METHOD AND APPARATUS FOR NEUTRALIZING THE BACTERIAL CONTENT IN HOSPITAL WASTE OR OTHER SPECIAL WASTE, SO AS TO BE ABLE TO DISPOSE OF SAID WASTE AS ORDINARY WASTE DESCRIPTION

The present invention relates to a method and an apparatus for treating products with microwaves and in particular for neutralizing the bacterial content in hospital waste or other special waste, so as to be able to dispose of said waste subsequently in a more rapid and low-cost manner as ordinary waste. The prior art which is closest to the invention includes the international patent application WO 2005/002639 which describes a method in which the waste, suitably shredded, is placed in a suitably moist and compacted state inside containers which are open upwards and which in sequence are connected sealingly via their upper opening to a sterilisation station which irradiates the waste, from the top downwards, with a microwave beam of suitable intensity and for a sufficient amount of time, after suitably depressurising the container so as to remove the air from the mass to be treated, so that the treatment is uniformly distributed over the entire height of the waste and so as to lower significantly the initial-boiling temperature of the liquids contained in the mass of the said waste to be treated, so as to reduce overall the sterilisation cycle time.

In order to be able to treat the waste over the entire height of the said containers, it is necessary to use a costly high-power magnetron. It is difficult to obtain treatment temperatures which are uniformly distributed over the height of the container and, in an attempt to heat the waste situated at the bottom of the container, at the temperature and for the time required for sterilisation thereof, there exists the danger of overheating the material which is situated at the top of the said container, closest to the magnetron, and triggering combustion which may give rise to other problems including soiling with carbon black the quartz partition which closes off the zone for connecting the container to the waveguide linked up to the magnetron, with a reduction in the permeability of the said partition in relation to the microwaves. Likewise in the known methods of the continuous type, such as those described in the patent applications published under the numbers EP 522.03, EP 410306 and JP 2003/175094, the waste placed inside containers or in loose form passes into a chamber where it is irradiated by the microwaves generated by magnetrons in fixed positions, so that in these solutions also the problems of the intermittent solution considered above also arise, in that the radiation must pass through over the entire height and/or over the entire thickness of the accumulated mass of waste to be treated.

A first object of the invention is to provide a process for sterilising waste inside containers of adequate capacity, and therefore a process of the cyclical type, which may be implemented in a limited amount of time, without the said aforementioned drawbacks of the prior art and using magnetrons which have a low power and a correspondingly low cost, for example a power of about 1 kW, such as those used in kitchen ovens. These and other objects are achieved with an apparatus as per the accompanying Claim 1 ) and successive dependent claims, based on the following proposed solution. The waste, suitably shredded, moistened and compacted, is loaded into a vessel which is permeable to microwaves - for example made of glass - and housed inside a mechanically stronger container - made of any suitable material - which is then closed in a sealed manner so as to withstand the pressures arising during the process. Means are provided for rotating said vessel about its axis, while waveguides connected to low-power magnetrons irradiate microwave beams at least radially and at different consecutive levels of the said vessel so as to treat the waste housed inside it, in a manner uniformly distributed over the entire height and over the entire width, without the danger of overheating associated with the prior art in that there is a continuous relative movement of each waveguide irradiating the microwaves with respect to the waste zone treated by the latter.

These and other characteristic features of the invention, which also comprises possible means for supplying and for emptying the treatment vessels, will appear more clearly from the following description of a preferred embodiment thereof, illustrated purely by way of a non-limiting example, in the figures of the accompanying sets of drawings in which:

- Fig. 1 shows a side view, with parts sectioned, of a first schematic embodiment of a waste sterilisation station;

- Fig. 1a shows details of the station according to Figure 1 sectioned along the line A- A;

- Fig. 2 shows details relating to a constructional variant of the sterilisation station according to Figure 1 ;

- Fig. 3 shows schematically a top plan view of a machine which comprises several sterilisation stations in a static position and at the instant when a unit for loading the waste to be sterilised is connected up to one of these stations;

- Fig. 3a shows a part of the machine according to Fig. 3 at the instant when a unit for unloading the sterilised waste is connected up to one of the treatment stations;

- Figs. 4 and 5 are schematic side elevation views of the means which respectively perform unloading of the bags of waste to be treated into a compaction unit and the means which clean and recover the containers inside which the said bagged waste was contained;

