Patent Publication Number: US-2017361329-A1

Title: Infectious waste disposal

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority benefit of U.S. Provisional Application Ser. No. 62/102,258 filed 12 Jan. 2015; the contents of which are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention in general relates to a system for treating infectious waste; and in particular to a medical waste handling and shredding sub-system with a built-in oxidizer to eliminate potential airborne infectious waste prior to transforming the medical waste into useful co-products, including hydrocarbon based gases, hydrocarbon-based liquids, precious metals, rare earths, and carbonized material in a system having as its transformative element an anerobic, negative pressure, or carbonization system. 
     BACKGROUND OF THE INVENTION 
     Infectious medical waste is generated in the research, diagnosis, treatment, or immunization of human beings or animals and has been, or is likely to have been contaminated by organisms capable of causing disease. Infectious medical waste includes items such as: cultures and stocks of microorganisms and biologicals; blood and blood products; pathological wastes; radiological contrast agents, syringe needles; animal carcasses, body parts, bedding and related wastes; isolation wastes; any residue resulting from a spill cleanup; and any waste mixed with or contaminated by infectious medical waste. Facilities which generate infectious medical waste include: hospitals, doctors offices, dentists, clinics, laboratories, research facilities, veterinarians, ambulance squads, and emergency medical service providers, etc. Infectious medical waste is even generated in homes by home health care providers and individuals, such as diabetics, who receive injections at home. 
     Before infectious medical waste can be disposed of the waste must be sterilized. Traditional sterilization methods include: incineration; steam treatment or autoclaving; and liquid waste may be disposed of in approved sanitary sewers. More recent methods that have been developed include microwave irradiation and use of various chemical washes. 
     Transforming waste from a liability to an asset is a high global priority. Currently employed technologies that rely on incineration to dispose of carbonaceous waste with useable quantities of heat being generated while requiring scrubbers and other pollution controls to limit gaseous and particulate pollutants from entering the environment. Incomplete combustion associated with conventional incinerators and the complexities of operation in compliance with regulatory requirements often mean that waste which would otherwise have value through processing is instead sent to a landfill or incinerated off-site at considerable expense. As medical waste often contains appreciable quantities of synthetic polymers including polyvinyl chloride (PVC), incineration of medical waste is often accompanied by release of chlorine, ClO x , SO x , and NO x  air pollutants that must be scrubbed from the emitted gases. Alternatives to incineration have met with limited success owing to complexity of design and operation outweighing the value of the byproducts from waste streams. Thus, the existing methods of disposing of infectious waste do not create energy or usable byproducts to justify replacement of traditional disposal methods 
     While there have been many advances in the treatment and disposal of infectious waste, there still exists a need for systems and methods for the safe treatment of infectious waste that maximize the economic return from the treated waste while also protecting the environment. 
     SUMMARY OF THE INVENTION 
     A system for treating infectious waste includes a sealed enclosure that houses a shredder that is fed by a belt conveyor that supplies the infectious waste running from the exterior of the sealed enclosure to the shredder. The shredder further includes a hopper to receive waste and a process airlock where shredded wasted material accumulates and is transferred to the feed conveyor. A rubberized exterior flap permits containerized and bagged waste to enter the sealed enclosure via the belt conveyor. The sealed enclosure may be maintained at a negative pressure. A thermal oxidizer in fluid communication with the sealed enclosure and a hood acts to destroy any airborne infectious matter from the sealed enclosure and any airborne infectious waste collected by the hood. The thermal oxidizer may be run on a mixture of natural gas and reaction-produced carbonization process gases re-circulated to transform heat through the use of either conventional steam boilers or through Organic Rankin Cycle strategies to operate electrical turbine generators, or in the alternative, to conventional or novel reciprocating engine driven generators. A feed conveyor transfers shredded material from the shredder to a carbonizer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a block diagram of an infectious waste treatment system according to an embodiment of the invention; 
         FIG. 2  is a side section view depicting an encapsulated shredding and infectious matter escape prevention sub-system according to an embodiment of the invention; 
         FIG. 3  is an oxidizer adapted for use with embodiments of the invention; and 
         FIG. 4  is a block diagram of a top loaded infectious waste treatment system according to an embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     The present invention has utility as a system for treating infectious waste. Through inclusion of a medical waste handling and shredding sub-system feeding partially processed waste to an oxidizer to eliminate potential airborne infectious waste prior to transforming the medical waste into useful co-products the aforementioned limitations of the prior art have been overcome. According to the present invention, medical waste is transformed into value added products including hydrocarbon based gases, hydrocarbon-based liquids, carbonized material, and recovered precious metals and rare earth materials in a system having as its transformative element an anerobic, negative pressure, or carbonization system. With medical waste as a feedstock for the production of valuable products, the present invention provides an economically viable and environmentally more responsible alternative to traditional methods of medical waste treatment. 
