The use of a safe, complete, and environmentally benign process is useful in the disposal of medical waste materials. Medical waste materials may be in liquid or solid form. Exemplary types of medical waste materials include human tissues and organs removed during a medical treatment process. Other exemplary medical waste materials include biological organisms, either living or dead, which result from activities in a medical laboratory.
The conventional method for disposing of medical waste materials uses incineration technology. In particular, the medical waste materials are placed within a container such as bin, and the container is placed within a natural gas or electric incinerator. The heat of the incinerator burns the medical waste material. However, incineration of medical waste materials can result in harmful gases, offensive odors, and other dangerous conditions. For example, the incinerated waste material may result in harmful, partially combusted gas species. Additionally, the medical waste material tends to coke on the incinerator. These and other issues make incineration of medical waste materials difficult.
A method and apparatus for incinerating contaminated biological and medical waste material is described. The incineration is achieved by complete oxidation of the biological or medical waste material within a non-thermal plasma generator. The oxidizer may be air, oxygen, steam, or a combination of at least two of air, oxygen, and steam. In one embodiment, the oxidizer is a chemical compound containing oxygen. Using a stoichiometrically excessive amount of oxygen facilitates full oxidation of the waste material. The incineration product resulting from the oxidation of the waste material may be, for example, a gas mixture or a solid.
Embodiments of a method are described. In one embodiment, the method includes introducing a volume of the medical waste material into a plasma zone of a non-thermal plasma generator. The method also includes introducing a volume of oxidizer into the plasma zone of the non-thermal plasma generator. The method also includes generating an electrical discharge between electrodes within the plasma zone of the non-thermal plasma generator to incinerate the medical waste material. Other embodiments of the method are also described.
Embodiments of a system are also described. In one embodiment, the system is a system to incinerate a medical waste material. An embodiment of the system includes a non-thermal plasma generator, an oxidizer channel, a medical waste channel, and a heater. The oxidizer channel is coupled to the non-thermal plasma generator. The oxidizer channel is configured to direct an oxidizer into a plasma zone of the non-thermal plasma generator. The medical waste channel is also coupled to the non-thermal plasma generator. The medical waste channel is configured to direct the medical waste material into the plasma zone of the non-thermal plasma generator. The heater is coupled to the medical waste channel to preheat the medical waste material prior to at least partial incineration in the plasma zone of the non-thermal plasma generator.
Another embodiment of the system includes a non-thermal plasma generator, an oxidizer channel, a medical waste channel, and a heat source. The oxidizer channel is coupled to the non-thermal plasma generator to direct an oxidizer into a plasma zone of the non-thermal plasma generator. The medical waste channel is coupled to the non-thermal plasma generator to direct the medical waste material into the plasma zone of the non-thermal plasma generator. The heat source is coupled to the non-thermal plasma generator to heat the plasma zone of the non-thermal plasma generator to an operating temperature to at least partially incinerate the medical waste material. Other embodiments of the system are also described.
Embodiments of an apparatus are also described. In one embodiment, the apparatus is an incineration apparatus. An embodiment of the incineration apparatus includes means for preheating a medical waste material, means for introducing the preheated medical waste material into a plasma zone of a non-thermal plasma generator, means for introducing an oxidizer into the plasma zone of the non-thermal plasma generator, and means for at least partially incinerating the medical waste material within the plasma zone of the non-thermal plasma generator. Other embodiments of the apparatus are also described.
Other aspects and advantages of embodiments of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which are illustrated by way of example of the various principles and embodiments of the invention.
Throughout the description, similar reference numbers may be used to identify similar elements.
In the following description, specific details of various embodiments are provided. However, some embodiments may be practiced with less than all of these specific details. In other instances, certain methods, procedures, components, structures, and/or functions are described in no more detail than to enable the various embodiments of the invention, for the sake of brevity and clarity.
In one embodiment, the medical waste source 102 supplies a biological or medical waste material to the gliding arc electric incineration system 104. The biological or medical waste material may be, for example, in liquid or solid form. However, the content and composition of the waste material that may be incinerated using the incineration system 100 is not limited. In one embodiment, the waste material is human tissues and organs removed during a medical treatment process. In another embodiment, the waste material is a living or dead biological material resulting from medical research activities. Additionally, in some embodiments, the biological or medical waste material may be introduced to the gliding electric arc incineration system 104 using a carrier material. For example, the biological or medical waste material may be entrained with a liquid or a gas, and the combination of the waste material and the carrier material is introduced into the gliding electric arc incineration system 104.