- Fig. 6 shows details of the unit which performs compaction of the waste and transfers it to a system for performing shredding and for filling the vessels of the sterilisation stations; - Fig. 7 shows a side view, with parts sectioned and again in schematic form, of the terminal part of the unit according to Figure 6 during filling of the vessel in a sterilisation station;

- Fig. 8 shows a top plan view of the means according to Figure 7;

- Fig. 9 shows details, in accordance with the cross-section IX-IX of Figure 8, of the spatula for performing compaction and for detecting the filled state of the vessels in the sterilisation stations;

- Fig. 10 shows a side view, with parts sectioned, of the set of means which perform emptying of the sterilised product from the vessel of each sterilisation station and bagging thereof. For the sake of simplicity of the description, the microwaves will be referred to below by the abbreviation MW. With reference to Figures 1 and 1A it can be seen that each waste sterilisation station S comprises a vessel 1 , which is for example made of glass or other suitable material which is MW-permeable, is of adequate mechanical strength, is easy to clean periodically, has a suitable capacity and is for example cylindrical in shape, has a round cross-section and is open upwards. The bottom 101 of the vessel 1 is provided externally and in a central position with any suitable means 2 for connection, for example if required removably, to the slow movement output shaft 103 of a gear motor 3 which is fixed onto support means 4 and which is designed, when operated, to cause rotation of the said vessel 1 at the correct speed of rotation about its axis Y which in the example in question is arranged vertically. The vessel 1 is enclosed with suitable play all the way around, by a strong chamber 5 which is made for example of Teflon or other suitable material which is MW-permeable, has a fixed bottom 105 and a top lid 205 which, upon operation, may be sealingly closed or may be opened by suitable means, as shown in continuous lines and broken lines, respectively. 6 denotes for example hinge means which connect the lid 205 to the body of the chamber 5, so as to allow the lid to be moved by movement means (not shown). Still with reference to Figure 1 it can be seen that the chamber 5 is enveloped both laterally and at the bottom by a metal casing 7 which is useful as a screened lining for preventing the dispersion externally of the treatment MW (see below), fixed onto the supports 104 and provided laterally, at different heights, with windows 8 which have, fixed thereto with a radial arrangement relative to the vessel 1 , the ends of waveguides 109 connected up to respective magnetrons 9 with a power for example of about 1 kW each, similar to those used in kitchen ovens. The said aforementioned windows 8 are distributed over the height of the composite chamber 7, 5 so that the MW beams which pass through them are forced to strike the waste situated inside the vessel 1 in a sufficiently uniform and distributed manner over the entire height, and from Figure 1a it can be seen that the same windows 8 are distributed over the circumference of the casing 7 so that the MW produced by the magnetrons 9 do not interfere negatively with each other and with the said magnetrons. Goods results have been achieved with the use of three magnetrons 9 distributed heightwise. However, there is nothing to prevent the operating capacity of each station being increased by increasing the height thereof and using four or more magnetrons and/or using an additional magnetron which is connected up to a window provided in an eccentric position on the bottom of the casing 7, so as to treat the waste also from the bottom upwards, improving the formation and the migration of steam over the entire height of the mass of waste to be treated, since, as a result of gravity, the water contained in the waste tends to accumulate on the bottom of the vessel 1.

Still with reference to Figure 1 it can be seen that the lid 205 is also lined externally with a metal plate 107 which is useful as MW screening and if necessary also as a mechanical reinforcement for the said lid 205.

Each sterilisation station S is provided with probes 10, 110 for detecting the temperature, inside the chamber 5, of draw-off pipes, situated also partly at the bottom, intercepted by valve means 11 , 111 , for internal depressuhsation of the said treatment chamber 5, and is also provided with at least one pipe with a valve means 12 connected to means for formation of the vacuum, and a pipe with valve means 13, connected to a pressure transducer (not shown) for detecting the treatment pressure. It is understood that the parts 10, 11 , 12 and 13 which in Figure 1 have been associated with the lid 205, 107, may be otherwise arranged at the top of the treatment chamber 5, 7 so as to eliminate the circuit problems which would arise from the mobility of the said lid.

