Note: Descriptions are shown in the official language in which they were submitted.
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= 4548-007 PCT-1
PCT/EP 2013/001221
WO 2013/159914
1
Reactor for gasifying and/or cleaning, in particular for depolymerizing
plastic material, and associated method
The invention relates to a reactor for gasifying and/or cleaning, especially
for
the depolymerizing of plastic material, with (a) a reactor vessel for
receiving a
starting material, especially the plastic material, (b) a metal bath which is
ar-
ranged in the reactor vessel and includes a liquid metallic material having a
metal bath melting temperature, (c) a heating system for heating the plastic
ma-
terial in the reactor vessel and (d) a residual material-removal device for at
least
partially removing residual material which are produced during the
gasification
and/or cleaning of the starting material.
A reactor of this sort is described in WO 2010/130 404 and is used to gasify
plastic materials, in particular polymers. To this end, the plastic material
is in-
troduced into the reactor vessel of the reactor, for example by extruder,
where it
comes into contact with a metal bath. The high temperatures and, where appli-
cable, the present catalytic effect of the metal bath cause the
depolymerization
of the plastic material.
The starting material may comprise materials, which are either completely
inert
or not fully gasified, such that residual material is deposited. This residual
mate-
rial must be removed from the reactor vessel so that it remains in constant op-
eration. It has been proven that the removal of the residual material is a
restric-
tive factor with regards to enabling an economic operation of the reactor.
The invention aims to improve the removal of residual material from the
reactor
vessel.
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DE 197 35 153 Al describes a method and a device for gasifying of residual
material. For this purpose, the starting material to be gasified is preferably
in-
troduced into a heated reactor, which has previously been filled with liquid
slag,
in such a way that an impulse causes the slag to rotate. The organic elements
of the starting material are gasified and the mineral elements are fused and
absorbed by the slag. This results in an increase in the volume of the slag.
Should the slag volume exceed a particular limit, part of the slag runs
through a
side opening of a centrally located pipe in the reactor into a water bath,
where it
then solidifies.
DE 196 29 544 C2 describes a method for processing polyvinylchloride. In this
method, the PVC is also added to a rotating slag bath, in which a gaseous part
is separated off and the remaining material is absorbed by the slag. The
result-
ing slag is also directed through a central outflow into a water bath.
The invention aims to improve the removal of the residual material from the re-
actor vessel.
The invention solves the problem by means of a reactor in accordance with the
preamble, wherein the residual material-removal device comprises an overflow
which is centrally arranged in the reactor vessel so that residual material
that
floating on the metal bath can be removed via the overflow. According to a sec-
ond aspect, the invention solves the problem by means of an operation method
for a reactor of this sort that includes the following steps: (i) raising a
gauge of a
metal bath so that the residual material enters the overflow, and (ii)
removing
the residual material through the overflow.
It has been proven that a centrally situated overflow is particularly well
suited for
the effective removal of residual material from the reactor vessel. It is thus
ad-
vantageous if the overflow is always at the same temperature as the metal bath
surrounding it. This eliminates the possibility of the residual material
cooling
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down and clumping together upon removal.
A further advantage is that the gas development that occurs during the opera-
tion of the reactor enhances the removal of the residual material. It is a
surpris-
ing revelation that the gas development on the radial outer edge of the inner
space of the reactor vessel is particularly large. The rising gas bubbles
slightly
raise the gauge of the metal bath over a period of time, such that the
residual
material floating on the metal bath experience a force acting radially
inwards.
This results in a radially inward flow of residual material, which can be
removed
particularly effectively through the centrally located overflow.
The surprising realisation that the residual material has a preferred
direction of
flow, namely radially inwards, also contributes to a relatively rapid movement
of
the residual material into the overflow. If the overflow is arranged radially
out-
wards, it may result in the formation of areas on the surface of the metal
bath in
which the residual material residence time is so high that the residual
material
clumps together. This results in the difficult removal of the residual
material
from the reactor vessel.
