Claims
- 1. A pyrolytic waste processing system comprising:a waste processing vessel including at least one plasma arc torch for pyrolizing waste in said processing vessel, the pyrolizing of waste generating product gases; a feed chamber for receiving waste and feeding the waste into said waste processing vessel; a scrubber in communication with said waste processing vessel for receiving, cooling and cleaning product gases generated within said waste processing vessel; a thermal oxidizer in communication with said scrubber for receiving and burning off product gases generated within said waste processing vessel; a gas supply unit for supplying gas to said plasma arc torch; a gas composition sensor for detecting a ratio of oxygen to product gases within said system; and a gas supply control unit coupled to said composition sensor and to said gas supply unit for causing said gas supply unit to switch the gas supplied to the plasma arc torch from air to an inert gas in response to signals received from the gas composition sensor indicating that the ratio of oxygen to product gases within said system is above a predetermined threshold.
- 2. The system of claim 1, wherein the predetermined ratio is 3% by volume.
- 3. The system of claim 1, further comprising a prechamber in communication with said feed chamber and through which waste is delivered to said feed chamber, and wherein:said gas supply unit communicates with said prechamber for feeding inert gas to the prechamber; and said gas supply control unit controls the amount of inert gas fed to the prechamber to maintain the volume percentage of oxygen relative to other gases in the prechamber below a predetermined threshold.
- 4. The system of claim 3, wherein said prechamber includes a first gate that opens for receiving waste and a second gate that opens for allowing the waste to enter said feed chamber.
- 5. The system of claim 1, wherein said gas supply unit communicates with said feed chamber for feeding inert gas to said feed chamber and wherein said gas supply control unit controls the amount of inert gas fed to said feed chamber in response to signals received from said gas composition sensor.
- 6. The system of claim 1, wherein:said waste processing vessel includes a tap for removing molten material from said processing vessel; said gas supply unit being in communication with said tap for feeding inert gas to said tap; and said gas supply control unit controlling the amount of inert gas fed to said tap in response to signals received from said gas composition sensor.
- 7. The system of claim 1, and further comprising at least one draft fan for drawing product gas out of said waste processing vessel and through said scrubber to maintain a predetermined pressure within said vessel, and wherein said gas supply unit communicates with said draft fan for feeding inert gas to said draft fan; andwherein said gas supply control unit controls the amount of inert gas fed to said draft fan in response to signals received from said gas composition sensor.
- 8. The system of claim 1, and wherein said gas supply control unit further controls said gas supply unit for switching the gas supplied to said plasma arc torch from inert gas back to air in response to signals received from said gas composition sensor indicating that the ratio of oxygen to product gases is below a predetermined threshold.
- 9. The system of claim 1, and wherein said gas supply unit delivers gas through a manifold coupled to said plasma arc torch.
- 10. The system of claim 1, and further comprising a waste feed control unit coupled to said feed chamber for varying the rate at which waste is fed into said waste processing vessel, said waste feed control unit varying the feed rate based upon said gas composition sensor.
- 11. The system of claim 10, wherein said gas supply control unit and said waste feed control unit operate concurrently.
- 12. The system of claim 1, wherein the inert gas comprises nitrogen.
- 13. The system of claim 1, further comprising:at least one draft fan in communication with said scrubber for drawing product gases out of said waste processing vessel through said scrubber to maintain a predetermined maximum pressure within said waste processing vessel and said scrubber, said draft fan being in communication with and delivering product gases to said thermal oxidizer, and a recirculation line for recirculating product gases from said draft fan through said scrubber; a draft fan inlet damper for regulating a flow of product gases from said scrubber to said draft fan; a draft fan discharge damper for regulating a flow of product gases from said draft fan to said thermal oxidizer; a draft fan recirculation damper for regulating a flow of product gases from said draft fan to said recirculation line; and a pressure balancing control unit coupled to said draft fan inlet damper, said draft fan discharge damper, and said draft fan recirculation damper to control the flows of product gases and thus to control pressures within said system.
- 14. The system of claim 13, wherein said pressure balancing control unit controls said draft fan inlet damper, said draft fan discharge damper, said draft fan recirculation damper to allow recirculation of product gases through said scrubber during interruptions in waste processing.
- 15. The system of claim 1, further comprising:at least one draft fan for drawing product gases out of said waste processing vessel through said scrubber and delivering the product gases to said thermal oxidizer; and a flame arrestor positioned between said draft fan and said thermal oxidizer for extinguishing flames propagating upstream from said thermal oxidizer towards said draft fan.
- 16. The system of claim 15, further comprising:a flame detector in said flame arrestor for detecting a flame within said flame arrestor; and an isolation valve positioned upstream from the flame arrestor, said isolation valve being adapted to close when said flame detector detects the presence of a flame.