Operation of the sterilisation station S as described, is simple and evident. With the lid 205, 107 raised, the vessel 1 is filled with waste V which is suitably shredded, moistened and compacted, as described further below, following which said lid is sealingly closed and a suitable degree of vacuum is provided in the station via the pipe 12. In synchronism the vessel 1 is rotated about its axis Y and the magnetrons 9 are activated so that the MW beams generated by the latter are forced to strike the waste V, increasing gradually its temperature and forming the steam with temperature and pressure characteristics such as to ensure uniform sterilisation of the said waste within a time period which may be easily defined using a simple algorithm or also by tests and which may be automatically managed by a microprocessor which is kept constantly informed of the said pressure and temperature values and which, if necessary, may cause partial opening of the solenoid valves 11 and/or 111 to prevent critical pressures being exceeded. The temperature and pressure probes associated with the station allow the said processor to control automatically the evolution of the processor, in terms of absolute safety, also with regard to the possibility of regulating automatically the temperature, operating pressure and if necessary also the speed of rotation of the vessel 1. The continuous rotation of the vessel 1 is such that the various layers of waste are situated adjacent to the MW output windows 8 with different zones of their circumference, with the advantage of avoiding peripheral overheating of the said layers and with the possibility of using low-power magnetrons, since it is sufficient for the MW beams produced by the latter to reach the axis Y of the vessel 1. The stresses caused by the pressure which gradually increases inside the sterilisation chamber, owing to the temperature generated by the MW and the phenomena resulting therefrom, are absorbed by the walls of the chamber 5, 105, 205 which must be suitably structured for this purpose.

Once sterilisation of the waste has been completed, the magnetrons 9 are de- energized, the valves 11 and 111 are opened in synchronism so as to depressuhse the inside of the treatment station and so as to bring it to the values of the external pressure, following which the lid 205, 107 is opened so as to allow emptying of the sterilised waste. The pump outlet, which provides the vacuum in the treatment station, via the valve 12, and the discharge pipes intercepted by the valves 11 , 111 , through which also the treatment vapour produced inside the said chamber flows out, all lead out into a recovery tank of a compaction unit which will described further below.

The embodiment shown in Figures 1 and 1a is a possible embodiment of a sterilisation station to which numerous constructional modifications and variations may be made. Figure 2 shows, for example, a variant where the metal casing T has thicknesses greater than those of the preceding solution, so as to replace, with regard to the pressure-resistance function, the preceding chamber 5 which may be eliminated. The new metal casing T will be closed sealingly at the top by a special removable lid, which has not been shown in the drawings since it may be deduced and easily realised by persons skilled in the art. Without the said chamber 5, each window 8 of the metal container 7', to which a waveguide 109 is connected up and fixed, is sealingly closed by an insert 14 which is MW-permeable, for example made of quartz and/or other suitable material.

Since the sterilisation time is the longest of the operating times associated with the various parts which make up a machine equipped with sterilisation stations of the type described, the invention envisages designing the said machine with a layout such as that shown in Figure 3, envisaging several treatment stations S1 , S2, S3, S4 arranged alongside each other and at the same distance from each other and with their axis Y for example situated on a circle arc B having its centre on a vertical axis C about which a loading station D and an adjacent unloading station E are able to swivel, said stations being connected to an upstream unit F which collects the waste to be treated and subjects it to suitable preparation operations described further below.

