Note: Descriptions are shown in the official language in which they were submitted.
WO 90/12602 ~~~~.~~~ PCT/US90/02043
APPARATUS AND PROCESS FOR TREATING MEDICAL
HAZARDOUS WASTES
The invention relates to an apparatus and a process for
treating medical hazardous wastes.
A large quantity of potentially infectious refuse, such as, for
example, non-returnable material, bandages, syringes and
cannulas which have come into contact with infectious patients
and of infectious refuse, such as, for example, wastes
microbially contaminated with bacteria, viruses or spores is
produced daily in hospitals, medical laboratories, doctors
practices and other establishments of the health service. These
medical hazardous wastes require special measures for preventing
infection during storage and transportation.
A known waste disposal measure is therefore to collect this
hazardous refuse~in securely sealed non-returnable containers
with subsequent incineration in special plants. The infection
hazards for the medical personnel and the risks in transpor-
tation to the incineration plant by means of road vehicles are,
however, great. In addition, the incineration costs for the
hazardous refuse is many times the costs for domestic refuse.
Another known waste disposal measure is to disinfect infectious
waste and consequently to process them to form wastes similar
to domestic refuse which can be removed or eliminated like
normal domestic refuse or can be supplied for recycling after
sorting. For this purpose, German Offenlegungsschrift
3,317,300 discloses a container for receiving specific hospital
waste which after filling and introducing a disinfectant can
either be placed in a microwave chamber or is itself equipped
with a microwave source, with the result that the hazardous
refuse is disinfected by a chemothermal destruction of the
microorganisms. This container makes possible only a batchwise
WO 90/12602 , PCT/US90/02043
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treatment of the hazardous refuse on a small scale, while
preparatory waste disposal steps, such as comminution of
the hazardous waste, do not ensure adequate infection
prevention. From the point of view of environmental
hygiene and the toxicity of the active disinfectant
substances, chemical processes of this type can also be
used only to a limited extent.
German patent specification 3,505,570 reveals an appar-
atus for treating infectious refuse with the aid of
microwaves in which disinfection of infectious refuse is
carried out in a continuously operating waste disposal
plant in order to keep the risk of infection due to the
release of infectious germs, bacteria etc. as low as
possible. This compact waste disposal plant comprises a
sluice room, a spray apparatus disposed therein for
moistening the refuse with water and optionally with an
addition of disinfectant, a refuse comminutor and a
microwave chamber. The microwave chamber is constructed
as a through tube which is at least partially transparent
to microwaves, along which several microwave sources
disposed adjacently to each other are provided. By means
of a conveying device, the comminuted and moistened
refuse is moved through the microwave chamber, in which
process the microwave radiation results in a considerable
heating of the refuse. The residence time of the refuse
in the microwave chamber is controlled via the tempera-
ture, it being essential to achieve a temperature of
approx. 135°C and above up to a maximum of 200°C, depend-
ing on the material. The residence time of the refuse in
the microwave chamber is then a few minutes . For through-
put times with acceptable economic cost, a waste disposal
plant of this type has not led to absolutely reliable
disinfection, and this made an increased use of disinfec-
tant necessary.
The object of the invention is therefore to provide an
apparatus and a process of the type mentioned which makes
possible a safe and reliable treatment for the disposal
",
- 3 -
of medical hazardous wastes in an economical and
environmentally friendly manner.
The obiect is achieved in accordance with the
invention which is one aspect in an apparatus for treating
moist, possibly to be moistened, infectious refuse with
microwaves in the form of an outwardly sealable structural
unit comprising a loading section having a loading chamber and
a cornrninutor, a treatment section, adjoining thereto, having a
microwave chamber which incorporates a conveying device for
rnoving the refuse past a plurality of microwave sources
arranged next to each other in the direction of travel,
wherein the treatment section is of two-stage construction,
having a first through chamber which is formed by a microwave
chamber having a dense microwave field distribution in the
direction of travel for heating up the refuse to or above a
selectable rninirnurn temperature, and having a second through
chamber which is connected to the output of the first through
chamber and is constructed as ternperature maintenance chamber
having an inlet and outlet for maintaining the refuse at at
least the rninirnurn temperature during a minimurn residence t irne .