The central location of the overflow does have the disadvantage that it is
more
difficult to exert an external influence, for example to remove residual
material
that has stuck together. However, the above advantages more than cornpen-
sate for this disadvantage.
The term reactor vessel should be understood in particular to mean a device
which, during operation, accommodates the metal bath, the filling element and
the starting material.
The term metal bath should be understood to mean a concentration of liquid
metal, in particular molten metal, which takes the form of a liquid at an
operat-
ing temperature of the reactor.
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In particular, the metal bath comprises Wood's metal, the Lipowitz alloy, the
Newton alloy, the Lichtenberg alloy and/or an alloy which contains gallium and
indium. In principle, the metal bath has a density of more than 9 grams per cu-
bic centimetre, so that the starting material experiences a strong buoyant
force.
The metallic material has a particular melting temperature of at least 300 C.
However, lower melting points are possible. The melting temperature preferably
has a maximum value of 600 C. During operation of the reactor, the metal bath
has a temperature of T from 300 C to 600 C.
According to a preferred embodiment, the overflow consists of a removal pipe
that is in thermal contact with the metal bath. This ensures that the removal
pipe is of the same temperature as the metal bath, thereby avoiding the possi-
bility of the materials clumping together when they cool down. The removal
pipe
is preferably a metal pipe, in particular a ferromagnetic metal pipe.
The term heater should be understood in particular to mean a device by means
of which the plastic material can be directly or indirectly heated. In
particular,
the heater is an induction heater by means of which one component of the re-
actor can be heated. For example, the filling elements are ferromagnetic, so
they can be heated by induction. However, it is conceivable that, in addition
or
alternatively to the filling elements, the overflow and/or the reactor vessel
are
ferromagnetic.
The starting material in particular is heated such that the filling elements
are
heated, which in turn heat the metal bath. The metal bath then transfers the
heat to the starting material.
The residual material removal device is in particular a device by means of
which the solid, fluid and/or paste-like matter that occurs during
gasification
and/or cleaning can be removed.
According to a preferred embodiment, a residual material support device is ar-
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ranged inside the removal pipe, which is designed to use a mechanical impact
to move residual material. For example, this may refer to a screw conveyor
that
can scrape along the inside of the removal pipe so as to prevent or remove
blockages.
5
The removal pipe preferably has an inner pipe diameter that is at least a
tenth
of an inner reactor vessel diameter of the reactor vessel. This enables the
effi-
cient removal of the residual material.
It is beneficial if the residual material removal device comprises a storage
ves-
sel and a gas-tight lock, such that the storage vessel can be detached from
the
reactor vessel, while remaining gas-proof in the process. In other words, it
is
possible to detach the storage vessel from the reactor vessel without allowing
the gas to infiltrate the reactor vessel and escaping out of the storage
vessel.
This reduces the risk of fire, as otherwise flammable gases can escape.
In the following, the invention will be explained in more detail with the aid
of a
drawing. It shows
Figure1 a reactor according to the invention for conducting a method ac-
cording to the invention.
Figure 1 shows a reactor 10 for gasifying a starting material in the form of
plas-
tic material 12, in particular polyolefin polymers. The reactor comprises, for
ex-
ample, an essentially cylindrical reactor vessel 14 for heating the plastic
mate-
rial 12, which is introduced into the reactor vessel 14 via an extruder 16.
The reactor 10 comprises a heater, for example an induction heater 18, which
has a number of coils 20.1, 20.2, ..., 20.4, by means of which an alternating
magnetic field is created in an inner space 22 of the reactor vessel 14. The
coils 20 (reference numbers without a numerical suffix refer to all respective
object) are connected with a power supply unit, not depicted, which induces an
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alternating current on the coils. The frequency f of the alternating current
is, for
example, in the region of 4 to 50 kHz. Higher frequencies are possible, but
they
lead to an increase in the so-called skin effect, which is undesirable.
