"Process and apparatus for neutralising bacterial contamination of solid hospital wastes and other suitably comminuted humidified materials " DESCRIPTION The invention relates to improvements in the method of processing and the corresponding machine described in international patent application published under number WO 2005/002639 on the 13.1.2005 which are particularly suitable for the sterilisation of solid hospital wastes using microwaves, in such a way that these wastes can be disposed of even directly from the outset as ordinary wastes, with considerably reduced costs in comparison with those of present disposal procedures using specialised systems. The process described in that patent application is characterised by the following sequence of operating stages: a) fine comminution of the wastes, alone or together with their container, in a controlled environment, in order to prevent the escape of contaminants to the exterior, b) suitable humidification of the mass of comminuted waste with water, c) placing and compaction of an appropriate quantity of comminuted humidified waste within treatment containers which are open at the top, which are transferred to the subsequent stages in processing through transport means, d) Leak-tight closure of each treatment container and connection of the latter to a source of microwaves of suitable power which heats the waste and the humidity confined within that container in order to create steam and all those conditions of temperature, time and pressure necessary to ensure sterilisation of the said wastes. During this stage the internal pressure within the container is regulated by a controlled discharge, so as not to exceed pre-set maximum values, and after this treatment stage the container is appropriately depressurised and reopened, e) Discharge of the sterilised wastes from the treatment containers, which may be followed by cleaning of the said containers and their reuse in the operating cycle. The following disadvantages have been encountered when experimentally performing the stage of sterilising a suitably comminuted and humidified charge of

wastes confined in appropriate quantity and with appropriate compaction in a container for treatment with microwaves as described in the patent application cited in the introduction:

1. The sterilisation cycle takes very long times and treatment has proved not to be uniform over the depth of the mass of waste placed in the treatment containers.

The invention is designed to overcome this first serious disadvantage, bringing about appropriate internal depressurisation within the sterilisation container with the wastes when this is sealed by the sterilisation head, before activating the microwave generator. This preventive depressurisation stage removes air from the mass of wastes in order to ensure that the treatment is uniformly distributed over the full depth of the wastes and substantially reduces the first boiling point of the liquids present in the mass of wastes being treated, reducing the sterilisation cycle times as a whole.

2. Determination of only the temperature at the bottom of the treatment containers proved to be insufficient, and major problems were encountered when positioning the temperature sensor in these treatment containers. The invention is intended to overcome this disadvantage by placing at least one window in the bottom part of the treatment container which allows local radiation of the heat within and at the base of the container to the exterior with provision for this heat to be detected through an external static infrared ray sensor separate from the container itself. Provision is also made for the possibility of detecting the temperature within the top of the treatment container, using means associated with the sterilisation head, in such a way that the treatment containers have no temperature sensors within them, with all the structural and operational advantages deriving from this condition. 3. Provision is also made for the possibility of optimising the treatment cycle using the wave reflected to the microwave generator. The invention provides for the use of means to detect the reflected wave which on the basis of this parameter automatically regulates the height at which the treatment container is located in order to vary the distance of the mass of wastes from the sterilisation head and to attenuate the reflected wave in this way. Means may be provided to optimise the

working cycle of the machine in relation to the reflected wave, for example to control the loading of the treatment containers and/or humidification and/or compression of the wastes in the containers, by feedback.

4. Means are also provided to neutralise the pollutants during the stages of depressurising the treatment containers during and after the sterilisation cycle for the corresponding charge of waste. The invention intends to overcome this disadvantage by providing filtration means to neutralise any bacterial contamination in all the fluids discharged from the treatment containers during the stage of sterilising the wastes contained within them. Further features of the invention and advantages deriving therefrom will be more apparent from the following description of a preferred embodiment of the aforementioned and other improvements illustrated by way of a non-restrictive example in the figures in the appended plates of drawings, in which:

- Figure 1 illustrates the station for the sterilisation of wastes confined in a treatment container, laterally and in partial cross-section,

- Figures 2 and 3 illustrate different embodiments of a local window radiating the internal temperature of the treatment containers on the bottom part thereof, laterally and in partial cross-section,

- Figure 4 is a plan view of the base of the piston of the sterilisation head which seals the tops of the treatment containers,

- Figure 5 illustrates other details of the piston in Figure 4, in cross-section along the line V-V,

- Figure 6 is a plan view of the base of the piston of the sterilisation head according to an alternative embodiment of the arrangement in Figure 4, - Figures 7 and 7a illustrate a number of construction details according to the cross- section VII-VII in Figure 6.