The waste to be treated is usually enclosed in plastic bags which are placed inside semi-rigid or rigid containers G which are placed vertically, in single file and with their opening upwards, on a feed conveyor 15 which, as shown in Figure 4, has a terminal part 115 with parallel belts and an independent movement, so as to ensure that the containers situated on the same conveyor 15 may, upon operation, be stopped, while the front container may be fed forwards separately and correctly positioned on an overturning fork member 16 which is pivotably mounted for example on a shaft 17 and which can be operated so as to rotate upwards, with a swivelling movement through 180 , so that, after the horizontal displacement lid-thruster 19 has opened the mouth of the hopper 18 (see below), the container G, which is kept open by special means 116 and is retained on the latter by other suitable means 216, is arranged upside down on the hopper 18 of a compaction operating unit, described further below, so that the bag H with the waste is made to fall into this hopper 18. When unloading of the bag H has been completed, when the fork member 16 is still in the raised position, a horizontal displacement lid-thruster 19 is activated and performs the dual function of covering the said hopper 18 at the top and transferring the empty container G onto an adjacent fork member 16' entirely similar to the fork member 16, also in a raised position and situated above a unit 20 where means 120, for example of the rotating brush type, operate, said means, when operated, being activated so as to clean the inside of the said container using a sterilising liquid which falls onto the bottom of the said unit 20 from which it is evacuated via a discharge pipe 220. When washing of the empty container G has been completed and once said associated means have been deactivated, means 320 which generate for example a hot air flow in order to dry the internal surfaces of the said container G are activated. Once cleaning of the empty container G has been performed, the two fork members 16, 16', rotate simultaneously 180 downwards, the second fork member so as to deposit the said clean container G onto the front part 115' of a conveyor 15' - parallel to the said aforementioned conveyor according to Figure 3 - which conveys away the empty and clean containers to a recycling centre, and the first fork member so as to be arranged in the low position for taking up a new container full of waste, to be inserted into the next work cycle. From Figure 6 it can be seen that the unit F comprises a screw press 21 , for example of the type described in Italian patent 257,243 dated 8/01/2003 and used for compacting waste and for extracting any liquid content from the latter, the said press being provided for this purpose with a feeder screw 121 with its discharge mouth directed upwards, having a frustoconical shape, with a diameter and a pitch of the helix suitably decreasing towards the outlet, being operated by an external gear motor 221 rotating in both directions and having a bottom chamber 321 , defined at the front by a base disc 421 of the said screw. The liquids contained in the waste, as a result of the compaction performed by the press, its inclination and the force of gravity, flow downwards, passing through openings in the said disc 421 , and accumulate inside the said bottom chamber 321 from where they flow out by means of gravity into a tank 22 to which the pipes with the solenoid valves 11 , 111 for depressurisation of the treatment stations S already considered and the pipe 220 for discharging the residual cleaning liquid used in the unit 20 for cleaning the containers G, as described above with reference to Figures 3, 4 and 5, are connected. The tank 22 is provided with maximum and minimum level sensors 23 and 123 and is served by a circuit 24 connected to the water mains via means which, controlled by the said sensors 23 and 123, ensure the constant presence of a sufficient quantity of liquid in the tank 22.

