraction. 3 Preferably 0.750~0.990 g / cm³ 3 Having a density within the range of and / or the high-solid fraction having a density of 0.650 to 1.300 g / cm³ at 20°C and 101325 Pa based on the total weight of the high-solid fraction. 3 Preferably 0.800 to 1.150 g / cm³ 3 The method according to any one of the above embodiments, having a density within the range of .

[0073] 26. The method according to any one of the above embodiments, wherein the temperature in the second separation unit in step (c) is in the range of 100 to 700°C, preferably 100 to 350°C, and more preferably 100 to 200°C.

[0074] 27. The method according to any one of the above embodiments, wherein the separation in the second separation unit in step (c) includes separation by gravity, filtration, and / or separation by centrifugation, preferably including separation by centrifugation.

[0075] 28. The method according to Embodiment 27, wherein the separation in the second separation unit in step (c) includes separation by centrifugal separation in combination with filtration or gravity separation.

[0076] 29. The method according to Embodiment 27, wherein the separation by centrifugation occurs before filtration or before gravity separation.

[0077] 30. The method according to any one of Embodiments 27 to 29, wherein the temperature during gravity separation or filtration is in the range of 180 to 700°C, the temperature during centrifugal separation is 200°C or less, more preferably in the range of 100 to 180°C, and / or the temperature during separation by centrifugal separation is in the range of 200 to 700°C.

[0078] 31. The method according to any one of the above embodiments, wherein the temperature in the second pyrolysis reactor in step (d) is in the range of 400 to 800°C, preferably in the range of 500 to 700°C.

[0079] 32. The method according to any one of the above embodiments, wherein the temperature during thermal decomposition in the second thermal decomposition reactor in step (d) is higher than the temperature during thermal decomposition in the first thermal decomposition reactor in step (a).

[0080] 33. The method according to Embodiment 32, wherein the temperature in the second pyrolysis reactor is 50°C or more, preferably 80°C or more, more preferably 100°C or more, even more preferably 150°C or more, and particularly 200°C or more, higher than the temperature in the first pyrolysis reactor.

[0081] 34. The method according to any one of the above embodiments, wherein the pressure in the second pyrolysis reactor in step (d) is in the range of 1 to 20 bar, preferably 2 to 12 bar, and more preferably 2 to 8 bar.

[0082] 35. The method according to any one of the above embodiments, wherein thermal decomposition is carried out in step (d) over a period of 1 to 90 minutes, preferably 1.5 to 5 minutes.

[0083] 36. The method according to any one of the above embodiments, wherein the ratio of the volumes of the first pyrolysis reactor and the second pyrolysis reactor is 10:3 or less, preferably in the range of 10:0.2 to 10:2, and more preferably in the range of 10:1 to 10:2.

[0084] 37. The method according to any one of the above embodiments, wherein the second thermal decomposition product comprises a solid, a gas, and / or a liquid.

[0085] 38. The method according to Embodiment 37, wherein the amount of the gas is 10% by weight or more, preferably 20% by weight or more, and more preferably 40% by weight or more, based on the total weight of the second thermal decomposition product.

[0086] 39. The method according to Embodiment 37 or Embodiment 38, wherein the gas contains 5% by weight or more, preferably 15% by weight or more, more preferably 20% by weight or more, and in particular 40% by weight or more, of carbon based on the total weight of the gas.

[0087] 40. The method according to Embodiment 39, wherein the carbon content preferably comprises methane, ethane, ethene, propane, propene, butane, butene, butadiene, or a mixture thereof.

[0088] 41. The method according to any one of Embodiments 37 to 40, wherein the liquid contains oil, preferably the oil contains light oil and heavy oil.

[0089] 42. The method according to Embodiment 41, wherein the diesel fuel preferably contains 3 to 14 carbon atoms per molecule, and / or the heavy fuel oil preferably contains 11 to 50 carbon atoms per molecule.

[0090] 43. The method according to any one of Embodiments 37 to 42, wherein the amount of the solid is 70% by weight or less, preferably 55% by weight or less, and more preferably 30% by weight or less, based on the total weight of the second pyrolysis product.

[0091] 44. The method according to any one of Embodiments 37 to 43, wherein the solid comprises an inorganic salt, a ceramic raw material, asphaltene, tar, and / or coke.

[0092] 45. Step (e): The method according to any one of Embodiments 37 to 44, further comprising separating at least a portion of the solid from the second pyrolysis product.