In a further aspect, the invention resides in a
process for continuously heat-treating particulate articles,
in particular for disinfecting, sterilizing or preserving, in
which the articles are first rnoistened and then passed through
a microwave field whose processing time is long enough to
carry out the heat treatment, wherein the articles are
loosened up in a first step and passed through the microwave
76222-2
T
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field while being mixed and are heated during this process to
a rninirnum ternperature with internal heating, and are at least
slightly compacted in a second step and are held at at least
the minimurn ternperature during a rninirnum residence time.
As a result of this, an apparatus and a process for
treating medical hazardous wastes are provided which make it
possible to reduce the germ count by thermal inactivation.
Rapidly heating the cornminuted rnoist refuse in the microwave
chamber and holding the refuse at at least one selectable
rninimum temperature for a rninirnum residence tune make it
possible to match the treatment to the initial germ count and
the germ types present in order to bring about an at least
partial denaturation of proteins and nucleic acids in the
bacteria, fungi and viruses under the influence of the moist
heat. This damage is irreversible and results in a safe
elirnination of the growth and reproduction functions. A
cont rol led part ial germ dest rust ion or inact ivat ion, and
consequently elirnination of pathogens which are contained in
or on the refuse particles can thus be achieved by a purely
thermal disinfection. Infectious refuse is rapidly
decontaminated with a high efficiency, the higher thermal
content of rnoist air being exploited.
At the same time, the apparatus may be a fixed
installation or rnay be exploited in mobile form. In areas
with hospitals and other health service establishments with
low refuse output, the apparatus may be accommodated, as a
motor vehicle fixture, in a container which is driven up to
76222-2
~,~'
- 3b -
the waste collection points of the hospitals at regular
intervals. The use of this decentralized waste disposal
system disposes of the medical wastes in an environment-
conserving arid cheap manner. The transportation of infectious
waste by road and the infection hazard resulting therefrom are
avoided. Because non-returnable collecting containers are no
longer necessary, the volume of waste is considerably reduced,
with the result that
76222-2
WO 90/12602 ,, 'PGT/US90/02043
- .,.~
the costs of-waste disposal are also reduced.
In the microwave chamber, the moist or moistened granu-
lated refuse material is heated directly by the micro-
waves, which achieves a rapid heating of the granulated
material to the boiling point of water. The steam forma- "
tion and steam flow associated increase the heating
therewith by indirect heating. Especially in the case of
a refuse-specific material with poor thenaal conductivity
such as, for example, plastics, this results in a sub
stantially faster and more economical heating of the
refuse load. To improve a uniform temperature distribu-
tion over the cross-section of a certain layer thickness,
the conveying device may be constructed as a microwave
field distributor in the form of a shaftless metal
conveying screw. This conveying screw consequently
produces not only a thorough mixing of the refuse to be
heated, but also produces multiple reflections, with the
result that the occasional differences in heating are
smoothed out by direct and indirect heating. Microwave
reflection from the walls of the microwave chamber can be
achieved by constructing the same as a metallic U trough.
Improved mixing can furthermore be achieved by an in-
clined installation of the microwave chamber and the
falling back of the granulated material produced thereby.
Finally, to avoid heat losses, the microwave chamber may
be insulated thermally and possibly have a back-up
heating system.
While the dense microwave field distribution is exploited
to achieve rapid heating in a first stage of the treat-
ment, a processing temperature or region is maintained in
a second stage in order to completely eliminate the
pathogenic gems . In order to maintain a minimum tempera-
ture, the temperature maintenance chamber is preferably
encased by a heating device. The refuse can be forced to
travel through the~cemperature maintenance chamber during
the selectable processing time by means of a conveying
device or under the action of gravity.
WO 90/12602 ~~~~,L,~,. ~ PGT/US90/02043
-
.:
For the purpose of semi-automatic or fully automatic
operation, the apparatus may incorporate a programmable
central control unit which monitors and controls the
three regions comprising loading and comminution, heat-
s ing, and temperature maintenance and makes possible a
particular matching of the operating mode to the type and
quantity of the hazardous refuse to be disposed of.