In Figure 1 , reference 1 indicates the known sterilisation container of cylindrical shape with a round cross-section, for example of stainless steel, which opens at the top through an opening 101 which is suitably flared on the inner edge and provided beneath with a forked appendage 201 which is open at the base, with a vertical key

301 on the side, which acts together with a seat 204 of matching shape provided on carousel 4 to hold container 1 with a predetermined angular orientation useful for what has been mentioned above. In order to prevent residues of treated wastes remaining within container 1 , the bottom edge of base 401 of that container is suitably rounded. Container 1 is vertically guided by guides with fixed wheels 3, for example three in number, in a mutually angular spacing of 120°, on carousel 4 which through cyclical rotation about its own vertical axis 104 driven by suitable means which are not shown transfers container 1 to the subsequent working stages of the machine, as for example described in patent application WO 2005/002639 cited in the introduction to this description. In Figure 1 container 1 moves from the loading station which has filled it with an appropriate quantity of comminuted humidified wastes 2 and it is then aligned with the means at the sterilisation station described below. As already mentioned in the previous application, it remains understood that other suitable means of transport may be provided instead of carousel 4 in order to transfer treatment containers 1 to the subsequent working stations of the machine. Basal forked appendage 201 of container 1 engages the head 5 of linear screw/nut actuator 105 mounted on a fixed supporting structure 6 driven by an electric motor 7 which is preferably of the electronic speed and phase control type, for example of the brushless or stepping type, controlled by a processor 8 which controls automatic operation of the entire station in question and which can interact with the other working stations of the machine, as more particularly specified previously. On the command of processor 8 container 1 is raised by actuator 5, 105, 7 and then the shaped part of the piston of sterilisation head 9 which is fixed through its own flange 109 to a supporting bracket 10 which is in turn fixed to an upright structure 1 1 , which is for example structurally connected to lower base 6 with said linear actuator 5-105, is inserted with a lateral seal into its upper opening 101.

From the detail in Figure 5 it will be seen that head 9 is provided laterally with a plurality of annular seats of which the closest to the base of the said head has a scraper 30, while all the other annular seats, which may also be in a different number from that illustrated, have corresponding resilient sealing strips 31 each forming an

outer ring 131 , of any suitable rigid material, for example any suitable thermohardening plastics material, which may be of the reinforced type, the external profile of which has for example the shape of an isosceles trapezium, for simplified assembly and to act together by matching the bevelled inner edge 101 of the upper opening of container 1. Ring 131 is designed to project slightly from the lateral surface of head 9 and to form a lateral seal with the inner lateral surface of container 1. Beneath each ring 131 there is provided at least one suitable resilient ring 231 which has the function of pressing outer ring 131 into contact with container 1 and of ensuring a seal between that ring 131 and the annular seat containing the anti- extrusion seals in question.

As described in patent application WO 2005/002639 cited in the introduction, head 9 is provided axially with a through duct 12, which is intercepted at the opposite ends by very pure quartz sheets 13, 1 13 with corresponding outer seals, where lower sheet 13 is held in place for example by a flange 14 secured by bolts 1 14 (Figures 4, 5) to the base of head 9, and upper sheet 1 13 is retained in its seat for example by the lower fixing flange to said head 9 of waveguide 15 connected to microwave generator 16, which has suitable characteristics, is powered by an appropriate interface 17 controlled by processor 8 and is designed for self-adjustment in relation to the reflected wave detected through means 18 of a known type located on generator 16 (see below).

On flange 109 of head 9 there is mounted a pressure sensor 19 which through a duct 20 detects any pressure leaks to chamber 21 through the two quartz sheets 13, 1 13 if lower quartz 13 should yield partly or totally, and this sensor 19 is operatively connected to processor 8 to indicate its status. A first two-way diverting joint 22 is also mounted on that flange 109 and is connected through a duct 23 of head 9 to a pressure offtake 24 which opens in the base of said head 9, as specified earlier. At least the following means are mounted on the two paths of joint 22: - A pressure sensor 25, which signals the pressure value present in container 1 during the wastes sterilisation stage to processor 8 through an appropriate electrical connection,

