DE102022116573A1 - Reactor unit for plastic thermolysis, plastic thermolysis plant and method for their operation - Google Patents

Abstract

The invention relates to a reactor unit for plastic thermolysis, a plastic thermolysis system containing the reactor unit and a method for operating the reactor unit or the plastic thermolysis system. They are used to efficiently extract fractionated hydrocarbons from plastic residues (4). The reactor unit comprises a melting reactor (1), in which a plastic melt (5) is circulated using a melt agitator (13), a pre-evaporator (2) and a post-evaporator (3). The pre-evaporator liquid (7) or post-evaporator liquid (8) located in the pre-evaporator (2) or in the post-evaporator (3) are extracted in a predetermined amount from the pre-evaporator (2) and/or the post-evaporator ( 3) branched off and fed into the plastic melt (5) to reduce its viscosity. Thanks to the viscosity control, the melt agitator (13) can be operated with low and uniform power consumption.

Description

The invention relates to a reactor unit for plastic thermolysis, a plastic thermolysis system containing the reactor unit and a method for operating the reactor unit or the plastic thermolysis system. They are used to obtain fractional hydrocarbons from plastic residues.

Due to the ever-increasing amount of plastic waste worldwide, the processes that can be used to convert plastic residues into industrially usable, recycled raw materials are rapidly becoming more important. These processes also include the processes with which fractionated, short-chain hydrocarbons can be obtained from plastic residues by thermolysis. Such procedures are, among others, in JP H 08034978 A , CN 1284537 A or US 4,584,421 A described.

To carry out plastic thermolysis, the plastic residues are fed to a reactor in which they are melted in the absence of air, broken down into short-chain hydrocarbons and evaporated. The short-chain hydrocarbons escaping in gaseous form are removed from the reactor and condensed. The condensed hydrocarbons ultimately form the majority of the recycled materials produced using these processes.

A process-technically and energetically optimized multi-stage process in which the melting and evaporation processes take place in several reactors is described WO 2005/071043 A1 . In the first reactor, the melting tank or melting reactor, the plastic residues are introduced and melted, as in the processes with only a single reactor. In contrast to the single-stage process, a liquid phase is transferred to an evaporation vessel, the second reactor, in which the evaporation essentially takes place. A reheater, the third reactor, is connected to the evaporation container in the same way and is used to evaporate residual liquids.

For homogenization, the plastic melt that forms in the melting reactor is continuously circulated using an agitator and in this way homogenized. Stirring promotes the liquefaction and evaporation of the plastic residues introduced.

However, the power consumption of the agitator drive required to homogenize the plastic melt can vary greatly depending on the composition of the plastic residues used as starting material. Through the in WO 2005/071043 A1 The multi-stage process described, ie by branching off the liquid phase, can achieve an equalization of the power consumption; However, it does result in the viscosity of the plastic melt increasing.

Tough plastic melts require particularly high performance from the agitator drive. Another disadvantage of highly tough plastic melts is that the reactions in the melting reactor take place more slowly, which ultimately affects the efficiency of the overall process.

The object of the invention is to provide a reactor unit for a multi-stage process for plastic thermolysis, a plastic thermolysis system containing the reactor unit and a method for operating the reactor unit or the plastic thermolysis system, which enable the plastic melt to be homogenized as quickly as possible in the melt reactor by stirring, whereby the The agitator used to stir the plastic melt can be operated with low and as uniform power consumption as possible, regardless of the composition of the starting material consisting of plastic residues.

This object is achieved by a reactor unit for plastic thermolysis according to claim 1, a plastic thermolysis system according to claim 5 and a method for their operation according to claim 9. Advantageous developments of the invention are described in the subclaims.

According to the invention, the reactor unit has a melting reactor, a pre-evaporator and a post-evaporator. When operating as intended, plastic residues are introduced into the melting reactor, which is also referred to as the first reactor, and melted in a generally known manner in the absence of air. The plastic melt received in the melting reactor is circulated and mixed using a melt agitator in the melting reactor. The melt agitator has a melt agitator drive, which causes the agitator's stirrer to rotate.

