Reactor

Abstract

The invention is based on a reactor (10a-d) for the continuous depolymerization of polymers, in particular polyolefins from polymer waste, comprising primary reactors (12a-d), heating units (14a, 14b, 14d) for heating and melting and at least partial depolymerization of the polymer in the primary reactors (12a-d), and at least one primary circulation unit (16a-d) for circulation of the molten polymer in the primary reactors (12a-d). The reactors (10a-d) comprise secondary reactors (18a, 18b, 18d) connected downstream of the primary reactors (12a-d) and forming a reactor cascade together with the primary reactors (12a-d).

Description

[Technical field]

[0001] The present invention relates to a reactor according to the preamble of claim 1, a depolymerization plant according to claim 18 and a method for the continuous depolymerization of polymers according to the preamble of claim 19. [Background technology]

[0002] As the waste volumes of plastic waste, such as packaging materials, tires, etc., increase, the demand for efficient technologies to utilize such waste streams increases. Here, the utilization of these purely material waste streams to form equivalent products is not always economically possible or often involves downcycling, for example due to the high demand for individual polymer groups in an unmixed state. Therefore, an efficient chemical utilization of the polymers contained in these waste streams is desired for their decomposition into individual monomers or oligomers and / or mixtures of monomers and oligomers and / or mixtures of different hydrocarbon fractions that can replace fossil hydrocarbons such as crude oil or natural gas, and the subsequent production of products of equivalent or higher value, such as fuels. In addition to the known methods for the chemical utilization of plastic waste, such as carbonization, low-temperature carbonization, or gasification of plastic waste, which are often not economically viable, methods for continuous depolymerization are also becoming the focus of research and development in the field of recycling technologies.

[0003] A method for the continuous depolymerization of polymers is already known from US Pat. No. 5,399,633. Here, a continuous process for the pyrolysis of polyethylene, polypropylene and polystyrene under slight overpressure in a stirred apparatus with an external pump and a heat exchanger is described, in which these polymers are indirectly heated, melted, partially depolymerized using a molten salt system as a heat transfer medium and then fed to a downstream connected, horizontally mounted, tubular second reactor with stirring blades for complete evaporation. However, for efficient implementation of the method, a degree of depolymerization of more than 90% is required in the stirred apparatus in order to be able to efficiently process the highly viscous residual fraction remaining in the horizontally mounted tubular second reactor. However, since an almost ideal mixing takes place in the stirred apparatus, the required degree of depolymerization is hardly achievable in practice, and therefore efficient implementation of the known method is hardly possible in practice. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 152205 Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to advantageously further develop the generic device and the generic method, in particular with regard to efficiency. This object is achieved according to the invention by the features of claims 1, 18 and 19, advantageous implementations and further developments of the invention can be inferred from the dependent claims. [Means for solving the problem]

[0006] The invention is based on a reactor for the continuous depolymerization of polymers, in particular polyolefins from polymer waste, which comprises a primary reactor, a heating unit for heating and melting and at least partial depolymerization of the polymer in the primary reactor, and at least one primary circulation unit for circulation of the molten polymer in the primary reactor.

[0007] It is proposed that the reactor comprises a secondary reactor which is connected downstream of the primary reactor and which forms, together with the primary reactor, a reactor cascade. Such an implementation advantageously makes it possible to provide a reactor with improved efficiency. Since the secondary reactor is connected downstream of the primary reactor, the required degree of depolymerization of more than 90% can advantageously be achieved in the reactor cascade, thus allowing efficient depolymerization. In combination with a molten salt system for indirect heat transfer in the primary and secondary reactors, already known from US Pat. No. 5,999,633, the efficiency can be advantageously further improved.

[0008] "Reactor" means a particularly functional component of a depolymerization plant, in particular a structural and / or functional component. The reactor may also include the entire depolymerization plant. The reactor and / or the depolymerization plant comprising the reactor is configured to carry out a method for continuous depolymerization of polymers, in particular polyolefins such as, but not limited to, polyethylene, polypropylene, and polystyrene. The reactor and / or the depolymerization plant preferably comprises a molten salt system, as already described in WO 2005 / 023996. The molten salt system is preferably configured for operation with a molten salt consisting essentially of potassium nitrate and / or sodium nitrate and / or potassium nitrite and / or sodium nitrite. The heating unit is preferably configured for indirect heat transfer via the molten salt system.

[0009] The primary reactor is preferably configured as a primary stirred reactor. The secondary reactor is preferably configured as a secondary stirred reactor. Preferentially, the secondary stirred reactor forms a stirred cascade together with the primary stirred reactor. The reactor may also include a tertiary reactor, which is connected downstream of the secondary reactor and may be configured similarly to the horizontally mounted tubular second depolymerization reactor described in particular in US Pat. No. 5,399,991. The tertiary reactor may form a reactor cascade together with the primary and secondary reactors. The primary and secondary reactors are preferably configured as vertical reactors and the tertiary reactor is configured as a horizontal reactor. The primary and secondary reactors are configured to process a medium viscosity molten polymer and the tertiary reactor is configured to process a high viscosity molten polymer. The tertiary reactor is configured to receive the molten polymer depolymerized in the primary and secondary reactors to a percentage of more than 90%. In the tertiary reactor, stirring arms are arranged, which are configured to throw the molten high-viscosity polymer against the inner wall of the tertiary reactor in a uniform distribution, thereby forming a thin layer. On the outer wall of the tertiary reactor, a tertiary heat exchanger is arranged, which is configured to further, in particular completely, depolymerize the high-viscosity molten polymer using heat supplied through the outer wall. The stirring arms in the tertiary reactor must be distinguished from stirring elements as may be arranged in the primary reactor and / or the secondary reactor. In principle, the reactor can comprise, in addition to the primary and secondary reactors, any number of further reactors that appear convenient to the person skilled in the art, in particular those further reactors that are connected downstream of the secondary reactor and upstream of the tertiary reactor, forming a reactor cascade together with the primary and secondary reactors.

[0010] As used herein, numerical words preceding certain terms, such as "first" and "second," serve merely to distinguish and / or assign objects to one another and do not imply a preexisting total number and / or ranking of the objects. In particular, a "second object" does not necessarily imply the existence of a "first object."