Further developments of the invention are to be found in
the description and the subclaims below.
The invention is explained in more detail below with
reference to the exemplary embodiments shown in the
accompanying diagrams.
Figure 1 shows a longitudinal section of a first ex-
emplary embodiment of an apparatus for treating
medical hazardous wastes,
Figures 2a and 2b each show a half cross section of a
microwave chamber of the apparatus according
to
Figure 1,
Figure 3 shows a block diagram of functional units of
the apparatus according to Figure 1,
Figure 4 shows a longitudinal section of another embodi-
ment of the loading and comminution region,
Figure 5 shows a longitudinal section of a second
exemplary embodiment of an apparatus for
treating medical hazardous wastes,
Figure 6 shows a longitudinal section of a third ex-
e~plary embodiment of an apparatus for treating
T,edical hazardous wastes,
Figure 7 shows a longitudinal section of a mobile
e:abodiment of an apparatus for treating medical
hazardous wastes.
Figure 1 shows a first exemplary embodiment of an ap-
paratus for treating medical hazardous wastes in a
container 1 which integrates a loading section, a treat-
WO 90/12602 PCT/US90/02043
ment section and an unloading section to fona a compact
waste disposal plant.
To receive the articles of refuse 2 to be treated, the
loading section first comprises a loading chamber 3 which
is constructed as a funnel and can be sealed in a fluid-
tight manner by means of a cover 4. The cover 4 is opened
and closed by means of hydraulic cylinders 5 by means of
which the cover 4 is mounted on the roof of the container
1. Disposed inside the loading chamber 3 is a pushing
device which is constructed as a rotating blade 6 and
which precomminutes the refuse load 2 and feeds it to a
refuse comminutor 7. The rotating blade 6 is driven by a
geared motor. One or more suction slots 8 of a suction
system 9 are disposed in the side walls 10 of the loading
chamber 3 and form a suction screen which sucks off any
atmospheric germs drawn up by opening the cover 4. In
general, with cover 4 opened, the filter system 8 remains
in operation in order to prevent any escape of germs from
the loading chamber 3. Preferably the filter system 9
comprises a roughing filter and a high-performance
suspended-material filter. The funnel with cover 4 and
suction system 9 provide the loading chamber 3 with the
function of a waste sluice. An injection connection 11
with associated valve is furthermore let into the side
wall 10 in order that superheated steam can be introduced
into the waste disposal plant far the purpose of decon-
tamination during stoppage, at shift end and also for
repair and maintenance operations.
In order that no germs deposit on the side walls 10 the
latter can furthermore be superficially heated using a
back-up heating system. The side walls 10 are heated to
a temperature of over 100°C, preferably to temperatures
between 10 5 °C and 14 0°C
The articles of waste 2 can be loaded manually, or
automatically by means of a lift-and-tip device 12 which
picks up waste containers 13 and empties them into the
WO 90/12602 ~~~~.~'~s~', ~ PCT/US90/02043
_ 7 -
loading chamber 3. For this purpose, the lift-and-tip
device 12 may be disposed at the rearside of the con-
tainer 1 and moves one or more refuse containers 13 in
the direction of the arrow for the particular loading
operation. The waste containers 13 are preferably 120 1
to 1100 1 containers. A hydraulic system 14 is provided
for actuating the lift-and-tip device 12. A weighing
device may be integrated into the lift-and-tip device 12
to determine the weight per waste container 13 and
possibly record it electronically.
The refuse comminutor 7, which also fonas part of the
loading section, comprises a cutting mechanism having two
contrary-running knife driving shafts 15 into which
cutting bodies and drivers are inserted. The cutting
bodies are so designed that a granulation of the waste
material fed with the aid of the rotating blade 6 is
achieved. The refuse is mixed at the same time. A con-
trollable electric motor is provided for driving the
refuse comminutor 7.
