WO2006008631A1

WO2006008631A1 - Sterilization equipment for hospital and other similar waste

Info

Publication number: WO2006008631A1
Application number: PCT/IB2005/002022
Authority: WO
Inventors: Sergio Zoni
Original assignee: Esambra Srl; Kotze, Gavin, Salomon
Priority date: 2004-07-15
Filing date: 2005-07-15
Publication date: 2006-01-26
Also published as: ITMI20041421A1

Abstract

The invention concerns an apparatus (1) comprising a container (2) with an opening and closing device (3) and a thermal plant (4) to heat the waste in the container (2), with an opening and closing device (3) for hermetically sealing the apparatus (1), a suction unit (5) for gases inside the container (2), which has a pressure below atmospheric pressure, and a purification unit (6) for gases sucked out of the steriliser with a high-voltage electrical charge, as well as a waste-crushing apparatus (26) with a mechanical stirring device (16) inside the container (2).

Description

STERILIZATION EQUIPMENT FOR HOSPITAL AND OTHER SIMILAR WASTE

Technical field of the invention

The aim of this invention is to create a sterilisation apparatus for hospital and similar refuse, for example for organic waste created by butcheries and food-processing plants.

Description of previous technology

It has been noted that there are various types of sterilisation devices for hospital and similar waste making use of pressurised saturated steam.

These sterilisation devices are mainly used in the sterilisation centres of hospitals and consist of autoclaves with a capacity of 15 to 5 000 litres. The thermal treatment consists of sterilisation in the autoclave using pressurised saturated steam and has the effect of eliminating micro-organisms as a result of the high temperature that develops in this humid environment.

The heating cycle begins with the injection of saturated steam until an operating temperature of between 120 and 135 ⁰C is achieved. The capacity of this type of device varies between 2 - 3 kg / hour for small machines and up to 600 kg / hour for the larger machines.

Another type of sterilisation device makes use of sterilisation by means of pressurised saturated steam as well as microwaves.

The sterilisation procedure takes place in a closed chamber into which saturated steam is injected at a pressure of 2 bar and which is then irradiated with electromagnetic waves at a frequency of 2,45 GHz. Inside the sterilisation device, a temperature of more than 132 ⁰C develops as a result of the pressure of the saturated steam, resulting in a heating effect of the microwaves which act on the water molecules.

To be able to guarantee the sterilisation of the waste, the system must generate an average temperature of more than 146° for three quarters of the sterilisation cycle and during the cycle the temperature may not drop to below 132 ⁰C.

The gaseous waste emitted by the plant is captured in the plant and subjected to an appropriate disinfection treatment, after which the gas is released into the atmosphere. Other sterilisation devices make use of sterilisation by means of a chemical / physical process. Such a device is used for the treatment of solid sanitary waste at atmospheric pressure and at a high temperature in a humid environment.

In a closed sterilisation cell, a powerful rotor disintegrates, mixes and heats the waste by means of vibration and friction. Once the temperature has reached 155 ⁰C, the mass is automatically sprayed with a water and sodium hypochloride for a brief period, while maintaining the required temperature for the prescribed period.

The final type of sterilisation device is one making use of sterilising radiation such as ionising radiation (γ-rays) or high-speed electrons (β-rays).

The machinery required for such a device is comprised of a labyrinth bunker with a transport system that channels the waste. The ionising radiation (γ-rays) used with radio-active sources has the effect of destroying the micro-organisms, but not instantly. The high-speed electrons (β-rays), on the other hand, have the effect of molecular degradation, along with chemical, physical and biological modifications.

The aforementioned techniques have some major drawbacks.

Sterilisation devices using saturated, pressurised steam have low limits within which sterilisation is effective, given the fact that the steam does not always succeed in penetrating into the waste container to effect complete sterilisation. The waste is in fact always collected inside special containers to avoid the disadvantage and necessity of opening the containers, which poses the risk of a harmful discharge of pathogenic and similar micro-organisms.