[0011] In this specification, "at least substantially" means that the deviation from a given value is in particular less than 25%, preferably less than 10% and particularly preferentially less than 5% of the stated value. "Configured" means specifically designed and / or equipped. The fact that an object is configured for a particular function means that the object fulfills and / or performs this particular function in at least one application and / or operational state.

[0012] It is further proposed that the reactor comprises a secondary circulation unit having at least one secondary circulation element for generating a radial flow in the secondary reactor. Such implementation advantageously allows for a further increase in efficiency. In particular, it allows for an improved circulation of the molten polymer and therefore an improved depolymerization in the secondary reactor. The secondary circulation unit may be embodied, for example, as a pump, and preferably comprises at least one secondary circulation element embodied as a stirring element. The secondary circulation unit preferably comprises a plurality of secondary circulation elements embodied as stirring elements, which are arranged one above the other on a common stirring shaft.

[0013] In addition, it is proposed that in at least one operating state, a plug flow is provided in the secondary reactor. This can advantageously further increase the efficiency of the melt depolymerization. The apparatus preferably comprises a flow generating unit configured to generate a plug flow. The flow generating unit comprises at least one inlet arranged in an upper region of the secondary reactor and at least one outlet arranged in a lower region of the secondary reactor. The secondary reactor preferably has a tubular basic shape to further assist in providing the plug flow. In principle, it is conceivable that alternatively or additionally, a plug flow is provided in the primary reactor.

[0014] It is further proposed that the primary circulation unit comprises at least one primary circulation element for generating an axial flow in the primary reactor. Such implementation advantageously allows to further increase the efficiency. The primary circulation unit may comprise at least one primary circulation line. The primary circulation unit may comprise a plurality of primary circulation elements. The at least one primary circulation element may be embodied as a pump configured to circulate a partial amount of the molten polymer from the primary reactor via the circulation line. Preferably, the at least one primary circulation element is embodied as a stirring element.

[0015] It is also proposed that the primary reactor comprises an outlet unit for feeding a partial flow of the molten polymer into the secondary reactor, the outlet unit comprising an overflow area. Such an implementation advantageously allows selective feeding of the molten polymer from the primary reactor into the secondary reactor.

[0016] In addition, it is proposed that the height of the overflow area is variably adjustable to set the residence time in the primary reactor. This advantageously allows for increased flexibility, in particular allowing a flexible adaptation of the residence time distribution to different compositions of the polymer to be depolymerized. Height adjustment is made possible, for example, by multiple overflow valves of the outlet unit arranged vertically above and below the overflow area.

[0017] In addition to this, it is proposed that the primary reactor is provided with at least one settling zone between the circulation area and the overflow area, which advantageously allows for an efficient operation, in particular an advantageous residence time distribution and thus a high degree of depolymerization in the primary reactor can be achieved.

[0018] It is further proposed that the reactor comprises a regulating unit configured to regulate the filling level of the molten polymer in the secondary reactor, which advantageously allows a particularly efficient and flexible operation. Preferably, the regulating unit comprises at least one filling level indicator controller (LIC) and at least one regulating valve controllable via a signal of the filling level indicator controller and configured to control and / or regulate the outlet of the molten polymer from the secondary reactor.

[0019] It is further proposed that the heating unit comprises at least one secondary heat exchanger arranged outside the secondary reactor and configured for heating the latter, which advantageously allows an efficient heat supply. Preferably, the secondary heat exchanger is configured as a shell heat exchanger and surrounds the secondary reactor along its circumferential direction. Preferably, the secondary heat exchanger is configured to operate via a molten salt system of the depolymerization plant.

[0020] It is further proposed that the heating unit comprises at least one primary heat exchanger, which advantageously allows efficient and gentle melting and heating of the polymer and partial depolymerization. Preferably, the primary heat exchanger is configured to operate via the molten salt system of the depolymerization plant. In particular, the primary heat exchanger is configured for heating the polymer in the primary reactor to a first temperature, preferably between 250°C and 350°C, and the secondary heat exchanger is configured for heating the polymer in the secondary reactor to a second temperature different from the first temperature, in particular higher than the first temperature, preferably between 380°C and 500°C, preferentially between 420°C and 480°C.

[0021] In a further aspect of the invention, which may in particular be considered both independently and in combination with the other aspects of the invention, it is proposed that the reactor comprises a guide tube arranged in the primary reactor for the separation of the two opposing axial flows in the primary reactor. Such an implementation advantageously allows for an efficient flow guidance in the primary reactor. In particular, the already molten polymer may be conveyed upwards in the guide tube in a first axial flow and, together with the newly added, not yet molten polymer, downwards outside the guide tube in a second axial flow. Alternatively, the flow direction may be reversed and the already molten polymer may be conveyed downwards in the guide tube in the first axial flow and upwards outside the guide tube in the second axial flow. Thus, a particularly efficient melting and depolymerization is possible.

[0022] In addition, it is proposed that the primary heat exchanger at least partially surrounds the guide tube in the circumferential direction. Such an implementation may advantageously allow for improved heat transfer.

[0023] In a further aspect of the invention, which may in particular be considered independently and in combination with the other aspects of the invention, it is proposed that the reactor comprises a pretreatment reactor for the pretreatment of chlorine-containing polymers, the pretreatment reactor being connected upstream of the primary reactor and forming a reactor cascade together with the primary reactor. Such an implementation advantageously allows for further efficiency improvement. In particular, resource efficiency can be improved in that in addition to polyolefins, chlorine-containing polymers, such as polyvinyl chloride and / or polyvinylidene chloride, can be depolymerized by the reactor. Furthermore, advantageously, safety can be increased if chlorine-containing components are separated in the pretreatment reactor, so that the formation of risky chlorine compounds, such as dioxins, which may be formed at higher temperatures in the primary and / or secondary reactors, is effectively prevented. Preferably, the pretreatment reactor and the components of the reactor arranged therein and / or directly connected downstream of the pretreatment reactor, such as pipelines, are made of corrosion-resistant materials, such as enamel and / or Hastelloy and / or titanium and / or zirconium and / or tantalum. The reactor is preferably configured for one-stage pretreatment of chlorine-containing polymers in the pretreatment reactor. Alternatively, however, it is also conceivable that the reactor is configured for a multi-stage pretreatment of the chlorine-containing polymer and for this purpose comprises a plurality of pretreatment reactors which may in particular be arranged in a pretreatment cascade.