Furthermore, the reactor unit has a pre-evaporator for receiving and partially evaporating a pre-evaporator liquid and a post-evaporator for receiving and residual evaporation of a post-evaporator liquid. The melting reactor is connected to the pre-evaporator via a pre-evaporator supply line, via which the pre-evaporator liquid forming in the area of the liquid level of the plastic melt in the melting reactor passes into the pre-evaporator. The pre-evaporation fer is in turn connected to the post-evaporator via a post-evaporator feed line, via which the post-evaporator liquid forming in the area of the liquid level of the pre-evaporator liquid in the pre-evaporator passes into the post-evaporator.

The pre-evaporator and the post-evaporator each also have a pre-evaporator outlet or a post-evaporator outlet, via which gases and/or vapors produced in the melting reactor, in the pre-evaporator or in the post-evaporator can be removed from the reactor unit as valuable materials. The bottom area of the pre-evaporator and the bottom area of the post-evaporator are commonly referred to as the pre-evaporator sump and the post-evaporator sump, respectively.

According to the invention, the reactor unit has a viscometer for determining the viscosity of the plastic melt in the melting reactor, a controllable refeed pump and a controller coupled to the viscometer and the refeed pump via signal lines. The controller is set up to control the delivery rate of the return pump depending on the viscosity of the plastic melt.

To discharge pre-evaporator liquid from the pre-evaporator sump and/or to discharge post-evaporator liquid from the secondary evaporator sump of the secondary evaporator, a return flow line connected to the refeed pump is connected to the pre-evaporator and/or to the secondary evaporator.

Furthermore, the reactor unit has a refeed line connected to the refeed pump and projecting into the melting reactor. The pre-evaporator liquid and/or post-evaporator liquid conveyed via the return flow line to the return feed pump enters the return feed line after passing through the return feed pump and reaches the melting reactor via this.

Within the melting reactor, the return feed line has an outlet opening from which the pre-evaporator liquid and/or the post-evaporator liquid from the return feed line enters the plastic melt and mixes with it. The introduction of the pre-evaporator liquid and/or the post-evaporator liquid into the plastic melt via the return feed line takes place in a quantity-controlled manner using the return feed pump set up for this purpose.

According to the method according to the invention for operating the reactor unit described above, the viscosity of the plastic melt is measured continuously during operation using the viscometer. The measured viscosity is then transmitted to the controller via signals. Depending on the measured or transmitted viscosity, the controller controls the feed pump in such a way that a predetermined amount of pre-evaporator liquid is diverted from the pre-evaporator sump of the pre-evaporator and/or the post-evaporator liquid from the post-evaporator sump of the post-evaporator by means of the re-feed pump and in the plastic melt is introduced into the melting reactor as soon as the measured viscosity of the plastic melt exceeds a predetermined maximum viscosity.

The direct, quantity-controlled introduction of the post-evaporator liquid and/or the pre-evaporator liquid into the plastic melt causes a reduction in the viscosity of the plastic melt by a limited amount. The plastic melt is therefore easier to mix or homogenize using the melt agitator. The associated limitation of the power consumption of the melt agitator drive helps, in addition to reducing the energy consumption of the melt agitator drive, to avoid mechanical overloads or blockages of the melt agitator.

Through the targeted or metered control of the amount of post-evaporator liquid and/or pre-evaporator liquid added to the plastic melt, the viscosity can be maintained at an optimal level suitable for carrying out the thermolysis. This justifies the higher efficiency of plastic thermolysis when using the reactor unit according to the invention or the viscosity-controlled operating method according to the invention.

Since the post-evaporator and/or pre-evaporator liquid produced for viscosity control in the multi-stage thermolysis process is specifically fed or metered back into the plastic melt, the process remains free of contamination. The post-evaporator or pre-evaporator liquid thus serves as the process's own viscosity adjusting agent, which ultimately returns from the melting reactor to the pre-evaporator or post-evaporator.

It is sufficient to regularly add small amounts of the post-evaporator liquid and/or the pre-evaporator liquid to the plastic melt in order to achieve the reduction of the viscosity to the desired level. The post-evaporator liquid from the post-evaporator is preferably used to control the viscosity in the melting reactor.