The waste compacted by the screw press 21 is fed to a shredder 25 connected up to the outlet of the said press 21 , so as to provide also this outlet with a constriction, necessary for obtaining better compaction of the said waste which is reduced to fine particles by the shredder 25 and discharged from the latter into the front hopper of a conveyor 26, for example of the screw type, which forms parts of the unit D for loading the waste, shown in Figure 3, and which for this purpose is connected to the shredder with the possibility of rotation about a vertical axis C and is connected to means for swivelling about this axis (not shown). As shown also in Figures 3 and 7, the screw conveyor 26 is inclined upwards and has an obliquely formed discharge mouth 126 which is open downwards and by means of which, upon operation, it can be positioned above the vessel 1 of a sterilisation station S which is open and in the loading condition. The mouth 126 of the conveyor 26 is normally closed by a pair of U-shaped flaps 27 and 127 which are horizontally hinged on respective shafts 28, 128 situated respectively at the top and bottom of the said mouth 126 and connected to drive means (not shown) so that the flap 27 is normally in the position for closing the mouth 126 and the flap 127 is raised onto the flap 27. Opening of the flaps is performed firstly with downwards rotation of the flap 127, followed by that of the flap 27. With their walls the flaps 27, 127 continue to co- operate with each other and form a vertical downwardly directed extension of the discharge mouth 126 which accompanies the waste supplied from this mouth directly inside the vessel 1. From Figure 7 it can be seen that, while the waste is being loaded into the vessel 1 , the latter rotates at the appropriate speed about its axis Y and this condition has the effect that the waste is uniformly distributed over the entire breadth of the vessel 1. A pipe 29 is fixed longitudinally onto the body of the conveyor 26 and with its discharge mouth 129 is open opposite the discharge mouth 126 of the said screw conveyor so as to introduce into the waste discharged into the vessel 1 , in predefined steps, suitable predetermined and controlled quantities of liquid which is drawn off from the tank 22 shown in Figure 6, via the pump 30. Using the compaction press 21 it is possible to remove from the waste nearly all the liquids which may be present therein, so as to be able to prepare better the said waste for shredding by the unit 25, but in particular so as to be able to hydrate subsequently the said waste directly inside the vessel 1 of the sterilisation station with a desired known amount of liquid which can be easily controlled in terms of quantity via the pump 30 and uniformly distributed in the mass of waste to be treated in that it is supplied in successive instants and into different zones of the rotating vessel 1 , the overall quantity of liquid introduced into the vessel 1 being sufficient to perform correctly and effectively the process of sterilisation of the mass of waste stored in this vessel. In order to ensure correct compaction of the waste loaded by the conveyor 26 into the vessel 1 of the sterilisation station S it is envisaged that a spatula 31 with suitable dimensions is lowered in synchronism, via its vertical rod 131 connected to suitable raising and lowering means (not shown), such that, when in the low position, it is situated alongside the zone for unloading the waste into the said vessel 1 , as shown in Figure 8, and is inclined transversely, as can be seen from Figure 9, so as to be gradually raised by the waste which gradually accumulates inside the vessel and with rotation of the latter is gradually positioned underneath the spatula 31 in question which may remain stationary or which may be cyclically raised and lowered with small strokes. Consequently, via the spatula 31 it is possible to subject the waste loaded into the vessel 1 to suitable compaction, making use for example of the weight of the said spatula and/or the thrust exerted on the rod 131 by any suitable static or dynamic means, not shown in that they may be easily realized by persons skilled in the art. At the same time, via transducers 32 which co-operate with the rod 131 or with the means for raising or lowering said rod, it is possible to detect the heightwise position of the spatula 31 and therefore detect the filled condition of the vessel 1. When filling of the vessel 1 has been completed, the screw of the conveyor 26 is reversed and, after a final desired quantity of liquid has been discharged, where required, via the pipe 29 onto the mass of waste, the spatula 31 is raised and protected inside the mouth 126, as shown in broken lines in Figure 7, the flaps 27, 127 are closed, the loading unit D is swivelled about the vertical axis C so that it can be positioned opposite the next sterilisation station S or so as to position, in relation to such a station, the unit E for unloading the sterilised waste, which may be structurally associated with the loading unit D, as shown in Figure 3a, while the previously filled station is closed and activated for sterilisation of the waste introduced therein. Operation of the unloading unit E is shown in Figure 10 where it can be seen that this unit is for example provided with a vertical screw conveyor 33, which is operated by an upper gear motor 133, open at the bottom with an obliquely formed mouth 233 and connected to raising and lowering means 34 which, in synchronism, insert it gradually with the said mouth 233 inside the vessel 1 with the sterilised waste V, while the same vessel is rotated slowly about its axis. The screw conveyor 33 is designed with suitable dimensions, relative to the cross-section of the vessel 1 , so as to collect all the waste contained in the latter and discharge it through its upper mouth 333 to which, for example, a bagging unit 35 may be connected, said unit being useful for collecting the sterilised waste and for being able to convey it away for disposal as ordinary waste. Once emptying of the vessel 1 has been completed, the conveyor 33 is raised with its mouth 233 beyond the window 36 of a protective casing 136 which is then closed by a flap 37 so as to prevent even the smallest dispersion of waste when the units D and E are swivelled for positioning opposite the successive sterilisation stations S1 -S4 of the machine. It is understood that the unloading unit E shown in Figure 10 is purely exemplary and that numerous modifications and variations may be made thereto, for example with the addition of an upper screw conveyor, so as to be able to move the waste more effectively towards the bagging unit 35 and if necessary with the addition of brushes and/or suction means so as to be able to perform complete emptying and in particular proper cleaning of the vessel 1 , making use also of the relative rotational and raising/lowering movement of the two parts. According to a further variant which also falls within the scope of the invention, the sterilisation stations S1 -S4 could be mounted with the possibility of being overturned on their supports, so as to discharge the sterilised waste downwards into a statically arranged storage station. Filling of the sterilisation stations would be performed in this case by the swivel loading unit D alone. According to another variant, the said sterilisation stations S1 -S4 may be differently designed so as to be movable in relation to the loading unit D and unloading unit E which in this case may have a static location, with the obvious advantages of staticity of the zone where the final bagging means 35 operate. The sterilisation units could, for example, be mounted on a carousel segment which swivels about the said vertical axis C shown in Figure 3 or could be mounted on a rectilinear transfer device performing an alternating or one-way, but always intermittent movement. In this case emptying and cleaning of the vessels 1 could be performed when the sterilisation stations travel along the bottom section of the transfer device supporting them, with the vessels 1 overturned and open downwards, while filling of these stations would be performed along the upper section of the said transfer device.