Sterilisation devices using saturated, pressurised steam plus microwaves can overcome this disadvantage, but the chamber in which the process takes place can only have a limited capacity.

In fact, sterilisation takes place inside a microwave chamber with a capacity of 70 - 150 litres.

Moreover, the heating period varies, depending on the composition of the material introduced, but may be half that of the microwaving period.

Another type of problem is posed by the aforementioned sterilisation devices making use of a chemical / physical process. In fact such devices do not attain high temperatures if the waste has a low viscosity, such as animal fat, which lubricates the system, thus resulting in a friction coefficient that is too low to bring about the desired increase in temperature and consequently the elimination of micro-organisms.

Moreover, such types of devices need a lot of power to function and are therefore less desirable from that point of view.

Another problem is represented by sterilisation devices using ionising radiation (γ-rays) and by high-speed electron devices (β-rays). Both these devices are a high-cost option, have a considerable size and have a high energy consumption. Moreover, it is necessary to protect and accurately monitor the system, which requires qualified staff, while the γ-ray devices, due to the continuous presence of a source of radio-activity, renders accessibility and installation on site difficult.

Such radiation devices may produce radio-active waste that is difficult to dispose of and are prone to producing undesirable by-products of fission, for example toxic bacteria with a resistance twenty times higher. Then there is also the technical problem that a sterilisation device for hospital and similar waste must ensure a complete and safe sterilisation of the waste, combined with a high speed of sterilisation.

Summary of the invention

In such a situation, the technical task that forms the basis for this invention is to devise a sterilisation device for hospital and similar waste that will to a large extent eliminate the aforementioned disadvantages.

The scope of this technical task includes the design of a sterilisation device for hospital and similar waste that will permit the proper and safe sterilisation of this waste. Another important aim of the invention is to construct a sterilisation device for hospital and similar waste that will guarantee a high capacity and a high sterilisation speed.

Another aim of the invention is to construct a sterilisation device for hospital and similar waste that can function without excessive energy consumption. A further, but not final aim of the invention is to construct a sterilisation device for hospital and similar waste that will not involve high costs or a large installation area.

The technical task and its specific aims are to obtain a sterilisation device for hospital and similar waste that provides a solution as expressed in the Claims detailed in the technical explanation that follows.

Explanation of the design

The description of the preferred execution for a sterilisation device for hospital and similar waste according to the invention is reinforced by the following diagrams of the units designed by way of a non-restrictive example:

Figure 1 shows a diagram of the complete device; and

Figure 2 shows a perspective drawing of the main element of the device.

Detailed technical explanation With reference to the aforementioned figure, the device according to the invention is generally indicated by the number 1. This device comprises a container 2 for the waste, opening and closing devices 3 for the container 2, which permit the loading and unloading of this container, as well as a thermal plant 4 for the waste, which acts directly on the waste at the surface of container 2.

Such a device 1 also comprises a suction unit 5 that sucks up the gases in the container 2 and which decreases the pressure inside this container. To allow the suction unit 5 to decrease the temperature in the container 2, it is necessary that the opening and closing devices 3 should seal hermetically, thus not permitting the passage of gases and liquids once they have been closed.

Such a container 2 should preferably be able to open and close completely hermetically to allow for assembly and periodic inspections. Moreover, there should be a purification unit 6 that purifies the gas sucked up by the suction unit 5. In detail, this should comprise a floor 2a on which the discharge from the container is deposited, with this floor preferably having a semi spherical structure.

Moreover, container 2 should contain a mechanical stirring device 16, which is driven by a motor 17. This mechanical stirring device 16 should preferably consist of a mixing element rotating around an axis 18 and having the same diameter as the semi spherical structure. This mixing element 16 shall have a circular or semi-circular shape and have a radius identical to the internal radius of the aforementioned semi spherical floor, thus permitting complete mixing.