The treatment section comprises a microwave chamber 16
and a temperature maintenance chamber 17. The connection
between the loading section and the treatment section is
provided by a transfer funnel 18 which is detachably
connected to the outlet of the refuse comminutor 7 and
the inlet of the microwave chamber 16. The transfer
funnel 18 is preferably flanged on. In the transfer
funnel 18, use is made of a spraying head 19 which is
connected to a water tank ZO fitted With a pump, but may
also be connected to an external water main. The spraying
device is used to spray in water in a controlled manner
to achieve uniform moistening of the granulated material
produced by the refuse comminutor 7 for the subsequent
treatment. The water paths are preferably shut off and
opined up by solenoid-operated valves. The spraying time
and rest time may be varied by means of a timer as a
function of the degree of moistness of the refuse load.
PCT/US90/02043
WO 90/12602
- a -
The transfer funnel 18 is exploited as intermediate
storage for the granulated material since the comminutor
7 generally provides more granulated material than the
microwave chamber 16 can handle. A filling level sensor
21 for a minimum and maximum filling level is disposed in
the region of the inlet and outlet to monitor the degree
of filling of the transfer funnel 18. The electric motor
of the refuse comminutor 7 is preferably controlled in a
manner such that the filling level of the transfer funnel
18 always varies between the minimum and maximum filling
level. The comminution operation can consequently be
regulated by means of the filling level sensors 21.
Finally, the transfer funnel may also incorporate a
further injection connection 11 for introducing the
superheated steam for decontaminating the emptied waste
disposal plant. A steam generator 22 is fitted to supply
these injection connections 11.
In the treatment section, the microwave chamber 16 is
used to heat the comminuted and moist, possibly mois-
tened, refuse in a continuous process with a selectable
conveying speed and layer thickness of the comminuted
refuse. The microwave chamber 16 comprises a duct-Like
through housing 23 in which a conveying device 24 is
disposed. Along the through housing 23, there is disposed
a central microwave source with a waveguide system or a
plurality of microwave sources 25 are disposed closely
adjacent to each other. To couple in the microwave
radiation, the through housing 23 has inlet openings 26
or is composed of material transparent to microwaves in
these regions. The microwave sources 25 may be disposed
at a plurality of sides of the through housing 23. Under
the action of the microwaves, the granulated material
travelling through is heated up by internal heating and
evaporated moisture. To trap the evaporating moisture,
the through housing 23 and the microwave sources 25
attached thereto form a sealed treatment chamber. As
conveying device 24, use may be made, for example, of a
conveying screw, a conveying belt or a conveying ram. The
WO 90/12602 ~,~~~~~~r. ' PCT/US90/02043
_ g
conveying device 24 removes the comminuted refuse from
the transfer funnel 18 and conveys it at an adjustable
speed to the outlet 27 of the microwave chamber 16. The
mixing of the conveyed granulated material may be im-
proved by installing the microwave chamber 16 with an
incline to achieve uniform irradiation and a good heat
exchange. Since the microwave chamber is always only
partially, preferably 2/3, filled, the granulated refuse
material consequently always partially falls back again.
The angle of inclination is preferably between 10° and
50°.
Figures 2a and 2b show the construction of the microwave
chamber 16 in detail. The through housing 23 is con-
structed as a U-shaped trough and the conveying device 24
comprises an open shaftless conveying helix which rotates
in the U-shaped trough. Trough and conveying helix are
composed of metal, preferably stainless steel, and
additional wearing bars 28 of a softer material are
provided on which the conveying helix runs. The trough 23
is closed in a fluid-tight manner by means of a trough
cover 29 on which the microwave sources 25 are mounted.
In the region of the microwave sources 25, the covering
function of the trough cover 29 may also be taken over by
the microwave sources 25 with guide system connected, as
is further explained below. The trough dimensions depend
on the required layer thickness in the microwave chamber
16, and the throughput quantity and throughput speed.
Owing to the absence of a shaft, the conveying helix has
a large free cross section which minimizes the risk of
clogging and plug formation. The conveying helix further-
more acts as a three-dimensional field distributor for
the microwaves coupled in, as a result of which the
material to be treated is more satisfactorily reached by
the microwave radiation. The conveying helix is driven by
a motor 30 whose rotary speed can be controlled.