- An electrically-operated valve 26, with a suitable upstream filter, controlled by processor 8 which intercepts a discharge duct 27 on which there is mounted a vacuum pump 28 of suitable characteristics, the electric motor 128 of which is also controlled by processor 8. Discharge duct 127 of pump 28 may be conveniently intercepted by a filter unit 29 of any type which is capable of removing any contaminant from the fluid passing through. Filter unit 29 may be usefully located to discharge the treated fluids, for example into one of the first working stations of the machine in question, for example the first stage in which the wastes are comminuted and humidified. As a branch from duct 27 there is provided a duct 227 connected to an electrically- operated valve 126 with a filter, also controlled by processor 8, which is the same as electrically-operated valve 26 and like that is connected by means of its own duct 23 to a pressure offtake 124 located on the base of head 9 at an angular spacing of 180° from pressure offtake 24. From the details in Figures 4 and 5 it will be seen that in order to have useful space for fitting pressure offtakes 24 and 124 on the base of head 9 axial duct 12 of said head 9 may be constructed having a rectangular cross-section and with suitably rounded corners. Pressure offtakes 24, 124 are positioned in relation to one of the greater sides of duct 12 and each of these has on the lower face of head 9 a seat 32 of circular cross-section which communicates to the exterior through a hole 33 provided in fixing flange 14 for lower quartz 13. Seat 32 (Figure 5) is formed of two recesses of inwardly decreasing diameter and in this is fixed by means of a bolt 34 a plug 35 provided with two cylindrical parts which match the recesses in the said seat but which have a slightly smaller diameter than that of those recesses and have a height such that a smaller amount of lateral and axial intercommunicating play is produced between parts 35 and 32, at which there ends a terminal branch 123 of duct 23 leading to diverter joint 22. According to a variant embodiment, not illustrated, the outermost cylindrical part of plug 35 may be in lateral contact with the corresponding outer part of seat 32 and may be provided laterally with a thread having several turns or grooves parallel to its own axis which provide the lateral play

necessary for the passage of fluids, but having a grid shape which better prevents the passage of large particles (see below).

Again from the detail in Figure 4 and Figure 1 it will be seen that at one of the two pressure offtakes 24, 124 flange 14 fixing quartz 13 bears a small hole 36 which exposes a thermometric sensor 37 housed in the base of head 9 and electrically connected through an output duct 38 to processor 8 to transmit information relating to the operating temperature at the top of wastes 2 present in treatment container 1 to it. As an alternative, or in combination with said sensor 37, provision may be made for the use of a thermometric sensor, not illustrated, which detects the temperature of the gas reaching diverter joint 22.

In order to determine the waste treatment temperature at the bottom of container 1 , each container may be provided laterally with a blind window 39 at a short distance from the base and in an appropriate angular relationship with key 301 , as better illustrated in the detail in Figure 2, formed by partial removal of the material making up the thickness of a lateral lower portion of said container 1 , in such a way that the said window closes on the inner surface of a plug 40 of the said material making up container 1. According to a structural variant illustrated in Figure 3, instead of blind window 39, a through window 139 may be provided in container 1 and this is then closed at one extremity, for example on the inner face of the container, with a plug 140, which is for example brazed and of any material which is a good conductor of heat and resistant to chemical and physical stresses, for example any alloy of aluminium, copper and/or other suitable materials. When container 1 is raised and connected to sterilisation head 9, as illustrated in Figure 1 , lateral window 39 or 139 of said container 1 lines up with and abuts against a static infrared ray sensor 41 which detects the desired bottom temperature and transmits it to processor 8 through a suitable electrical connection. If container 1 is raised and connected to head 9 through a constant predetermined lifting travel, sensor 41 is for example mounted on upright 1 1. The sterilisation station as described operates as follows. When container 1 has been coupled to head 9, processor 8 causes valves 26, 126 to open and activates

motor 128 of vacuum pump 28 to form a suitable vacuum, for example between -0.5 and -1 bar, for example approximately -0.8 bar, within treatment container 1 to remove the pockets of air from the mass of waste which would impede heat treatment of the mass and also to reduce the first boiling point of the liquids in the said wastes present within container 1 when these are subsequently subjected to the process of sterilisation with microwaves, all in such a way that sterilisation which is uniformly distributed through the full depth of the mass of wastes can be carried out in short treatment times in comparison with those in the prior art. The gas sucked out by pump 28 passes through filter 29 which removes contaminants of all kinds. This preventive stage of vacuum formation may be controlled by a vacuum meter, not illustrated, or may be programmed in terms of time with electronic monitoring of the power produced by electric motor 128 of pump 28. This suction stage also makes it possible to determine the effectiveness of seals 31 for head 9 and container 1 at the start of each cycle and to indicate any need for maintenance work on these components, and also to stop operation of the machine during the stage of activation of pump 28 when the preset vacuum in container 1 and/or other parameters correlated with that is not attained.