The suction unit 5 should preferably keep the interior of container 2 at a specific pressure that is lower than atmospheric pressure, i.e. preferably at about 0.5 bar, by continuously sucking up the gases produced by evaporation of the liquid substances inside the waste.

To perform its task, the suction unit 5 should preferably consist of a suction pump 7 and a pipe 8 that is connected to the opening and closing devices 3 or, more conveniently, to container 2, where it should be connected to the top of the container in such a way that the risk of sucking up some of the refuse deposited on the floor 2a is avoided. Moreover, the pipe 8 should preferably have a valve 8a at its inlet that will permit the link between the container 2 and the pipe 8 to be closed.

The gases sucked up by the suction unit 5 are channelled towards the purification unit 6, more precisely via a conduit 9, which should preferably form part of the purification unit 6. While the gas passes through the conduit 9, it is sterilised by means of a special sterilisation device 10. This device should preferably sterilise by means of ionisation radiation created by means of a strong electrostatic field of about 48 000 Volt, which produces a strong electric discharge. Similar purification unit 6 is being marketed under the name "Electrostatic Precipitator".

The thermal plant 4 may be one of several types, with the preferred solution, in the application described for the device 1 , is one in which the heating takes place by means of a liquid 11 , which is heated in a special boiler 12, which operates by means of the combustion of gas or other fuels.

The liquid heated in this boiler 12 must be conveyed by means of a specific device 13, such as a pump, into a pipe system 14, which will transport it to a specific heating unit 15. The latter unit must be located in the proximity of the container 2 and must heat the container and thus, indirectly the waste it contains. Such a heating unit 15 should preferably consist of a double bottom on the floor 2a of the container 2, which should contain the liquid 11 , which will thus come into direct contact with the external wall of the container 2 and will thus dissipate a minimum amount of energy.

The liquid 11 will preferably be a liquid with a high boiling point, higher than that of water, which will allow for consistent heating of the waste. This liquid 11 should preferably be oil, because of its high boiling point and low cost, thus making it possible to increase the temperature to above 170 ⁰C and preferably to about 200 ⁰C.

Finally, the opening and closing devices 3 should be divided into loading devices 19 and unloading devices 20. The device 1 should preferably also contain a waste crushing device 26 at the top of container 2 and linked to the latter. The waste crushing device 26 should preferably make use of two cogwheels 27 to crush the waste.

The loading devices 19, which are located in the proximity of the container 2 and the waste-crushing device 26, ensure that the waste is inserted into the crushing device 26 and thus transferred into the container 2.

The unloading devices 20 should preferably be located at the bottom of the abovementioned container 2. Both the loading and unloading devices 19 and 20 are linked to the container 2 by means of special openings 21 and 22 respectively, with opening 22 of the unloading device 20 preferably being positioned in the zone of least gravitational potential of the floor 2a to allow for the complete unloading of the waste by gravity.

In this last case, the mechanical stirring device 16, which is configured according to the above description, has the advantage of preventing opening 22 from being blocked by compact or similar waste, due to the fact that, located in the proximity of opening 22, it ensures the continuous free flow of the latter.

The loading and unloading devices 19 and 20 are also equipped with hermetic seals 23 and 24 respectively. Moreover, the unloading device 20 comprises a suction device 25 that discharges the waste from this container by means of a special conduit 28, which is linked to a specific storage bin, container or similar device.

The function of the plant, the structure of which has been described above, is as follows:

The waste is inserted into crushing device 26, which uses a cogwheel 27 to crush the waste and to conduct it to container 2. At this point the hermetic seal 23 of the loading device is opened and the waste enters the container 2 and collects on its floor 2a. This crushed waste still contains a lot of humidity due to its content of organic and similar waste. Once the waste has been inserted into the container 2, the opening 3 is hermetically sealed, valve 8a opens and sets into motion the suction pump 7, which creates the desired low pressure inside the container 2. The gases sucked up by the suction pump 7 pass through the pipe 8 and the conduit 9, which forms part of the purification unit 6, and are sterilised by means of a sterilisation device 10, which acts by means of electric power.

