RU2295978C2 - Method for carrying out thermal sterilization of infected waste materials - Google Patents

Abstract

FIELD: medical engineering.

SUBSTANCE: method involves crushing and heating infected waste material by means of heat source mounted inside of the sealed thermally insulated case in inert gas medium at least to a temperature of 250°C. Vapor and gases thus formed are discharged from the sealed case heated at least to 800°C and cooled next to it. Received sterilized material is cooled with water during its unloading when moving along the line from tightly thermally insulated case.

EFFECT: enhanced effectiveness of sterilization without use of chemical reagents being used.

1 dwg

Description

The invention relates to a method for the thermal effect on waste and can be used, in particular, for thermal sterilization of infected medical waste: dressings, syringes, bandages, plastic and glass bottles, razors, blades, etc.

Sterilization - the complete release of various substances, objects from living microorganisms.

Known chemical, physical and gas sterilization methods.

Chemical sterilization methods include the processing of objects, including vapors of antiseptic substances, for example formaldehyde, ethylene oxide, hydrogen peroxide (US Pat. No. 2000810, IPC A 61 L 2/04, publ. 15.10.93).

The main disadvantage of chemical processing methods is the contamination of sterilized objects with processed toxic substances, the removal of which in many cases is difficult.

Among physical methods, methods of exposure to high temperatures are widespread: hot air, steam under pressure (AS USSR No. 1025431, IPC A 61 L 2/06, publ. 1983), radiation sterilization, treatment with UV rays, microwave radiation (US Pat. . RU, No. 2001630, IPC A 61 L 2/12, publ. 30.10.93; 2221592, IPC A 61 L 2/12, publ. 2004.01.20).

A known method of thermal sterilization of waste, in particular medical waste, including the operation of grinding and / or powdering waste under the action of a cutting force, at a temperature necessary for sterilization (WO, 92/127738, A 61 L 2/06, 1992). The method provides an additional external supply of heat to the ground mass.

The known utilization unit of the Sterimed series is intended for grinding and disinfecting during mixing with a 0.5% solution of the Stericide disinfectant of medical waste generated as a result of the use of materials and disposable products in medical institutions (advertising brochure Medical waste disposers , M.S.M., Euromedic Ecology).

Company NEWSTER s.r.l. (San Giovanni, Italy) has developed a destructor sterilizer specifically for hospitals, small and medium-sized laboratories. The technology is based on the use of a bactericide and includes the process of destruction of the material by grinding it in an airtight chamber mill, the use of high temperature (150 ° -160 ° C) obtained from shock and friction of the material at a high speed of its rotation, sterilization by the method of breaking protein molecules at the moment spraying water and a bactericide into the chamber (Promotional brochure of the sterilization installation "Newster-10" of the company "NESTER srl").

Existing recycling technologies have fundamental shortcomings, the main of which is that carrying out the process at relatively low temperatures does not allow to obtain completely sterilized medical waste without additional treatment with chemical preparations.

In the patent RU №2128522, IPC A 61111/00, publ. 1999.04.10, a method for sterilization or disinfection of waste, in particular infected medical waste, in a sealed chamber, including the operation of grinding and / or powdering of waste under the action of a cutting force, which is ensured only by friction, to achieve a temperature in the waste mass of 150-180 ° C in the absence of direct or indirect additional heat. The sterilization or disinfection temperature is controlled by means of a metered supply of liquid water to the crushed waste inside the chamber body. At the end of this stage, the temperature is reduced due to the metered supply of water into the chamber while reducing the effect of cutting force. After the heating step, the sterilized waste is cooled to 50-80 ° C by blowing air into the jacket of the chamber and unloading the sterilized material. The precipitates formed during processing are adsorbed in a water adsorber.

In one embodiment of the invention, the feed water contains sodium hypochlorite, in another, a concentrated aqueous solution of sodium hypochlorite is fed into the waste mass inside the housing during the sterilization cycle.

