Note: Descriptions are shown in the official language in which they were submitted.
CA 02299860 2000-03-02
Code: 476-74886
Ref.: 032025.005
INSTALLATION FOR THE VACUUM-THERMAL
TREATMENT OF MATERIALS
Description
The invention concerns an installation for the vacuum-thermal treatment of
materials that
contain at least one evaporable component, in particular for the disposal of
waste materials of
large electrical devices such as transformers and capacitors that contain PCB-
containing
insulating oils, which features at least one heatable treatment chamber with a
feed opening that is
located in an overhead position and can be shut by means of a feed valve, with
a heating device,
a vacuum pump and a condenser for discharged vapors. PCBs are extremely
dangerous
substances. But also when disposing of other materials such as soils,
dangerous substances like
e.g. dioxin (the "Seveso poison") and furan compounds can develop which, under
certain
processing conditions, may re-form again even after they have been destroyed.
PCBs are polychlorinated biphenyls or polychlorobenzenes with a differing
number of
chlorine atoms, e.g. with one through ten chlorine atoms and up to 209 isomers
with a chlorine
content of between approximately 19% and 71 %. They are exceedingly toxic and
have a
carcinogenic effect. They are mainly absorbed through the skin but also partly
through the air
and the lungs causing damage to the liver and nervous system as well as
changes in the blood
pattern. PCBs accumulate in fat tissue. They should not be incinerated if it
can be helped.
Incineration requires temperatures of over 1200°C and an oxygen-rich
atmosphere since,
otherwise, the dioxins (Seveso poison) and furan compounds, which are also
toxic, are formed.
Because of their high dielectric constant and their flame-inhibiting effect,
as well as because of
their good thermal conductivity they have been used for many years as cooling
and insulating
fluids and as heat transmission oils in transformers and electric capacitors,
partly in pure form,
and partly as additives to other oils (ROMPP CHEMIE LEXIKON [Rompp Chemical
Dictionary], Georg Thieme Verlag, Stuttgart - New York, Vol. M-Pk, 1995, pp.
3243-3245).
Worldwide a large number of such large electrical devices are still used.
Meanwhile,
however, the use, storage and even the transportation [of PCBs] have been
prohibited in most
countries. In spite of high incineration temperatures, the risk of re-
combination into toxic
substances remains.
The type of disposal depends on the concentration of the PCBs: at a PCB
content of over
SO mg/Kg the waste material disposal of the transformers or other electrical
devices must be
performed in accordance with special procedures. For Germany alone, the amount
of special
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waste was or will be 300,000 tons of PCB waste for the years 1989 through
2000, which consists
of 95,000 tons of 1 through 50% PCB, of which 56 tons came from transformers
and 17,000 tons
from large-scale capacitors (ROMPP LEXIKON LJMWELT [Rompp Environmental
Dictionary],
Stuttgart-New York, 1993, pp. 536-538).
Installations for vacuum-thermal treatment have so far been configured as
single-chamber
devices with a rather limited productivity, in particular since the treatment
chambers and their
installations must follow a time-temperature profile that is quite time
consuming:
From DE 44 15 093 A1, such a single-chamber installation is known in which oil
residues are removed from randomly deposited hollow bodies such as oil filters
of motor
vehicles and uncrushed oil cans by means of distillation under vacuum, the so-
called VTR
Process (Vacuum-Thermal Recycling). The quantity of residual oil per filter
can amount to 250
g. It is useful but not necessary to compress such hollow bodies in a press
prior to the VTR
treatment to make better use of the volume of the vacuum chamber. It concerns
very small parts.
The re-processing of PCB-containing oils is not addressed.
From EP 0 423 039 A1 and the corresponding DE 690 OS 411 T2, such single-
chamber
furnaces are known in which non-crumbling material consisting of small pieces
is first heated to
the final temperature under atmospheric pressure, and then subsequently
decontaminated under
vacuum. Pieces of wood and metal from transformers and wound plates from
capacitors made of
paper and aluminum foil are mentioned as materials. Decontaminating
transformer wood at
260-280°C, a duration of 18 hours is indicated; 67 hours for the
decontamination of wound
capacitor plates with carbonization of the paper at 285°C. Disposal of
waste materials from
complete large-scale installations with a larger portion of insulation oils or
total quantity thereof
is not described, and not possible either with the known process.
