Note: Descriptions are shown in the official language in which they were submitted.
= CA 02246364 1998-08-10
PROCESS FOR THERMAL DISINFECTION OF WASTE
PARTICULARLY THAT WITH BIOLOGICAL RISKS AND
DEVICE FOR IMPLEMENTING THIS PROCESS
This invention consists of a process for thermal
disinfecting of waste particularly that with biological
risks and a device for implementing this process.
The known medical disinfecting method from a
technical point are as follows:
Wastes can be collected for treatment in a
specialized area such as an incinerator or an installation
for thermal treatment (overheated steam, high frequencies
microwave, etc.). However, multiple manipulations
(grinding, eventual sorting) are necessary as well as an
intermediary storage for up to many days all of which cause
an unacceptable proliferation of pathogenic germs and
contamination risks all along the treatment chain (trash
bin, grinder, vehicle used for transport, etc.);
The wastes can be treated in place in order to
eliminate the proliferation problem during the intermediary
storage. Machines using jets of ozone or of disinfectant
solutions are currently being developed, but they cannot
disinfect closed ob~ects such as needles used to take blood
samples, into which the disinfecting agents do not enter.
Other machines thermal this time, are beginning to
be used but they require the grinding of wastes for a better
thermal transfer of either overheated steam or a radio-
frequency source for a more rapid heating. They are meant
CA 02246364 1998-08-10
for large treatment capacities (20 to 250 kg/hr) and they
represent an important investment as they require a large
space which frequently leads to placing them far from the
waste generating site, which brings up again the problem of
intermediate storage and the proliferation of germs.
The problem of small medical structures such as
medical practitioners or small laboratories doing analyses,
is not solved.
In fact, these small structures generate from 0.1
to 5 kg of wastes per day and are subjected to high fees for
the transport and treatment of these wastes in an adequate
installation.
In order to solve these inconveniences, one of the
goals of the present invention is to propose a process for
disinfecting wastes which can be used on the site where the
wastes are being generated, which reduces contamination in a
meaningful way and which can disinfect small quantities of
wastes for an economical cost and a minimum congestion.
The process according to the invention is for the
thermal disinfecting of wastes, particularly those with
biological risks, featuring a compaction chamber in which
the wastes are subjected to pressure, the gasses given off
by the compaction are filtered before being released and the
chamber is leak proofed and heat is applied controlling
simultaneously the temperature and the pressure inside the
chamber, the temperature being maintained within a range of
100~C to 200~C, all parts having been in contact with the
CA 02246364 1998-08-10
waste are also disinfected. The heat temperature is
favorably kept above 134~C.
According to a preferred method of the invention,
the wastes are covered beforehand with polymer, preferably
composite, or placed in a polymer sack, preferably
composite, before being brought into the compacting chamber.
Preferably, the sack is made of composite polymer with a
polypropylene or polyamide exterior covering and a
polyethylene interior lining.
According to another preferred method of the
invention, the process also includes the decompression of
the compaction chamber, the cooling of the chamber and its
compacted waste to a temperature below 60~C, its return to
atmospheric pressure and the removal of the waste.
Another goal of the invention is to propose the
implementation of this process by means of a device which
includes a riser collar 1, a jack 2 operated piston 3, a
compaction chamber 4, a filter 6, a thermal block 17, a sack
11 filled with waste to be disinfected, means of heating,
means of leak proofing the device and a thermal insulation.
Preferably, the heat is produced with electric heating
elements and/or voltage-dependent resistors.
According to a preferred method of the invention,
the device also includes a pressure transducer and/or a
strain gauge 14, and/or an extractor 16 and/or an evacuation
opening 15 coupled with a gate 12 with or without a frame.
Preferably, the face of the ~ack 2 which is in
CA 02246364 1998-08-10
contact with the wastes has lugs 10.
The piston 3 is hydraulically or mechanically
operated or driven by an electric motor.
According to a preferred method of the invention,
the leak proofing of the device is provided by O-ring seals
or by suitably fitted inflatable rings strategically placed
and/or with insulation gates 12 and 14.
Preferably, the jack 2, the compaction chamber 4 and
the riser collar are completely or partially made of
stainless metal of sufficient hardness not to be scratched
or deteriorated during the compacting of needles and
scalpels.
Preferably, the jack 2, the compaction chamber 4 and
the riser collar 1 are totally or partially made of or
covered with metal of high thermal conductivity.