     Referring now to the figures, embodiments of an inventive infectious waste system are described.  FIG. 1  is a block diagram of an infectious waste treatment system  100  according to an embodiment of the invention. An encapsulated shredding and infectious matter escape prevention sub-system  104  encloses a shredder in a negative pressure sealed environment that acts to contain residue and contaminants from escaping into the environment during the shredding operation. The infectious waste is loaded into the sub-system  104  via belt conveyor  102 . The belt conveyor  102  introduces the infectious or contaminated waste in bags or containers into the subsystem  104 . An oxidizer  130  destroys any airborne infectious matter that exits through hood  128  at the top of the sub-system  104 . 
     As used herein an oxidizer is defined to also include a thermal oxidizer and catalytic oxidizer; such systems are commercially available and in widespread usage. 
     Feed conveyor  126  transfers the shredded material from the sub-system  104  to the carbonizer  142 . It is appreciated that feed conveyor  126  also includes augers, shuttle bins, and other conventional devices to transit shredded material. 
       FIG. 2  is a side section view depicting the encapsulated shredding and infectious matter escape prevention sub-system  104 . The dotted lines represent the containment walls  106  that enclose the shredder  116 . The enclosure of the sub-system  104  is maintained at a negative pressure to draw in air (as opposed to expelling air) as represented by the arrows into the vents  114 , as well as into the exterior flap  108  that permits containerized waste to enter the sub-system  104  via the belt conveyor  102 , and other openings such as for the feed conveyor  126  and service door  112 . The exterior flap  108  is readily formed of rubberized materials, polymeric sheeting, as well as metals. Service door  112  is provided in some inventive embodiments to allow service workers to enter the enclosure. It is appreciated that a service person may be required to wear protective clothing and a filter mask. In a specific embodiment the service door  112  may be a double door airlock, where only one door is open at a time to minimize the escape of contaminants into the environment. In still other embodiments, the air handling system modifies operation during opening of the service door  112  to maintain a negative pressure during opening to inhibit airborne escape of potential pathogens. Hopper flap  110  acts to allow containerized waste to enter the hopper  118  of the shredder  116 , while also acting as a seal around the belt conveyor  102 . The hopper flap  110  is readily formed of rubberized materials, polymeric sheeting, as well as metals. At the bottom of the hopper  118 , an auger  122  that is driven by one or more motors  120  shreds the waste. In an embodiment the motors  120  may be variable frequency drive (VFD) motors. The shredded material is accumulated in a process airlock  125  that supplies material to a feed conveyor  126 . Levels and presence of material within the hopper  118  and the process airlock  125  are controlled via sensors  124 . In a specific embodiment the sensors  124  are through beam sensors (TBS). Feed conveyor  126  is sealed to the process airlock  125 , and transports the shredded material from the sub-system  104  to the carbonizer  142 . Hood  128  collects airborne contaminants for introduction into the oxidizer (TO)  130 . 