This procedure is rendered necessary by the fact that the gases sucked up may contain hazardous micro-organisms that could be potentially harmful. Meanwhile, the thermal plant starts to operate: the boiler 12 heats the liquid 11 , i.e. oil, bringing it to a temperature of about 200⁰C. The pump 13 circulates the liquid 11 in the pipes 14, with the liquid thus reaching the heating unit 15 and circulating continuously, in such a way that there is always high-temperature liquid present in the heating unit 15. The liquid 11 in the heating unit 15 thus heats the container 2 and thus the waste it contains.

Due to the heating process, the humidity and liquid within the waste evaporates, creating gases that increase the pressure inside the container 2.

The suction unit 5, which keeps the pressure in the container constant, sucks up these gases and conducts them to the purification unit 6, where they are sterilised.

In the meantime, the waste is continuously mixed by means of a mechanical stirring device 16, which ensures that the waste is heated homogeneously.

After about 20 minutes of heating, all bacteria in the container have been eliminated and all the humidity and liquid in the waste has been eliminated by evaporation and suction, and sterilised in purification unit 6.

This phase should preferably be followed by a phase during which the waste is completely dehydrated by sucking up the gases by turning up the suction unit 5, thus creating a pressure close to a vacuum inside the container 2.

At this point the refuse has been sterilised and dried and may be discharged by means of the unloading device 20. For this purpose, the opening 22 is opened by means of the opening device 20 and valve 8a closes, thus preventing the suction unit 5 from operating.

After this operation, the pressure in the container 2 returns to atmospheric pressure, the suction device 25 is put into operation and unloads the waste into bags or similar containers via channel 28.

The sterilisation cycle has therefore been completed and the container 2 can again be loaded to commence the next sterilisation cycle.

The invention comprises a new procedure for the sterilisation of hospital and similar waste.

In essence, this takes place by accumulating the waste in .a container 2, heating the waste and discharging it, followed by a phase of depressurisation of the container 2 that coincides with the heating phase and the extraction of the gases that entered container 2 along with the waste and which have been formed by the evaporation of the liquid present in the waste in container 2.

In addition, suction takes place continuously during the entire heating time.

A phase of purification of the gases extracted from the container 2 may also be provided.

During the execution of the aforementioned procedure, it is advantageous to provide continuous mixing of the waste in the container during the heating phase. At the end of the aforementioned procedure, it is advantageous to provide a phase of dehydration of the waste by sucking off the gases with more intensity, thus causing the pressure in container 2 to drop close to a vacuum.

This procedure should preferably be preceded by a phase of crushing the waste that is to be put into the container. The phase of unloading the waste should preferably involve the re-pressurisation of the container 2 to atmospheric pressure, followed by sucking off the waste by means of a suction device 25. This invention has some major advantages. In fact, the device 1 guarantees perfect sterilisation of both the waste and the gas that is in contact with it. Heating takes place to a very high temperature of about 200 ⁰C, which guarantees high-efficiency sterilisation, in particular if the waste has been crushed in such a way that the heat can penetrate deeply.

The purification unit 6 also guarantees the sterilisation of the gases that have come into contact with the non-sterilised waste. Moreover, device 1 requires less energy than a plant that sterilises by means of a chemical / physical process or by irradiation.

Most of the energy is in fact required for heating the waste and may be obtained by means of combustion rather than from electricity, thus guaranteeing low operating costs. Another advantage is constituted by the fact that the device 1 guarantees high¬ speed and high-capacity sterilisation.

The container 2 can, in fact, hold about 300 kg, which can be sterilised in a 20-minute cycle, i.e. a sterilisation capacity of more than 600 kg / hour, which is superior to that of a larger autoclave.

Moreover, after crushing, the waste is homogeneous and the time required for sterilisation will not be influenced by the nature of the waste, which is the case with other sterilisation devices that sterilise by means of saturated, pressurised water vapour and microwaves.