After the vacuum stage electrically-operated valves 26, 126 are caused to close, motor 128 of pump 28 is switched off and unit 17, 16 is caused to irradiate the mass of wastes present in container 1 sealed by head 9 with microwaves. For the sterilisation stage it is necessary to reach a preset temperature value, for example around 150°C, in container 1 and hold that temperature for a time which is also preset, for example approximately 9-10 seconds, to ensure destruction of all the bacterial contamination present in the mass of wastes being treated, without the latter undergoing any combustion phenomena. During the sterilisation cycle processor 8 takes into consideration the lowest temperature value detected through sensors 37 and 41 and the correct treatment time is correlated with that value through an appropriate table in the software of said processor 8. During the sterilisation stage processor 8 also senses the pressure established in container 1 through sensor 25. If the preset operating temperature is not attained at the ends of

container 1 during the time of the sterilisation cycle, the sterilisation cycle continues until the desired temperature is reached, while a pressure having a preset limit value, for example around 8 bar, is maintained within container 1 through the alternate offset opening of electrically-operated valves 26, 126 with activation of suction unit 28, 128. During this stage electrically-operated valves 26, 126 are activated one at a time for short periods so as to modulate discharge and prevent the flow of heavy particles to them, even though these particles would in any event be stopped by the filters located upstream from each electrically-operated valve. At the end of the sterilisation cycle power is switched off from microwave source 16, 17 and valves 26, 126 are first opened cyclically in an offset way as previously stated for the stage of controlling the internal pressure and are then opened simultaneously and suction unit 28, 128 is activated to return the interior of container 1 to atmospheric pressure within a short time so that said container 1 can be lowered by actuator 5, 105, 7, disconnecting it from head 9 and returning it to carousel 4 or other appropriate transfer means to the next workstation. In exceptional circumstances, if the preset temperatures are not attained within container 1 during the maximum time for the sterilisation cycle, after the aforesaid stage of depressurisation and disconnection of the container from treatment head 9 the container may be moved to the loading station to be provided with a sufficient quantity of water necessary for re humidification of the wastes and that container may then be transferred to the sterilisation station for repetition of a further working cycle during which it will be easier to achieve the preset parametric treatment parameters. In the course of stage 18 processor 8 is also ready to detect the magnitude of the reflected wave towards magnetron 16 and may be provided with software capable of processing this parameter together with the operating temperature and pressure parameters in container 1 and to control the operating functions of one or more of the downstream stations through its own output 108, for example in order to conveniently vary the degree of humidification of the wastes and/or their compaction and/or the quantity placed within the treatment containers so as to optimise operation of the sterilising machine through these feedback controls. At the same time the said

processor 8 can act to attenuate the value of the reflected wave, by altering the position of container 1 as regards its height through motor 7 of actuator 5-105 so as to vary the distance between head 9 and the top surface of the mass of wastes present in said container 1 without prejudice to the seal connecting that container with treatment head 9.

If automatic regulation of the position of container 1 in height is provided in order to attenuate the reflected wave, infrared sensor 41 is mounted on a small slide 42 which runs in a vertical guide 43 against resilient means 44 which tend to press the said slide towards the bottom resting position, this guide being fixed on upright 1 1 and being designed to act together with an appendage 45 secured in any suitable manner in bracket form at the base of each container 1. When the container 1 with wastes 2 is raised to engage with treatment head 9, appendage 45 touches the bottom of slide 42 and infrared sensor 41 comes into line with and remains in line with window 39, 139 radiating the inner bottom temperature of that container. The vertical movement of slide 42 may be detected by an encoder 46 which transmits information relating to the actual height position of the container 1 to processor 8 in order to interface these with the virtual indications originating from the encoder associated with electric motor 7. In order to achieve more uniform radiation of the microwaves within the mass of wastes present in container 1 , which is circular in plan, the modifications now described with reference to Figures 6, 7, 7a have recently been made to the equipment. Axial duct 12 of head 9 is constructed with a circular cross-section and quartzes 13, 1 13 are circular in plan, with a very much greater surface area than in the arrangement in Figure 4 and better distributed over the projection in plan of the mass of wastes undergoing treatment. Lower quartz 13 is held in its seat through an annular ferrule 14 of very limited amplitude which is fixed to the base of head 9 by suitably distributed bolts 1 14 as in the arrangement in Figures 6 and 7a. In this case ducts 23, 123 connecting to electrically-operated valves 26, 126 abut beneath against small blades 47, 147 provided on the upper surface of ferrule 14 opening onto the outer lateral surface of that ferrule, the diameter of which is suitably smaller

than the internal diameter of container 1. According to a different embodiment illustrated in Figure 7b, ferrule 14' is part of an internally threaded ring which is screwed into a corresponding threaded part 48 of the lower lateral surface of head 9 and which is provided with an internal annular recess 49 in the upper edge in contact therewith at which there terminate ducts 23, 123 connecting to electrically-operated valves 26, 126 and small holes 50 opened on the lower surface of said ferrule 14' which laterally bears the annular seat containing scraper 30. In the arrangement in Figures 6 and 7a, temperature sensor 37 may be located in the base of head 9, as in the arrangement in Figure 4. In the arrangement in Figure 7b it is however difficult to fit said temperature sensor 37, as a result of which this will be replaced by a thermometric sensor, not illustrated, which detects the temperature of the gases arriving for example at diverting joint 22.