       FIG. 3  is a block diagram of an oxidizer  130  adapted for use with embodiments of the invention that acts as a fume incinerator for the containment room of sub-system  104 . Large particle screener  132  filters out particles from the exhaust stream of airborne contaminants. A filter differential sensor may be employed to detect when a filter is clogged and requires replacement. A blower  134  draws in the exhaust stream and blows the exhaust stream into the combustion tube  138 . A gas supply  136  supplies fuel for burners in the combustion tube  138 . In specific embodiments the oxidizer  130  is run on a mixture of natural gas and reaction-produced carbonization process gases re-circulated to transform the heat through the use of either conventional steam boilers or to Organic Rankin Cycle strategies to operate electrical turbine generators, or in the alternative, to reciprocating engine driven generators, and thereby generate the heat needed to produce power while also operating the carbonization process in the carbonizer  142 . This heat capture produces more waste heat than is used to heat water and generate steam for turbines or steam reciprocating engines. This heat in some inventive embodiments is used to preheat feedstock or for other larger process purposes. The pre-processing heating system preheats feedstock material prior to entering the reactor tube to both reduce moisture and improve overall system yield. Roof exhaust stack  140  vents cleaned exhaust to the environment. 
     An apparatus for anaerobic thermal transformation processing as carbonizer  142  to convert waste into bio-gas; bio-oil; carbonized materials; non-organic ash is detailed in U.S. Pat. No. 8,801,904; the contents of which are incorporated herein by reference. 
       FIG. 4  illustrates a block diagram of a shredder feed system  200  for treatment and recovery of usable products from waste feedstock illustratively including medical and infectious waste, where the carbonizer  142  is that described with respect to the aforementioned drawings. The feed system  200  utilizes conveyers  204  to feed and transport containers  202  of waste into and through the pre-shred air-lock tunnel  210  and into a shred feed hopper  216 . The pre-shred air-lock tunnel  210  has an airtight open and close inlet valve (door)  206  and an outlet valve (door)  212  to the shred feed hopper  216 . The pre-shred air-lock tunnel  210  may have nitrogen inputted at valve  208  to provide an inert atmosphere in the air-lock tunnel  210 . In a specific embodiment the waste may be treated with a wet scrubber  214 . Medical waste that contains appreciable quantities of synthetic polymers including polyvinyl chloride (PVC), when incinerated is often accompanied by release of chlorine, ClO x , SO x , and NO x  air pollutants that are preferably scrubbed from the emitted gases to limit air pollution. The wet scrubber  214  facilitates a reaction with chloride gas to yield a resultant hydrochloric acid (HCl) product. In order to withstand corrosion caused by HCl, and other byproducts produced in operation of an inventive system, system components are readily formed of solid-solution-strengthened, high-temperature corrosion-resistant alloys that are generally rich in nickel and chromium/cobalt as major constituents with illustratively include 37Ni-29Co-28Cr-2Fe-2.75Si-0.5Mn-0.5Ti-0.05C-1W-1Mo-1Cb, S13Cr, 316L (S31603), 22 Cr duplex, 25 Cr duplex, 28 (N08028), 825 (N08825), 2550 (N06975), 625 (N06625) C-276 (N10276), where parentheticals correspond to the UNS numbers for a particular alloy. These alloys are resistant to the effects of HCl may be used in the construction of one or more of the wet scrubber  214 , shred feed hopper  216 , shredder  218 , and other components of the system  200  that may contact the corrosive HCl and chlorine, such as the sealed enclosure, the shredder, the belt conveyor, the oxidizer, or the feed conveyor. 
     Continuing with  FIG. 4 , the shredder  218  may be a two or four shaft shredder that is mounted so that all shredded waste material and liquids exit the bottom of the shredder  218  into a collection hopper  220  that meters and distributes the waste with a post-shred air-lock  222  directly into a carbonizer  142 . It is appreciated, precious metals and rare-earth materials for example associated with medical imaging may be obtained by burning off the carbon product to obtain carbon dioxide and the resultant metal materials. For example, contrast agents used for radiological procedures are a source of precious metals and rare earths. Gasses from the air-lock tunnel are managed with an oxygen sensor  226  and escaping particulate is filtered with a high-efficiency particulate air (HEPA) filter  228 . and is the expelled through a blower  230  to an oxidizer illustratively including a thermal oxidizer. 
     As a person skilled in the art will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of this invention defined in the following claims.