On the other hand, the ~rame can be fitted with a
thrust block 19.
According to a method unique to the invention, the
filter 6 is placed in such a way that the temperature of
this filter and of the space between it and the wastes is
essentially the same as the temperature in the compaction
area. The filter 6 is preferably of very high efficiency
such as a mineral membrane and/or active carbon and/or
teflon felt.
According to another method unique to the invention,
the pressure transducer and/or the strain gauge are
installed on the hydraulic system of the piston 3.
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The following detailed description refers to the
enclosed figures which illustrate (non restrictively) the
invention:
Figures 1, 2 and 3 show sections of the invention's
device.
Figure 1 shows sections of the device in position,
ready to receive the waste sack;
Figure 2 shows sections of the device in a closed
position during the treatment;
Figure 3 shows sections of the device in position
for the evacuation of the compacted wastes;
Figure 4 shows detailed sections of the jack 2, the
compaction chamber 4 and its riser collar 1 with which the
wastes 11 are compacted and heated.
Figure 1 shows a device for implementing the process
according to the invention, made up of a riser collar 1, a
jack 2 equipped with a piston 3, a compaction chamber 4, a
thermal block 17 and a sack ll filled with wastes to be
disinfected.
The sack 11 filled with wastes is placed in the
compaction area. The material used for this sack is chosen
according to the temperature of the treatment to be applied.
Preferably, the sack is made of polymer, preferably
composite, of high thickness. It is advantageous to use a
sack made of composite polymer with a polypropylene or
polyamide exterior and an interior lining of polyethylene.
The waste sack 11 is then placed in the compaction
CA 02246364 1998-08-10
chamber 4 when the jack 2 and its piston 3 are freed. The
jack 2 and the piston 3 are then put into place above the
compaction chamber either manually or using motorization
(not shown). The piston 3, which can be either hydraulic or
mechanical driven by an electric motor, can then lower the
jack 2.
The jack 2 comprises a hollow metallic section which
can be made of stainless metal to reduce the corrosion
caused by usage conditions (hot and humid and under pressure
with the possibility of certain acids being present).
Preferably, the exterior of the jack is made of sufficiently
hard metal not to be scratched or deteriorated during the
compacting of stainless metal needles and scalpels.
According to a mode unique to the invention, the
jack interior is filled or covered with a metal with a high
thermal conductivity, such as aluminum. This special
characteristic makes it possible to bring the jack 2, the
filter 6 and the space between the waste sack 11, to the
temperature in the compacting area in the most rapid and
homogeneous way. Formation of temperature gradients is thus
avoided as these would produce condensation on the cooler
parts during the heating cycle. This condensation would be
susceptible to dampen the filter 6 and thus damage it. The
filter is thus disinfected during each treatment, limiting
the risks of the accumulation of bacteriological or viral
contamination. Preferably, the filter is not in contact
with the waste. According to a unique method of the
CA 02246364 l998-08-lO
invention, the filter 6 is directly in contact with the
interior face of the jack.
According to yet another method of the invention,
the compaction chamber 4 and the riser collar 1 are made of
stainless metal to limit corrosion caused by conditions of
use (hot, humid, hot and under pressure, with the
possibility of certain acids being present), of sufficient
hardness not to be scratched by needles or scalpels.
Preferably, the riser collar 1 is made of conducting metal,
since one of its functions, apart from guiding, is to bring
heat to the upper part of the chamber. The riser collar is
in contact with the upper part of the jack, near one or many
resistances.
According to a method unique to the invention,
during compaction, the air is evacuated toward the filter
and the insulation gate 14 by means of holes 7. These holes
are necessary for air passage but they also serve the
function of letting go through the condensation that could
form when the filter 6 and the gate 14 are in the jack 2, on
its interior aluminum walls.
Preferably, the compaction chamber 4 and the jack 2,
are equipped with heating elements with electrical
resistances, eventually combined with a temperature
regulator such as a thermostat. According to a preferred
method of the invention, the interior jack wall which comes
in contact with wastes is equipped with one or many
resistances.
CA 02246364 1998-08-10
According to an advantageous variant of the
invention, these resistances are voltage-dependent resistors
with an electric conductivity such that they stop
functioning when they reach the Curie temperature. They
thus regulate themselves at a predetermined temperature in
line with their composition. This allows the saving of a
regulator and ensures that the temperature will not over
rise following a malfunction of a regulator.
