Method for depolymerizing a polymer into one or more monomers

Abstract

A method for depolymerizing a polymer into one or more monomers. A fluidized reactor system is provided that includes a pyrolysis chamber (2), a combustion chamber (12), and a bed material that circulates from the combustion chamber (12) to the pyrolysis chamber (2) via a transport zone (30). A feedstock containing 60% or more polymer based on the weight of the feedstock is introduced into the pyrolysis chamber (2), and a pyrolysis process is carried out at a temperature within the range of 450 to 650 °C in the bed material to obtain a depolymerized polymer product gas containing monomers. By circulating the bed material, sufficient heat for carrying out the pyrolysis process can be transferred from the combustion chamber (12) to the pyrolysis chamber (2).

Description

Technical Field

[0001] The present invention relates to an improved method for depolymerizing a polymer into one or more monomers. More particularly, this improved method is for increasing the yield of one or more monomers by reducing side reactions and reducing the amount of contaminants present in the depolymerized polymer product gas.

Background Art

[0002] International Publication No. WO 2008 / 108644 pamphlet and International Publication No. WO 2014 / 070001 pamphlet disclose an apparatus for generating product gas from biomass. The fuel (e.g., biomass) supplied to the riser in the reactor typically contains 80 wt% volatile components and 20 wt% substantially solid carbon or char. When the biomass supplied to the riser is heated in a low oxygen or oxygen-free environment to a temperature above 800 °C, for example, a temperature between 850 and 900 °C, the biomass is pyrolyzed and product gas is generated. The solid carbon and char only undergo pyrolysis to a limited extent, and therefore this material needs to be burned in a separate combustion zone of the reactor.

[0003] U.S. Patent No. 10,731,080 and U.S. Patent No. 11,041,123 disclose a method for recovering waste plastics including a system for recovering styrene monomer from waste polystyrene. The waste stream is first densified into a melt and then sent to a continuous feed non-catalytic pyrolysis system. This pyrolysis system includes a heated self-cleaning twin screw reactor that supplies heat through different heating zones for the decomposition or depolymerization of the plastic feedstock. Such a screw reactor system has insufficient temperature control, exhibits large temperature gradients, and inevitably results in over-depolymerized plastics.

[0004] International Publication No. WO 2021 / 053074 pamphlet and International Publication No. WO 2021 / 053075 pamphlet disclose a method for depolymerizing polystyrene based on fluidized bed technology. The polystyrene is fed into a pyrolysis reactor and fluidized and heated by steam. Using steam in such a manner results in a significantly diluted product gas, requiring additional complex technologies to recover styrene.

[0005] The use of a pyrolysis reactor in which fluidization and heating are performed using air is also known. One of the disadvantages of using hot air in a pyrolysis reactor is that the product may carbonize. Another disadvantage is that the combustion products are diluted with nitrogen and carbon dioxide, thereby reducing the efficiency of downstream condensation. The downstream condensation efficiency decreases because the dew point of the condensable components decreases.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] Therefore, one of the objects of the embodiments of the present invention is to address one or more of the above or other problems.

MEANS FOR SOLVING THE PROBLEMS

[0007] In a first aspect, the present invention is a method for depolymerizing a polymer into one or more monomers, comprising: (a) providing a fluidized reactor system including a pyrolysis chamber, a combustion chamber, and a bed material that circulates from the combustion chamber to the pyrolysis chamber via a transport zone; and (b) introducing a feed material containing 60% or more of the polymer based on the weight of the feedstock into the pyrolysis chamber and performing a pyrolysis process at a temperature in the range of 450 to 650 °C in the bed material to obtain a depolymerized polymer product gas containing monomers, wherein sufficient heat for performing the pyrolysis process is transferred from the combustion chamber to the pyrolysis chamber by the circulation of the bed material.

[0008] In a second aspect, the present invention relates to the use of a fluidized reactor system comprising a pyrolysis chamber for depolymerizing a polymer in a feedstock comprising 60% or more polymer, based on the weight of the feedstock, into one or more monomers, a combustion chamber, and a bed material that circulates from the combustion chamber to the pyrolysis chamber via a transport zone.

[0009] Furthermore, all defined features for the method according to the invention are equally applicable to the use according to the invention, and vice versa.

[0010] In the method according to the invention, heat generated in the combustion chamber can be transferred to the pyrolysis chamber via circulation of the bed material. The bed material preferably circulates continuously from the combustion chamber to the pyrolysis chamber via a closed system or loop. In other words, the bed material preferably circulates continuously via a closed loop between the combustion chamber and the pyrolysis chamber.

[0011] By reducing the circulation rate of the bed material, the temperature difference between the combustion chamber and the pyrolysis chamber can be increased. This allows for a higher combustion temperature, thereby enabling the temperature maintained in the pyrolysis chamber to be lowered. A further advantage is that excessive decomposition of the polymer is prevented or minimized, thereby increasing the yield of monomer product. Increasing the circulation rate can also prevent or minimize side reactions. The circulation rate of the bed material may be 10 to 100 kg of circulating bed material per kg of feedstock, more preferably 20 to 60 kg per kg of feedstock.

[0012] By increasing the circulation rate of the bed material, the temperature difference between the combustion chamber and the pyrolysis chamber can be decreased. This enables a higher temperature to be achieved in the pyrolysis chamber. The circulation rate of the bed material may be 10 to 100 kg of circulating bed material per kg of feedstock, more preferably 20 to 60 kg per kg of feedstock.

[0013] Furthermore, by directly applying heat through the bed material, all or substantially all of the heat for the pyrolysis process is obtained by the bed material, so that the polymer mixture is exposed to a substantially uniform temperature in the pyrolysis chamber. In contrast, in conventional heating techniques where heat is applied indirectly through the walls of the pyrolysis reaction vessel or through internal heat pipes, hot spots of temperature and high surface temperatures occur. These hot spots of temperature and high surface temperatures cause excessive decomposition of the polymer. For example, the temperature of the chamber wall or in the vicinity thereof in a conventional naphtha cracking apparatus can easily be 200 °C higher than the temperature required for the decomposition of naphtha and naphtha gas. Therefore, by applying heat through the bed material, side reactions such as the decomposition of the monomer of the product are prevented or minimized, and thus the yield of the monomer product increases.

[0014] The high-temperature bed material is preferably sand such as crystalline quartz sand.

[0015] The pyrolysis process can be carried out at 400 to 700 °C, preferably 450 to 650 °C, and even more preferably 450 to 600 °C. The temperature of the pyrolysis process is selected according to the type of polymer used, i.e., the temperature at which the polymer depolymerizes.

[0016] In the combustion chamber, the combustion process is carried out at a higher temperature than the pyrolysis process. In the combustion chamber, the combustion process can be carried out at a temperature that is only 30 to 130 °C, preferably 30 to 70 °C, higher than the pyrolysis process. For example, the pyrolysis process is carried out at a temperature in the range of 400 to 700 °C, and the combustion process is carried out at a temperature that is only 30 to 130 °C higher than the pyrolysis process. As a further example, the pyrolysis process is carried out at a temperature in the range of 450 to 650 °C, and the combustion process is carried out at a temperature that is only 30 to 70 °C higher than the pyrolysis process. Temperatures above 750 °C are not desirable in the pyrolysis chamber because the monomer units are further decomposed to obtain product gas containing light hydrocarbon gas, heavy hydrocarbon oil fraction, and solid residue. When the temperature is lowered, the amounts of these fractions decrease.