For viscosity-dependent control of the process, additional plastic residues can be introduced into the plastic melt as soon as the measured viscosity of the plastic melt falls below a predetermined minimum viscosity.

Preferably, the viscometer is the melt stirrer itself, which is driven by the melt stirrer drive. The melt stirrer also functions as a measuring stirrer, i.e. i.e., the torque and/or the speed of the melt agitator drive are the measured variables for determining or characterizing the viscosity of the plastic melt.

The melting reactor can have a sedimentation department in the area near the bottom for settling non-melting or difficult-melting residues. The sedimentation department can be emptied via a closable residue discharge channel.

According to a design variant of the melting reactor with the sedimentation department, the melt agitator is arranged vertically in the melting reactor, above the sedimentation department. The outlet opening of the return feed line protruding into the melt reactor faces the melt agitator and is arranged between the sedimentation department and the melt agitator, with the outlet end region of the return feed line being aligned axially towards the melt agitator. The introduction of the pre-evaporator liquid and/or the post-evaporator liquid close to the agitator contributes to the rapid mixing of the pre-evaporator liquid and/or the post-evaporator liquid with the plastic melt.

It can also be provided that the melt agitator has a vertically aligned hollow shaft of the melt agitator. The internal channel of the melt agitator hollow shaft forms part of the return feed line; The outlet opening of the return feed line is arranged at the bottom end of the melt agitator hollow shaft. In addition to the introduction of the pre-evaporator liquid and/or the post-evaporator liquid into the plastic melt close to the agitator, the structural design of the melt agitator with the melt agitator hollow shaft offers the advantage that no additional pipeline is required in the melt reactor.

The plastic thermolysis plant according to the invention comprises the reactor unit described. It is operated according to the viscosity-controlled process. In addition to the reactor unit, the plastic thermolysis system also has a plastic input unit connected to the melting reactor for supplying the plastic residues and a fractionation unit with a quench connected to the pre-evaporator outlet and the post-evaporator outlet for liquefying and fractionating the gases and vapors discharged from the reactor unit.

The plastic input unit is preferably designed as a conveyor and lock system for pre-compacting the plastic residues and for introducing gas-free or low-gas plastic residues into the melting reactor. Such a conveyor and lock system is available, for example WO 2007/076744 A1 described.

Furthermore, the plastic thermolysis system can have a separation stage connected to the melting reactor for separating substances that disrupt thermolysis from the reactor unit. A suitable separation level is in WO 2009/087080 A2 disclosed.

• 1: eine schematische Schnittdarstellung einer ersten Ausführung der Reaktoreneinheit bzw. Kunststoffthermolyseanlage; und
• 2: eine schematische Schnittdarstellung einer zweiten Ausführung der Reaktoreneinheit bzw. Kunststoffthermolyseanlage.

The invention is explained in more detail below using exemplary embodiments and with reference to the schematic drawings, where the same or similar features are provided with the same reference numerals. To do this show:

• 1 : a schematic sectional view of a first embodiment of the reactor unit or plastic thermolysis system; and
• 2 : a schematic sectional view of a second version of the reactor unit or plastic thermolysis system.

The ones in the 1 and the 2 The reactor unit or plastic thermolysis system shown comprises three reactors, namely the melting reactor 1, the pre-evaporator 2 and the post-evaporator 3.

The plastic residues 4 are fed into the melting reactor 1 via the plastic insertion unit 10. The melting reactor 1 is heated by means of the melting reactor heater 17 in order to melt the plastic residues 4. The plastic melt 5 formed from the melted plastic residues 4 is circulated by means of the melt agitator 13. The melt agitator 13 is driven by the melt agitator drive 12 in the form of an electric motor.

In the bottom area of the melting reactor 1 there is the sedimentation department 11, in which the non-melting or difficult-melting residues 6 can settle. The residue discharge channel 18 is used to remove the residue materials 6 from the melting reactor 1, via which the Sedimentation department 11 can be emptied with the residue discharge valve 19 open. The residue discharge fitting 19 is symbolically shown as a valve, but can also be designed as a flap, for example.