In one embodiment, the gliding electric arc incineration system 104 is a high energy plasma arc system. Additionally, some embodiments of the gliding electric arc incineration system 104 are referred to as non-thermal plasma generators or systems because the process employed by the gliding electric arc incineration system 104 does not provide a substantial heat input (e.g., compared to conventional incineration systems) for the incineration reaction. It should also be noted that, although the illustrated incineration system 100 includes a gliding electric arc incineration system 104, other embodiments of the incineration system 100 may include other types of non-thermal plasma generators such as a dielectric barrier discharge (DBD), a corona discharge, a pulsed corona discharge, and the like.
In order to facilitate the incineration process implemented by the gliding electric arc incineration system 104, the oxidizer source 106 supplies an oxidizer, or oxidant, to the gliding electric arc incineration system 104. In one embodiment, the oxidizer controller 108 controls the amount of oxidizer such as oxygen that is supplied to gliding electric arc incineration system 104. For example, the oxidizer controller 108 may control the flow rate of the oxidizer from the oxidizer source 106 to the gliding electric arc incineration system 104. The oxidizer may be air, oxygen, steam (H2O), or another type of oxidizer. In some embodiments, oxygen may be used instead of air in order to lower the overall volume of oxidized gas. Embodiments of the oxidizer controller 108 include a manually controlled valve, an electronically controlled valve, a pressure regulator, an orifice of specified dimensions, or another type of flow controller. Another embodiment of the oxidizer controller 108 incorporates an oxidant composition sensor feedback system.
In one embodiment, the oxidizer mixes with the waste material within the gliding electric arc incineration system 104. Alternatively, the waste material and the oxidizer may be premixed before the mixture is injected into the gliding electric arc incineration system 104. Additionally, the oxidizer, the waste material, or a mixture of the oxidizer and the waste material may be preheated prior to injection into the gliding electric arc incineration system 104.
In general, the gliding electric arc incineration system 104 oxidizes the waste material and outputs an incineration product that is free or substantially free of harmful materials. More specific details of the incineration process are described below with reference to the following figures. It should be noted that the incineration process depends, at least in part, on the amount of oxidizer that is combined with the waste material and the temperature of the reaction. In some instances, it may be beneficial to input heat into the gliding electric arc incineration system 104 to increase the effectiveness of the incineration process.
In one embodiment, full oxidation (referred to simply as oxidation) of the waste material produces an incineration product. Full oxidation occurs when the amount of oxygen used in the incineration reaction is more than a stoichiometric amount of oxygen. In some embodiments, 5-100% excess of stoichiometric oxygen levels are used to implement full oxidation within the incineration process. An exemplary oxidation equation is:
Other equations may be used to describe other types of reformation and oxidation processes. Another exemplary oxidation equation utilizes CnHmOk such as:
C6H12O5(Cellulose)+6O2→6CO2+5H2O
The incineration process implemented using the gliding electric arc incineration system 104 may be endothermic or exothermic. In some instances, given the composition of biological and medical waste material, heat may be input into the gliding electric arc system 104 to facilitate incineration. For example, it may be useful to maintain part or all of the gliding electric arc incineration system 104 at an operating temperature within an operating temperature range for efficient operation of the gliding electric arc incineration system 104. In one embodiment, the gliding electric arc incineration system 104 is mounted within a furnace (refer to
Alternatively, or in addition to generally heating the gliding electrical arc incineration system 104, some embodiments of the incineration system 100 may preheat the medical waste material from the medical waste source 102, the oxidizer from the oxidizer source 106, or both. The waste material and/or the oxidizer may be preheated individually at the respective sources or at some point prior to entering the gliding electric arc incineration system 104. For example, the waste material may be preheated within the medical waste channel which couples the medical waste source 102 to the gliding electric arc incineration system 104. Alternatively, the waste material and/or the oxidizer may be preheated individually within the gliding electric arc incineration system 104. In another embodiment, the waste material and the oxidizer may be mixed and preheated together as a mixture before or after entering the gliding electric arc incineration system 104.