The heating in the microwave chamber 16 is achieved by
two different heat injections while the material is
PGT/US90/02043
WO 90/12602 ~~~~~~~ r
- 10 -
passing through. A first heat injection is carried out by
the microwave sources 25, 12 of which are disposed next
to each other in this case but their number may, however,
be between 1 and 20 depending on power level. The micro-
s wave energy produced by the individual microwave sources
25 is in each case coupled in via a waveguide 31 and
deflectors 32, which form a resonance chamber 33, into
the treatment chamber 34 of the microwave chamber 16. The
deflectors 32 are attached to the trough 23 by means of
detachable attachment devices 35. To produce a dense
microwave field distribution, the resonance chambers 33
are disposed next to each other. To prevent
refuse particles and moisture entering the waveguide 31
and the resonance chamber 33, the treatment chamber 34 is
covered at the top by means of sheets 38 of a material
which is transparent to microwaves such as, for example,
polytetrafluoroethylene (PTFE). The switch-on time of the
microwave sources 25 can be controlled. The electrical
power may be supplied via a plug connection 37 (see
Figure 1). The switch-on times are selected in a manner
such that the microwaves heat the granulated material to
or above a selectable minimum temperature in order that
the required thermal treatment, for example a disinfec-
tion, can be carried out. To guarantee heating at least
to the minimum temperature, the conveying speed and
filling levels are automatically adjusted.
A second heat injection is used to back up the heating
produced by the microwaves. For this purpose, the trough
23 is surrounded by a heating device. According to Figure
2a, the heating device comprises electrical heating coils
which are preferably disposed immediately next to the
wall of the trough 23. According to Figure 2b, the
heating device comprises a double-walled partial jacket
38 for a heat transfer medium such as, for example,
35 thermal oil or superheated steam, which partial jacket is
also preferably disposed immediately next to the wall of
the trough 23. A thermal insulation 39, which is screened
on the outside by a covering 41, is adjacently installed
WO 90/12602 ~~~~.~~ ~ PGT/US90/02043
- 11 -
in both designs. This second heat injection may comprise
different heating circuits in order that a controlled
continuous quantity of heat can be fed to the individual
regions of the microwave chamber 16. The temperature
reached by the granulated material is determined in the
region of the inlet 43 of the temperature maintenance
chamber 17 by means of a measuring sensor 42. To therm-
ally disinfect a moist medium, the minimum temperature is
above 95°C and is preferably 98°C to 102°C.
The outlet 27 of the microwave chamber 16 is connected to
the inlet 43 of the temperature maintenance chamber 17.
The temperature maintenance chamber 17 comprises a duct-
like through housing 44 in which the temperature treat-
ment of the granulated material takes place in a con-
tinuous process. The heated granulated material supplied
by the conveying device 24 of the microwave chamber 16 is
taken over by means of a conveying device 45 and passed
through the temperature maintenance chamber 17 during a
selectable minimum residence time. During this time, the
granulated material is held at at least the minimum
temperature. According to Figure 1, the through housing
44 is encased on the outside by a heating device 46 which
is constructed, for example, as in the case of the
microwave chamber 16. The heat introduced by the heating
device 46 prevents the granulated material cooling down,
with the result that the temperature produced in the
microwave chamber 16 can be maintained. A temperature
level may optionally be adjusted between inlet 43 and
outlet 48 of the temperature maintenance chamber 17, in
which case the inlet and outlet temperature must have at
least a minimum temperature necessary for the treatment
operation. To monitor the treatment operation, the inlet
temperature is measured and documented by means of the
measuring sensor 42 and the outlet temperature of the
granulated material in the temperature maintenance
chamber 17 by means of a measuring sensor 47.