[0024] It is further proposed that the heating unit comprises at least one pretreatment heat exchanger for heating and melting and at least partial depolymerization of the chlorine-containing polymer, which advantageously allows further improvement in efficiency.Preferably, the pretreatment heat exchanger is arranged to operate via the molten salt system of the depolymerization plant.

[0025] It is further proposed that the reactor comprises a pretreatment circulation unit, which is arranged in the pretreatment reactor for circulation of molten chlorine-containing polymer.This can advantageously further improve the efficiency of pretreatment.Pretreatment circulation unit preferably comprises at least one stirring element.Pretreatment circulation unit may alternatively or additionally comprise at least one circulation pump.

[0026] It is further proposed that the reactor comprises a wet separator unit for the work-up of the gas phase arising in the pretreatment reactor, connected to the pretreatment reactor, which advantageously allows an efficient work-up of the gas phase arising in the pretreatment reactor, the wet separator unit being preferably configured for the work-up by NaOH washing.

[0027] In addition to this, it is proposed that the reactor comprises a static mixer unit arranged fluidly between the pretreatment reactor and the primary reactor in order to separate residual amounts of chlorine from the liquid phase arising in the pretreatment reactor. This advantageously allows to further improve the efficiency and safety of the reactor. In particular, if the residual amounts of chlorine are completely separated before entering the primary reactor, the primary reactor as well as the pipelines and plant parts of the depolymerization plant connected downstream of the primary reactor can be advantageously manufactured from less expensive grades and therefore more cost-effective materials, since the corrosion resistance requirements are correspondingly lower. The static mixer unit preferably comprises at least one static mixer configured to add calcium oxide and convert the residual amounts of chlorine into calcium chloride.

[0028] The invention further relates to a depolymerization plant having a reactor according to one of the above-mentioned implementations and at least one fractionator for further processing of the gaseous depolymerization products arising in the primary reactor and / or the secondary reactor. Such a depolymerization plant is particularly distinguished by advantageous properties, in particular with regard to the efficiency achievable by the reactor. In addition to the reactor and the fractionator, the depolymerization plant may also comprise further units and elements, in particular suitable pipelines, heat exchangers for condensation of the products arising in gaseous form in the fractionator, etc. The depolymerization plant is realized differently from a steam cracker.

[0029] The present invention is further based on a method for the continuous depolymerization of polymers by means of a depolymerization plant as described above, in which the polymer is fed to a primary reactor, heated, melted and at least partially depolymerized in the primary reactor by circulation through a primary circulation unit and heat supply by a heating unit, and the gaseous depolymerization product resulting in the primary reactor is fed to rectification in a rectification column.

[0030] It is proposed that at least a partial stream of the molten polymer is fed to a secondary reactor, where it is further depolymerized with heat provided by a heating unit, and the depolymerization product resulting in the secondary reactor is fed to rectification in a rectification unit. Such a method advantageously enables a particularly efficient continuous depolymerization of the polymer. The heating, melting and depolymerization of the polymer can advantageously be carried out without liquid and / or gaseous auxiliary phases. The depolymerization is preferably carried out without the supply of water vapor, in particular unlike the so-called steam cracker process.

[0031] It is further proposed to feed the bottom product arising in the rectification column to a secondary reactor and / or to the primary reactor, which advantageously allows the efficiency of the process to be further improved, in particular when feeding the bottom product arising in the rectification column to a secondary reactor and / or to the primary reactor, the product yield can be increased.

[0032] In an advantageous implementation, it is proposed that the method comprises a pretreatment step, in which the chlorine-containing polymer is pretreated before being fed into the primary reactor, and the chlorine-containing components are separated during the process, which advantageously allows the efficiency of the method to be further improved, since the chlorine-containing polymer can be used.

[0033] The reactor, depolymerization plant and method according to the invention are not limited to the above-mentioned applications and implementations, in particular, to perform the functions described herein, the reactor and / or depolymerization plant according to the invention may comprise a different number of individual elements, components and units than given herein.

[0034] Further advantages will become apparent from the following description of the drawings, in which two exemplary embodiments of the invention are shown. The drawings, the specification and the claims contain a number of combinations of features, which a person skilled in the art will consider individually and in a deliberate manner and will find further advantageous combinations. [Brief description of the drawings]

[0035] [Figure 1] FIG. 1 shows a schematic piping and instrumentation flow diagram of a depolymerization by reactor for continuous depolymerization of polymers. [Diagram 2] A further exemplary embodiment of a depolymerization plant having a reactor for the continuous depolymerization of a polymer is shown in a schematic piping and instrumentation flow diagram. [Diagram 3] FIG. 1 shows in a schematic diagram the primary reactor of a reactor for the continuous depolymerization of polymers. [Figure 4] FIG. 2 shows a further exemplary embodiment of a depolymerization plant with a reactor for the continuous depolymerization of a polymer in a schematic piping and instrumentation flow diagram. [Diagram 5] FIG. 1 shows a schematic process flow chart to illustrate a method for continuous depolymerization of polymers by a depolymerization plant. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Description of exemplary embodiments 1 shows a schematic piping and instrumentation flow diagram of a depolymerization plant 60a. The depolymerization plant 60a comprises a reactor 10a for the continuous depolymerization of polymers, in particular for the depolymerization of polyolefins, such as polyethylene and / or polypropylene and / or polystyrene, from polymer waste (not shown).

[0037] The depolymerization plant 60a comprises a rotary valve 62a, a conveyor screw 64a, and an inlet 66a comprising a cooling section 68a connected to a cooling water cycle 70a.