[0017] To control the circulation rate of the bed material, the fluidizing gas can typically be moved from the product recovery unit of the fluidized reactor system into the transport zone. The fluidizing gas can be moved into the transport zone in two or more regions. Preferably, by varying the ratio of the fluidizing gas moved into the first region of the transport zone to the second region of the transport zone, the temperature difference between the combustion chamber and the pyrolysis chamber is increased or decreased. In a preferred embodiment, the transport zone includes a first region that allows for a downflow of the bed material from the combustion chamber and a second region that allows for an upflow of the bed material to the pyrolysis chamber. The fluidizing gas can be moved into the upstream portion of the second region and into the downstream portion of the second region. The terms upstream portion and downstream potion are used to indicate the direction of flow of the bed material through the fluidized reactor system. In other words, the bed material circulates from the first region into the upstream portion and then into the downstream portion before moving to the pyrolysis chamber. To control the circulation rate of the bed material, the fluidizing gas can typically be moved from the product recovery unit (40) of the fluidized reactor system into the pyrolysis chamber. By varying the amount of the fluidizing gas moved into the transport zone and / or the pyrolysis chamber, the circulation rate of the bed material may be increased or decreased. The advantages associated with increasing and decreasing the circulation rate of the bed material are as discussed above. By varying the amount of the fluidizing gas moved into two or more regions of the transport zone, the circulation rate of the bed material may be increased or decreased. Thus, by varying the amount of the fluidizing gas as described above such that the circulation rate of the bed material is increased or decreased, the temperature difference between the combustion chamber and the pyrolysis chamber can be decreased or increased. Preferably, the fluidizing gas is moved only into the second region of the transport zone, in other words, the fluidizing gas is not moved into the first region of the transport zone.

[0018] A particulate removal unit communicating with the product recovery unit can be provided, whereby the depolymerized polymer product gas can be transferred to the product recovery unit through the particulate removal unit. Solid particulates such as ash can be transferred from the particulate removal unit to the combustion chamber.

[0019] In a preferred embodiment, by adding more fluidizing gas into the downstream portion of the second region than into the upstream portion of the second region, the circulation rate of the bed material is decreased. Here, the ratio of the fluidizing gas added to the upstream portion to the downstream portion is 1:1 to 6, typically 1:1.5 to 4. By adding less fluidizing gas into the downstream portion of the second region than into the upstream portion of the second region, the circulation rate of the bed material is increased. Here, the ratio of the fluidizing gas added to the upstream portion to the downstream portion is 1 to 6:1, typically 1.5 to 4:1.

[0020] In a further preferred embodiment, by adding more fluidizing gas into the downstream portion of the second region and / or into the pyrolysis chamber than into the upstream portion of the second region, the circulation rate of the bed material is decreased. Here, the ratio of the fluidizing gas added to the upstream portion to the downstream portion and / or to the pyrolysis chamber is 1:1 to 6, typically 1:1.5 to 4. By adding less fluidizing gas into the downstream portion of the second region and / or into the pyrolysis chamber than into the upstream portion of the second region, the circulation rate of the bed material is increased. Here, the ratio of the fluidizing gas added to the upstream portion to the downstream portion 35 and / or to the pyrolysis chamber is 1 to 6:1, typically 1.5 to 4:1.

[0021] The fluidizing gas can also be transferred into the first region. Thereby, the circulation of the bed material into the pyrolysis chamber is promoted. Thus, the fluidized reactor system can add different amounts of fluidizing gas to the transport zone and / or the pyrolysis chamber, whereby the moving speed can be controlled during operation. A further advantage of providing two or more regions for adding the fluidizing gas is the case where a part of the region becomes closed or partially closed.

[0022] The above method can further include moving the depolymerized polymer product gas into a product recovery unit to isolate one or more monomers.

[0023] The fluidizing gas can be moved from the product recovery unit. Alternatively, or in addition to this, the fluidizing gas can be moved from an external source. The fluidizing gas can be moved from the product recovery unit into the transport zone and / or the pyrolysis chamber.

[0024] The fluidizing gas can be moved from an external source into the combustion chamber. In other words, the fluidizing gas used in the combustion chamber is not obtained from the product recovery unit. The fluidizing gas introduced into the combustion chamber can be air.

[0025] The velocity of the fluidizing gas in the second region of the transport zone can be 0.5 - 3 m / s, preferably 1 - 2.5 m / s, and even more preferably 2 m / s. The velocity of the fluidizing gas in the upstream portion and / or the downstream portion of the second region of the transport zone can be 0.5 - 3 m / s, preferably 1 - 2.5 m / s, and even more preferably 2 m / s. Within this velocity range, the bed material can be moved by actually fluidizing the bed material.

[0026] The velocity of the fluidizing gas in the pyrolysis chamber can be 3 - 7 m / s, preferably 4 - 6 m / s. Within these velocity ranges, it is possible for the bed material to mix into the sedimentation chamber through the pyrolysis chamber. A further advantage of these velocity ranges is that they enable the bed material to be discharged from the pyrolysis chamber and circulated into the combustion chamber.

[0027] The velocity of the fluidizing gas is determined by the density of the fluidizing gas and the particle size of the bed material. Generally, the particle size has a greater influence than the density of the fluidizing gas.

[0028] The bed material can have a dp50 of 240 - 280 μm, preferably 260 μm. The average particle size is determined using laser diffraction particle size analysis, for example, using a Malvern Mastersizer.

[0029] The feedstock can be provided as flakes having a thickness of 0.25 - 3 mm. For example, the feedstock can be obtained from a waste stream, which is provided as flakes having a thickness of 0.25 - 3 mm. At least 50%, preferably at least 75%, even more preferably at least 90% of the feedstock can be provided as flakes. In order to prevent the flakes from being discharged from the riser before being depolymerized, the dp50 of the bed material can be reduced. As an example, flakes having a thickness of 0.25 - 3 mm are beneficial in reducing the dp50 of the bed material to 100 - 240 μm, preferably to 180 μm. The waste stream can include a PS waste stream such as the waste stream of a PS yogurt cup.

[0030] The density of the fluidizing gas in the transport zone is 0.9 - 1.1 kg / Nm 3 、preferably 1.0 kg / Nm 3 and can be. The density of the fluidizing gas in the upstream part and / or downstream part of the second region of the transport zone is 0.9 - 1.1 kg / Nm 3 、preferably 1.0 kg / Nm 3 and can be. The density of the fluidized bed material in the transport zone is 900 - 1100 kg / m 3 、preferably 1000 kg / m 3 and can be. The density of the fluidized bed material in the upstream part and / or downstream part of the second region of the transport zone is 900 - 1100 kg / m 3 、preferably 1000 kg / m 3 and can be.