The conveying device 45 comprises a conveying screw
WO 90/12602 PCT/US90/02043
which, like the one in the microwave chamber 16, is of
shiftless construction. The conveying screw 45 is driven
by a motor 49 with controllable rotary speed. Its rotary
speed is matched to the conveying helix 24 in a manner
such that a certain compacting of the granulated
material, which is initially loose for heating by micro-
waves, is brought about in the temperature maintenance
chamber 17, as a result of which the heat conduction is
improved in this treatment phase and the heat losses are
reduced. Metals, preferably stainless steel, are
envisaged as the material for the through housing 44 and
the conveying device 45. However, plastics or ceramic
materials may also be used. Since the treatment operation
is complete at the outlet 48 of the temperature main-
tenance chamber 17, an adjoining unloading section may
comprise only an ejection opening or, as shown in Figure
1, it may have an unloading screw 50, driven by a motor
51, which can be swung laterally out of the container 1.
The container 1 shown in Figure 1 can be a stationary
installation or, according to Figure 1, be disposed on a
motor vehicle trailer 52 for mobile use. A space heating
system 53 ensures an adequate ambient temperature.
The waste disposal plant may be operated manually, or
semiautomatically or fully automatically. All the essen-
tial controlled variables and monitoring functions are
incorporated in a process-control computer 54. The center
piece of the process-control computer 54 is a stored-
program control system which contains an operating
program for switch and sensor scanning, motor and source
control, and monitoring and driving the indicators. The
function units connected to the process-control computer
54 are shown in a block circuit diagram of Figure 3 for
the loading and comminution region, the heating region
and the temperature maintenance region with unloading
system. The controlled variables of the function units
which affect each other are denoted by connecting lines
with arrows. This measure ensures that the variables,
WO 90/12602 PCT/US90/02043
- 13 - _
critical for a thermal treatment, in particular a disin-
fection, of minimum temperature and maintenance duration
are maintained and deviations are automatically
corrected.
The mode of operation of the apparatus described above
for treating medical hazardous wastes is described below
for exemplary technical data relating to purely thermal
disinfection of hazardous wastes.
To operate a plant with a processing capacity of 100 to
300 kg/h, the trough heating systems and the funnel
heating systems are first switched on. Once the specified
set temperature is reached, water and air pressure are
available and the cover of the loading sluice is closed,
the plant can be switched to automatic operation observ-
ing the safety requirements and loaded.
The lift-and-tip device 12, which also controls the
opening of the cover 4, ejects wastes from the containers
13 to be emptied into the opened funnel 3. After the
cover 4 has closed, the suction system 8 is switched off.
The rotating blade 6 and the comminutor 7 are then set in
operation. The rotating blade 6 shreds the articles of
waste and feeds them in a controlled manner to the
comminutor 7 which provides for granulation and mixing.
The granulated material then drops into the intermediate
funnel 18 with automatic filling level monitoring and
controlled moistening. The filling level monitoring
regulates the comminution operation by switching off the
comminutor 17 if the intermediate funnel 18 is filled and
stopping the further process sequence if the intermediate
funnel 18 is empty. If the lower filling level sensor 21
indicates the presence of granulated material, the
conveying helixes of the microwave chamber 16 and the
temperature maintenance chamber 17 and, with a time
delay, the microwave sources 25 are automatically switch-
ed on. The thermal disinfection is now initiated. The
granulated material is heated in the microwave chamber at
WO 90/12602 ' PCT/US90/02043
~c,Q~;~~~'~'.
- 14 -
a microwave frequency of 2,450 I~iz approved here for
industrial purposes. The granulated material is passed at
a defined conveying speed through the microwave chamber
16 where a rapid direct production of heat is brought
about in the material as a function of the dielectric
properties. This effect is increased further by the water
added which evaporates under the action of the micro-
waves. This application of vapor is maintained in the
microwave chamber 16 since at the outlet side a natural
seal is built up by the granulated material transferred
to the temperature maintenance chamber 17. The granulated
material temperature reached is subject to monitoring. If
it drops below a minimum temperature, the conveying speed
is reduced until the minimum temperature is reached
again. In this process, the rotary speed of the conveying
helix 24 is adjusted to the mean throughput level (kg/h)
and the minimum temperature to be reached.