Another major advantage is the fact that the waste is discharged in the form of "pellets" or blocks, dried and of a similar size. The pellets or blocks are light and easily transported, which ultimately reduces the cost of transport.

The invention may be modified and varied within the scope of the concept of the invention. For example, the device 10 may be comprised of an absolute filter instead of a filter that permits the passage of air but not of contaminating particles or bacteria and viruses, which must be periodically disinfected or exchanged. Other modifications of the thermal plant 4 are possible, for example by using electricity or by having the heat penetrate directly into the container 2, in direct contact with the waste, as well as other modifications that may be possible.

All these details may be replaced with equivalent elements and materials of any form or dimensions.

Claims

CLAIMS:

1) A sterilisation device for hospital and similar waste, comprising a container for this waste, devices for opening and closing this container for the purposes of replenishing its contents and unloading the waste: characterised by the fact that these opening and closing devices have hermetic seals as well as by the fact that they comprise a suction device for gases that creates a pressure that is lower than atmospheric pressure inside this container and a purification unit for the gases thus sucked off.

2) A device in accordance with Claim 1 , in which the suction unit comprises a conduit leading towards this container and this purification unit, as well as a suction pump that is active in combination with this conduit.

3) A device in accordance with Claim 1 , in which this gas purification unit comprises a sterilisation device to sterilise the gases by means of high-voltage electrical discharge.

4) A device in accordance with Claim 1 , comprising a crushing device for the refuse located at the top of this container and linked to it.

5) A device in accordance with Claim 1 , in which the thermal plant comprises: a liquid, a boiler to heat this liquid, a heating unit for the container, which is linked to the container and which contains the liquid, and a circulation device to transport the liquid towards the boiler and the heating unit.

6) A device in accordance with Claim 5 in which the fluid is oil.

7) A device in accordance with Claim 5, in which the fluid is heated to a temperature in excess of 170 ⁰C.

8) A device in accordance with Claim 5, in which the container comprises a floor with a double bottom containing the liquid and constituting the heating unit. 9) A device in accordance with Claim 1 , in which the interior of the container is equipped with a mechanical stirring device for the refuse.

10) A device in accordance with Claim 9, in which this container comprises a floor with a semi spherical structure in which the mechanical stirring device consists of a mixing device rotating around an axis having the same diameter as this semi spherical structure.

11) A device in accordance with Claim 10, in which this mixing element essentially has a semi-circular shape with a radius that is essentially identical to the aforementioned semi spherical floor.

12) A device in accordance with Claim 1 , in which the opening and closing devices used for unloading purposes are located in the floor zone with the least gravitational potential.

13) A device in accordance with Claim 1 , comprising a suction device used to unload waste from this container.

14) A sterilisation procedure for hospital and similar waste, comprising a phase of accumulating the waste in a container, a phase of heating the waste and a phase of unloading the waste, characterised by the fact that it comprises: a phase of depressurisation of this container that is simultaneous with the heating phase and the extraction of gases from this container, as well as a purification phase for the extracted gases.

15) A device in accordance with Claim 14, in which the depressurisation phase takes place continuously during the heating phase, to remove the gases that are produced by the evaporation of the liquid substances present in the waste.

16) A device in accordance with Claim 14, in which a phase of crushing the waste precedes the waste-accumulation phase. 17) A procedure in accordance with Claim 14, in which a device for continuously mixing the waste in this container during the heating phase is provided.

18) A procedure in accordance with Claim 18, in which the unloading phase comprises the re-pressurisation of the container to atmospheric pressure and the subsequent suctioning off of the waste.

19) A procedure in accordance with Claim 14, in which a dehydration phase for the sterilised waste is provided by means of depressurisation of the container with a pressure lower than 0.1 bar.

20) A device and process, characterised by the fact that they may comprise any combination of the aforementioned technical solutions.