A deceleration device 24 is arranged in the inner space 22 of the reactor
vessel
14, by means of which the upward flow of liquefied plastic material 12 in the
reactor vessel 14 can be slowed down. The deceleration device 24 comprises a
number of movable filling elements 25.1, 25.2, ... arranged in the inner space
22. These elements are made of ferromagnetic material and in the present in-
vention take the form of spheres with a radius R. The sphere radius R may be
between 0.5 and 50 millimetres, for example.
As a result of their ferromagnetic properties, the filling elements 25 are
heated
by the induction heater 18 and thereby heat a metal melt 26, i.e. molten
metal,
present in the reactor vessel 14. The specification that an object such as the
filling elements 25 is made of ferromagnetic material means that the object is
ferromagnetic at a room temperature of 23 C.
The filling elements 25 have a Curie temperature TC,25, above which the mag-
netic susceptibility x sinks abruptly. The connection to the electromagnetic
field
emitted by the induction heater suddenly becomes smaller and the filling ele-
ment's 25 heat emission reduces dramatically. The heat input created by the
induction heater is thus lower with hot filling elements than cold filling
elements.
The metal melt 26 has a melting point of TSchmelz = 300 C and is introduced
into
the reactor vessel 14 to a filling level of Hfclii. Along with the plastic
material, it
fills the spaces of the filling elements 25. For example, the metal melt 26 is
made of Wood's metal, the Lipowitz alloy, the Newton alloy, the Lichtenberg
alloy and/or an alloy that comprises gallium and indium. In principle, the
metal
melt 26 has a density of at least 9 grams per cubic centimetre, so that the
plas-
tic material 12 experiences a strong buoyant force. This buoyancy accelerates
the plastic material 12. The filling elements 25 counteract this acceleration.
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A temperature T prevails in the reactor vessel 14: this temperature is above a
reaction temperature TR at which the plastic material 12 gradually
disintegrates.
In this process, gas bubbles 28 are formed, which move upwards. The metal
melt 26 can have a catalytic effect on the disintegration process, such that
the
reactor 10 may refer to a thermo catalytic depolymerisation reactor. The
plastic
material 12 introduced via the extruder 16 enters the inner space 22 through
an
entry opening 30, which is preferably located on the base of the reactor
vessel
14.
The deceleration device 24 may comprise restraint devices, such as a grid
stretched across a frame, whose mesh is so small that the filling elements 25
cannot move upwards through it. However, this is not necessary. For example,
a filling of spheres is sufficient, as depicted here. The distribution of the
filling
elements 25, in the present case the spheres, is schematically depicted in fig-
ure 1.
As a result of their buoyancy, one part of the filling elements 25 floats in
the
metal melt 26 and another part is pressed into the metal melt 26 by filling
ele-
ments 25 that are positioned further up. The filling elements 25 are also de-
picted in figure 1 in a constant radius R. It is possible that the filling
elements
have variable radii, wherein, for example, the radius R decreases in an upward
direction.
In addition to this, figure 1 depicts a removal pipe 36 arranged in the
reactor
vessel 14, via which the residual material 38 floating on the metal bath can
be
removed. In the present case, the removal pipe 36 runs coaxially to a
longitudi-
nal axis L of the reactor vessel 14. The residual material 38 is, for example,
im-
purities of the plastic material 12 and/or the additional catalyst which can
be
introduced via the extruder 16 or a second available extruder.
The removal pipe 36 can be made of ferromagnetic pipe material with a pipe
,
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Curie temperature Tc,36. As a result, the removal pipe 36 heats up to -1c,36
when
the induction heater 18 is driven with a sufficiently high power. The pipe
mate-
rial Curie temperature 1-c,36 may, for example, correspond to the filling
element
Curie temperature Tc,25, 1: it may also be lower or higher. However, it is
also
possible that the removal pipe 36 is constructed using a non-ferromagnetic ma-
terial, such as an austenitic steel or titan.