The final structural group for the disinfection is the
temperature maintenance chamber 17 with its maintenance
zone. In this maintenance zone, the granulated material
is held at the minimum temperature, achieved by means of
microwaves, of over 95°C to eliminate the pathogenic
germs. The minimum residence time depends on the number
of germs, the germ type and the filling quantity. The
maintenance time can be adjusted in a controlled manner
by means of the speed of the conveying screw 45. The
minimum temperature is demonstrated by documenting the
automatically measured inlet and outlet temperature.
Temperature losses are compensated for by the backup
heating. If the intermediate funnel 18 is empty, the
microwaves sources 25 and, with a certain lag, the
conveying ~evices 24, 26 are first switched off
automatically. The treated granulated material is ejected
for removal. After the completion of work, the plant is
steam-disinfected.
A process according to the invention for continuously
heat-treating particulate articles, in particular for
WO 90/12602 'r~'~.~ 7"~.~~'- ~ PCT/US90/02043
- 15 -
disinfecting, sterilizing or preserving, comprises the
following two steps. In a first step, the comminuted or
already partly particulate articles are loosened up after
carrying out moistening with an aqueous medium and passed
through a microwave field while mixing the entire cross
section of the conveyed layer thickness, and heated in
this process to a minimum temperature with internal
heating. In a second step, the articles so heated are at
least slightly compacted and held at at least the minimum
temperature during a minimum residence time. To maintain
this minimum temperature with heat losses occurring, the
articles can be heated indirectly during this holding
phase so that any drop below the minimum temperature is
avoided. This ensures, with as low a radiation of micro-
wave energy as possible, the heating required for the
heat treatment and, in addition, employed far the subse-
quent steps, which creates a high efficiency. In this
process, the articles may be held, for example, at the
minimum temperature until they are dried. If the use of
disinfectants is additionally required for a treatment
operation, spray injection of the same is possible during
the first and/or second step.
Figure 4 shows another embodiment of the loading and
comminution region, in particular the loading chamber 3,
which is constructed as a three-chamber sluice. The
loading chamber has an essentially cylindrical hollow
body 55 which is provided at the bottom with a funnel-
type discharge section 56. Disposed centrally in the
hollow body 55 is a sluice wheel 57 with three sluice
paddles 58 each extending outwards at an angle of 120° in
each case. The sluice paddles subdivide the hollow body
55 into three chambers which are separated from each
other and which rotate anticlockwise in the direction of
the arrow when the sluice wheel 57 turns. The sluice
chambers pass through in sequence a filling station 59,
a transfer station 60 and a disinfection station 61. The
passage through the three stations 59, 60, 61 is des-
cribed below for one chamber. If the sluice wheel 58 is
WO 90/12602 - ,
PCT/US90/02043
- 16 - _.
in the position shown in Figure 4, wastes 2 can be loaded
into the chamber situated in the filling station after
the cover 4 has been opened. Turning through I20° rotates
this chamber with the wastes 2 received into the transfer
station 60, where the rotating blade 6 operates and a
transfer to the comminutor 7 takes place. The emptied
chamber is then brought to the disinfection station 61
which is equipped with at least one spraying head 62 for
introducing a disinfection mist and which can be ex-
tracted with a suction system 9 according to Figure 1.
The first chamber, freed of germs, is then transferred
again to the filling station. The chambers rotated
through 120° and 240° with respect to this chamber pass
through said stations 59, 60, 61 with a displacement in
time, as a result of which continuous loading with wastes
2 is possible. The region of the loading chamber opened
for a loading is consequently always germ-free.