Also, from EP 0 672 743 A1, a mufti-chamber continuous-process installation is
known
that is, however, rather expensive and still requires long cycling times as
the process step with
the longest dwell time prevents expeditious passage through the installation.
If the treatment
chambers are made as long as is required by the process step requiring the
longest dwell time,
which is also known from the EP 0 505 278 A1, the installation loses
flexibility for other
applications since the individual process steps can be of different duration
while the length of the
chambers cannot be modified. In addition, a continuous process installation
completely breaks
down in the event that one single chamber experiences a malfunction.
As materials, not only the initially mentioned large-scale electrical devices
from the
transformer and capacitor group that contain PCB-containing insulation oils
can be considered
but also soil and other bulk or crumbling materials that are contaminated with
toxic or
environmentally critical heavy metals, hydrocarbons etc. These materials are
usually bad thermal
CA 02299860 2000-03-02
conductors with a high thermal inertia since, in the most inaccessible places,
a sufficiently high
temperature must be reached to guarantee the complete extraction of certain
contaminants.
Due to strict environmental protection regulations, such materials must be
processed in
large quantities in very different forms and consistencies, and today's
capacities by far do not
suffice to meet each regulations in the near-term.
Therefore, the invention is based on the development of an installation of the
initially
described type with a high productivity and flexibility that will make it
possible to operate
rapidly with differing time profiles as may be required by different
materials.
The stated task is solved for the aforementioned installation by means of:
a) at least one additional treatment chamber that is correlated with at least
one heatable
treatment chamber in a serial arrangement that features a feed opening, which
can be shut by a
feed valve, and a heat exchanger,
b) at least one transport chamber that is open toward the bottom and
horizontally
movable, that is positioned above the treatment chamber, and that can be
connected to each of
the treatment chambers in a gas-tight and flush alignment manner, and that is
of sufficient height
to accommodate the material completely and
c) a lifting device starting at the transport chamber by means of which the
material
together with the transport chamber can be transported from one treatment
chamber to the other.
The subject of the invention completely solves the stated task, i.e., the
installation
features high productivity and flexibility and makes it possible to process
rapidly with different
time-temperature profiles set according to the material properties.
In this context it can be particularly advantageous - either individually or
in combination
- i f:
* at least one of the treatment chambers is a cooling chamber and its heat
exchanger is a
cooler;
* a vacuum pump and a condenser for the discharged vapors are assigned to the
cooled
treatment chamber, as well;
* at least two horizontally movable transport chambers, each with a lifting
device, are
located above the treatment chambers, with which they can be connected in a
gas-tight and flush
alignment manner;
* the feed valves are each positioned in a valve housing that, on its topside,
features a
sealing seat for the vacuum-tight docking of the transport chambers;
* the directions in which the feed valves can be moved as well as the
longitudinal axes of
the valve housings have a vertical orientation in relation to the series of
treatment chambers;
* the treatment chambers are arranged in a linear series, and there is one
loading station
at one of its ends and one unloading station at its other end;
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* at least part of the treatment chambers are connected to vacuum pumps and
condensers,
or alternatively, if
* the vacuum pumps and condensers are arranged in parallel to the series of
treatment
chambers in the event that several vacuum pumps and condensers are assigned to
a group of
treatment chambers;
* the suction lines of the vacuum pumps are connected to the bases of the
treatment
chambers;
* the valve housings are connected to the vacuum pumps via an additional
suction line
and the transport chambers, when they are docked onto the sealing seats, can
be evacuated
through the valve housings;
* the treatment chambers with the heating devices are designed as vacuum
induction;
furnaces;
* for the treatment of bulk or granulated material, batch containers are
provided featuring
an interior and an exterior wall connected to each other by means of a base,
in particular, at least
one of the walls is perforated, grid-shaped or mesh-shaped;
* the outside of the treatment chamber is surrounded by at least one induction
heater;
* the inside of the treatment chamber features at least one device consisting
of heating
resistors;
* the treatment chamber is positioned between two rows of pillars on which an
operation
platform rests, and/or if
* rails are attached to the operating platform on which the transport chamber
can be
moved in an upright position by means of wheels.