[0031] In one embodiment, the velocity of the fluidizing gas in the upstream portion and / or the downstream portion of the second region of the transport zone may be 0.5 to 3 m / s, preferably 1 to 2.5 m / s, and even more preferably 2 m / s; the bed material may have a dp50 of 240 to 280 μm, preferably 260 μm; and the density of the fluidizing gas in the upstream portion and / or the downstream portion of the second region of the transport zone may be 0.9 to 1.1 kg / Nm 3 , preferably 1.0 kg / Nm 3 and may be so.

[0032] The velocity of the bed material in the first region may be 0.05 to 0.15 m / s, preferably 0.1 m / s. The density of the bed material may be 1440 to 1760 kg / m 3 , preferably 1600 kg / m 3 and may be so.

[0033] In the upper portion (downstream portion) and / or the lower portion (upstream portion) of the pyrolysis chamber, the velocity of the fluidizing gas may be 3 to 7 m / s, preferably 4 to 6 m / s. The density of the fluidized bed material in the upper portion and / or the lower portion of the pyrolysis chamber may be 90 to 110 kg / m 3 , preferably 100 kg / m 3 and may be so. The density of the fluidizing gas in the upper portion and / or the lower portion of the pyrolysis chamber may be 2.25 to 2.75 kg / Nm 3 , preferably 2.50 kg / Nm 3 and may be so.

[0034] The fluidizing gas can be treated before being transferred to the fluidized reactor system. The fluidizing gas may be HCN, NH 3 , HCl, H 2To remove inorganic components such as S or COS, it can be treated by washing in a scrubber that is either neutral, acidic, or caustic. In addition to this, or alternatively, the fluidized gas can be treated by using a catalyst bed for hydrogenating olefins, thereby avoiding the reaction of olefins with each other, for example, by a polymerization reaction that produces heavier hydrocarbons. In addition to this, or alternatively, the fluidized gas can be treated by passing it through a suitable membrane to remove hydrogen from the fluidized gas. This prevents or reduces the entry of contaminants into the pyrolysis chamber and / or the combustion chamber.

[0035] The fluidized gas is preferably generated from the product gas of the pyrolysis process and has a low water content. Therefore, the product gas generated in the pyrolysis chamber can be transferred to the product recovery unit, and the separated fluidized gas can be returned to the pyrolysis chamber for recycling and / or transferred to the transport zone. The depolymerized product gas in the pyrolysis chamber can have a water dew point of 10 - 40 °C, preferably 10 - 30 °C. The fluidized gas from the product recovery unit can have a water dew point of 0 - 10 °C, preferably 5 °C. The fact that the fluidized gas has a low water content helps to lower the water dew point of the depolymerized polymer product gas, which is beneficial for optimizing the recovery of the monomer components of the constituents. The introduction of the fluidized gas from the product recovery unit into the pyrolysis chamber helps to minimize / reduce the water dew point of the depolymerized polymer product gas generated by the pyrolysis chamber. A further advantage of adding the fluidized gas to the pyrolysis chamber is that the depolymerized polymer product gas is diluted, preventing or reducing the polymerization of monomer units. The dilution ratio can be 0.2 - 1.0 kg gas / kg hydrocarbon. As an example, the product gas is monomer / dimer / trimer (C 8 H 8 , C 16 H 16 , and C 24 H 24 ), olefins (C 2 H 4 , C 3H 6 ) and H 2 can include. Remove components having a 1:1 H:C ratio and recycle olefins or H with a 2:1 2 to reduce the risk of soot formation, which is due to the carbon formation equilibrium isotherm. A fluidization gas with a high hydrogen content helps reduce soot formation in the pyrolysis chamber.

[0036] The advantage of returning the non-condensable gas to the pyrolysis chamber is associated with the high hydrogen content. This gas is non-condensable at temperatures in the range of 5 - 20 °C under ambient conditions, i.e., atmospheric conditions or near them.

[0037] Preferably, the above method further includes moving the fraction produced by the pyrolysis process into a combustion chamber and carrying out a combustion process in a high-temperature bed material to obtain flue gas. This fraction can include un-converted char.

[0038] The above method can further include moving flue gas from the combustion chamber and at least a portion of the non-condensable gas and / or energy source from the product recovery unit to a heat recovery system, which includes an afterburner. The term "fluidizing gas" can be used synonymously with "non-condensable gas" and "energy source". Preferably, the flue gas and at least a portion of the non-condensable gas and / or energy source are sent to the afterburner of the heat recovery system to combust molecules (such as methane) that cannot be combusted at the low temperatures used in the combustion chamber. The amount of non-condensable gas sent to the afterburner / heat recovery system can be 40 wt% to 75 wt%, preferably 60% to 70% of the total non-condensable gas. The portion of the non-condensable gas that is sent directly to the afterburner / heat recovery system rather than indirectly through the combustion chamber serves to maintain the temperature of the pyrolysis chamber and the combustion chamber at a sufficiently low level when the combustion chamber is operated superstoichiometrically, thereby preventing or minimizing side reactions such as decomposition. The combustion chamber can also be operated sub-stoichiometrically. When operated stoichiometrically, the non-condensable gas can be introduced into the combustion chamber before being sent to the afterburner / heat recovery system. Preferably, an excess of non-condensable gas can be used to operate the combustion chamber stoichiometrically to perform selective combustion of the non-condensable gas.

[0039] The terms sub-stoichiometrically and superstoichiometrically are defined by the value of lambda. Lambda represents the ratio of the amount of oxygen present in the combustion chamber compared to the amount that should have been present for "complete" combustion. Thus, when the mixture contains the exact amount of oxygen required to combust the fuel present, this ratio is 1 to 1 and lambda is 1.00. When operated stoichiometrically, lambda can be 0.4 to 0.7, typically 0.6. When operated superstoichiometrically, lambda can be 1.2 to 1.3.

[0040] When used in or transferred as part of a fluidized reactor system that does not use a gas or energy source as a fluidizing agent, for example when the fluidizing agent is transferred from a product recovery unit to a combustion chamber, the fluidizing gas is more appropriately referred to as a non-condensable gas or energy source. Thus, the method can further include isolating a non-condensable gas and / or energy source from the depolymerized polymer product gas and optionally transferring at least a portion of the non-condensable gas and / or energy source to the combustion chamber. This advantageously compensates for low internal carbon transport. Non-condensable gases can include CO, H 2 , CH 4 , N 2 , monomers, and combinations thereof. Energy sources can include fossil fuels, solid biomass, waste feedstocks, hydrocarbon condensates obtained from product recovery, or combinations thereof. It can be a further advantage that sufficient energy is obtained for the pyrolysis process. The energy source can be gaseous, liquid, or solid. The advantage of transferring the non-condensable gas / energy source into the combustion chamber is that the non-condensable gas or energy source functions as an energy source, thereby compensating for the low residual char transported internally and the low residual char passing through it when a particulate removal unit (e.g., cyclone) is used. Preferably, more non-condensable gas or energy source than is required to obtain sufficient energy for the combustion reaction is transferred into the combustion chamber. For example, the non-condensable gas or energy source can include a gas that is easily combustible in the combustion chamber and a gas with low combustibility that is only combustible in an afterburner / heat recovery system. Thus, by providing an excess of non-condensable gas or energy source, a sufficient supply of easily combustible gas is ensured. The ratio of the non-condensable gas from the product recovery system introduced into the afterburner / heat recovery system to the amount introduced into the combustion chamber is between 0 and 0.25, preferably between 0 and 0.10. When the temperature in the combustion chamber is high enough, combustion can be carried out using excess air and most of the non-condensable gas is sent directly to the afterburner.