[0038] The reactor 10a comprises a primary reactor 12a. The primary reactor 12a is connected to an inlet 66a. For the operation of the depolymerization plant 60a, for example, polymer waste from a sack can be fed to the primary reactor 12a by a conveyor screw 64a via the inlet 66a through a rotary valve 62a with simultaneous feeding of nitrogen as inert gas from a nitrogen feed line 72a. The cooling section 68a here prevents premature melting of the polymer waste and thus blocking of the inlet 66a.

[0039] The reactor 10a further comprises a heating unit 14a for heating and melting the polymer in the primary reactor 12a and for at least partial depolymerization. The heating unit 14a comprises at least one primary heat exchanger 40a.

[0040] The reactor 10a includes a guide tube 42a arranged in the primary reactor 12a to separate two opposing axial flows in the primary reactor 12a. The primary heat exchanger 40a is realized as a shell heat exchanger and is arranged outside the primary reactor.

[0041] The molten salt is used as a heat medium for the operation of the primary heat exchanger 40a. The depolymerization plant 60a comprises a molten salt system 74a having a molten salt tank 76a and a heating device 78a, such as a melting furnace. Molten salt consisting essentially of potassium nitrate and / or sodium nitrite and / or potassium nitrite and / or sodium nitrite is transported by a submersible pump (not shown) from the molten salt tank 76a through a suitable pipeline to the primary heat exchanger 40a and from there back into the molten salt tank 76a.

[0042] The reactor 10a further comprises a primary circulation unit 16a. The primary circulation unit 16a is configured for the circulation of the molten polymer in the primary reactor 12a. The primary circulation unit 16a comprises at least one primary circulation element 26a for generating an axial flow in the primary reactor 12a. In this case, the primary circulation unit 16a is realized as a primary stirring unit 24a. The primary circulation element 26a of the primary circulation unit 16a is realized as a primary stirring element 58a. The primary circulation element 26a realized as a primary stirring element 58a is arranged in the circulation area 34a of the primary reactor 12a, i.e. in the guide tube 42a.

[0043] In the operating state of the reactor 10a, the molten polymer is forced into a first axial flow upwards in the guide tube 42a by the primary stirring element 58a. Above the guide tube 42a, the molten polymer flows downwards in a second axial flow outside the guide tube 42a together with further polymer waste added via the inlet 66a, which is melted by the primary heat exchanger 40a. During this process, the molten polymer is partially depolymerized. Alternatively, the reverse flow direction is also conceivable, in which the molten polymer is forced into a first axial flow downwards in the guide tube 42a by the primary stirring element 58a and rises again in a second axial flow upwards outside the guide tube.

[0044] The depolymerization plant 60a comprises a fractionator 56a connected to the primary reactor 12a. The gaseous depolymerization product produced in the operating primary reactor 12a is fed to a first stage of the fractionator 56a.

[0045] The reactor 10a includes a secondary reactor 18a connected downstream of the primary reactor 12a and forming a reactor cascade together with the primary reactor 12a. The primary reactor 12a comprises an outlet unit 28a for feeding a partial stream of molten polymer into the secondary reactor 18a. The outlet unit 28a comprises an overflow region 30a. The primary reactor 12a comprises at least one settling zone 32a. The settling zone 32a is arranged between the circulation region 34a and the overflow region 30a. In operation, a partial stream of polymer molten in the primary reactor 12a passes via the settling zone 32a into the overflow region 30a and from there is transferred into the secondary reactor 18a.

[0046] The reactor 10a comprises a secondary circulation unit 20a with at least one secondary circulation element 22a for creating a radial flow in the secondary reactor 18a. In this case, the secondary circulation unit 20a is realized as a secondary stirring unit 80a. The secondary circulation element 22a of the secondary circulation unit 20a is embodied as a secondary stirring element 82a. In this case, the secondary circulation unit 20a comprises a plurality of secondary circulation elements 22a, which are embodied as secondary stirring elements 82a and are vertically connected to one another above the other to the stirring shaft. For the sake of clarity, in FIG. 1 only one of the secondary circulation elements 22a is given a reference number.

[0047] The heating unit 14a comprises at least one secondary heat exchanger 38a. The secondary heat exchanger 38a is arranged outside the secondary reactor 18a. The secondary heat exchanger 38a is configured for heating the secondary reactor 18a. In this case, the secondary heat exchanger 38a is realized as a shell heat exchanger and arranged circumferentially around the secondary reactor 18a. The secondary heat exchanger 38a is fed via a molten salt system 74a. In FIG. 1, the molten salt system 74a is shown simplified for clarity. Preferably, the molten salt system 74a comprises two separate molten salt cycles for feeding the primary heat exchanger 40a and the secondary heat exchanger 38a so that the polymers in the primary reactor 12 and the secondary reactor 18 can be heated to different temperatures. In operation, the molten polymer is fed from the primary reactor 12a into the secondary reactor 18a at an upper region and withdrawn at a lower region. As it passes through the secondary reactor 18a, the polymer is moved outwardly toward the vessel wall by the radial flow generated by the secondary circulation element 22a where it is further heated by the secondary heat exchanger 38a. The resulting gaseous depolymerization products rise and are fed to the second stage of the fractionator 56a.