Figure 5 shows a second exemplary embodiment of the
apparatus for treating medical wastes. The temperature
maintenance chamber 17 is in this case constructed as a
compact large-volume container 63. This container 63 is
installed essentially vertically so that after the plant
has been put into operation, the granulated material
heated up in the microwave chamber 16 drops down under
the action of gravity into the container 63 and fills the
latter. In order to prevent material which has not yet
been adequately thermally treated escaping during the
first filling of the container 63, the container 63 is
sealed at the bottom with a removable cover 64. The
granulated material loaded into the container 63 remains
in the latter for a minimum residence time at at least
the minimum temperature. Depending on the required
thermal treatment, e.g. disinfection, the minimum tem-
perature and minimum residence time can be corres-
pondingly adjusted and checked by means of the tempera-
ture measuring sensors 42, 47. For continuous operation,
the cover 64 is removed after a first filling of the
container 63. The granulated material transferred from
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the conveying device of the microwave chamber 16 to the
temperature maintenance chamber causes the granulated
material already loaded into the container 63 to travel
through. The dimensions of the container 63 can be
matched to the throughput quantity of the plant. The
cross section of the unloading device 50 connected to the
bottom of the container 63 is of smaller construction
than the cross section of the conveying duct of the
microwave chamber 16 so that more granulated material is
constantly transferred from the microwave chamber 16 to
the container 63 than can be delivered by the latter via
the unloading device 50, as a result of which a compact-
ing of the granulated material in the container 63 is
achieved.
The second heat injection for the microwave chamber 16
and an indirect heating of the granulated material in the
container 63 is carried out in the case of the plant
according to Figure 5 by means of a heat transfer medium.
For this purpose, the microwave chamber 16 and the
container 63 have chambered walls with a double jacket 65
through which the heat transfer medium, for example
thermal oil, superheated steam, is pumped from a reser-
voir 68. The double jackets 65 of the microwave chamber
16 and of the container 63 are connected to each other to
form a circuit for the heat transfer medium via pipelines
69 in which a pump 71 and at least one valve 72 are
fitted for supply and control. The heating device of the
loading funnel 3 can also be fed from this heat transfer
circuit. The preheating of the granulated material thus
achieved in the intermediate funnel 18 is checked by
means of temperature sensors 67. In other respects, the
plant can be constructed as described in relation to
Figures 1 to 4 and may also be equipped with an electri-
cal heating system.
Figure 6 shows a third exemplary embodiment of an ap-
paratus for treating medical hazardous wastes in which
the heat produced in the microwave irradiation of the
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- 18 -
moistened waste can be at least partially recovered. For
this purpose a circulating air pipeline 73 which can be
shut off and which is led into the loading chamber 3 is
connected in the region of the outlet 27 of the microwave
chamber 16. Hot air can be sucked out of the housing duct
23 of the microwave chamber 16 by means of a pump 74
inserted in the circulating air pipeline 73 and fed to
the funnel-type loading chamber 3. In other respects,
this plant does not differ from that described in Figure
1.
Figure 7 shows a mobile embodiment of an apparatus for
treating medical wastes. As described in relation to
Figure 1, this plant comprises a loading section with
loading chamber 3, comminutor 7 and intermediate funnel
18, a treatment section with microwave chamber 16 and
also a temperature maintenance chamber and an unloading
section, said operating units .being accommodated in a
container 1 which forms the superstructure of a motor
vehicle 75. To simplify the graphical representation, the
temperature maintenance chamber and the unloading section
have been omitted. The plant is furthermore equipped with
a heating device, described in relation to Figure 5, by
means of circulation of heat transfer oil. In this case,
heat transfer oil is envisaged as heat transfer medium.
Pipelines 69 with pump 71 inserted and valve 72 connect
the reservoir 68 to the double-walled jackets 65 of the
housing duct 23 of the microwave chamber 16 and of the
funnel 3. A radiator 76 of the space heating system 53
(see Figure 1) is fed via pipelines 70. An exhaust gas
heat exchanger 77 which is disposed around the exhaust 78
of the motor vehicle 75 is provided to heat up the heat
transfer oil stored in the reservoir 68. The reservoir
68 is connected to the exhaust gas heat exchanger 77 via
pipelines 79 to heat up the heat transfer medium. To
monitor and safeguard the heating of the heat transfer
oil, an expansion vessel 80, a safety valve 81 and a
pressure gauge 82 are connected to the reservoir 68. The
heat produced in the internal combustion engine of the
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- 19 -
motor vehicle can thus be employed for the thermal
treatment operation on the medical hazardous refuse in a
manner such that the plant is heated up during the drive
to the points of use without additional energy costs and
preheating times and dwell times of the plant are mini-
mized.