Effects and advantages of these further embodiments of the subject matter of
the
invention are more closely explained in the detailed description.
Embodiment examples of the subject matter of the invention are more closely
explained
based on Figures 1-5.
Shown are:
Figure 1, a vertical section through a single treatment chamber with a docked
transport
chamber just before the material is lowered into the treatment chamber and the
pertinent process
schematic,
Figure 2, a lateral view of a serial installation consisting of six treatment
chambers, one
of which is a cooling chamber that interacts with five vacuum induction
furnaces,
Figure 3, the serial installation according to Figure 2 with differing
positions of the two
transport chambers and marked transport routes,
Figure 4, a batch container in perspective view and
CA 02299860 2000-03-02
Figure 5, a vertical section through a second embodiment example of a single
treatment
chamber with a docked transport section while the material is being lowered
into the treatment
chamber.
In Figure 1, a single station 1 of an installation for the vacuum-thermal
treatment of
material 2 is shown, which in the present case is a transformer containing a
charge of PCB-
containing insulating oil. Station 1 contains a heatable treatment chamber 3
that is surrounded by
a heating device 4 in the shape of an induction coil and that is basically a
vacuum induction
furnace. A feed opening 5 is located overhead and can be shut by means of a
feed valve 6.that is
located in a valve housing 7. This valve housing 7 not only extends above the
treatment
chamber 3, it also protrudes laterally which permits the feed valve 6 to be
moved into the dashed
position 6a. The valve housing 7 is connected to a vacuum pump 9 via a suction
line 8 and can,
therefore, be evacuated independently from the treatment chamber 3. Valves 10
and 11 serve to
flood with an inert gas and to shut off the line, respectively.
The treatment chamber 3 features a bottom 12 from where a suction line 13 with
a large
cross section is first routed into a condenser 14 that is positioned up-stream
from the vacuum
pump 9. A first condenser 15 is a grilling condenser in which a washing fluid
lSa is circulated by
means of a pump 15b. A second condenser 16 is a surface condenser in which a
cooling fluid is
circulated through a cooling fluid aggregate 17. The suction line sections 13a
and 13b conduct
the residual exhaust fumes and vapors to the vacuum pump 9 downstream from
which, for safety
reasons, another cleaning unit 18, that could e.g. also be an activated carbon
filter, is connected
via a line 13c. From there the residual gases, with the degree of purity
required by law, go to
exhaust chimney 19, of which only a sketch is included in the drawing.
The following is also essential: the treatment chamber 3 is connected to a
stop valve 21
via a further line 20 to an inert gas line that is not shown in the drawing,
and by means of which
the treatment chamber, after a first evacuation, can be flooded with an inert
gas (e.g., nitrogen
[sic]) in order to remove surrounding air. However, the inert gas influx is
shut off after the
flooding so that no flooding or transport gas is routed or circulated through
the treatment
chamber. This causes the vapor pressure of the hydrocarbons to gradually
increase with the
mounting temperature in the treatment chamber. The hydrocarbons accelerate the
heating
through re-condensation on relatively cooler parts of the material 2. The
pressure inside the
treatment chamber 3 is sensed by a pressure sensor 22 and controlled via a
control unit 23 that
acts upon a control valve 24 in the suction line section 13a. This makes it
possible to initially
maintain a vapor pressure just below the atmospheric pressure and that
guarantees ideal heating
conditions preventing overpressure from gas or vapor expansion. The control
valve 24 will only
open fully when the temperature has been reached at which, by means of the
full performance
CA 02299860 2000-03-02
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[range] of the vacuum pumps, a pressure reduction that is below the specific
vapor pressure
curves of all of the hydrocarbons, and an abrupt evaporation through boiling
become possible.