The pre-evaporator liquid 7, which forms in the melt reactor 1 in the plastic melt 5 and, due to the density, accumulates in the area of the liquid level of the plastic melt 5, reaches the pre-evaporator 2 via the pre-evaporator supply line 20. In addition to the pre-evaporator liquid 7, the gases and gases already formed in the melt reactor 1 also reach Vapors 9 through the pre-evaporator supply line 20 into the pre-evaporator 2.

After leaving the melting reactor 1, the pre-evaporator liquid 7 fills the pre-evaporator 2 and is in turn heated and evaporated in this by means of the pre-evaporator heater 26. The resulting gases and vapors 9 are discharged via the pre-evaporator exhaust 28 - for example to a fractionation unit (not shown) of the plastic thermolysis plant.

The pre-evaporator agitator 24, which is driven by the pre-evaporator agitator drive 22, is used to circulate the pre-evaporator liquid 7 in the pre-evaporator 2. The bottom area of the pre-evaporator 2 or the pre-evaporator liquid 7 located in the pre-evaporator 2 forms the pre-evaporator sump 30. The pre-evaporator 2 is in the area of the pre-evaporator sump 30 Pre-evaporator discharge channel 32 connected or protrudes into the pre-evaporator sump 30. If necessary, the pre-evaporator 2 can be emptied via the pre-evaporator discharge channel 32 by opening the pre-evaporator drain fitting 34.

The post-evaporator liquid 8, which forms in the pre-evaporator liquid 7 in the pre-evaporator 2 and accumulates in the area of the liquid level of the pre-evaporator liquid 7 due to density, reaches the post-evaporator 3 via the post-evaporator supply line 21.

After leaving the pre-evaporator 2, the post-evaporator liquid 8 fills the post-evaporator 3 and is in turn heated and evaporated in this by means of the post-evaporator heater 27. The resulting gases and vapors 9 are removed via the post-evaporator flue 29, which is combined with the pre-evaporation flue 28.

The post-evaporator agitator 25, which is driven by the post-evaporator agitator drive 23, is used to circulate the post-evaporator liquid 8 in the post-evaporator 3. The bottom area of the post-evaporator 3 or the post-evaporator liquid 8 located in the post-evaporator 3 forms the post-evaporator sump 31. The post-evaporator sump 31 is attached to the post-evaporator 3 in the area of the post-evaporator sump 31 Post-evaporator discharge channel 33 is connected or protrudes into the post-evaporator sump 31. If necessary, the post-evaporator 3 can be emptied via the post-evaporator discharge channel 33 by opening the post-evaporator drain valve 35.

The return flow line 38 leading to the return feed pump 15 is connected on the one hand via the pre-evaporator return flow fitting 36 to a branch of the pre-evaporator discharge channel 32 and on the other hand via the post-evaporator return flow fitting 37 to a branch of the post-evaporator discharge channel 33. By means of the pre-evaporator reflux valve 36, the flow rate of the pre-evaporator liquid 7 from the pre-evaporator discharge channel 32 into the reflux line 38 is controlled. In the same way, the post-evaporator reflux valve 37 is used to control the flow rate of the post-evaporator liquid 8 from the post-evaporator discharge channel 33 into the reflux line 38. By setting or controlling the pre-evaporator reflux valve 36 and the post-evaporator reflux valve 37, it is specified whether only the pre-evaporator liquid 7, only the post-evaporator liquid 8 or a specific mixture of both is fed to the return feed pump 15.

The pre-evaporator liquid 7 and/or the post-evaporator liquid 8 is controlled by the return feed pump 15, i.e. H. in a predetermined amount or dosage, via the return feed line 39 into the plastic melt 5 located in the melting reactor 1. In the plastic melt 5 circulated by the stirring movement, the metered amount of the pre-evaporator liquid 7 and/or the post-evaporator liquid 8 is distributed quickly and thus brings about a reduction in the viscosity of the plastic melt 5.

To determine the viscosity, the torque and the speed of the melt agitator drive 12 are recorded and transmitted to the controller 14 via the signal line 16. The melt agitator drive 12 thus functions simultaneously as a drive for the melt agitator 13 and as a viscometer. The return feed pump 15 is controlled by means of the controller 14, which in turn is connected to the return feed pump 15 via the signal lines 16.

