The present invention relates to a device and a method for the pyrolysis of organic starting
material.
A pyrolysis describes in general a thermal splitting of organic compounds. Here, in the
absence of oxygen and at high temperatures, for ex 5 ample between 300°C and 900°C, the
bonds within larger molecules of a source material are forced to break. By means of the
pyrolysis of the solid source material, as a rule, gases, liquids and solids are obtained,
wherein the gases and liquids are discharged from a pyrolysis vapor resulting from the
pyrolysis. The proportions and combinations are in this regard dependent on the source
10 material, the pyrolysis temperature, the pressure conditions and the duration of the reaction.
When polymers are subjected to pyrolysis, an associated polymer frequently results
as a part of the pyrolysis vapor.
Devices and methods for the pyrolysis of organic starting materials are basically known.
For example, from the publication EP 0 592 057 B1, a method is known for the pyrolysis
15 of old tires, in which the old tires are broken down in a pyrolysis in a metal bath under
3
conditions of reduced pressure and in the absence of air and water. The pyrolysis vapor
resulting from the pyrolysis is separated off into a gaseous or a liquid phase after cooling.
Furthermore, the method provides that a part of the gaseous phase is subsequently
supplied back into the reactor interior above the metal bath and that moreover oxygen is
continuously supplied to the reactor interior 5 above the metal bath. In the method known
from this publication, the pyrolysis reaction is predominantly controlled by regulating the
speed of the gas flow in the reaction chamber.
A method in which the pyrolysis is carried out in a continuous process in a rotary kiln
reactor is known from DE 10 2014 015 281 A1.
10 An important product which can be obtained from the pyrolysis of old tires is soot, in
particular valuable soot described as “carbon black” which has a large specific surface
area.
In order to generate a material which is suitable for the further processing to form recovered
carbon black, a continuous process for the depolymerization or pyrolysis of waste
15 rubber must be carried out such that
1. the reaction temperature and quantity of reaction heat achieves the
depolymerization of the rubber components and nevertheless a further deeper
splitting of the hydrocarbons to form carbon is avoided,
2. the conditions in the reactor after the end of the reaction phase (zone) ensure a
20 virtually complete removal of the hydrocarbon residues from the remaining flow of
solids, and
3. the hot gaseous fission products are guided rapidly out of the reactor interior at the
location of their formation and are cooled abruptly, in order to avoid recombination
(renewed polymerization) of the fission products and thus the formation of high25
boiling components and their deposition on the solid.
Material from pyrolysis processes which is suitable for the further processing to form
recovered carbon black is characterized in that the proportion in the material which can
be extracted by toluene – e.g. the oil content – is less than 1%, preferably less than 0.5%.
Furthermore, the morphology of the carbon particles is decisive for the intended use as a
30 filler in rubber and plastic applications. Additional carbon formed in the pyrolysis does not
have the morphological properties of conventional carbon black and reduces the quality
4
of the end product. The proportion of the total carbon described as oil-carbon or also
“char” should not exceed 2%.
A technical problem upon which the present invention is based is the creation of an
improved device for the continuous pyrolysis of organic starting material.
According to the invention, a system is proposed for th 5 e pyrolysis of waste material, in
particular for the depolymerization of comminuted old tire material, and for producing a
starting material which can be further processed to form recovered carbon black. The
system comprises at least one rotary kiln reactor, a quenching unit and burner unit.
The rotary kiln reactor has a reactor drum, rotating during operation about a longitudinal
10 axis, having a drum wall which encloses a reactor interior. On the inner side of the drum
wall are arranged conveying devices which, when the reactor drum rotates, effect a
conveying of the waste material to be processed. The reactor interior has at least one
heating zone, a reaction zone and a degassing zone. The reactor drum has a waste
material inlet and a (pyrolysis) solids outlet and a (pyrolysis) gas outlet. The reactor drum
15 is enclosed by a heating jacket housing and is rotationally mounted such that the reactor
drum can turn about can turn about its rotational axis within the heating jacket housing.
The heating jacket housing encloses a heating jacket space which is delimited inside by
the drum wall of the reactor drum.