It is advantageous to use voltage-dependent
resistors with a limit of 230~C, which, taking into account
the contact thermal resistances, will ensure a stable
temperature at their level of approximately 200~C (for waste
treatment at 134~C it is possible to use voltage-dependent
resistors regulating themselves at 180~C). It is to be
noted that heating waste above 200~C is superfluous and
could cause problems in the decomposition of certain
plastics with toxic compounds (cyanures). Preferably, the
heating temperature stands at between 100~C and 200~C, and
offers better advantages at 134~C.
According to a unique method of the invention, the
compaction chamber 4 is also equipped with a pressure
transducer and/or a strain gauge (not shown). If the
piston 3 is hydraulic, this pressure captor and/or strain
gauge can be advantageously installed on the hydraulic
system of the piston. This placement makes it possible to
be aware of the hydraulic circuit pressure and thus the
pressure put on the jack 2, by the vapor pressure following
CA 02246364 1998-08-10
_ g _
the heating of wastes.
According to an advantageous method of the
invention, if the piston 3 is mechanical and driven by an
electric motor, a strain gauge is placed on the piston 3.
This gauge will make it possible to know what pressure is
placed on the said piston and it represents an alternative
to the use of a pressure captor.
Preferably, the filter 6 is one of very high
efficiency such as a mineral membrane and/or activated
carbon and/or teflon felt. Preferably, the filter is made
of teflon felt which permits a filtration at 0.2 um. This
filter is set against the joint 21 with springs 25 to ensure
leak proofing toward the exterior. The exterior face of the
filter emerges in a plenum 22 attached to an insulation
gate 14. This insulation gate is attached to a vent 5 and
to a small extractor 16.
According to a preferred method of the invention,
the grouping made up of the compaction chamber 4, the
filter 6, the riser collar 1, the jack 2 and the gate 14 is
thermally insulated and thus it is disinfected during each
operation.
The use of a metallic sheath and of a thermal block
may be necessary; for a disinfecting machine capable of
treating waste masses of approximately 1 kg or a non-
compacted volume of approximately 10 liters (0.1 density)
will have for a diameter of approximately 160 mm for the
chamber (and so as well, for the compacting jack) a
CA 02246364 1998-08-10
-- 10 --
compaction chamber and a riser collar height of 500 mm. The
flat bundle of compacted wastes will thus have a height of
approximately 50 mm (density of compacted wastes next to 1).
It would be very difficult and long to ensure heat
distribution on such a height in a material such as
stainless metal which is a poor heat conductor, even with a
very good thermal block. An aluminum sheath and the
installation of a good thermal block resolve this problem.
Preferably, the metal sheathing is attached to the piston.
According to a method unique to the invention, the
chamber and the piston are sufficiently adjusted to limit
the extrusion of wastes in the slit. However,
advantageously, a stainless metal rake with a diameter very
slightly larger than that of the piston, is installed on the
lower part of the piston, before the joint. This rake
serves to avoid the extrusion toward the waste joint and
thus protects the joint from destruction.
According to yet another method unique to the
invention, the device is perfectly leak proof. This leak
proofing is obtained through strategically placed seals and
insulation gates 12 and 14. These seals can be O-ring or
inflatable seals.
According to a uni~ue method of the invention, an
evacuation opening 15 in the insulation gate 12 permits,
when necessary, the evacuation of the over abundant juices
after disinfecting, or the treatment of liquid wastes.
During operation of the process of the invention,
CA 02246364 1998-08-10
-- 11 --
the wastes are placed in a compaction area and put under
pressure; the air in the waste sack 11 is sucked through the
openings 7 and the filter 6 and is evacuated through the
insulation gate 14, in an open position. The jack 2 goes
down slowly if the seal 8 is an inflatable ring; exterior
air is even sucked by the space between the chamber 4 and
the jack 2, thus avoiding all contamination from spreading
outside the machine. If the leak proofing is obtained by
means of an O-ring seal, the leak proofing between the
chamber 4 and the jack 2, is effective immediately when the
seal is in contact with the chamber and the air present in
the wastes can escape only by going through the filter. A
pressure captor (not shown) ensures that the pressure
obtained in the press does not reach unacceptable levels,
which would result in an automatic opening of the insulation
gate 14 or the opening of a valve on the hydraulic circuit
of the piston 3, enabling it to rise.