The above descriptions are for the two exemplary embodiments 1 and the 2 identical. The two exemplary embodiments only differ in terms of the design of the return feed line 39.

In the exemplary embodiment according to 1 the return feed line 39 is designed in the form of a guide cone or guide cone arranged above the sedimentation department 11. The outlet opening of the return feed line 39 is aligned counter to the plumb direction, towards the melt agitator 13 and is arranged centrally in the area of the cone or cone tip. The pre-evaporator liquid 7 and/or post-evaporator liquid 8 emerging from the return feed line 39 into the plastic melt 5 is quickly distributed in the plastic melt 5 by the introduction near the stirrer.

In the exemplary embodiment according to 2 the pre-evaporator liquid 7 and/or the post-evaporator liquid 8 is introduced into the plastic melt 5 at a similar position - and thus with a comparable effect - above the (not designated) guide cone. In contrast to the exemplary embodiment according to the 1 has the melt agitator 13 according to 2 a melt agitator hollow shaft 40, the inner channel of which forms part of the return feed line 39, namely the part ending in the plastic melt 5. The pre-evaporator liquid 7 and/or the post-evaporator liquid 8 are thus introduced directly from the interior of the melt agitator hollow shaft 40 into the plastic melt 5.

Reference symbol list

1

Melting reactor

2

Pre-evaporator or pre-evaporation reactor

3

Post-evaporator or post-evaporation reactor

4

Plastic residue

5

Plastic melt

6

Residual substances

7

Pre-evaporator liquid

8th

Post-evaporator liquid

9

gases and vapors

10

Plastic entry unit

11

sedimentation department

12

Melt agitator drive

13

Melt agitator

14

Regulator

15

Return pump

16

Signal line

17

Melting reactor heater

18

Residue discharge channel

19

Residue discharge fitting

20

Pre-evaporator supply line

21

Post-evaporator supply line

22

Pre-evaporator agitator drive

23

Post-evaporator agitator drive

24

Pre-evaporator agitator

25

Post-evaporator agitator

26

Pre-evaporator heater

27

After-evaporator heating

28

Pre-evaporator extraction

29

Post-evaporator exhaust

30

Pre-evaporator sump

31

Post-evaporator sump

32

Pre-evaporator discharge channel

33

Post-evaporator discharge channel

34

Pre-evaporator drain fitting

35

After-evaporator drain fitting

36

Pre-evaporator reflux fitting

37

After-evaporator reflux fitting

38

Return line

39

Return feed line

40

Melt agitator hollow shaft

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP H08034978 A [0002]
• CN 1284537 A [0002]
• US 4584421 A [0002]
• WO 2005/071043 A1 [0004, 0006]
• WO 2007/076744 A1 [0028]
• WO 2009/087080 A2 [0029]

Claims (10)