The reactor vessel 14 is constructed of a wall material on at least the side
fac-
ing the inner space 22. The wall material may be ferromagnetic, for example
iron or magnetic steel. Alternatively, the wall material may also be non-
magnetic.
If the wall material is ferromagnetic, it has a wall material Curie
temperature
Tc,i 4. This may be lower than the filling element Curie temperature Tc,25. In
this
case, the wall of the reactor vessel 14 is colder during operation than the
filling
elements 25.
The removal pipe 36 is part of a pollutant removal system 40. As typical resid-
ual material impurities 38, such as sand, have a lower density than the metal
bath 26, they float and can be removed at the top. In addition, the pollutant
re-
moval system 40 comprises a storage vessel, which may also be referred to as
a settling tank 48, that collects residual material. The residual material 38
may
contain not entirely depolymerized organic material, alongside inorganic mate-
rial. The organic material floats on the inorganic material and can be lead
back
into the reactor vessel 14 through a recycling pipeline 50 on the bottom of
the
container.
The reactor 10 comprises a gas outlet 42 that flows into a condenser 44 and
removes the resulting gas. The fluid material leaving the condenser 44 lands
in
a collector 46.
The reactor described can be operated with, for example, waste oil as a
starting
=
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material instead of plastic material, and then be used for recycling and
process-
ing.
A method according to the invention is conducted by initially raising the
gauge
Hfull, for example, by introducing the metal bath 26 to the reactor vessel 14.
This
may occur by introducing solid metal spheres made of the metallic material
into
the reactor vessel 14 so that they melt. It is also possible to increase the
flow of
plastic material 12, in particular by operating the extruder at a higher
power.
This increases the volume of both gasified and non-gasified plastic material
present in the reactor vessel 14, so that the gauge Hui rises, for example in
the
form of the removal pipe 36. The residual material 38 are then removed: this
means that they either automatically flow through the removal pipe or they are
transported through the removal device by a corresponding device, in the pre-
sent case the removal pipe 36.
It can be advantageous to lower the supply of plastic material prior to
raising
the metal gauge so as to reduce the formation of gas bubbles. This has the ad-
vantage that less gas bubbles form, thereby decreasing losses in the metal
bath caused by splattering.
The gauge will preferably be lowered again after raising the gauge in the
metal
bath and removing the residual material through the overflow, for example by
draining the metal bath.
It is preferable if a gauge of the metal bath is set such that the residual
material
layer is set at a thickness H38 of at least 10cm, whereby the thickness H38
may
fall below this value when the metal bath gauge is raised for the removal of
the
residual material through the overflow.
In other words, the fact that the residual material layer has a thickness H38
of at
least 10cm should be understood to mean that this thickness is achieved and
exceeded at least 75% of the time. The thickness H38 is the distance from the
= CA 02870350 2014-10-10
boundary layer between the metal bath and residual material layer to the upper
edge of the residual material layer on the other. The thickness is preferably
regulated by means of a feedback control system. This means that the reactor
10 has a thickness registration device, which is not depicted, by means of
5 which the thickness H38 can be recorded. Should a maximum thickness
H38 be
exceeded, the above described method for the removal of residual material is
conducted.
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Reference list
Reactor 50 Recycling pipeline
12 Plastic material
14 Reactor vessel x Magnetic susceptibility
16 Extruder f Frequency
18 Induction heater L Longitudinal axis
Sphere radius
Coil Hfcill Filling height, gauge
22 Inner space H38 Thickness
24 Deceleration device
Filling elements d14 Reactor vessel inner diame-
26 Metal bath ter
28 Gas bubble d36 Pipe inner diameter
Entry opening
32 Catalyst TSchmelz Metal bath melting
34 Outer wall temperature
36 Removal pipe T Temperature
38 Residual material TR Reaction temperature
-1c,36 Pipe material Curie tern-
Pollutant removal system perature
42 Gas outlet 1-c,25 Filling element Curie tern-
44 Condenser perature
46 Collector Tc,14 Wall material Curie tern-
48 Settling tank perature