The burner unit is designed for burning gas (preferably pyrolysis gas) to form a heating
20 gas and for generating a heating gas flow through the heating jacket space and to this
end is connected via heating gas supply lines to the heating jacket housing such that the
heating gas can be conducted into the heating jacket space, such that the reactor drum
located in the heating jacket space can be heated indirectly from the outside by means of
the heating gas.
25 The quenching unit is connected to the gas outlet of the rotary kiln reactor and is designed
for cooling pyrolysis gases resulting in the reactor interior during operation.
According to the invention, several heating gas outlet flaps are distributed across the
length of the heating jacket housing, which allow the flow of the heating gas through the
heating jacket space to be influenced such that respectively different heat quantities can
30 be supplied to the heating zone, the reaction zone, and the degassing zone in the reaction
interior.
5
Preferably, the conveying devices are transport spirals which are formed by projections
extending along a helical path, starting from the drum wall and protruding to the inside
into the reactor interior.
Preferably, the helical turns of the transport spirals have a different pitch in the reaction
zone and in the degassing zone, in order in this 5 manner to optimize the remain times of
the pyrolysis material in the different zones.
The knowledge upon which the invention is based regarding the specific process conditions
and constructional characteristics of the components of the system result in solutions,
in order, on the one hand, to further improve the effectiveness of the method in its
10 use for the pyrolysis of old tires/old rubber, and on the other hand to guarantee the required
quality of the pyrolysis products.
The invention involves the knowledge that for continuously working systems – in contrast
to pyrolysis processes which work on a batch basis (intermittently) – particular challenges
arise in order to guarantee a high level of process stability and even product qualities
15 over a long period of operation. For this reason, a finely-tuned (regulated) process workflow
for the entire system of rotary kiln reactor, quenching unit and burner system is
necessary. A further problem for a permanently stable process management consists in
the solid particles carried along with the hot fission gases in the transition from the reactor
interior to the quenching unit being gradually deposited, and can ultimately result in a
20 blockage of the pipeline between reactor and quenching unit.
With the system according to the invention and the method according to the invention, it
is possible to adapt the remain times of the pyrolysis material in the individual zones in
the interior of the reactor chamber such that the respective processes such as heating,
fission reaction (pyrolysis/depolymerization) and residual degassing take place complete25
ly and in the relevant zones at a predetermined rotational speed of the reactor drum and
with continuous passage of pyrolysis material. To this end, the transport spirals in the
interior of the reactor drum have different pitches depending on the zones. The drum
diameter of individual longitudinal portions of the reactor drum and the spacing between
the helical turns of the transport spirals is also zone-related and selected such that fill
30 level and mixing of the fill are sufficient for the process currently running. In addition to a
gut thermal transition from the reactor jacket space to the drum wall and from the drum
wall to the pyrolysis material, it is necessary, for a sufficient transition of material and
heat, for the solid fill to be well mixed. The mixing is realized by lifting blades arranged in
the helical turns.
6
By means of the rotation of the reactor drum and the movement of the material in the
reactor drum, a portion of the solids is churned and transported away with the hot fission
gases. A disadvantage of a previous reactor construction was the arrangement of the gas
outlet at the end of the reactor drum. Thus, the solid (in the form of dust) churned up in
the degassing zone is borne by the fission gases 5 resulting in the reaction zone and is
carried out. In order to avoid this problem, preferably a pyrolysis gas outlet pipe is provided
with which the fission gases can be removed directly from the reaction zone and
guided to the quenching unit. A pyrolysis gas outlet pipe protruding at the outlet into the
reactor drum and passing through the degassing zone as far as the end of the reaction
10 zone has established itself as a solution for countering this disadvantage. At the same
time, this solution guarantees that the fission products are able to leave the reactor interior
more rapidly and thus the aforementioned disadvantages (recombination and additional
formation of fission carbon) are also avoided, and thus the quality of the recovered
carbon black is improved.
15 A complete retention of solids from the gas phase is not possible, even with the aforementioned
solution. In the longer term, deposits of coke-like compounds and carbon dust
form in the pyrolysis gas outlet pipe between quenching unit and reactor chamber. Their
removal is achieved by a pipe-cleaning device which is operated at regular intervals (e.g.
twice weekly). During the pipe cleaning procedure, the pyrolysis process is briefly inter20
rupted, in that no material is supplied, in order to interrupt the formation of fission gas.