The method described in paragraph 1 of this patent does not allow the effective sterilization of infected waste, because the temperature achieved and maintained only by friction during grinding or powdering of waste (150-160 ° C) is insufficient to destroy live spore-forming or non-spore-forming microorganisms. In order for the treated waste to be classified as non-hazardous waste of medical facilities (class A according to the classification of the Russian Federation of medical waste, corresponding to the hazard class according to the State Classifier no lower than 4th) and buried at ordinary landfills, it is required to submit it to the mass of waste inside the building sterilization cycle time concentrated aqueous sodium hypochlorite solution, i.e. use chemical reagent treatment. In addition, the amount of heat required to achieve and maintain the specified sterilization temperature in the waste mass only due to friction is generated for a long time, more than 30 minutes.

The objective of the present invention is to create an effective method of sterilization of infected waste (due to high temperature), which allows to obtain sterilized material without additional chemical treatment, which can be buried in ordinary landfills for the disposal of municipal solid waste (not lower than 4th hazard class or class A ), and at the same time a safe method of sterilization (by eliminating spontaneous combustion of waste). The task also consists in increasing the environmental and economic parameters of the processing method without chemical reagents and, in addition, in reducing the processing time of infected waste.

A method for thermal sterilization of infected waste, in particular infected medical waste, in a sealed thermally insulated body, including the operation of grinding and heating the sterilized waste to a temperature of at least 250 ° C due to the grinding process and additional heat from a source located inside the housing, is proposed, and also cooling the sterilized material, while grinding and heating operations are carried out in an atmosphere that does not support oxidation, cooling is carried out by supplying water they are sterilized outside the sealed thermally insulated case, and the exhaust gases, vapors and air are passed for neutralization through a device having a temperature of at least 800 ° C, followed by cooling.

According to the invention, an atmosphere that does not support oxidation is created by aspirating the air and the resulting gas mixture by a vacuum pump.

It is possible that an inert gas, such as nitrogen, is used as an atmosphere that does not support oxidation by displacing air from the casing.

It is possible that an atmosphere that does not support oxidation is created by displacing air with water vapor generated by heating wet waste.

In addition, a variant is possible when the heating of infected waste is carried out due to electricity.

It is possible to supply water by spraying or spraying it onto sterilized waste to cool it outside the casing.

Evacuation is carried out in the initial stage of heating sterilized waste.

The differences of the proposed method are that the sterilization temperature of infected waste (250 ° C and above) is achieved and maintained in the waste mass by the heat of friction in the presence of an additional supply of heat, the source of which is located in the area of the sealed enclosure, sterilization is carried out under conditions that do not support oxidation, and the sterilized material is cooled outside the sealed enclosure.

The method is implemented by the device (Fig. 1), which contains a sealed thermally insulated casing containing infected waste, a rotor inside the casing, equipped with elements capable of grinding infected waste, a heating source located inside the casing, for example, heating elements, a vacuum pump or a cylinder with a compressed inert gas located outside the device, nozzles for spraying or spraying water in a liquid state.

The temperature of the waste mass inside the enclosure, at least 250 ° C, created due to the heat of friction and direct additional heat supply, allows you to completely destroy pathogenic and living spore-forming and non-spore-forming microorganisms and, most importantly, sterilize the waste without the use of chemicals. The resulting crushed sterilized material can be assigned to the 4th hazard class or class A and buried in ordinary landfills for the disposal of municipal solid waste. After reaching the sterilization temperature, this temperature is maintained for 10 minutes.

To eliminate spontaneous combustion of waste at high temperature, the grinding and heating of the waste is carried out in vacuum by suctioning air and gas mixture with a vacuum pump or in an inert gas atmosphere, in particular nitrogen, or in an atmosphere of moist air.

Spraying or spraying water in a liquid state onto heated waste outside the sealed enclosure can significantly reduce heat loss during a repeated cycle and processing time, as after the completion of the next cycle, which ends with the unloading of the sterilized material and the device is stopped, it is not necessary to re-heat the cooled case of the device.

At the end of the cycle, the waste is ground and cooled to a temperature of 50-60 ° C.

The method of thermal sterilization of waste is implemented as follows.