[0048] The reactor 10a includes a tertiary reactor 88a connected downstream of the secondary reactor 18a. The tertiary reactor 88a is mounted horizontally and is equipped with an agitator arm 92a. In operation, a plug flow is provided in the secondary reactor 18a. The polymer that has not yet been depolymerized slowly sinks downwards in the secondary reactor 18a and is fed to the tertiary reactor 88a. The reactor 10a comprises a regulation unit 36a. The plug flow is provided by the regulation unit 36a. The regulation unit 36a is configured to regulate the fill level of the molten polymer in the secondary reactor 18a. The regulation unit 36a comprises a fill level indicator controller 84a and a regulation valve 86a. The regulation valve 86a is controlled via the fill level indicator controller 84a. A connecting line connects the outlet of the lower region of the secondary reactor 18a to the tertiary reactor 88a. The polymer is removed from the secondary reactor 18a by a pump via the outlet and is partially transferred directly into the tertiary reactor 88a when the regulation valve 86a is open. Furthermore, a heat exchanger 126a is arranged in the connecting line, which is connected to the salt cycle 74a. A partial flow of the polymer removed from the secondary reactor 18a, or the total amount if the control valve 86a is closed, is further heated via a heat exchanger 126a, where the resulting gaseous depolymerization product is fed to the third stage of the fractionator 56a and the remaining liquid phase is fed to the tertiary reactor. The heating unit 14a is arranged as a shell heat exchanger outside the tertiary reactor 88a and comprises a tertiary heat exchanger 90a fed via a molten salt system 74a. By means of the stirring arm 92a, the molten polymer is thrown so as to be uniformly distributed against the inner wall of the tertiary reactor 88a while forming a thin layer, and is further depolymerized by the heat fed via the tertiary heat exchanger 90a. The gaseous depolymerization product resulting in the tertiary reactor 88a is fed to the third stage of the fractionator 56a. The remaining residual amount of carbon black and inorganic components is fed to a disposal unit 94a, from where it is discharged as a residual fraction 108a. The products produced in fractionator 56a emerge in gaseous form at the top of fractionator 56a, are partially condensed by heat exchanger 98a and are fed to vessel 102a. The depolymerization products can be recovered from vessel 102a in the form of a gaseous light fraction 104a and in the form of a liquid heavy fraction 106a. A portion of the products, particularly from light fraction 104a, can be used, for example, for the operation of heating device 78a of molten salt cycle 74a.The heat exchanger 98a is operated by a hot water cycle 96a. The fractionator 56a is fed via a diesel feed 100a. Alternatively or additionally, it is contemplated that the fractionator 56a is fed via a heavy end 106a. The bottoms product arising in the fractionator 56a can then be fed to the secondary reactor 18a and / or the primary reactor 12a.

[0049] Three further exemplary embodiments of the present invention are shown in Figures 2 to 4. The following description and drawings are substantially limited to the differences between the exemplary embodiments, and for components having the same name, in particular the same reference numbers, reference may in principle also be made to the drawings and / or descriptions of the other exemplary embodiments, in particular to Figure 1. To distinguish the exemplary embodiments, the letter a is added to the reference numbers of the exemplary embodiments in Figure 1. In the exemplary embodiments of Figures 2 to 4, the letter a is replaced by letters b to d.

[0050] FIG. 2 shows in a schematic piping and instrumentation flow diagram a further exemplary embodiment of a depolymerization plant 60b having a reactor 10b for the continuous depolymerization of a polymer. In addition to the depolymerization of polyolefins such as polyethylene and / or polypropylene and / or polystyrene, reactor 10b is also configured for the depolymerization of chlorine-containing polymers, such as polyvinyl chloride.

[0051] As in the previous exemplary embodiment, reactor 10b comprises a primary reactor 12b, a secondary reactor 18b, and a tertiary reactor 88b. Reactor 10b further comprises a pretreatment reactor 44b for pretreatment of the chlorine-containing polymer. Pretreatment reactor 44b is connected upstream of primary reactor 12b and forms a reactor cascade with primary reactor 12b.

[0052] The reactor 10b comprises a heating unit 14b, which is fed through a molten salt system 74b, as in the previous exemplary embodiment. The heating unit 14b comprises at least one pretreatment heat exchanger 46b for heating and melting the chlorine-containing polymer and at least partially depolymerizing it. In FIG. 2, the molten salt system 74b is shown in a simplified form for clarity. Preferably, the molten salt system 74b comprises three separate molten salt cycles (not shown), namely a first molten salt cycle for feeding the primary heat exchanger 40b for heating the primary reactor 12b, a second molten salt cycle for feeding the secondary heat exchanger 38b for heating the secondary reactor 18b, and a third molten salt cycle for feeding the pretreatment heat exchanger 46b, so that the polymers in the pretreatment reactor 44b, the primary reactor 12, and the secondary reactor 18 can be heated to different temperatures, respectively. In principle, it is also conceivable to use only a single molten salt cycle starting from a molten salt tank and leading first through the secondary heat exchanger 38b, then through the primary heat exchanger 40b and then through the pretreatment heat exchanger 46b, so that the polymer can be heated to different temperatures in the pretreatment reactor 44b, the primary reactor 12 and the secondary reactor 18, respectively.

[0053] The reactor 10b comprises a pretreatment circulation unit 48b arranged in the pretreatment reactor 44b for the circulation of the molten chlorine-containing polymer. The pretreatment circulation unit 48b comprises a pretreatment circulation element 50b embodied as a stirring element.

[0054] The reactor 10b comprises a wet separator unit 52b connected to the pretreatment reactor 44b for the aftertreatment of the gas phase arising in the pretreatment reactor 44b. The wet separator unit 52b is configured for NaOH scrubbing of hydrochloric acid from the gas phase arising in the pretreatment reactor 44b and is supplied via a sodium hydroxide feed 128b. In the operating state of the reactor 10b, the sodium chloride-containing water arising in the wet separator unit 52b during the NaOH scrubbing can be recovered as a sodium chloride fraction 130b. The resulting waste gas is discharged as a waste gas fraction 132b.

[0055] The reactor 10b includes a static mixer unit 54b fluidly disposed between the pretreatment reactor 44b and the primary reactor 12b for separating residual amounts of chlorine from the liquid phase produced in the pretreatment reactor 44b. The liquid phase produced in the operating pretreatment reactor 44b is fed to the static mixer unit 54b, where calcium oxide is fed via calcium oxide feed 134b to convert the chlorine-containing components remaining in the liquid phase to calcium chloride. The molten polymer from which the chlorine-containing components have been removed is fed to the primary reactor 12b.

[0056] Regarding the function of the primary reactor 12b, reference can be made primarily to the above description of the previous exemplary embodiment. The primary reactor 12b comprises an outlet unit 28b for feeding a partial flow of the molten polymer to the secondary reactor 18b, which is connected downstream of the primary reactor 12b. The outlet unit 28b comprises an overflow area 30b. In contrast to the previous exemplary embodiment, the height of the overflow area 30b is variably adjustable to set the residence time in the primary reactor 12b. For this purpose, the outlet unit 28b comprises a first overflow valve 136b, a second overflow valve 138b arranged above the first overflow valve 136b, and a third overflow valve 140b arranged above the second overflow valve 138b. Depending on whether the overflow region 30b is connected to the secondary reactor 18b via overflow valve 136b, 138b, 140b, the residence time in the primary reactor 12b can be variably adjusted to allow flexible response to different compositions of the polymer starting material.

