CA2051445C - Apparatus and process for treating medical hazardous wastes - Google Patents

Apparatus and process for treating medical hazardous wastes

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Publication number
CA2051445C
CA2051445C CA002051445A CA2051445A CA2051445C CA 2051445 C CA2051445 C CA 2051445C CA 002051445 A CA002051445 A CA 002051445A CA 2051445 A CA2051445 A CA 2051445A CA 2051445 C CA2051445 C CA 2051445C
Authority
CA
Canada
Prior art keywords
chamber
microwave
refuse
temperature
heating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
CA002051445A
Other languages
French (fr)
Other versions
CA2051445A1 (en
Inventor
Helmut Goldner
Reinhold Kammann
Heinz Leinski
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ABB Environmental Services Inc
Original Assignee
ABB Environmental Services Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to DE3912751A priority Critical patent/DE3912751C1/de
Priority to DEP3912751.6 priority
Application filed by ABB Environmental Services Inc filed Critical ABB Environmental Services Inc
Priority to PCT/US1990/002043 priority patent/WO1990012602A1/en
Publication of CA2051445A1 publication Critical patent/CA2051445A1/en
Application granted granted Critical
Publication of CA2051445C publication Critical patent/CA2051445C/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHTING NOT OTHERWISE PROVIDED FOR
    • H05B6/00Heating by electric, magnetic, or electromagnetic fields
    • H05B6/64Heating using microwaves
    • H05B6/78Arrangements for continuous movement of material
    • H05B6/784Arrangements for continuous movement of material wherein the material is moved using a tubular transport line, e.g. screw transport systems
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61LMETHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION, OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS, OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS, OR SURGICAL ARTICLES
    • A61L11/00Methods specially adapted for refuse
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B09DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09BDISPOSAL OF SOLID WASTE
    • B09B3/00Destroying solid waste or transforming solid waste or contaminated solids into something useful or harmless
    • B09B3/0075Disposal of medical waste
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHTING NOT OTHERWISE PROVIDED FOR
    • H05B6/00Heating by electric, magnetic, or electromagnetic fields
    • H05B6/64Heating using microwaves
    • H05B6/78Arrangements for continuous movement of material
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHTING NOT OTHERWISE PROVIDED FOR
    • H05B2206/00Aspects relating to heating by electric, magnetic, or electromagnetic fields covered by group H05B6/00
    • H05B2206/04Heating using microwaves
    • H05B2206/045Microwave disinfection, sterilization, destruction of waste...

Abstract

The invention relates to an apparatus and a process for treating medical hazardous wastes to process them into waste similar to domestic refuse which can be removed or disposed of like normal domestic refuse or can be supplied for recycling after sorting. The infectious refuse is passed through a microwave chamber fitted with a plurality of microwave sources disposed next to each other and subjected to a disinfection therein. To achieve a safe and reliable treatment for decontaminating medical hazardous wastes in an economical and environmentally friendly manner, the apparatus comprises a two-stage construction of microwave chamber and temperature maintenance chamber. The microwave chamber has a dense microwave field distribution for heating the refuse to or above a selectable minimum temperature. Connected to the outlet of the microwave chamber is the temperature maintenance chamber which holds the refuse at at least the minimum temperature during a minimum residence time.

Description

2 ~~~~.~~~ 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 ~~Jc-,"~~~ - 2 -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 ", 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 T

- 3a -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 ~,~' - 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 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-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.

- 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 WO 90/12602 ~~~~~~~ r 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 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 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, - 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~;~~~'~'.

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 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 - , - 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 ~~~~~~~~'~ ' PCT/US90/02043 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 WO 90/12602 ~~~~-~'~ ~ PCT/US90/02043 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 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.