When compaction is finished, if an inflatable ring
is used for leak proofing 8, this ring is set in motion and
the insulation gate 14 is closed to leak proof the treatment
area where the compacted wastes are. The electrical
resistances 9 and 13 are set in ~otion up to the pre-
determined temperature. The temperature and the pressure
inside the treatment area are simultaneously controlled by
either a thermocouple or a platinum probe.
Preferably, the wastes are first covered with
polymer, preferably composite, or placed in a polymer sack,
CA 02246364 1998-08-10
,
- 12 -
preferably composite, before being brought into the
compaction area. A preferred method of the invention
consists in using a polymer composite sack, the exterior of
which is of polypropylene or polyamide and the interior of
polyethylene.
The whole made up of the compaction chamber and the
jack is thermally insulated; thermal losses are very small
because of the 10 cm thick thermal block 17. As an example,
for a machine capable of treating waste sacks of 1 to 2 kg,
that is to say a compaction chamber of an interior diameter
of 160 mm and a height of compacted wastes of approximately
50 mm, thermal losses are estimated at 250 w for a treatment
temperature of 180~C.
The time required for the process according to the
invention is variable and depends on the temperature to
which the operator wished to bring the waste sack 11. For
example, for a treatment at 130~C, the time required to
bring the temperature up to it could be approximately one
hour and the treatment time of approximately one hour. At
180~C, the temperature rise could take approximately two
hours and the treatment time could be only a few minutes.
Heating is stopped when the required treatment time
is reached. The compacted waste may be left in place until
cooled, which, considering the good thermal insulation
around the chamber and the jack, will require several hours,
thus improving the treatment, or the compacted waste can be
removed to treat another sack full of waste. In this case,
CA 02246364 1998-08-10
- 13 -
the insulation gate is opened gradually which helps to
release the overheated water contained in the waste (blood,
urine, etc...) and to release it as vapor. This release
cools the flat bundle of compacted wastes faster.
The next step consists in cooling the compaction
area down to a temperature below 60~C, to bring back this
area to atmospheric pressure and to release the compacted
waste sack. To do so the piston 3 is activated to raise the
jack 2. For the unmoulding proper, according to a unique
method of the invention, the device of the invention, has
two additional characteristics:
the chamber 4 has a counter clearance;
the face of the jack 2 which is in contact with the
compacted waste is equipped with lugs 10 which serve to hook
the compacted waste to the jack 2 during its rise.
After complete release of the jack 2 and the mass of
compacted waste, a small movement of the mass from the jack
caused by the thrust block 19 on the frame causes them to
dissociate and to drop the compacted waste mass in the
trolley 18. It is then possible to treat another sack full
of waste.
Figure 3 shows the press in position for the release
of compacted wastes; according to a preferred method of the
invention, the frame is equipped with a thrust block 19,
which facilitates the release of compacted wastes and which,
more importantly, ensures that the release of the waste is
done without direct physical contact with the operator.
CA 02246364 l998-08-l0
- 14 -
The device according to the invention can also be
used for disinfecting medical material meant to be used
again, such as metallic material such as scalpels,
containers, çtc.
The functioning of this device makes it possible to
compact wastes while trapping cont~m;n~ted particles and
vesicles in the air caught in the wastes and released during
compaction.
This step in the compacting offers the advantage of
increasing the waste density up to a value close to its
theoretic density to considerably improve the thermal
conductivity of the wastes and to thus reduce the length of
time required to bring all the wastes in a homogeneous way
to a temperature sufficient for disinfection.
The use of conventional heating, notably thermal
conduction from the heated press walls is thus made possible
by the compacting of wastes which see their density and
their thermal conductivity reach their optimal values.
But there is also another important advantage which
is the possibility of treating waste indiscriminately,
whether it is entirely metallic or totally without water or
showing no dielectric losses, while processes using
microwave energy sources or high frequency do not make this
possible.
On the other hand, the whole of the press is
thermally insulated so that all parts which could have been
contaminated are brought to the same temperature and are
CA 02246364 1998-08-10
. .
thus also disinfected during the treatment.
We can therefore see that the device provides
disinfecting of waste with biological risks without
contaminating superfluous material such as a grinder while
self decontaminating during each operation.
Also, the process according to the invention avoids
the release of foul-smelling odors. By compacting the waste
sack 11 before heating and by treating it in a leak-proofed
area, the degassing and so the odors, are considerably
reduced.