[0057] A further difference of the primary reactor 12b with respect to the primary reactor 12a of the previous exemplary embodiment is that the stirring shaft for driving the primary circulation element 26b of the primary circulation unit 16b, realized as a primary stirring element 58b, is introduced into the primary reactor 12b from above, while the stirring shaft of the primary stirring element 58a of FIG. 1 is inserted into the primary reactor 12a from below.

[0058] For further components and functions of the depolymerization plant 60b, reference may be made to the above description of the previous exemplary embodiment. 3 shows in a schematic diagram the primary reactor 12c of a reactor 10c for the continuous depolymerization of polymers. In contrast to the primary reactors 12a and 12b of the previous exemplary embodiment, the primary reactor 12c is realized without a guide tube.

[0059] The reactor 10c comprises a primary circulation unit 16c. The primary circulation unit 16c is configured for the circulation of the molten polymer in the primary reactor 12c. The primary circulation unit 16c comprises at least one primary circulation element 26c for creating an axial flow in the primary reactor 12c. As in the previous exemplary embodiment, the primary circulation unit 16c is realized as a primary stirring unit 24c and comprises the primary circulation element 26c embodied as a primary stirring element 58c. The primary circulation unit 16c comprises a further primary circulation element 110c. The further primary circulation element 110c is realized as a circulation pump 112c. In principle, it is also conceivable to omit the primary stirring element 58c and to operate the primary reactor 12c only with the circulation pump 112c.

[0060] The reactor 10c comprises a heating unit 14c for heating and melting the polymer in the primary reactor 12c and for at least partial depolymerization. The heating unit 14c comprises at least one primary heat exchanger 40c. The primary heat exchanger 40c is arranged outside the primary reactor 12c on the circulation line 114c of the primary reactor 12c.

[0061] In the operating state of the reactor 10c, the molten polymer can be pumped from the lower region of the primary reactor 12c through the circulation line 114c by the circulation pump 112c, further heated by the primary heat exchanger 40c, and pumped back into the primary reactor 12c at the upper region. Alternatively, the reverse pumping direction through the circulation line 114c is also contemplated.

[0062] In principle, the secondary reactors 18a, 18b shown in the previous exemplary embodiment and / or the pretreatment reactor 44b of the second exemplary embodiment can be implemented similarly to the primary reactor 12c shown in this exemplary embodiment and can include the features described above with respect to the primary reactor 12c.

[0063] The reactor 10c is part of a depolymerization plant 60c, which comprises a secondary reactor (not shown) connected downstream of the primary reactor 12c and forming a reactor cascade together with the primary reactor 12c. Except for the differences with respect to the primary reactor 12c, reference can be made to the above description of the depolymerization plant 60a or the depolymerization plant 60b of the previous exemplary embodiment for the implementation of the depolymerization plant 60c.

[0064] FIG. 4 illustrates in a schematic piping and instrumentation flow diagram a further exemplary embodiment of a depolymerization plant 60d having a reactor 10d for the continuous depolymerization of a polymer. The depolymerization plant 60d differs from the depolymerization plant 60b of the second exemplary embodiment with respect to the implementation of the primary reactor 14d of the reactor 10d. The reactor 14d comprises a heating unit 14d having a primary heat exchanger 40d. The reactor 10d further comprises a guide tube 42d configured to separate two opposing axial flows in the primary reactor 14d. In contrast to the previous exemplary embodiment, the primary heat exchanger 40d is arranged in the primary reactor 14d and at least partially surrounds the guide tube 42d in the circumferential direction. The primary heat exchanger 40d is realized as a shell-and-tube heat exchanger, comprising a number of tubes with flow passages (not numbered) arranged between them.

[0065] The reactor 10d further comprises a primary circulation unit 16d. The primary circulation unit 16d is configured for the circulation of the molten polymer in the primary reactor 12d. As in the previous exemplary embodiment, the primary circulation unit 16d comprises at least one primary circulation element 26d for creating an axial flow in the primary reactor 12d. In this case, the primary circulation unit 16d is realized as a primary stirring unit 24d. The primary circulation element 26d of the primary circulation unit 16d is realized as a primary stirring element 58d and is arranged in a guide tube 42d.

[0066] In the operating state of the reactor 10d, the molten polymer can be forced into a first axial flow upward in the guide tube 42d by the primary stirring element 58d. Above the guide tube 42d, the molten polymer flows downward through the passages between the tubes of the primary heat exchanger in a second axial flow outside the guide tube 42d, together with additional polymer waste added via inlet 66d, which is melted by the primary heat exchanger 40d. During this process, the molten polymer is partially depolymerized.

[0067] The reactor 10d comprises a pretreatment reactor 44d for the pretreatment of the chlorine-containing polymer. The pretreatment reactor 44d is connected upstream of the primary reactor 12d and forms a reactor cascade together with the primary reactor 12d. The heating unit 14d comprises at least one pretreatment heat exchanger 46d for the heating and melting and at least partial depolymerization of the chlorine-containing polymer. In this case, the pretreatment reactor 44d is realized similarly to the exemplary embodiment of FIG. 2. However, it is alternatively conceivable that the reactor 10d comprises an additional guide tube (not shown) arranged in the pretreatment reactor 44d. Furthermore, it is conceivable that the pretreatment heat exchanger 46d is arranged in the pretreatment reactor 44d and circumferentially surrounds the additional guide tube, so that the pretreatment reactor 44d is realized substantially identical to the primary reactor 10d.

[0068] For further components and functions of the depolymerization plant 60d, reference may otherwise be made to the above description of the exemplary embodiment of FIG. In principle, further combinations of the features described with reference to the previous exemplary embodiments are conceivable: for example, the primary reactor and the secondary reactor and / or the pretreatment reactor may be realized to be substantially identical to each other, or the features described above with respect to one reactor may be transferred to one or more of the other reactors as well.