[0093] 46. ​​The method according to Embodiment 45, wherein the separation in step (e) includes separation by gravity, filtration, and / or centrifugation, preferably including filtration.

[0094] 47. The method according to Embodiment 46, wherein the filtration includes separation using a filter medium containing activated carbon or bleached earth.

[0095] 48. The method according to any one of Embodiments 45 to 47, wherein the solid is dried after step (e) at a temperature preferably in the range of 50 to 250°C, more preferably 100 to 200°C, in particular 130 to 160°C, and / or for a period of 120 minutes or less, preferably 5 to 60 minutes.

[0096] 49. The method according to any one of Embodiments 37 to 48, wherein the gas and / or liquid are separated from each other by fractional distillation.

[0097] 50. The method according to Embodiment 49, wherein the gas and / or liquid are separated into individual components by fractional distillation.

[0098] 51. A device for the thermal decomposition of plastics, particularly waste plastics, according to the method of one of Embodiments 1 to 50, A first pyrolysis reactor for thermally decomposing the aforementioned plastic, A first separation unit for separating the thermal decomposition residue from the first thermal decomposition product, A second separation unit for separating the pyrolysis residue into the low-solid fraction and the high-solid fraction, A second pyrolysis reactor for pyrolyzing the aforementioned high-solid fraction. The device, including the device.

[0099] 52. The device according to Embodiment 50, further comprising a supply device for adding a diluent to the plastic before thermal decomposition in the first thermal decomposition reactor.

[0100] 53. The device according to Embodiment 50 or Embodiment 52, wherein the first pyrolysis reactor and / or the second pyrolysis reactor is a screw reactor, a fluidized bed reactor, a rotary tube reactor, or a coker, preferably a coker.

[0101] 54. The device according to any one of embodiments 51 to 53, wherein the first separation unit includes an evaporator, a cyclone, and / or a hydrocyclone, in particular a hydrocyclone.

[0102] 55. The device according to any one of Embodiments 51 to 54, wherein the second separation unit includes a gravity separation device, a filter, a centrifuge, and / or a hydrocyclone, preferably including a hydrocyclone.

[0103] 56. The device according to Embodiment 55, wherein the second separation unit includes the hydrocyclone in combination with the filter or the gravity separation device, and the hydrocyclone is preferably located upstream of the filter or the gravity separation device.

[0104] 57. The device according to any one of embodiments 51 to 56, further comprising a solid-separation device for separating at least a portion of the solid from the second pyrolysis product.

[0105] 58. The device according to any one of embodiments 51 to 57, further comprising a distillation apparatus for separating gas and / or liquid from the second pyrolysis product.

[0106] The present invention will be described in more detail below with reference to the illustrations of several embodiments, but the present invention is not limited thereto.

[0107] Figure 1 shows a flowchart of the method for thermal decomposition of plastics.

[0108] As can be seen from Figure 1, a plastic containing 50% or more by weight of polyolefin is supplied to an extruder 1, where it is plasticized and degassed. The plasticized plastic, having a temperature of 120°C or higher, is then added to a static mixer 2. In the static mixer 2, a diluent 3 may be added to the plasticized plastic to reduce its viscosity. Alternatively, or in addition to the diluent 3, a portion of the liquid fraction 4 separated from the first pyrolysis product 6 may be mixed with the plasticized plastic to reduce its viscosity. The resulting mixture is then supplied to a pyrolysis reactor 5, where the plastic is pyrolyzed at a temperature of 350-700°C. As a result, a first pyrolysis product 6 is obtained, comprising a gaseous fraction, a liquid fraction, and a pyrolysis residue. The first pyrolysis product 6 is supplied to a first separation unit 7, which includes a hydrocyclone and is connected downstream of the first pyrolysis reactor 5. First, the gaseous fraction is at least partially separated in the hydrocyclone. The separated portion of the gaseous fraction 8 can then be further separated into light oil (e.g., having a boiling point range of 35 to 225°C) and heavy oil (e.g., having a boiling point range of 225 to 410°C) (not shown). Furthermore, the liquid fraction is at least partially separated in the hydrocyclone. The separated portion of the liquid fraction 4 can be discharged through the outlet 9 of the hydrocyclone and reused in the method for reducing the viscosity of the plastic as described above. At least a portion of the pyrolysis residue, at least partially including the pyrolysis residue, is discharged through the outlet 10 located at the bottom of the hydrocyclone.