Above the entire arrangement as described there is a ceiling crane 25 with a
crane
trolley 26, but it should be mentioned in consideration of Figure 2 that in
reality this ceiling
crane extends perpendicular to the plane of the drawing.
The crane trolley 26 moves a lifting device 27 with a cable winch 28 that has
a lifting
cable 28a to which a grab 28b is attached, which can be lifted and lowered
independently from
the lifting device 27. From the lifting device 27, a transport chamber 29
hangs down that is
closed toward its top and open at the bottom and is of such height that the
full height of the
material 2 is completely contained in it.
The valve chamber 7 features at its top side a sealing seat 30 for the lower
edge of the
transport chamber 29, which, by means of the lifting device 27, can be docked
onto the sealing
seat. For this purpose the material 2, in the spatial position shown in the
drawing, is moved over
the transport chamber by means of the crane trolley 26. In the position shown
in Figure l, with
the feed valve 6 shut, first the valve chamber 7 and the transport chamber 29
are evacuated via
the suction line 8, and subsequently flooded with inert gas via the valve 10.
Comparable
conditions are created in treatment chamber 3 by suction line 13 and inert gas
line 20. As soon as
the person has equalized approximately, the feed valve 6 is moved into the
open position 6a and
the material 2 is lowered by means of the hook 28b into the treatment chamber
3 to the
position 2a marked by a dashed line. The feed valve 6 is closed and the
material in position 2a
undergoes a vacuum-thermal treatment.
The transport chamber 29 can meanwhile be moved to other positions or
treatment
chambers and fulfill specific functions there.
As soon as treatment is finished, this transport chamber 29 (or if applicable
another
available transport chamber 29.2) is moved into the position shown in the
drawing again, and the
aforementioned motion patterns and pressure conditions are reversed.
As Figure 2 shows, a total of five heatable treatment chambers 3, 3.2, 3.3,
3.4 and 3.5 are
positioned, in a serial arrangement, but the serial arrangement does not have
to be linear; it can
also be polygonal or circular. An installation with the desired capacity can
also be accomplished
by positioning several such installations in a parallel arrangement.
Another treatment chamber 31 is configured as a cooling chamber containing a
heat
exchanger 32 inside it, through which a coolant is circulated. This
significantly accelerates the
sequence of operating steps. Treatment chamber 31 also features an overhead
feed opening 34
that can be shut by means of a feed valve 33, an analogous pump that is not
shown and a
condenser for vapors that are still open at least at the beginning of the
cooling phase.
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It is obvious that the two horizontally movable transport chambers 29 and 29.2
can be
connected to each of the treatment chambers 3 through 3.5 and 31, in a gas-
tight and flush
aligned manner, and that the material 2 together with the transport chambers
29 and 29.2 can be
moved from one treatment chamber to the next. Each of the transport chambers
features a lifting
device 27 with a cable winch 28, and can be connected to each of the treatment
chambers (31,
3 through 3.5) in a gas-tight and flush alignment manner.
As seen from a comparison between Figures i and 2, the moving directions of
the feed
valves 6 and the longitudinal axes of the valve housings 7 have an orientation
that is
perpendicular to the series of treatment chambers 31 and 3 through 3.5. The
treatment
chambers 31 and 3 through 3.5 are arranged in a linear series with a loading
station 35 at one end
and an unloading station 36 at the other, both located within the active range
of the transport
chambers 29 or 29.2.
The vacuum pumps 9 and the condensers 14 are arranged in a row that is
parallel to the
series of treatment chambers 31 and 3 through 3.5.
In each case the valve housings 7 are connected via an additional suction line
8 to the
vacuum pumps 9 and the transport chambers 29 and 29.2 can be evacuated through
the valve
housings 7 while docked on the sealing seats 30.
Figure 3 shows individual steps of reloading processes: a cooled-down material
2 has
been brought from the cooled treatment chamber 31 via transport route 37 into
the unloading
station 36. From the heated treatment chamber 3.5, degasified material 2 is in
the process of
being raised in order to be subsequently transported immediately via the
transport route 38 into
the cooled treatment chamber 31 that has just become available. From the
loading station 35, still
partly cold material 2 has just been lifted up for the purpose of being
subsequently taken via
transport route 39, into the heated treatment chamber 3.5 that has just become
available. It goes
without saying that the pieces of material contained in the individual
treatment chambers can
have very different temperatures depending on the process step, and depending
on what point the
treatment process has progressed to in each individual case.
