Electric heating – Microwave heating – With diverse device
Reexamination Certificate
1999-08-25
2001-07-17
Leung, Philip H. (Department: 3742)
Electric heating
Microwave heating
With diverse device
C219S680000, C219S759000, C422S021000
Reexamination Certificate
active
06262405
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to use of microwave energy to treat medical waste materials. Medical waste comprises a diverse mixture of materials which may include metal, glass, plastic, paper, various other organic materials. Further, many of these materials have been exposed to bacterial or viral pathogens.
Medical waste disposal presents multiple concerns. Foremost, medical waste represents a biological hazard. Accordingly, typically, medical waste must be sterilized through heat or chemical methods prior to its subsequent handling and disposal. Secondly, many components of the medical waste stream remain hazardous following sterilization. For instance, “sharps”, such as syringe needles, scalpel blades, razors, glass pipettes, lances, and similar items remain a physical risk to waste handlers and create additional problems in waste packaging. Sharp objects within the waste can readily puncture bags or other containers used to segregate the waste.
Further, the sheer volume of medical waste contributes to the high cost of disposal. In recent years, there has been an increased reliance upon disposable, pre-sterilized instrumentation and supplies. As a result, there is a great deal of waste generated including plastic vials and containers, disposable surgical gowns and drapes, used dressings and gauze material, and similar high bulk waste materials. Such materials add greatly to the waste stream and the resulting disposal cost of medical waste.
Yet an additional problem relates to the large number of waste generating sites. Each doctor's office, clinic, veterinary facility, hospital, and other health care facility where patients are seen and treated generate medical waste. Heretofore, it has not been possible to effectively treat the waste at each location where generated. As a result, the waste has to be properly packaged, sterilized, and shipped to a subsequent disposal facility.
Finally, the traditional methods of handling medical waste have done very little to alter the form, structure, and physical identity of the waste. Recognizable medical waste is an obstacle to introducing medical waste into the normal sanitation waste stream. As a result, there is a need to alter the physical state of the medical waste so as to produce an unrecognizable, yet harmless waste product. Accordingly, there remains much room for improvement and variation within the art.
2. Description of Related Art
It is known in the art to use microwaves to sterilize and to further treat medical waste. U.S. Pat. No. 5,166,488 to Peppard, incorporated herein by reference, teaches an apparatus which uses microwaves to melt hypodermic syringes. U.S. Pat. No. 4,940,865 provides an apparatus for melting materials using microwaves. However, the efficiency of these microwave treatments are questionable in that these techniques result in the generation of gaseous and airborne particulates which require costly filtering and containment systems. As such, these systems are not suitable for small volume waste generators such as an individual medical office or clinic. Accordingly, there remains room for improvement within the art of microwave processing of waste.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an apparatus and process which uses microwave radiation to physically transform a diverse waste material into an unrecognizable end product.
It is a further object of this invention to provide an apparatus and a process to treat off-gas emissions from the microwave destruction of medical waste such that the treated emissions may be discharged into the atmosphere.
It is a further and more particular object of this invention to provide a two-stage microwave treatment apparatus and process wherein a first microwave chamber is used to treat a solid or liquid waste material and a second microwave waste chamber is used to treat the generated off-gases from the first chamber.
It is a further and more particular object of this invention to provide a medical waste disposal apparatus and process which uses hybrid microwave heating and improves the efficiency of the process for treatment of a wide range of materials.
It is still a further and more particular object of this invention to provide an apparatus and process for simultaneously treating a mixture of paper, plastic, liquids, glass, and metal containing waste, wherein the volume and physical shape of the waste is transformed into an unrecognizable solid end product (example, ash) and the resulting off-gas emissions are further treated with additional microwave radiation, transforming the off-gas emissions into a gaseous end product which may be safely released into the atmosphere.
It is also a feature of the proposed technology to allow: a) disinfection; b) sterilization; and c) destruction of medical wastes, dependent on customer needs.
These and other objects of the invention are accomplished by an apparatus and process that provides for a tandem hybrid microwave waste disposal system comprising:
a first combustion chamber for housing medical waste and in communication with a source of microwaves;
a second combustion chamber in communication with a second source of microwaves, the second combustion chamber having an input region in communication with a first end of a conduit, a second end of the conduit in communication with the first combustion chamber, the second combustion chamber further defining a susceptor defining a gas permeable matrix;
an exhaust port in communication with an output region of the second combustion chamber, wherein evolved combustion off-gases from the first combustion chamber pass through the conduit into an input region of the second combustion chamber whereby the susceptor matrix and other possible constituents, such as ion-exchange type materials, are maintained at an effective temperature for treating the off-gases, the treated off-gases exiting through an exhaust port.
Such an apparatus enables the process of treating medical waste comprising:
providing a supply of medical waste material within a combustion chamber, passing a fluid stream through the combustion chamber;
exposing the medical waste material to a combination of microwave energy and radiant energy, the radiant energy supplied by a susceptor in proximity to the medical waste material;
directing off-gases from the first combustion chamber to a second combustion chamber;
radiating the off-gases in the combustion chamber with microwave energy;
retaining the off-gases within the second combustion chamber until an effective amount of off-gases are destroyed, thereby providing treated off-gases; and
venting the treated off-gases.
The invention is an improvement over prior methods of using microwave energy to treat medical waste. The present invention provides a sterilization process, a physical transformation process, and a subsequent off-gas treatment process such that the medical waste, following treatment, has been rendered to a releasable off-gas and a charred mixture of powder, and/or melted glass, and melted metal. The off-gases associated with the microwave treatment are combusted to innocuous end products in association with high temperature environments produced by microwave energy in combination with selected susceptor material. The resulting treated medical waste is a decontaminated and sterilized material which may be disposed of in a normal sanitation waste stream.
REFERENCES:
patent: 4940865 (1990-07-01), Johnson et al.
patent: 5035858 (1991-07-01), Held et al.
patent: 5166488 (1992-11-01), Peppard
patent: 5213758 (1993-05-01), Kawashima et al.
patent: 5270000 (1993-12-01), Goldner et al.
patent: 5277868 (1994-01-01), Langford
patent: 5322603 (1994-06-01), Kameda et al.
patent: 5348235 (1994-09-01), Pappas
patent: 5429799 (1995-07-01), Sheih et al.
patent: 5441622 (1995-08-01), Langford
patent: 5540886 (1996-07-01), Warmbier et al.
patent: 5968400 (1999-10-01), Wicks et al.
Clark David E.
Schulz Rebecca L.
Wicks George G.
Dority & Manning PA
Leung Philip H.
Westinghouse Savannah River Company
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