[0041] The above method can further include hydrogenating olefins present in the non-condensable gas and / or energy source before being sent to the pyrolysis chamber.

[0042] The above method can further include moving at least a portion of the non-condensable gas and / or energy source from the product recovery unit to the pyrolysis chamber to fluidize the pyrolysis chamber. Advantageously, this minimizes the water dew point of the depolymerized polymer product gas. A further advantage of moving the non-condensable gas and / or energy source into the pyrolysis chamber is that the depolymerized polymer product gas is diluted, reducing the risk of polymerization of monomer units.

[0043] At least a portion of the non-condensable gas and / or energy source can be used in the production of chemicals. Preferably, hydrogen and / or olefins from the non-condensable gas and / or energy source are used in the production of chemicals. For example, olefins can be converted to methanol. As a further example, olefins can be converted to benzene, toluene, or xylene by aromatization.

[0044] The fluidizing gas, non-condensable gas, or energy source can include olefins and hydrogen. Optionally, olefins and hydrogen can be recovered from a portion of the fluidizing gas. Optionally, olefins can be converted to benzene, ethylene, and xylene by catalytic aromatization. Based on the total weight, the fluidizing gas can include 30 - 50% hydrogen based on the weight of the fluidizing gas. The fluidizing gas can include 10 - 40%, preferably 15 - 30% olefins based on the weight of the fluidizing gas. Based on the total volume, the fluidizing gas can include 30 - 50% hydrogen based on the volume of the fluidizing gas. The fluidizing gas can include 10 - 40%, preferably 15 - 30% olefins based on the volume of the fluidizing gas.

[0045] The fluidized reactor system can further include a downcomer that can circulate the bed material from the pyrolysis chamber to the combustion chamber. The downcomer can be coaxially arranged around the pyrolysis chamber. During use, the bed material flows into the downcomer over the upper part of the pyrolysis chamber and then circulates into the combustion chamber. Thus, the layer of the bed material always surrounds the pyrolysis chamber and functions as an insulating layer between the wall of the pyrolysis chamber and the downcomer. Thereby, the radial transfer of heat from the combustion chamber to the pyrolysis chamber is reduced, thereby preventing the wall of the pyrolysis chamber from being heated to a high temperature that can cause further decomposition.

[0046] The velocity of the fluidizing gas and / or non-condensable gas / energy source is controlled by a flow transmitter in the fluidized reactor system.

[0047] The combustion chamber can be arranged to surround at least a part of the pyrolysis chamber. The pyrolysis chamber can be arranged at or substantially at the center within the combustion chamber.

[0048] The above method further includes moving the depolymerized polymer product gas from the pyrolysis chamber to a particulate removal unit (e.g., including a cyclone) before moving it to the product recovery unit. The cyclone advantageously removes particulates from the product gas or obtains a suitable solid particulate to hydrocarbon ratio in the product gas.

[0049] The above method can further include isolating dimers and trimers from the depolymerized polymer product gas and moving the dimers and trimers to the pyrolysis chamber. Thereby, the dimers and trimers can be further decomposed into monomer units, thereby increasing the yield of the isolated monomers.

[0050] The above method can further include feeding a feedstock into a pyrolysis chamber by a feed screw. In one embodiment, preferably by the feed screw, the feeding rate of the feedstock is 0.3 to 1.0 m / s.

[0051] Preferably, the feedstock contains 5% to 15%, more preferably 5% to 10% water based on the weight of the feedstock. Preferably, the feedstock contains 1% to 10%, preferably 2% to 5% ash based on the weight of the feedstock.

[0052] Alternatively, the polymer contains 5% to 15%, more preferably 5% to 10% water based on the total weight of the polymer. Preferably, the polymer contains 1% to 10%, preferably 2% to 5% ash based on the total weight of the polymer.

[0053] A pressure control valve can be used to adjust the pressure of the depolymerized polymer product gas exiting the pyrolysis chamber and heading towards the product recovery unit. The advantage of using a pressure control valve is that the change in the pressure difference of the depolymerized polymer product gas between the pyrolysis chamber and the product recovery unit is compensated to ensure a constant operating pressure of the depolymerized polymer product gas.

[0054] The term "polymer" is used to mean any type of feedstock / fuel containing polymers. Polymers are typically present in a mixture containing polymers. In the mixture, the polymer can be combined with other polymers and / or non-polymer components. For example, the feedstock can include biomass or waste of biological origin, plastic waste (such as linear hydrocarbon plastic waste), or binders and fillers present in plastics. As a further example, the feedstock can contain polymers. Preferably, the feedstock contains 60% or more, preferably 80% or more polymers based on the weight of the feedstock. The term "polymer" is used to mean at least one polymer.

[0055] The polymer mixture may be polystyrene, polyvinyl chloride, polymethyl methacrylate, polytetrafluoroethylene, or a combination thereof. Preferably, the polymer mixture mainly comprises one or more of polystyrene, polyvinyl chloride, polymethyl methacrylate, or polytetrafluoroethylene. Even more preferably, the polymer mixture mainly comprises polystyrene. The polymer mixture may comprise 60 to 100%, preferably 80 to 100% of polystyrene, polyvinyl chloride, polymethyl methacrylate, or polytetrafluoroethylene, based on the weight of all polymers in the polymer mixture. The polymer mixture may comprise 60 to 100%, preferably 80 to 100% of polystyrene, based on the weight of all polymers in the polymer mixture.

[0056] According to a further aspect of the present invention, there is provided the use of a fluidized reactor system comprising a pyrolysis chamber (2) for depolymerizing a polymer into one or more monomers, a combustion chamber (12), and a bed material circulating from the combustion chamber (12) to the pyrolysis chamber (2) via a transport zone (30).

[0057] The pyrolysis process can be carried out at a temperature in the range of 400 to 750 °C, preferably 450 to 650 °C, in the bed material to obtain a depolymerized polymer product gas containing monomers.

[0058] The temperature difference between the combustion chamber and the pyrolysis chamber can be adjusted by changing the ratio of the fluidizing gas moved into the first region of the transport zone to the second region of the transport zone.

[0059] The temperature difference between the combustion chamber and the pyrolysis chamber can be increased or decreased by changing the circulation rate of the bed material.

[0060] The embodiments described above can also be summarized by the following clauses.

[0061] 1. A method for depolymerizing a polymer into one or more monomers, comprising: (a) providing a fluid reactor system including a pyrolysis chamber (2), a combustion chamber (12), and a bed material that circulates from the combustion chamber (12) to the pyrolysis chamber (2) via a transport zone (30); (b) introducing the polymer into the pyrolysis chamber (2) and performing a pyrolysis process at a temperature within the range of 400 to 750 °C in the bed material to obtain a depolymerized polymer product gas containing monomers. By circulating the bed material, sufficient heat for performing the pyrolysis process is transferred from the combustion chamber (12) to the pyrolysis chamber (2). Method.

