Gasifying system and method
Systems and methods for treating carbon-containing waste materials include a gasifying system, a drier system for pre-drying the material, and an energy-recovery system for recovering waste heat and/or producer gas from the gasifying system/method for use in pre-drying the material. The energy-recovery system can include a recirculation system for recovering the waste heat and/or a thermal oxidizer or other combustion device for burning the producer gas, along with a heat-transfer-loop for transferring the recovered heat energy to the drier for pre-drying the material. In another aspect of the invention, the gasifying systems and methods use a thermal-screw conveyor with a product chamber and rotary thermal screws, and an oxygen-delivery system configured for delivering oxygen into the product chamber for immediate absorption into the material, with or without the dryer system and/or the energy-recovery system.
1. A system for treating carbon-containing material, comprising:
a gasifying system adapted to gasify a carbon-containing material, the gasifying system comprising:
a thermal-screw conveyor comprising:
a product chamber defined by a housing wall;
a plurality of rotary thermal screws each including a rotor and flighting that intermeshes with the flighting of an adjacent one of the rotary thermal screws, the plurality of rotary thermal screws configured to transfer heat to the carbon-containing material and to convey the carbon-containing material through the product chamber;
a dedicated actuator for each of the plurality of rotary thermal screws; and
a control system including controls for operating each of the actuators independently to drive the rotary thermal screws at the same or differing speeds while controlling clocking so that the flightings of the plurality of rotary thermal screws do not collide with each other; and
an oxygen delivery system including nozzles formed at orifices in the housing wall.
2. The system of claim 1 , wherein the oxygen delivery system includes a trunk line and a series of feeder lines, the feeder lines extending from the trunk line and terminating with the nozzles.
3. The system of claim 1 , wherein each rotor and flighting of the plurality of rotary thermal screws defines internal passageways containing a thermal fluid.
4. The system of claim 1 , wherein the housing wall is double walled to define at least one internal passageway containing a thermal fluid.
5. The system of claim 1 , wherein the thermal-screw conveyor is configured to operate at a temperature up to 1400° F.
6. The system of claim 1 , wherein the control system further comprises:
a controller;
a screw-position sensor for each of the plurality of rotary thermal screws, the screw-position sensor in communication with the controller;
an adjustable speed drive for each dedicated actuator, the adjustable speed drive in communication with the controller; and
a control program operable by the controller.
7. The system of claim 1 , further comprising a drier system adapted to pre-dry the material for delivery to the gasifying system.
8. The system of claim 7 , further comprising an energy-recovery system adapted to recover waste energy from the gasifying system and deliver the recovered waste energy to the gasifying system or the drier system.
9. The system of claim 1 , wherein the nozzles are positioned adjacent an apex of a recess at a center of a bottom portion of the housing wall in series along an axis of the housing.
10. The system of claim 9 , wherein the nozzles are staggered, alternating between positions immediately to one side or the other of the apex of the of the recessed portion of the housing wall in a balanced arrangement to avoid hot spots.
11. The system of claim 1 , further comprising a series of deflectors positioned adjacent the nozzles, the deflectors extending inward from the housing wall and angled to extend over the nozzles, covering the nozzles so that biosolids material does not backflow into the nozzles.
12. The system of claim 2 , further comprising a series of control valves, with a control valve in each feeder line.