- 17. The system of claim 16, further comprising:a draft fan inlet damper for regulating flow of product gases into said draft fan; a draft fan discharge damper for regulating flow of product gases from said draft fan to said thermal oxidizer; a draft fan recirculation damper for regulating flow of product gases from said draft fan to said recirculation line; and an interlocking control unit for receiving signals from said isolation valve, said interlocking control unit closing said draft fan discharge damper, opening said draft fan recirculation damper, halting operation of said plasma arc torch, and halting the feeding of waste into said waste processing vessel upon closure of said isolation valve.
- 18. The system of claim 15, further comprising:a flame detector for detecting the presence of a flame within said flame arrestor; a draft fan inlet damper for regulating flow of product gases into said draft fan; a draft fan discharge damper for regulating flow of product gases from said draft fan to said thermal oxidizer; a draft fan recirculation damper for regulating flow of product gases from said draft fan to said recirculation line; and an interlocking control unit for receiving signals from said flame detector, said interlocking control unit closing said draft fan discharge damper, opening said draft fan recirculation damper, halting operation of said plasma arc torch and halting the feeding of waste into said waste processing vessel when said flame detector detects the presence of a flame.
- 19. A pyrolytic waste processing system comprising:a waste processing vessel including at least one plasma arc torch for pyrolizing waste within said waste processing vessel, the pyrolizing of waste generating product gases; a feed chamber in communication through a feed conduit with said waste processing vessel for feeding waste to be pyrolized into said waste processing vessel; a gas supply unit in communication with at least said plasma arc torch for delivering gas to said torch and, through said torch, to said waste processing vessel; a gas composition sensor for sensing a ratio of oxygen to product gases in said system; an exhaust conduit for directing gases away from said waste processing vessel; a scrubber in communication with said exhaust conduit for cooling and cleaning product gases generated within said waste processing vessel; a gas supply control unit coupled to said composition sensor and to said gas supply unit for causing said gas supply unit to supply an inert gas at least to said plasma arc torch in response to signals received from said gas composition sensor indicating that the ratio of oxygen to product gases in said system is in excess of a predetermined threshold, thereby maintaining a safe ratio of oxygen to product gases in said system.
- 20. The system of claim 19, and further comprising:a thermal oxidizer communicating with said exhaust conduit downstream of said scrubber for burning off product gases generated within said waste processing vessel; a flame arrestor in said exhaust conduit upstream of said thermal oxidizer for extinguishing flames propagating upstream from said thermal oxidizer; a flame detector in said flame arrestor for detecting a flame within said flame arrestors; an isolation valve upstream from said flame arrestor, said isolation valve being adapted to close when said flame detector detects a flame; and an interlocking control unit coupled to said flame detector and to said gas supply unit for receiving signals from said flame detector, and controlling a supply of inert gas to said system in response thereto.
- 21. The system of claim 19, further comprising:a flame arrestor for extinguishing flames propagating upstream from said thermal oxidizer; a flame detector for detecting a flame within said flame arrestor; an automatic isolation valve positioned upstream from said flame arrestor that closes when said flame detector detects a flame; and an interlocking control unit coupled to receive signals from said isolation valve, said interlocking control unit controlling said gas supply unit to supply inert gas to said system in response to closure of said isolation valve.
- 22. The system of claim 19, and further comprising a waste feed control unit coupled to said feed chamber for varying the rate at which waste is supplied to said waste processing chamber in response to signals received from the gas composition sensor, said waste feed control unit operating concurrently with said gas supply control unit in order to maintain a preselected ratio of oxygen to product gas in the system.
- 23. A pyrolytic waste processing system comprising:a waste processing vessel including at least one plasma arc torch for pyrolizing waste within said waste processing vessel, the pyrolizing of waste producing product gases; a feed chamber coupled to said waste processing vessel through a feed conduit for delivering waste to said waste processing vessel; an exhaust conduit communicating with said waste processing vessel for directing product gases generated within said waste processing vessel away from said waste processing vessel; a scrubber communicating with said exhaust conduit for cleaning and cooling product gas generated within said waste processing vessel; a thermal oxidizer communicating with said exhaust conduit downstream of said scrubber for receiving and burning off product gases generated within waste processing vessel; a gas composition sensor for detecting a ratio of oxygen to product gases in said system; and a waste feed control unit coupled to said gas composition sensor and to said feed chamber for varying the rate at which waste is fed to said waste processing vessel in response to signals from said gas composition sensor to maintain a preselected ratio of oxygen to product gases in said system.
Government Interests
This invention was made with Government support under contract #97RKW-224746 awarded by the Tennessee Valley Authority. The Government has certain rights in the invention.
US Referenced Citations (20)