The illustrated incineration system 110 shown in
In one embodiment, the waste material and the oxidizer are introduced into the preheat zone 113. Within the preheat zone 113, the waste material and the oxidizer are preheated (represented by the heat transfer Q1) individually or together. In an alternative embodiment, one or both of the waste material and the oxidizer may bypass the preheat zone 113. The waste material and the oxidizer then pass to the plasma zone 114 from the preheat zone 113 (or pass directly to the plasma zone from the respective sources, bypassing the preheat zone 113). Within the plasma zone, the waste material is at least partially incinerated by a non-thermal plasma generator (refer to
After ionization, the reactants pass to the post-plasma reaction zone 116, which facilitates homogenization of the oxidized composition. Within the post-plasma reaction zone 116, some of the reactants and the products of the reactants are oxygen rich while others are oxygen lean. A homogenization material such as a solid state oxygen storage compound within the post-plasma reaction zone 116 acts as a chemical buffering compound to physically mix, or homogenize, the oxidation reactants and products. Hence, the oxygen storage compound absorbs oxygen from oxygen-rich packets and releases oxygen to oxygen-lean packets. This provides both spatial and temporal mixing of the reactants to help the reaction continue to completion. In some embodiments, the post-plasma reaction zone 116 also facilitates equilibration of gas species and transfer of heat.
The heat transfer zone 118 also facilitates heat transfer (represented by the heat transfer Q2) from the incineration product to the surrounding environment. In some embodiments, the heat transfer zone 118 is implemented with passive heat transfer components which transfer heat, for example, from the oxidation product to the homogenization material and to the physical components (e.g., housing) of the gliding electrical arc incineration system 104. Other embodiments use active heat transfer components to implement the heat transfer zone 118. For example, forced air over the exterior surface of a housing of the gliding electric arc oxidation system 104 may facilitate heat transfer from the housing to the nearby air currents. As another example, an active stream of a cooling medium may be used to quench an oxidation product. In another embodiment, the gliding electric arc incineration system 104 may be configured to facilitate heat transfer from the heat transfer zone 118 to the preheat zone 113 to preheat the waste material and/or the oxidizer.
The electrical signals on the electrodes 122 produce a high electrical field gradient between each pair of electrodes 122. For example, if there is a separation of 2 millimeters between a pair of electrodes 122, the electrical potential between the electrodes 122 of about 6-9 kV can create an electrical arc to initiate formation of plasma.
The mixture of the waste material and the oxidizer enters and flows axially through the plasma generator 120 (in the direction indicated by the arrow). The high voltage between the electrodes 122 ionizes the mixture of reactants, which allows current to flow between the electrodes 122 in the form of an arc 124, as shown in
Due to the flow of the mixture into the plasma generator 120, the ionized particles are forced downstream, as shown in
Eventually, the gap between the electrodes 122 becomes wide enough that the current ceases to flow between the electrodes 122. However, the ionized particles continue to move downstream under the influence of the mixture. Once the current stops flowing between the electrodes 122, the electrical potential increases on the electrodes 122 until the current arcs again, as shown in
In order to introduce the waste material and the oxidizer into the plasma generator 120, the gliding electric arc incineration system 130 includes multiple channels, or conduits. In the illustrated embodiment, the gliding electric arc incineration system 130 includes a first channel 138 for the waste material and a second channel 140 for the oxidizer. The first channel is also referred to as the medical waste channel, and the second channel is also referred to as the oxidizer channel. The medical waste and oxidizer channels 138 and 140 join at a mixing manifold 142, which facilitates premixing of the waste material and the oxidizer. In other embodiments, the waste material and the oxidizer may be introduced separately into the plasma generator 120. Additionally, the locations of the medical waste and oxidizer channels 138 and 140 may be arranged in a different configuration.
In order to contain the reactants during the incineration process, and to contain the incineration product resulting from the incineration process, the plasma generator 120 and the housing 134 may be placed within an outer shell 144. In one embodiment, the outer shell 144 facilitates heat transfer to and/or from the gliding electric arc incineration system 130. Additionally, the outer shell 144 is fabricated from steel or another material having sufficient strength and stability at the operating temperatures of the gliding electric arc incineration system 130.
In order to remove the incineration product (e.g., including any carbon dioxide, steam, etc.) from the annular region 146 of the outer shell 144, the gliding electric arc incineration system 130 includes an exhaust channel 148. In one embodiment, the exhaust channel is coupled to a collector ring manifold 150 that circumscribes the housing 134 and has one or more openings to allow the incineration product to flow to the exhaust channel 148. In the illustrated embodiment, the incineration product is exhausted out the exhaust channel 148 at approximately the same end as the intake channels 138 and 140 for the waste material and the oxidizer. This configuration may facilitate easy maintenance of the gliding electric arc incineration system 130 since all of the inlet, outlet, and electrical connections are in about the same place. Other embodiments of the gliding electric arc incineration system 130 may have alternative configurations to exhaust the incineration products from the outer shell 144.