[0062] 2. The method according to clause 1, wherein the pyrolysis process is carried out at 400 to 700 °C, preferably 450 to 650 °C.

[0063] 3. The method according to clause 1 or 2, wherein the combustion process is carried out in the combustion chamber at a temperature 30 to 130 °C, preferably 30 to 70 °C, higher than the pyrolysis process.

[0064] 4. The method according to any of the preceding clauses, wherein by decreasing the circulation rate of the bed material, the temperature difference between the combustion chamber (12) and the pyrolysis chamber (2) increases, and by increasing the circulation rate of the bed material, the temperature difference between the combustion chamber (12) and the pyrolysis chamber (2) decreases.

[0065] 5. The method according to clause 4, wherein the circulation rate of the bed material is 10 to 100 kg of circulating bed material per kg of feedstock, more preferably 20 to 60 kg per kg of feedstock.

[0066] 6. A method according to any preceding clause, wherein to control the circulation rate of the bed material, the fluidizing gas is moved from the product recovery unit (40) of the fluidized reactor system, typically, into the transport zone (30).

[0067] 7. A method according to clause 6, wherein the fluidizing gas is moved into the transport zone (30) in two or more regions.

[0068] 8. A method according to clause 7, wherein the temperature difference between the combustion chamber (12) and the pyrolysis chamber (2) is increased or decreased by changing the ratio of the fluidizing gas moved into the first region of the transport zone to the second region of the transport zone.

[0069] 9. A method according to any preceding clause, wherein the transport zone (30) includes a first region (32) that allows a downflow of the bed material from the combustion chamber (12) and a second region (34) that allows an upflow of the bed material to the pyrolysis chamber (2).

[0070] 10. A method according to clause 9, wherein the fluidizing gas is moved into the upstream portion (36) and the downstream portion (35) of the second region (34).

[0071] 11. A method according to any of clauses 6 to 10, wherein the velocity of the fluidizing gas in the transport zone (30) is 0.5 to 3 m / s, preferably 1 to 2.5 m / s.

[0072] 12. A method according to clause 10, wherein the velocity of the fluidizing gas in the upstream portion (36) and / or the downstream portion (35) is 0.5 to 3 m / s, preferably 1 to 2.5 m / s, and more preferably 2 m / s.

[0073] 13. A method according to any preceding clause, wherein to control the circulation rate of the bed material, the fluidizing gas is moved from the product recovery unit (40) of the fluidized reactor system, typically, into the pyrolysis chamber (2).

[0074] 14. The method according to clause 13, wherein the velocity of the fluidizing gas in the pyrolysis chamber (2) is 3 to 7 m / s, preferably 4 to 6 m / s.

[0075] 15. (c) The method according to any preceding clause, further comprising moving the depolymerized polymer product gas into the product recovery unit (40) and isolating one or more monomers.

[0076] 16. The method according to clause 15, further comprising isolating a non-condensable gas and / or an energy source from the depolymerized polymer product gas.

[0077] 17. The method according to clause 16, further comprising moving at least a portion of the non-condensable gas and / or the energy source into the combustion chamber (12).

[0078] 18. The method according to clause 16 or 17, further comprising moving the flue gas from the combustion chamber (12) and at least a portion of the non-condensable gas and / or the energy source from the product recovery unit (40) into a heat recovery system, the heat recovery system including an afterburner (58).

[0079] 19. The method according to any one of clauses 16 to 18, further comprising moving at least a portion of the non-condensable gas and / or the energy source into the pyrolysis chamber (2) to fluidize the pyrolysis chamber.

[0080] 20. The method according to clause 19, further comprising hydrogenating the olefins present in the non-condensable gas and / or the energy source before moving it into the pyrolysis chamber (2).

[0081] 21. The method according to any one of clauses 16 to 20, wherein at least a portion of the non-condensable gas and / or the energy source is used in the production of chemicals, preferably hydrogen and / or olefins from the non-condensable gas and / or the energy source are used in the production of chemicals.

[0082] 22. The method according to any one of clauses 15 to 21, further comprising isolating dimers and trimers from the depolymerized polymer product gas and transferring the dimers and trimers to the pyrolysis chamber (2).

[0083] 23. The method according to any preceding clause, wherein the combustion chamber (12) is operated stoichiometrically.

[0084] 24. The method according to any preceding clause, wherein the polymer mixture mainly comprises one or more of polystyrene, polyvinyl chloride, polymethyl methacrylate, or polytetrafluoroethylene, preferably polystyrene.

[0085] 25. Use of a fluidized reactor system comprising a pyrolysis chamber (2) for depolymerizing a polymer into one or more monomers, a combustion chamber (12), and a bed material circulating from the combustion chamber (12) to the pyrolysis chamber (2) via a transport zone (30).

[0086] 26. Use of the fluidized reactor system according to clause 25, wherein the pyrolysis process is carried out in the bed material at a temperature in the range of 400 to 750 °C to obtain a depolymerized polymer product gas containing monomers.

[0087] 27. Use of the fluidized reactor system according to clause 25 or 26, wherein the temperature difference between the combustion chamber and the pyrolysis chamber is adjusted by changing the ratio of the fluidizing gas transferred into the first region of the transport zone with respect to the second region of the transport zone.

[0088] 28. Use of the fluidized reactor system according to any one of clauses 25 to 27, wherein the temperature difference between the combustion chamber and the pyrolysis chamber is increased or decreased by changing the circulation rate of the bed material.

Brief Description of the Drawings

[0089]

Figure 1

Mode for Carrying Out the Invention

[0090] In one embodiment shown in the schematic diagram of FIG. 1, a fluidized reactor system is provided for depolymerizing a polymer into one or more monomers. The reactor system includes a pyrolysis chamber 2 connected to a polymer mixture input section 4 (which can include a polymer silo), a first fluidizing gas input section 6, a second fluidizing gas input section 8, and a product gas discharge section 10. A combustion chamber 12 bounded by a wall 14 at least partially surrounds the pyrolysis chamber 2 and is connected to a flue gas discharge section 16 and a non-condensable gas or energy source input section 18. The non-condensable gas or energy source input section is arranged to supply a combustible gas source to the combustion chamber 12 to heat the bed material. The combustion chamber 12 is also connected to an external fluidizing gas input section 20. The combustion chamber 12 includes a fluidized bed zone 22, an air chamber 24 located below the bed zone 22, and a freeboard 26 located above the fluidized bed zone 22. A downcomer 28 is also provided to enable the transfer of bed material, char, and a portion of the product gas (typically 1-2% by weight of the total weight of the product gas) from the pyrolysis chamber 2 to the combustion chamber 12. The pyrolysis chamber 2 and the combustion chamber 12 are connected via a transport zone 30. The transport zone 30 includes a first region 32 that enables the downflow of bed material from the combustion chamber 12 and a second region 34 that enables the upflow of bed material to the pyrolysis chamber 2. The second region 34 includes a downstream portion 35 and an upstream portion 36. The first region 32 is connected to a third fluidizing gas input section 38 for supplying fluidizing gas to the pyrolysis chamber 2 via the transport zone 30. The pyrolysis chamber 2 is connected to the first fluidizing gas input section 6 via the transport zone 30. Alternatively, the first fluidizing gas input section 6 is connected to the upstream portion 36 of the second region 34 such that the fluidizing fluid flows into the second region 34, whereby the fluidizing liquid moves into the pyrolysis chamber 2. The pyrolysis chamber 2 can be connected to the second fluidizing gas input section 8 via the transport zone 30. Alternatively, the second fluidizing gas input section 8 is connected to the downstream portion 35 of the second region 34 such that the fluidizing fluid flows into the second region 34, whereby the fluidizing liquid moves into the pyrolysis chamber 2.Alternatively, the second fluidizing gas inlet 8 is directly connected to the pyrolysis chamber 2 such that the fluidizing fluid flows directly into the pyrolysis chamber 2. The second region 34 may be part of the pyrolysis chamber 2. The transport zone 30 is for circulating the bed material between the combustion chamber 12 and the pyrolysis chamber 2. The product gas discharge 10 can be directly connected to a product recovery unit 40 (which can include one or more quench towers), or can be connected to a particulate removal unit 42 such as a cyclone. The product recovery unit 40 includes a fluidizing / non-condensable gas discharge 44 that is in fluid communication with the first, second, and third fluidizing gas inlets 6, 8, and 38 and the energy source inlet 18. The product recovery unit 40 further includes several product discharges such as a monomer discharge 46, a dimer discharge 48, and a trimer discharge 50. The particulate removal unit 42 includes a product gas discharge 52 that communicates with the product recovery unit 40. The particulate removal unit 42 also includes a solid discharge 54 that communicates with the combustion chamber 12 for introducing solids such as ash into the combustion chamber 12.