[0109] As can be further seen in Figure 1, the pyrolysis residue discharged from the outlet 10 is supplied to a second separation unit 11 having a hydrocyclone 12 and a filter 13, where the residue is separated into a low solid fraction 14 and a high solid fraction 15. The low solid fraction has a liquid content in the range of 80 to 100% by weight based on the total weight of the low solid fraction, and / or the high solid fraction has a liquid content in the range of 50 to 95% by weight based on the total weight of the high solid fraction. The low solid fraction 14 may be reused in the method by adding the plasticized plastic to at least a portion of the low solid fraction 14 in the mixer 2 for viscosity reduction. The high-solid fraction 15 is then pyrolyzed in a second pyrolysis reactor 16 at a temperature in the range of 500 to 700°C, the temperature in the second pyrolysis reactor 16 being at least 80°C higher than that of the first pyrolysis reactor 5 in order to obtain the second pyrolysis product 17. At least a portion of the solid is separated from the second pyrolysis product 17 by a solid-separation device 18 having a filter. In this case, the filter medium of the filter contains activated carbon. The separated portion of the solid 19 is dried in an oven 20 at a temperature of 100 to 200°C. Subsequently, individual components can be separated from the solid and reused (not shown). The remainder of the second pyrolysis product can be separated into gas 22 and liquid 23 in a distillation apparatus 21 by fractional distillation, or it can also be separated into one or more gaseous components and / or one or more liquid components.

Claims

1. A method for thermally decomposing plastics, especially waste plastics, (a) A step of obtaining a first pyrolysis product by pyrolyzing the plastic in a first pyrolysis reactor, (b) A step of separating the pyrolysis residue from the first pyrolysis product in the first separation unit, (c) A step of separating the pyrolysis residue into a low solid fraction and a high solid fraction in a second separation unit, and (d) A step of obtaining a second pyrolysis product by pyrolyzing the high-solid fraction in a second pyrolysis reactor. The method, including the method described above.

2. The method according to claim 1, wherein the pyrolysis residue separated in step (b) has a boiling point of 250°C or higher.

3. The method according to claim 1 or claim 2, wherein the low solid fraction has a liquid content in the range of 80 to 100% by weight based on the total weight of the low solid fraction, and / or the high solid fraction has a liquid content in the range of 50 to 95% by weight based on the total weight of the high solid fraction.

4. The method according to any one of claims 1 to 3, wherein the separation in the second separation unit in step (c) includes separation by centrifugal separation.

5. The method according to claim 4, wherein the separation in the second separation unit in step (c) includes separation by centrifugal separation in combination with filtration or gravity separation.

6. The method according to any one of claims 1 to 5, wherein the ratio of the volumes of the first pyrolysis reactor and the second pyrolysis reactor is 10:3 or less.

7. The method according to any one of claims 1 to 6, wherein the second thermal decomposition product includes a solid, a gas, and / or a liquid.

8. The method according to claim 7, wherein the gas contains carbon in a proportion of 20% by weight or more based on the total weight of the gas.

9. The method according to claim 7 or claim 8, wherein the amount of the solid is 70% by weight or less based on the total weight of the second thermal decomposition product.

10. Step (e): The method according to any one of claims 1 to 9, further comprising separating at least a portion of the solid from the second thermal decomposition product.

11. The method according to claim 10, wherein the separation in step (e) includes filtration, preferably filtration using a filter medium containing activated carbon or bleached earth.

12. A device for thermally decomposing plastics, particularly waste plastics, by the method described in any one of claims 1 to 11, A first pyrolysis reactor (5) for thermally decomposing the aforementioned plastic, A first separation unit (7) that separates the pyrolysis residue from the first pyrolysis product, A second separation unit (11) separates the pyrolysis residue into the low-solid fraction and the high-solid fraction, and A second pyrolysis reactor (16) for pyrolyzing the aforementioned high-solid fraction. The device, including the device.

13. The device according to claim 12, wherein the second separation unit (11) includes a hydrocyclone (12).

14. The device according to claim 13, wherein the second separation unit (11) includes the hydrocyclone (12) in combination with a filter (13) or a gravity separation device.

15. The device according to any one of claims 12 to 14, further comprising a solid-separation device (18) for separating at least a portion of the solid from the second pyrolysis product.

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