The illustrated gliding electric arc incineration system 130 also includes a heater 152 coupled to the medical waste channel 138. In one embodiment, the heater 152 preheats the medical waste material within the medical waste channel 138 before the medical waste material enters the plasma zone of the gliding electric arc incineration system 130. Depending on the organic and inorganic content of the medical waste, it may be preheated from slightly above ambient to higher temperatures. In one embodiment, the medical waste is preheated to a range of between 50° C. to 400° C.
The illustrated gliding electric arc incineration system 160 of
In another embodiment, the gliding electric arc incineration system 160 facilitates heat transfer to the plasma zone, for example, to facilitate an endothermic incineration process. The illustrated gliding electric arc incineration system 160 includes a heat source 154 coupled to the outer shell 144. The heat source 154 supplies a heating agent in thermal proximity to the outer wall of the housing 134 (e.g., within the annular region 146 of the outer shell 144) to transfer heat from the heating agent to the plasma zone of the gliding electric arc incineration system 160. The heating agent may be a gas or a liquid. For example, the heating agent may be air. Although not shown in detail, the heating agent may be circulated within or exhausted from the outer shell 144.
In one embodiment, the gliding electric arc incineration system 160 is initially heated by introducing a mixture of a gaseous hydrocarbon and air. Exemplary gaseous hydrocarbons include natural gas, liquefied petroleum gas (LPG), propane, methane, and butane. Once the temperature of the gliding electric arc oxidation system 160 reaches an operating temperature of about 800° C., the flow of the gaseous hydrocarbon is turned off and waste material is introduced. The flow rates of oxidizer and waste material are adjusted to maintain a proper stoichiometric ratio, while the total flow is adjusted to maintain the plasma generator 120 at a particular operating temperature or within an operating temperature range.
The illustrated gliding electric arc oxidation system 160 also includes a homogenization material 166 located in the channel 136 of the housing 134. The homogenization material 166 serves one or more of a variety of functions. In some embodiments, the homogenization material 166 facilitates homogenization of the incineration product by transferring oxygen from the oxidizer to the waste material. In some embodiments, the homogenization material 166 also provides both spatial and temporal mixing of the reactants to help the reaction continue to completion. In some embodiments, the homogenization material 166 also facilitates equilibration of gas species. In some embodiments, the homogenization material 166 also facilitates heat transfer, for example, from the incineration product to the homogenization material 166 and from the homogenization material 166 to the housing 134. In some embodiments, the homogenization material 166 may provide additional functionality.
The illustrated gliding electric arc incineration system 160 also includes a ceramic insulator 168 to electrically insulate the electrodes 122 from the housing 134. Alternatively, the gliding electric arc incineration system 160 may include an air gap between the electrodes 122 and the housing 134. While the dimensions of the air gap may vary in different implementations depending on the operating electrical properties and the fabrication materials used, the air gap should be sufficient to provide electrical isolation between the electrodes 122 and the housing 134 so that electrical current does not arc from the electrodes 122 to the housing 134.
In some embodiments, the bottom mounting plate 184 may be removed from the flanges 172 and 174 to remove the mixing manifold 142 and the electrodes 122 from the housing 134 and the outer shell 144. Additionally, in some embodiments, one or more notches 190 are formed in the bottom mounting plate 184 to facilitate proper alignment of the mixing manifold 142 with the channels 138 and 140.
Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that the described feature, operation, structure, or characteristic may be implemented in at least one embodiment. Thus, the phrases “in one embodiment,” “in an embodiment,” and similar phrases throughout this specification may, but do not necessarily, refer to the same embodiment.
Furthermore, the described features, operations, structures, or characteristics of the described embodiments may be combined in any suitable manner. Hence, the numerous details provided here, such as examples of electrode configurations, housing configurations, substrate configurations, channel configurations, catalyst configurations, and so forth, provide an understanding of several embodiments of the invention. However, some embodiments may be practiced without one or more of the specific details, or with other features operations, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in at least some of the figures for the sake of brevity and clarity.
Although specific embodiments of the invention have been described and illustrated, the invention is not to be limited to the specific forms or arrangements of parts so described and illustrated. The scope of the invention is to be defined by the claims appended hereto and their equivalents.
This application claims the benefit of U.S. Provisional Application No. 60/807,363, filed on Jul. 14, 2006, which is incorporated by reference herein in its entirety. This application also claims the benefit of U.S. Provisional Application No. 60/891,166, filed on Feb. 22, 2007, which is incorporated by reference herein in its entirety.
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