[0091] In use, the bed material (preferably sand such as crystalline quartz sand) is continuously circulated between the pyrolysis chamber 2 and the combustion chamber 12 via the downcomer 28 and the transport zone 30. A polymer mixture is introduced into the pyrolysis chamber 2 via the polymer mixture inlet 4, and the pyrolysis process is carried out at a temperature in the range of 400 to 750 °C, preferably 450 to 650 °C, in the bed material to produce a depolymerized polymer product gas and a by-fraction. This by-fraction is transferred from the pyrolysis chamber 2 to the combustion chamber 12 by the bed material (via the sedimentation chamber 56 and the downcomer 28) and burns in the fluidized bed zone 22 in the presence of air at a temperature higher than that of the pyrolysis process by 30 to 130 °C to obtain flue gas, which is used to heat the bed material in the combustion chamber 12. Next, the flue gas exits the combustion chamber 12 via the freeboard. The flue gas contains one or more of the components of N 2 , CO 2、 H 2 O, and non-condensable gases (see Table 8). The flue gas contains the following pollutants: NO x , SOx It may also contain one or more of and HCl. The bed material maintains the heat of the combustion process, and the heat is used in the pyrolysis process by circulating the bed material from the combustion chamber 12 to the pyrolysis chamber 2 through the transport zone 30. To pyrolyze the polymer mixture in the pyrolysis chamber 2, by using the heat obtained in the combustion process, a temperature difference occurs between the combustion chamber 12 and the pyrolysis chamber 2. Increasing the circulation rate of the bed material reduces the temperature difference between the combustion chamber 12 and the pyrolysis chamber 2, thereby reducing the temperature achieved in the combustion chamber 2. The lower temperature achieved means that the risk of excessive decomposition is reduced due to the temperature drop at the bottom of the pyrolysis zone. When the circulation rate of the bed material decreases, the temperature difference between the combustion chamber 12 and the pyrolysis chamber 2 increases, thereby maintaining a low temperature in the pyrolysis chamber 2 while increasing the combustion temperature.

[0092] The first, second, and third fluidization gas inlets 6, 8, and 38, the external fluidization gas inlet 20, and the energy source inlet 18 can advantageously be used in combination with each other or separately from each other. The first, second, and third fluidization gas inlets 6, 8, and 38, the external fluidization gas inlet 20, and the energy source inlet 18 are used to control the temperature in the pyrolysis chamber 2 and the combustion chamber 12. The fluidization gas / non-condensable gas (preferably tail gas) from the product recovery unit 40 is used to control the flow rate of the bed material passing through the transport zone 30. In particular, the velocity of the fluidization gas in the second region 34 of the transport zone 30 may be 0.5 to 3 m / s, preferably 0.5 to 2 m / s. The velocity of the fluidization gas in the pyrolysis chamber 2 may be 3 to 7 m / s, preferably 4 to 6 m / s.

[0093] By the first fluidizing gas inlet 6, the fluidizing gas moves into the upstream portion 38 of the second region 34 of the transport zone 30. By the second fluidizing gas inlet 8, the fluidizing gas moves into the downstream portion 35 of the second region 34 of the transport zone 30. By the third fluidizing gas inlet 38, the fluidizing gas moves into the first region 32 of the transport zone 30. By the external fluidizing gas inlet 20, the fluidizing gas moves into the air chamber 24 of the combustion chamber 12. The bed material flows from the first region 32 of the transport zone 30 to the second region 34 of the transport zone 30. In the first region 32, the fluidizing gas flows downward from the combustion chamber 12. In the second region 34, the fluidizing gas flows upward from the combustion chamber 12 and into the pyrolysis chamber 2. In order to control the circulation rate of the bed material, the fluidizing gas can be moved into the pyrolysis chamber 2. By changing the amount of the fluidizing gas moving into the transport zone 30 and / or the pyrolysis chamber 2, the circulation rate of the bed material can be increased or decreased.

[0094] By adding more fluidizing gas into the downstream portion 35 of the second region 34 than into the upstream portion 36 of the second region 34, the circulation rate of the bed material decreases. Here, the ratio of the fluidizing gas added to the upstream portion 36 to the downstream portion 35 is 1:1 to 6, typically 1:1.5 to 2. By adding less fluidizing gas into the downstream portion 35 of the second region 34 than into the upstream portion 36 of the second region 34, the circulation rate of the bed material increases. Here, the ratio of the fluidizing gas added to the upstream portion 36 to the downstream portion 35 is 1 to 6:1, typically 1.5 to 4:1. Alternatively, by adding more fluidizing gas into the downstream portion 35 and / or the pyrolysis chamber 2 of the second region 34 than into the upstream portion 36 of the second region 34, the circulation rate of the bed material decreases. Here, the ratio of the fluidizing gas added to the upstream portion 36 to the downstream portion 35 and / or the pyrolysis chamber 2 is 1:1 to 6, typically 1:1.5 to 2. By adding less fluidizing gas into the downstream portion 35 and / or the pyrolysis chamber 2 of the second region 34 than into the upstream portion 36 of the second region 34, the circulation rate of the bed material increases. Here, the ratio of the fluidizing gas added to the upstream portion 36 to the downstream portion 35 and / or the pyrolysis chamber is 1 to 6:1, typically 1.5 to 4:1. The fluidizing gas can also be moved into the first region 32. Thus, the fluidized reactor system can add different amounts of fluidizing gas to the transport zone 30 and / or the pyrolysis chamber 2, thereby controlling the movement speed during operation.