[0069] FIG. 5 shows a schematic process flow chart to illustrate a method for continuous depolymerization of polymers by a depolymerization plant, where the depolymerization plant 60a, the depolymerization plant 60b, or the depolymerization plant 60c, or the depolymerization plant 60d of the previous exemplary embodiments can be used to carry out the method.

[0070] The method comprises at least three method steps. In a first method step 118 of the method, the polymer, in particular in the form of polymer waste, is fed to a primary reactor 12a, 12b, 12c, 12d. In the primary reactor 12a, 12b, 12c, 12d, the polymer is heated, melted and at least partially depolymerized by circulation through a primary circulation unit 24a, 24b, 24c, 24d and heat supply through a heating unit 14a, 14b, 14c, 14d, where the gaseous depolymerization product resulting in the process is fed to rectification in a rectification column 56a, 56b, 56d. Preferably, the polymer is heated in the first method step 118 to a temperature between 250 ° C. and 350 ° C., particularly preferentially to 300 ° C. In a second method step 120 of the method, at least a partial stream of the molten polymer is fed to the secondary reactors 18a, 18b, 18d and further depolymerized by heat supply from the heating units 14a, 14b, 14c, 14d, and the gaseous depolymerized products resulting in the process are fed to the rectification columns 56a, 56b, 56d. Preferably, the partial stream is heated in the second method step 120 to a temperature of 380°C to 500°C, particularly preferentially 420°C to 480°C. In a third method step 122 of the method, the components from the secondary reactors 18a, 18b that have not yet been depolymerized in the method steps 118, 120 are fed to the tertiary reactors 88a, 88b, 88d for further depolymerization, either directly or via heat exchangers 126a, 126b, 126d. In a third process step 122, the gaseous depolymerization products originating in the feed to the tertiary reactors 88a, 88b and / or originating in the tertiary reactors 88a, 88b are fed to the rectification towers 56a, 56b. Simultaneously with the process steps 118, 120, 122, rectification of the gaseous depolymerization products is carried out in the rectification towers 56a, 56b, 56d, and the bottom products originating in the rectification towers 56a, 56b are fed to the secondary reactors 18a, 18b, 18d and / or the primary reactors 12a, 12b, 12c, 12d. After subsequent partial condensation of the products originating at the top of the rectification towers 56a, 56b, 56d, they are partially condensed via the heat exchanger 98a. After this, the light fractions 104a, 104b, 104d and the heavy fractions 106a, 106b, 106d can be recovered.

[0071] For the treatment of chlorine-containing polymers, the method may include an optional pretreatment step 116 located upstream of the first method step 118. In the pretreatment step 116, the chlorine-containing polymer is pretreated before being fed into the primary reactors 12a, 12b, 12c, 12d, and the chlorine-containing components are separated in the process.

[0072] The pretreatment step 116 is preferably realized by the pretreatment reactor 44b described in the second exemplary embodiment or by the pretreatment reactor 44d described in the fourth exemplary embodiment and by a static mixer unit 54b or a mixing unit 54d connected thereto. The chlorine-containing polymer is heated, melted and at least partially depolymerized in the pretreatment reactor 44b, 44d by the pretreatment heat exchanger 46b, 46d. The post-treatment of the gas phase resulting in the pretreatment reactor 44b, 44d is realized by NaOH washing in the wet separator unit 52b, 52d. The resulting liquid phase is fed to the static mixer unit 54b, 54d, where the residual chlorine fraction is converted to calcium chloride in the static mixer unit 54b, 54d by adding calcium oxide. The molten polymer from which the chlorine-containing components have been removed is fed to the primary reactor 12b, 12d, where the first method step 118 is then carried out. [Explanation of symbols]

[0073] 10...reactor, 12...primary reactor, 14...heating unit, 16...primary circulation unit, 18...secondary reactor, 20...secondary circulation unit, 22...secondary circulation element, 24...primary stirring unit, 26...primary circulation element, 28...outlet unit, 30...overflow area, 32...settling zone, 34...circulation area, 36...regulating unit, 38...secondary heat exchanger, 40...primary heat exchanger, 42...guide tube, 44...pretreatment reactor, 46...pretreatment heat exchanger, 48...pretreatment circulation unit, 50...pretreatment circulation element, 52...wet separator, 54...static mixer unit, 56...rectification column, 58...primary stirring element, 60...depolymerization plant, 62...rotary valve, 64...conveyor screw, 66...inlet, 68...cooling section, 70...cooling water cycle, 72...nitrogen supply line, 74...molten salt system, 76...molten salt tank, 78... Heating device, 80... secondary stirring unit, 82... secondary stirring element, 84... fill level indicator controller, 86... control valve, 88... tertiary reactor, 90... tertiary heat exchanger, 92... stirring arm, 94... reject unit, 96... hot water cycle, 98... heat exchanger, 100... diesel feed, 102... vessel, 104... light end, 106... heavy end, 108... residue fraction, 110... further primary circulation elements, 112... circulation Pump, 114...circulation line, 116...pretreatment step, 118...first method step, 120...second method step, 122...third method step, 126...heat exchanger, 128...sodium hydroxide supply, 130...sodium chloride fraction, 132...waste gas fraction, 134...calcium oxide supply, 136...first overflow valve, 138...second overflow valve, 140...third overflow valve.

Claims

1. A reactor (10a - 10d) for the continuous depolymerization of polyolefins from polymers, especially polymer waste, comprising: a primary reactor (12a - d); a heating unit (14a - d) for heating and melting the polymer and at least partially depolymerizing it within the primary reactor (12a - d); at least one primary circulation unit (16a - d) for circulating the molten polymer within the primary reactor (12a - d), in a reactor (10a - 10d), a secondary reactor (18a, 18b, 18c) connected downstream of the primary reactor (12a - d) and forming a reactor cascade together with the primary reactor (12a - d).

2. The reactor (10a - 10d) according to claim 1, comprising a secondary circulation unit (20a, 20b, 20d) having at least one secondary circulation element (22a, 22b, 22d) for generating a radial flow within the secondary reactor (18a, 18b, 18c).

3. The reactor (10a - 10d) according to claim 1 or 2, wherein in at least one operating state, a plug flow is provided within the secondary reactor (18a, 18b, 18c).