The pipe-cleaning device is characterized in that a cleaning element which fills the entire
pipe diameter of the pyrolysis gas outlet pipe is guided by means of a gear rack through
the pyrolysis gas outlet pipe – starting at the quench entrance and reaching to the pipe
end within the reactor drum, wherein the deposits are removed and transported as far as
25 an input opening of the pyrolysis gas outlet pipe, and thus enter into the reaction zone of
the reactor drum. Subsequently, the gear rack with the cleaning element is moved back
again and thus removed completely from the pyrolysis gas outlet pipe. The gear rack is
driven by a drive unit with a gear motor and a gearwheel. In the rest position, the gear
rack, the cleaning element and the drive gearwheel are in a sealed pipe piece situated
30 directly opposite to the pyrolysis gas outlet pipe.

Claims
1. System (10) for the pyrolysis of waste material, wherein the system comprises at
least one rotary kiln reactor (14), a quenching unit (16) and a burner unit (12), and
the rotary kiln reactor (14) has a reactor drum (18), rotating during operation about
a longitudinal axis, having a drum wall ( 5 36) which encloses a reactor interior (28),
on the inner side of the drum wall (36) are arranged conveying devices (52) which,
when the reactor drum (18) rotates, effect a conveying of the waste material to be
processed,
the reactor interior (28) has at least one heating zone (30), a reaction zone (32)
10 and a degassing zone (34),
the reactor drum (18) has a waste material inlet (22) and a pyrolysis solids outlet
(24) and a pyrolysis gas outlet (26) and is enclosed by a heating jacket housing
(20) and is rotationally mounted such that the reactor drum (18) can turn about its
rotational axis within the heating jacket housing (20), wherein the heating jacket
15 housing (20) encloses a heating jacket space (38) which is delimited inside by the
drum wall (36) of the reactor drum (18),
the burner unit (12) is designed for burning gas to form a heating gas and for
generating a heating gas flow through the heating jacket space (38) and to this end
is connected via a heating gas supply line (40) to the heating jacket housing (20)
20 such that the heating gas can be conducted into the heating jacket space (38) such
that the reactor drum (18) located in the heating jacket space (38) can be heated
indirectly from the outside by means of the heating gas, and
the quenching unit (16) is connected to the gas outlet (26) of the rotary kiln reactor
(14) and is designed for cooling pyrolysis gases resulting in the reactor interior dur25
ing operation,
characterized in that several heating gas outlet flaps (44) are distributed across the
length of the heating jacket housing (20), which allow the flow of the heating gas
through the heating jacket space (38) to be influenced such that respectively different
heat quantities can be supplied to the heating zone (30), the reaction zone (32)
30 and the degassing zone (34) in the reaction interior.
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2. System for pyrolysis according to claim 1, characterized in that the conveying
devices are transport spirals (52) which are formed by projections extending along
a helical path, starting from the drum wall (36) and protruding to the inside into the
reactor interior, wherein the helical turns of the transport spirals have a different
pitch in the reaction 5 zone (32) and in the degassing zone (34).
3. System for pyrolysis according to claim 1 or 2, characterized in that the reactor
drum (18) has different drum diameters along its longitudinal axis and the drum diameter
has its maximum size in the reaction zone (32).
4. System for pyrolysis according to at least one of claims 1 to 3, characterized in that
10 the system comprises a burner unit (12) and two rotary kiln reactors (14) each having
one quenching unit (16).
5. System for pyrolysis according to at least one of claims 1 to 4, characterized in that
each rotary kiln reactor (14) is assigned a quenching unit (16) for condensation and
cooling the fission gases and the inner pressure in the rotary kiln reactor (14) and
15 the quenching unit (16) can be regulated by an exhaust fan (94) for suctioning the
fission gas products which are not condensed.