[0095] The flow rate of the fluidizing gas may be the same at each of the first, second, and third fluidizing gas inlets 6, 8, and 38. Alternatively, the flow rate of the fluidizing gas may be different at one or more of the first, second, and third fluidizing gas inlets 6, 8, and 38. Preferably, the fluidizing gas is obtained from the product recovery unit 40, exits the product recovery unit 40, and moves to the first, second, and third fluidizing gas inlets 6, 8, and 38 via the fluidizing gas / non-condensable gas discharge section 44. The depolymerized polymer product gas preferably moves to the particulate removal unit 42 before moving to the product recovery unit 40, and solid particulates are removed. The depolymerized polymer product gas moves from the product gas discharge section 10 of the pyrolysis chamber 2 to the particulate removal unit 42. Subsequently, the depolymerized polymer product gas moves from the product gas discharge section 52 of the particulate removal unit 42 to the product recovery unit 40. A pressure control valve can be used to adjust the pressure of the depolymerized polymer product gas exiting the pyrolysis chamber 2 and heading towards the product recovery unit 40. The advantage of using a pressure control valve is that the pressure difference of the depolymerized polymer product gas between the pyrolysis chamber 2 and the product recovery unit 40 is compensated to ensure a constant operating pressure of the depolymerized polymer product gas. The gas ash removed by the particulate removal unit 42 can be moved to the combustion chamber 12 via the solid discharge section 54.

[0096] The depolymerized polymer product gas is sorted and isolated to obtain one or more product streams, which are then transferred from the product recovery unit 40 using one or more discharge sections (such as the monomer discharge section 46, the dimer discharge section 48, and the trimer discharge section 50). The dimer and trimer products can be returned to the pyrolysis chamber 2 for further pyrolysis or used as another energy source in the combustion chamber 12. Typically, the dimer and trimer products are added to the opposite polymer mixture feed section 4. Alternatively, the polymer mixture is added to the dimer and trimer products. Other non-polymer products such as tar can also be isolated, and these can be returned to the pyrolysis chamber 2 for further pyrolysis or used as another energy source in the combustion chamber 12. Tar can contain alkylstyrene, benzene, alkylbenzene, cycloalkane, alkylcycloalkane, naphthalene, or combinations thereof. The type of polymer product is determined by the type of one or more polymers used in the polymer mixture. For example, monomeric styrene is obtained from polystyrene (PS), monomeric vinyl chloride (VC) is obtained from polyvinyl chloride (PVC), monomeric methyl methacrylate (MMA) is obtained from polymethyl methacrylate (PMMA), and when polytetrafluoroethylene (PTFE) is used, tetrafluoroethylene (TFE) is the monomer. Part or all of the flue gas from the combustion chamber 12 and / or the non-condensable gas from the product recovery unit 40 can be transferred to an afterburner 58 that forms part of the heat recovery system. The use of the afterburner 58 is preferred because the temperature in the combustion chamber 12 is insufficient to burn all components of the by-mixture. An air supply section 60 is provided to the afterburner 58 to further burn the gas at a high temperature such as 850 - 950 °C, preferably 850 - 900 °C. These temperature ranges avoid the melting of ash and harmful chemicals while complying with waste incineration directives.Next, the high-temperature flue gas is sent to the flue gas cooler 62 and then moves to the flue gas filter 64, where two product streams are obtained: a clean flue gas stream 66 and a fly ash stream 68. The ratio of the non-condensable gas directly introduced from the product recovery system 40 into the afterburner 58 to the amount introduced into the combustion chamber 12 is between 0 and 0.25, preferably between 0 and 0.10. If the temperature in the combustion chamber 12 is too high, combustion can be carried out using excess air, and most of the non-condensable gas is sent directly to the afterburner 58. A recirculation blower 70 can also be provided to increase the pressure of the fluidized / non-condensable gas from the product recovery unit 40 before downstream circulation.

[0097] The polymer mixture input section 4 can include a feed screw. Due to the backflow of gas and / or bed material, the feed screw often exhibits a high operating temperature, which causes the polymer mixture in the screw feed to melt, and subsequently, blockage of the screw feed can occur. By introducing the polymer mixture by fuel supply at a sufficiently high rate, the temperature of the feed screw decreases. Preferably, the fuel supply rate represented by the rate passing through the feed screw is 0.3 m / s to 1.0 m / s. The temperature of the feed screw can also be decreased by cooling the screw and its closed casing with air at 60 to 80 °C from the outside of the casing so as to pass through the air chamber and towards the pyrolysis zone. The temperature of the feed screw can also be decreased by adding water and / or ash to the polymer mixture. Alternatively, when the polymer mixture is derived from biomass, it can have a sufficient water content, so there is no need to add additional water to the polymer mixture. The polymer mixture preferably contains 5% to 15%, more preferably 5% to 10% water based on the weight of the polymer mixture. The polymer mixture preferably contains 1% to 10%, preferably 2% to 5% ash based on the weight of the polymer mixture. Bottom ash can be removed from the combustion chamber 12 through the ash discharge section 72. In particular, the bottom ash can be transported from the combustion chamber 12 to the transport zone 30 and then removed through the ash discharge section 72. As an example, a 2% amount of ash gives a 40% coverage of polymer particles with a 1 mm layer of ash.

Example

[0098] The following three tests of polystyrene mixtures were conducted (see Table 1).

[0099]

Table 1

[0100] Polystyrene mixtures B and C were depolymerized at temperatures between 380 °C and 700 °C using the method according to the invention, and the styrene content was measured (see Table 2). The highest styrene yields were obtained with PS mix B and PS mix C at 600 °C.

[0101]

Table 2

[0102] Polystyrene mixtures A and B were depolymerized at a temperature of 580 °C using the method according to the invention (i.e., heat is obtained using a high-temperature bed material that circulates internally between the pyrolysis zone and the combustion zone), and the styrene content was measured (see Table 3).

[0103]

Table 3

[0104] Table 4 shows the sand flow and the sand-to-fuel ratio as a function of the fluidization gas velocity passing through the transport zone 30. By adding more fluidization gas in the non-fluidized region 36 and less in the upflow region 34 or the pyrolysis chamber 2, the operating temperature of the pyrolysis chamber 2 can be changed. This redistribution of the fluidization gas can increase the flow of the fluidization gas (i.e., sand) passing through the transport zone 30 without mechanically changing the size of the transport zone 30, so that the temperature difference between the pyrolysis chamber 2 and the combustion chamber 12 changes. Increasing the velocity can thereby be increased significantly.

[0105]

Table 4

[0106] Tests were also conducted to examine the melting behavior of three types of plastics (polypropylene (PP), polyethylene (PE), and polystyrene (PS)). These plastics were shown to be able to start melting at temperatures between 140 and 200 °C without becoming low-viscosity liquids (see Table 5). Due to this behavior, plastic blockages could sometimes occur inside the supply screw that is conventionally operated at high temperatures.

[0107]

Table 5

[0108] To lower the operating temperature of the supply screw, it was found that by means of high PS fuel supply and the combination of high PS fuel supply and water, the operating temperature of the supply screw decreased, thereby avoiding the melting of the polystyrene mixture during screw feeding (see Table 6).