4. The reactor (10a - 10d) according to claim 1 or 2, wherein the primary circulation unit (16a - d) comprises at least one primary circulation element (26a - d) for generating an axial flow within the primary reactor (12a - d).

5. The reactor (10a - 10d) according to claim 1 or 2, wherein the primary reactor (12a - d) comprises an outlet unit (28a, 28b, 28d) for supplying a partial flow of the molten polymer into the secondary reactor (18a, 18b, 18c), and the outlet unit (28a, 28b, 28d) comprises an overflow region (30a, 30b, 30d).

6. The reactor (10b, 10d) according to claim 5, wherein the height of the overflow region (30b, 30d) is variably adjustable to set the residence time within the primary reactor (12b, 12d).

7. The reactor (10a, 10b, 10d) according to claim 5, The reactor (10a, 10b, 10d) of the first stage has at least one sedimentation zone (32a, 32b, 32d) between the circulation region (34a, 34b, 34d) and the overflow region (30a, 30b, 30d).

8. In the reactor (10a, 10b, 10d) according to claim 1 or 2, The reactor (10a, 10b, 10d) comprising an adjustment unit (36a, 36b, 36d) configured to adjust the filling level of the molten polymer in the secondary reactor (18a, 18b, 18c).

9. In the reactor (10a, 10b, 10d) according to claim 1 or 2, The reactor (10a, 10b, 10d) comprising at least one secondary heat exchanger (38a, 38b, 38d) in which the heating unit (14a, 14b, 14d) is arranged outside the secondary reactor (18a, 18b, 18c) and configured to heat the secondary reactor (18a, 18b, 18d).

10. In the reactor (10a - 10d) according to claim 1 or 2, The reactor (10a - 10d) in which the heating unit (14a - d) comprises at least one primary heat exchanger (40a - d).

11. A reactor (10a - 10d) for the continuous depolymerization of polyolefins from polymers, particularly polymer waste, A first-stage reactor (12a - d), A heating unit (14a - d) for heating and melting the polymer in the first-stage reactor (12a - d) and for at least partial depolymerization, In the reactor (10a, 10b, 10d) having at least one primary circulation unit (16a - d) for circulating the molten polymer in the first-stage reactor (12a - d), The reactor (10a, 10b, 10d) comprising guide tubes (42a, 42b, 42d) arranged in the first-stage reactor (12a, 12b, 12d) for the separation of two opposing axial flows in the first-stage reactor (12a, 12b, 12d).

12. In the reactor (10d) according to claim 10, The reactor (10d) in which the primary heat exchanger (40d) at least partially surrounds the guide tube (42d) in the circumferential direction.

13. A reactor (10a - 10d) for the continuous depolymerization of polyolefins from polymers, particularly polymer waste, A first-stage reactor (12a - d), A heating unit (14a - d) for heating and melting the polymer and at least partially depolymerizing it in the primary reactors (12a - d), and at least one primary circulation unit (16a - d) for circulating the molten polymer in the primary reactors (12a - d), in a reaction apparatus (10b, 10d), comprising a pretreatment reactor (44b, 44d) for pretreatment of the chlorine - containing polymer, wherein the pretreatment reactor (44b, 44d) is connected upstream of the primary reactor (12b, 12d) and forms a reactor cascade together with the primary reactor (12b, 12d), the reaction apparatus (10b, 10d).

14. In the reaction apparatus (10b, 10d) according to claim 13, a heat unit (14b, 14d) comprising at least one pretreatment heat exchanger (46b, 46d) for heating and melting the chlorine - containing polymer and at least partially depolymerizing it, the reaction apparatus (10b, 10d).

15. In the reaction apparatus (10b, 10d) according to claim 13, comprising a pretreatment circulation unit (48b, 48d) arranged in the pretreatment reactor (44b, 44d) for circulating the molten chlorine - containing polymer, the reaction apparatus (10b, 10d).

16. In the reaction apparatus (10b, 10d) according to claim 13, comprising a wet separation unit (52b, 52d) connected to the pretreatment reactor (44b, 44d) and for post - treating the gas phase generated in the pretreatment reactor (44b, 44d), the reaction apparatus (10b, 10d).

17. In the reaction apparatus (10b, 10d) according to claim 13, for separating the residual amount of chlorine from the liquid phase generated in the pretreatment reactor (44b, 44d), comprising a static mixer unit (54b, 54d) fluidly arranged between the pretreatment reactor (44b, 44d) and the primary reactor (12a - d), the reaction apparatus (10b, 10d).

18. A depolymerization plant (60a - 60d), comprising the reaction apparatus according to claim 1 or 2, and at least one rectification column (56a, 56b, 56d) for further treating the gaseous depolymerization products generated in the primary reactor (12a - d) and / or the secondary reactor (18a, 18b, 18d), the depolymerization plant (60a - 60d).

19. A method for continuous depolymerization of a polymer by the depolymerization plant (60a - 60d) according to claim 18, The polymer is supplied to the primary reactors (12a - d), heated, melted, and at least partially depolymerized in the primary reactors (12a - d) by circulation by the primary circulation units (24a - d) and heat supply by the heating units (14a - d). A method in which the gaseous depolymerization products generated in the primary reactors (12a - d) are supplied for rectification in the rectification columns (56a, 56b, 56d). At least a partial stream of the molten polymer is supplied to the secondary reactors (18a, 18b, 18d) and further depolymerized by the heat supplied by the heating units (14a, 14b, 14d). A method in which the gaseous depolymerization products generated in the secondary reactors (18a, 18b, 18d) are supplied for rectification in the rectification columns (56a, 56b, 56d).

20. In the method according to claim 19,[[]]END]] A method of supplying the bottoms product generated in the rectification columns (56a, 56b, 56d) to the secondary reactors (18a, 18b, 18d) and / or the primary reactors (12a - d).

21. In the method according to claim 19,[[]]END]] A pretreatment step (116) in which the chlorine - containing polymer is pretreated before being supplied into the primary reactors (12b, 12d) and the chlorine - containing components are separated during the process.[[]]END]] A method comprising this.[[]]END]]

Images