Claims (36)

1. 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 comminutor, a treatment section, adjoining thereto, having a microwave chamber which incorporates a conveying device for moving 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 minimum temperature, and having a second through chamber which is connected to the output of the first through chamber and is constructed as temperature maintenance chamber having an inlet and outlet for maintaining the refuse at at least the minimum temperature during a minimum residence time.
2. The apparatus as claimed in claim 1 wherein the temperature maintenance chamber incorporates a heating device for indirectly heating the refuse.
3. The apparatus as claimed in claim 2 wherein the heating device can be operated electrically, with fuel oil or with superheated steam.
4. The apparatus as claimed in claim 2 wherein temperature sensors are disposed at the inlet and outlet of the temperature maintenance chamber.
5. The apparatus as claimed in claim 1 wherein the temperature maintenance chamber is formed by a housing duct in which a conveying helix is disposed.
6. The apparatus as claimed in claim 5 wherein the temperature maintenance chamber is at an angle of inclination, rising from said inlet end to said outlet end.
7. The apparatus as claimed in claim 1 wherein the temperature maintenance chamber comprises a storage container with a selectable cross-section for a minimum filling quantity, which container has an outlet opening at the bottom for discharging the refuse under the action of gravity.
8. The apparatus as claimed in claim 7 wherein a housing duct of the microwave chamber has a larger diameter than a conveying duct of the unloading device in order to at least partially compact the refuse in the temperature maintenance chamber.
9. The apparatus as claimed in claim 1 wherein an unloading device is disposed at the outlet of the temperature maintenance chamber.
10. The apparatus as claimed in claim 1 wherein the microwave chamber is equipped with a housing duct in which a conveying device is disposed which operates as a microwave field distributor.
11. The apparatus as claimed in claim 10 wherein the conveying device is constructed as a shaftless conveying screw made of stainless steel.
12. The apparatus as claimed in claim 1 wherein the microwave chamber comprises a U-shaped trough with a mountable trough cover to which the microwave sources are attached.
13. The apparatus as claimed in claim 12 wherein the trough is composed of stainless steel, and incorporates wearing bars on which the conveying helix rests.
14. The apparatus as claimed in claim 12 wherein the trough is separated from the microwave sources by means of a sheet of polytetrafluoroethylene (PTFE) in a fluid-tight manner.
15. The apparatus as claimed in claim 12 wherein the trough is equipped with a heating device, disposed on the outside for heating the trough walls.
16. The apparatus as claimed in claim 15 wherein the heating device is formed by a double jacket for a heat transfer medium and an insulating layer disposed around the jacket.
17. The apparatus as claimed in claim 1 wherein the microwave sources are attached to the microwave chamber via a waveguide in each case with a resonance cavity attached, the resonance cavity being disposed adjacent to each other essentially without spacing.
18. The apparatus as claimed in claim 1 wherein individual microwave sources are attached to the microwave chamber via a common waveguide with attached resonance chamber.
19. The apparatus as claimed in claim 1 wherein a transfer funnel is provided between the comminutor and the microwave chamber.
20. The apparatus as claimed in claim 19 wherein the inlet and outlet of the transfer funnel are equipped with a filling level sensor.
21. The apparatus as claimed in claim 19 wherein a spraying device is disposed in the transfer funnel for moistening the comminuted refuse fed in.
22. The apparatus as claimed in claim 19 wherein an injection connection for supplying steam to the apparatus is provided in the transfer funnel.
23. The apparatus as claimed in claim 1 wherein the loading chamber is constructed as a funnel-type loading sluice with a sealable cover.
24. The apparatus as claimed in claim 23 wherein the funnel walls are of heatable construction.
25. The apparatus as claimed in claim 1 wherein a pushing device, in particular a rotating blade, is disposed in the loading chamber for precomminuting the refuse.
26. The apparatus as claimed in claim 1 wherein the loading chamber is connected to a suction system which removes the air, which is possibly encumbered with germs, from the loading chamber before the same is opened.
27. The apparatus as claimed in claim 1 wherein a lift-and-tip device for containers filled with refuse is disposed at the loading chamber.
28. The apparatus as claimed in claim 27 wherein the lift-and-tip device incorporates a weighing device.
29. The apparatus as claimed in claim 1 wherein the apparatus is of mobile construction as the superstructure of a motor vehicle.
30. The apparatus as claimed in claim 29 wherein an exhaust gas exchanger is provided to heat the heat transfer medium.
31. The apparatus as claimed in claim 1 wherein the loading chamber is constructed as a multi-chamber sluice with a rotating sluice wheel.
32. The apparatus as claimed in claim 1 wherein a measuring and regulating device is provided for determining the speed of travel as a function of the minimum temperature, to which device the filling level measuring sensor of the transfer region, the temperature sensor of the temperature maintenance chamber and the drive devices for the conveying device in the microwave chamber and possibly the temperature maintenance chamber are connected.
33. A process for continuously heat-treating particulate articles, in particular for disinfecting, sterilizing or preserving, in which the articles are first moistened 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 field while being mixed and are heated during this process to a minimum temperature with internal heating, and are at least slightly compacted in a second step and are held at at least the minimum temperature during a minimum residence time.
34. The process as claimed in claim 33 wherein the temperature conditions are regulated in the second step by an indirect heating.
35. The process as claimed in claim 33 wherein the articles are held at the minimum temperature until they are dried.
36. The process as claimed in claim 35 wherein the minimum temperature for disinfecting medical hazardous refuse is between 98°C and 102°C.
CA002051445A 1989-04-19 1990-04-16 Apparatus and process for treating medical hazardous wastes Expired - Lifetime CA2051445C (en)