Infected medical waste 1 is loaded into a steel sealed thermally insulated casing 2 of the crusher (granulator). The device is closed by a lid 3 manually or automatically. A rotor 4 rotates inside the housing 2 at a high speed, for example 1500 rpm. A vacuum is created by the vacuum pump 5 or the device housing is filled with an inert gas from a cylinder 6 with compressed gas, for example nitrogen, or moist air, or carbon dioxide (carbon dioxide).

The sterilization temperature, equal to at least 250 ° C, is achieved not only due to the heat realized from friction, but also from an internal source located inside the housing, for example, heating elements 7. Inside the storage tank 8 there is a nozzle 9 (or nozzle) for spraying or spraying water. Nozzles can be placed outside the storage tank, for example, on the route of the sterilized material from the device body - crusher (granulator) to the storage tank. Air, vapors and exhaust gases are passed for neutralization through the calcination device 10 with a temperature of at least 800 ° C, and they are cooled in a refrigerator with a water lock 11.

Examples of the method.

Example 1

10 kg of infected medical waste 1 with bacteria of the genus Staphylococcus, bacteria of the Escherichia coli group and non-fermenting gram-negative bacteria are loaded into a metal sealed thermally insulated casing 2 of the device — crushers (granulators) with a diameter of, for example, 600 mm and a height of 800 mm, equipped with a rotor 4 with knives. Then the body of the device 2 is closed with a cover 3. A vacuum is created by a vacuum pump 5. The rotor 4 and internal heating are turned on 7. A temperature of 250 ° C is reached for 10 minutes, which is maintained for 10 minutes, after which the gate of the discharge hatch 12 opens. Hot sterilized crushed the material is automatically unloaded from the sealed enclosure 2. The stage of cooling the sterilized material begins by spraying water from the nozzle 9 into the storage tank 8 onto the neutralized (sterilized) material 13. Amount of water - okol about 1.5 liters. The sterilization efficiency of the method in accordance with the sanitary-epidemiological conclusion is 100% (vegetative and spore forms of bacteria, viruses). Due to the fact that the sterilized material is cooled by water, it does not contain viruses, bacteria and fungi (pathogenic and living spore-forming and non-spore-forming microorganisms). Air, vapors and the resulting exhaust gases are neutralized in the calcination chamber 10, cooled using a refrigerator with a water lock 11 and removed into the atmosphere.

Example 2. With the modified parameters of example 1. The sterilization temperature of 350 ° C. The temperature of the calcination chamber is 900 ° C. The sterilization efficiency is 100%.

Example 3. With the modified conditions of example 1. The crusher (granulator) 2 casing is filled with an inert gas - nitrogen from a cylinder 6. The sterilization efficiency is 100%.

Example 4. With the modified conditions of example 1. The case of the crusher (granulator) 2 is filled with argon. The sterilization efficiency is 100%.

Example 5. With the modified conditions of example 1. The air of the casing 2 of the crusher (granulator) is filled with water vapor generated by the heating of wet waste. The effectiveness of the method is 100%.

Example 6. With the modified conditions of example 1. The housing of the device 2 crusher (granulator) is filled with carbon dioxide. The effectiveness of the method is 100%.

The proposed thermal sterilization method provides a high level of sterilization of infected wastes, namely it ensures the transfer of extremely hazardous wastes (class B) and hazardous (risky) wastes (class B) into non-hazardous wastes of medical facilities (class A) without the use of chemicals. A device that implements the proposed method does not require special preparation of the premises. The method is safe, allows you to process a wide range of objects and materials, environmentally friendly.

Claims (1)

The method of thermal sterilization of infected waste, in particular infected medical waste, in which the sealed and thermally insulated casing is ground and the infected waste is crushed and heated to a temperature of at least 250 ° C, while the vapors and gases formed are removed from the sealed casing by heating them at least to a temperature of 800 ° C followed by cooling, and the resulting sterilized material is cooled with water, characterized in that the heating of the infected waste is carried out using and heat source located inside the enclosure in an inert gas environment, and the sterilized material is cooled during unloading along the route from the sealed thermally insulated enclosure.