[0109]

Table 6

[0110] It was found that when using a conventional cyclone, a large amount of ash (fine powder) is not separated from the depolymerized polymer product gas. As a result of the high ash content, it was found that the condensed depolymerized polymer product exhibits a high viscosity, which becomes a problem in the quenching system of the product recovery unit. Therefore, a new cyclone was used to promote the separation of ash particles from the depolymerized polymer product gas and to aggregate the ash particles inside the cyclone for a sufficient time. Therefore, this cyclone is smaller than the conventional cyclone and has more interactions inside the particles, but is taller to obtain sufficient residence time for the particles to be collected. Table 7 shows the particle size distribution of the ash remaining in the depolymerized polymer product gas in units of mg / Nm 3 as a function of the input particle size distribution.

[0111]

Table 7

[0112] Table 8 shows the individual components of the fluidized gas / non-condensable gas / energy source obtained by the depolymerization of polystyrene at 580 °C, together with the relevant autoignition temperatures.

[0113] [Table 8]

Claims

1. A method for depolymerizing a polymer into one or more monomers: (a) To provide a fluid reactor system comprising a pyrolysis chamber (2), a combustion chamber (12), and a floor material circulating from the combustion chamber (12) to the pyrolysis chamber (2) via a transport zone (30); (b) A method comprising introducing the supply material containing 60% or more polymer based on the weight of the supply material into the pyrolysis chamber (2), carrying out a pyrolysis process in the floor material at a temperature in the range of 450 to 650°C to obtain a depolymerized polymer product gas containing the monomer; wherein sufficient heat to carry out the pyrolysis process is transferred from the combustion chamber (12) to the pyrolysis chamber (2) by the circulation of the floor material.

2. The method according to claim 1, wherein the supplied raw material mainly comprises one or more of polystyrene, polyvinyl chloride, polymethyl methacrylate, or polytetrafluorethylene.

3. The method according to claim 1, wherein the supplied raw material contains 60 to 100% polystyrene based on the weight of the total polymer in the supplied raw material.

4. - The combustion process is carried out in the combustion chamber at a temperature 30 to 130°C, preferably 30 to 70°C higher than the temperature of the pyrolysis process; and / or - The method according to any one of claims 1 to 3, wherein the temperature difference between the combustion chamber (12) and the pyrolysis chamber (2) increases by reducing the circulation rate of the floor material, and the temperature difference between the combustion chamber (12) and the pyrolysis chamber (2) decreases by increasing the circulation rate of the floor material, preferably the circulation rate of the floor material is 10 to 100 kg of circulating floor material per 1 kg of raw material, more preferably 20 to 60 kg per 1 kg.

5. The method according to any one of claims 1 to 3, wherein, in order to control the circulation rate of the floor material, the fluidizing gas is moved, typically from the product recovery unit (40) of the fluid reactor system, into the transport zone (30), optionally in two or more regions, and preferably by changing the ratio of the fluidizing gas moved into the first region of the transport zone to a second region of the transport zone, thereby increasing or decreasing the temperature difference between the combustion chamber (12) and the pyrolysis chamber (2).

6. The method according to any one of claims 1 to 3, wherein the transport zone (30) includes a first region (32) that allows a downflow of the floor material from the combustion chamber (12) and a second region (34) that allows an upflow of the floor material to the pyrolysis chamber (2), and preferably moves a fluidizing gas through an upstream portion (36) of the second region (34) and through a downstream portion (35) of the second region (34), preferably having a velocity of 0.5 to 3 m / s, preferably 1 to 2.5 m / s, and more preferably 2 m / s.

7. The method according to claim 5, wherein the velocity of the fluidizing gas in the transport zone (30) is 0.5 to 3 m / s, preferably 1 to 2.5 m / s.

8. The method according to claim 6, wherein the velocity of the fluidizing gas in the transport zone (30) is 0.5 to 3 m / s, preferably 1 to 2.5 m / s.

9. The method according to any one of claims 1 to 3, wherein, in order to control the circulation rate of the floor material, the fluidizing gas is moved, typically from the product recovery unit (40) of the fluid reactor system into the pyrolysis chamber (2), preferably, the velocity of the fluidizing gas in the pyrolysis chamber (2) is 3 to 7 m / s, preferably 4 to 6 m / s.

10. (c) Further comprising transferring the depolymerized polymer-producing gas into a product recovery unit (40) to isolate one or more monomers, optionally including the following: - Isolating non-condensable gases and / or energy sources from the depolymerized polymer-producing gases; - Transferring at least a portion of the non-condensable gas and / or energy source isolated from the depolymerized polymer-producing gas to the combustion chamber (12); - Transferring at least a portion of the non-condensable gas and / or energy source isolated from the flue gas from the combustion chamber (12) and the depolymerized polymer product gas from the product recovery unit (40) to a heat recovery system, wherein the heat recovery system includes an afterburner (58), and preferably transfers 40 to 75%, more preferably 60 to 70%, of the total weight of the non-condensable gas to the heat recovery system; - To fluidize the pyrolysis chamber, transfer at least a portion of the non-condensable gas isolated from the depolymerized polymer product gas and / or the energy source into the pyrolysis chamber (2), preferably by hydrogenating the olefins present in the non-condensable gas and / or the energy source before transferring them into the pyrolysis chamber (2); - Using the non-condensable gas isolated from the depolymerized polymer-producing gas and / or at least a portion of the energy source to produce chemical substances, preferably hydrogen and / or olefins; - Isolating the dimer and trimer from the depolymerized polymer gas, and transferring the dimer and trimer to the pyrolysis chamber (2), The method according to any one of claims 1 to 3, wherein one or more of the above apply.

11. The method according to any one of claims 1 to 3, wherein a non-condensable gas and / or energy source is isolated from the depolymerized polymer-producing gas, and 40 to 75%, preferably 60 to 70%, of the total weight of the non-condensable gas and / or energy source from the combustion chamber (12) and the product recovery unit (40) is used to supply heat to a heat recovery system, the heat recovery system comprising an afterburner (58).

12. The method according to any one of claims 1 to 3, wherein the combustion chamber (12) is operated quasi-stoichiometrically.

13. The supplied raw material is provided as flakes having a thickness of 0.25 to 3 mm, and / or The method according to any one of claims 1 to 3, wherein at least 50%, preferably at least 75%, and more preferably at least 90% of the supply raw material is provided as flakes.

14. Use of a fluid reactor system comprising a pyrolysis chamber (2), a combustion chamber (12), and a floor material circulating from the combustion chamber (12) to the pyrolysis chamber (2) via a transport zone (30) for depolymerizing the polymer in the supply material, which contains 60% or more polymer based on the weight of the supply material, into one or more monomers.

15. below: - To obtain a depolymerized polymer gas containing the monomer, a thermal decomposition process is carried out in the floor material at a temperature in the range of 450 to 650°C; - Adjusting the temperature difference between the combustion chamber and the pyrolysis chamber by changing the ratio of the fluidized gas moved into the first region of the transport zone to the second region of the transport zone; - By changing the circulation rate of the floor material, the temperature difference between the combustion chamber and the pyrolysis chamber is increased or decreased. Use of the fluid reactor system according to claim 14, wherein one or more of the following apply.

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