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DE3912751A DE3912751C1 (en) 1989-04-19 1989-04-19
DEP3912751.6 1989-04-19
PCT/US1990/002043 WO1990012602A1 (en) 1989-04-19 1990-04-16 Apparatus and process for treating medical hazardous wastes

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JP (1) JPH06147B2 (en)
AT (1) AT401471B (en)
CA (1) CA2051445C (en)
CH (1) CH678849A5 (en)
DD (1) DD297334A5 (en)
DE (1) DE3912751C1 (en)
DK (1) DK96090A (en)
FI (1) FI95206C (en)
FR (1) FR2646083B1 (en)
GB (1) GB2232594B (en)
IE (1) IE62068B1 (en)
IT (1) IT1233196B (en)
NO (1) NO175087C (en)
PT (1) PT93791B (en)
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AT401471B (en) 1996-09-25
FI893159D0 (en)
GB2232594A (en) 1990-12-19
EP0393231B1 (en) 1991-12-18
EP0393231A1 (en) 1990-10-24
IT8967742D0 (en) 1989-09-05
DD297334A5 (en) 1992-01-09
IT1233196B (en) 1992-03-16
FR2646083A1 (en) 1990-10-26
NO175087C (en) 1994-08-31
WO1990012602A1 (en) 1990-11-01
CH678849A5 (en) 1991-11-15
JPH04500765A (en) 1992-02-13
GB2232594B (en) 1992-08-26
NO891896D0 (en) 1989-05-09
FR2646083B1 (en) 1991-07-26
ATA108689A (en) 1996-02-15
PT93791A (en) 1990-11-20
PT93791B (en) 1997-10-31
JPH06147B2 (en) 1994-01-05
FI95206B (en) 1995-09-29
CA2051445A1 (en) 1990-10-20
NO175087B (en) 1994-05-24
DK96090D0 (en) 1990-04-18
DE3912751C1 (en) 1990-09-27
FI893159A0 (en) 1989-06-28
FI95206C (en) 1996-01-10
NO891896L (en) 1990-10-22
DK96090A (en) 1990-10-11
GB8912542D0 (en) 1989-07-19
IE62068B1 (en) 1994-12-14
FI893159A (en) 1990-10-20
IE892091L (en) 1990-10-19

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