Reactor unit for plastic thermolysis, comprising - a melting reactor (1) for melting plastic residues (4) introduced into the melting reactor (1) and for receiving the plastic melt (5) formed from the plastic residues (4), - a pre-evaporator (2) for receiving and for partially evaporating a pre-evaporator liquid (7), and - a post-evaporator (3) for receiving and residual evaporation of a post-evaporator liquid (8), wherein - the melt reactor (1) has a melt agitator (13) driven by a melt agitator drive (12) for circulating and mixing the plastic melt (5), - the melt reactor (1) is connected to the pre-evaporator (2) via a pre-evaporator supply line (20), via which the pre-evaporator liquid (2) which forms in the area of the liquid level of the plastic melt (5) in the melt reactor (1) 7) passes into the pre-evaporator (2), - the pre-evaporator (2) is connected to the post-evaporator (3) via a post-evaporator supply line (21), via which the pre-evaporator liquid (7) in the pre-evaporator (2) forms in the area of the liquid level Post-evaporator liquid (7) passes into the post-evaporator (2), and - the pre-evaporator (2) has a pre-evaporator outlet (28) and the post-evaporator (3) has a post-evaporator outlet (29), via which in the melting reactor (1), in the pre-evaporator (2) or gases and/or vapors (9) arising in the post-evaporator (3) can be removed from the reactor unit as valuable materials, characterized in that the reactor unit further has: - a viscometer for determining the viscosity of the plastic melt (5) in the melting reactor (1), a controllable refeed pump (15) and a controller (14) coupled to the viscometer and the refeed pump (15) via signal lines (16), the controller (14) being used to control the delivery rate of the refeed pump (15) depending on the viscosity of the plastic melt ( 5) is set up; - a return flow line (38) connected to the return feed pump (15), the return flow line (38) being connected to the pre-evaporator (2) for discharging pre-evaporator liquid (7) from the pre-evaporator sump (30) of the pre-evaporator (2) and/or with the post-evaporator (3) for discharging post-evaporator liquid (8) from the post-evaporator sump (31) of the post-evaporator (3); - a return feed line (39) connected to the return feed pump (15) and projecting into the melting reactor (1) for the quantity-controlled introduction of the pre-evaporator liquid (7) and/or post-evaporator liquid (8) conveyed via the return flow line (38) to the return feed pump (15) from a Exit opening of the return feed line (39) into the plastic melt (5). reactor unit Claim 1 , characterized in that the viscometer is the melt agitator (13) driven by means of the melt agitator drive (12), the torque and/or the speed of the melt agitator drive (12) being the measured variables for determining the viscosity of the plastic melt (5). . reactor unit Claim 1 or 2 , characterized in that the melting reactor (1) has a sedimentation department (11) in the area near the bottom for settling non-melting or difficult-melting residues (6), the sedimentation department (11) being able to be emptied via a closable residue discharge channel (18). reactor unit Claim 3 , characterized in that the melt agitator (13) is arranged vertically in the melting reactor (1) and above the sedimentation department (11), with the outlet opening of the return feed line (39) projecting into the melting reactor (1) facing the melt agitator (13) between the sedimentation department (11) and the melt agitator (13) are arranged and the outlet end region of the return feed line (39) is aligned axially towards the melt agitator (13). Reactor unit according to one of the Claims 1 until 3 , characterized in that the melt agitator (13) has a vertically aligned melt agitator hollow shaft (40), the internal channel of the melt agitator hollow shaft (40) forming part of the return feed line (39), and wherein the outlet opening of the return feed line (39) is arranged at the bottom end of the melt agitator hollow shaft (40). Plastic thermolysis plant, comprising a reactor unit according to one of Claims 1 until 5 , characterized in that the plastic thermolysis system also has a plastic feed unit (10) connected to the melting reactor (1) for supplying the plastic residues (4) and a fractionation unit with a quench for liquefaction and connected to the pre-evaporator extract (28) and the post-evaporator extract (29). Fractionation of the gases and vapors (9) discharged from the reactor unit. Plastic thermolysis plant Claim 6 , characterized in that the plastic one support unit (10) has a conveyor and lock system for pre-compacting the plastic residues (4) and for introducing gas-free or low-gas plastic residues (4) into the melting reactor (1). Plastic thermolysis plant Claim 6 or 7 , characterized in that the plastic thermolysis plant also has a separation stage connected to the melting reactor (1) for separating substances that disrupt thermolysis from the reactor unit. Method for operating a reactor unit according to one of the Claims 1 until 5 or a plastic thermolysis system according to one of the Claims 6 until 8th , characterized in that the viscosity of the plastic melt (5) is continuously measured during operation using the viscometer and transmitted to the controller (14) by means of signals, with the feed pump (15) controlled by the controller (14) depending on the transmitted viscosity a predetermined amount of the pre-evaporator liquid (7) is discharged from the pre-evaporator sump (30) of the pre-evaporator (2) and/or the post-evaporator liquid (8) from the post-evaporator sump (31) of the post-evaporator (3) and into the plastic melt (5) in the melting reactor (1 ) is initiated as soon as the measured viscosity of the plastic melt (5) exceeds a predetermined maximum viscosity. Procedure according to Claim 9 , characterized in that additional plastic residues (4) are introduced into the plastic melt (5) as soon as the measured viscosity of the plastic melt (5) falls below a predetermined minimum viscosity.

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