Basically, each treatment station can be equipped as shown in Figure 1, i.e.
it can
constitute an independently functioning unit that is ready for operation
independent from the
other treatment stations. However, it is also possible to combine several
treatment stations, if
necessary all, into a group and to connect them to a central unit "Z," which,
in figure 1, is
surrounded by a dotted/dashed line. In order to be able to regulate the
pressure in each treatment
chamber independently, a control valve 24a is provided in the suction line 13
as an alternative to
the control valve 24 with a (dashed) connection to the control unit 23.
Figure 4 shows a hollow cylindrical batch container 40 for pourable or free-
flowing
material featuring an interior wall 41, an exterior wall 42 and a ring-shaped
bottom 43 that is
CA 02299860 2000-03-02
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entirely or partially provided with perforations 44, as indicated by the cross-
hatching. For heat
and substance exchange, this has the advantage of providing a large
surface/volume ratio with
low material depth.
In Figure 5, which shows a second embodiment example of the invention,
identical parts
or parts with analogous functions as in Figures 1-3 are marked with identical
designations. The
treatment chamber is of a type in which the heating device 4 has been
substituted with an internal
resistor heater. The outside of treatment chamber 3 is surrounded by thermal
insulation material
45. The suction line 13 exits from the treatment chamber 3 at approximately
half its height.
Figure 1 is referred to for the treatment of exhaust gases and vapors.
An operating platform 48 rests on two rows of pillars 46 and 47 and on it, two
parallel
rails 49 and 50 are mounted that replace the crane bridge 25 shown in Figures
1-3. The transport
chamber 29 features four transport rolls 52 over four outrigger legs 51 by
which means the
treatment chamber 3 can be roiled in a stable position in a direction that is
perpendicular to the
plane of the drawing.
From the lifting cable 28a hangs a transport cage 53, in which two
transformers are
positioned on top of each other as the material 2 to be treated, and that
rests with its upper
edge 53a, in a lowered position on the support element 54. A sealing flange 55
serves as a
support for a feed valve, which is not shown here, that closes the treatment
chamber 3 during
vacuum treatment. The arrangement corresponds approximately with the movement
phase
according to position 3.5 in Figure 3. The overall height, however, is
markedly lower than that in
Figures 1 through 3, which has an advantageous effect on the ceiling height of
the building
required for the installation.
List
of
desi
nations
1 Station
2 Material
2a Position (material)
3 Treatment chamber
3.2 Treatment chamber
3.3 Treatment chamber
3.4 Treatment chamber
3.5 Treatment chamber
4 Heating device
S Feed opening
6 Feed valve
6a Position
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7 Valve housing
8 Suction line
9 Vacuum pump
Valve
11 Valve
12 Base
13 Suction line
13a Section of suction
line
13b Section of suction
line
13c Line
14 Condensation unit
Condenser
15a Washing fluid
1 Pump
Sb
16 Condenser
17 Coolant aggregate
18 Cleaning device
19 Exhaust chimney
Inert gas line
21 Stop valve
22 Pressure sensor
23 Control unit
24 Control valve
24a Control valve
Crane bridge
26 Crane trolley
27 Lifting device
28 Cable winch
28a Lifting cable
28b Hook
29 Transport chamber
29.2Transport chamber
Sealing seat
31 Treatment chamber
32 Heat exchanger
33 Feed valve
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34 Feed opening
35 Loading station
36 Unloading station
37 Transport route
38 Transport route
39 Transport route
40 Batch container
41 Interior wall
42 Exterior wall
43 Bottom
44 Perforations
45 Heat insulation
material
46 Row of pillars
47 Row of pillars
48 Operating platform
49 Rail
SO Rail
51 Outrigger leg
52 Transport rolls
53 Transport cage
53a Edge
54 Support elements
55 Sealing flange