6. System for pyrolysis according to at least one of claims 1 to 5, characterized by a
pyrolysis gas outlet pipe (62) protruding on the discharge side into the reactor drum
(18) of the rotary kiln reactor (14) for removing the gaseous fission products from
20 the reaction zone (32) and for passing the fission gases to the quenching unit (16).
7. System for pyrolysis according to claim 6, characterized by a circular-shaped
cleaning element (82), provided for cleaning the pyrolysis gas outlet pipe (62),
which encloses the pipe cross-section and which, connected with a gear rack (84),
can be moved forwards and backwards and in the case of which the gear rack (84)
25 is driven by way of a drive gear (90).
8. System for pyrolysis according to claim 7, in which the resting position of cleaning
element (82) and gear rack (84) is in a pipe piece (92) situated opposite to the pyrolysis
gas outlet pipe (62) and this pipe piece (92) is sealed to the environment.
9. System for pyrolysis according to claim 7 or 8 in which the drive energy is transmit30
ted to the gear rack by means of an outlying gear motor with a gas-tight shaft
through-passage to the gearwheel.
20
10. System for pyrolysis according to at least one of claims 1 to 9 for the targeted
adaptation of the zone-related remain times of the pyrolysis material within the reactor
drum, characterized in that the transport spirals (52) have different spacings
and pitches, the diameter of the reactor drum is adapted to the individual zones.
11. System for pyrolysis according to at least one of claims 5 1 to 10, characterized in
that between the conveying devices (52), small lifting blades (54) are arranged at
regular intervals for the improved mixing of the fill in the reactor drum (18).
12. Method for generating pyrolysis solid material from old rubber for the further use as
a starting material for the production of recovered carbon black by means of a sys10
tem according to claims 1 to 11, characterized in that the heating gas generated in
the burner unit is mixed with a recirculated heating gas and is supplied by heating
gas inlet flaps (50) to the heating jacket space (38) of the rotary kiln reactor (14),
wherein the heat quantity and its distribution is supplied according to requirements
to the reactor interiors (28), in that the heat flow distribution is adjusted by heating
15 gas outlet flaps (44) arranged over the heating jacket spaces (38) and their degree
of opening, wherein the heating gases of both rotary kiln reactors (14) leaving the
heating jacket spaces (38) are combined in a heating gas recirculation line (46) and
are supplied to a heating gas mixing section (48).
13. Method according to claim 12, characterized in that surplus heating gas is guided
20 past the rotary kiln reactors (14) by way of a bypass and is supplied to a further
thermal use.
14. Method according to claim 12 or 13, in which the heating gas generated in the
burner unit (12) has a temperature of 850 to 900°C, preferably 870°C.
15. Method according to at least one of claims 12 to 14, in which the temperature of
25 the heating gas mixture of recirculated heating gas and the heating gas from the
burner unit has a temperature of between 580 and 680°C, preferably 650°C.
16. Method according to at least one of claims 12 to 15, in which the distribution of the
heating gas flow in the reactor jacket is adjusted by means of the opening degree
of three to five, preferably four heating gas outlet flaps (44) distributed evenly along
30 the axis and arranged at the top.
17. Method according to claim 16, in which the heating gas outlet flaps (44) are adjusted
such that a heat distribution in the form of heating gas volume flow results in the
21
proportion of 18% to 22% for the heating zone (30), 65% to 75% for the reaction
zone (32) and 8% to 12% for the degassing zone (34).
18. Method according to at least one of claims 12 to 17, in which the inner pressure in
the rotary kiln reactor (14) and the quenching unit (16) is between 0.5 and 1.5 mbar
5 above atmospheric pressure.
19. Method according to claims 17 and 18 in which, by increasing or reducing a
quench cooling capacity and therewith the outlet temperature of the fission gases,
the quantity of fission gas which is not condensed is influenced such that requirement
fluctuations in the heating capacity of the burner unit are to the main extent
10 compensated, as a result of which the use of primary energy sources such as natural
gas or liquid gas can be avoided.
20. Method according to claims 17 to 19, in which the two suction fans supply the
syngas/pyrolysis gas to a common burner system and realize a supply pressure of
20 to 60 mbar above atmospheric pressure, preferably 40 mbar above atmospheric
15 pressure.