An organic waste decomposition system and method is described having two reaction vessels in tandem, each using superheated steam augmented by oxygen for decomposing a wide variety of organic compounds to reduce both mass and volume. Decomposition takes place quickly when a steam/oxygen mixture is injected into a fluidized bed of ceramic beads. The speed of the fluidizing gas mixture agitates the beads that then help to break up solid wastes, and the oxygen allows some oxidation to offset the thermal requirements of drying, pyrolysis, and steam reforming. Most of the pyrolysis takes place in the first stage, setting up the second stage for completion of pyrolysis and adjustment or gasification of the waste form using co-reactants to change the oxidation state of inorganics and using temperature to partition metallic wastes.
This application is a continuation-in-part of U. S. patent application Ser. No. 08/680,380, filed on Jul. 15, 1996, entitled "Method and Apparatus for the Volume Reduction and Processing of Nuclear Waste" by Rolf Hesbol and Bradley Mason now U.S. Pat. No. 5,909,654, which is itself a continuation-in-part of U.S. patent application Ser. No. 08/403,758, filed on Mar. 17, 1995, U.S. Pat. No. 5,536,896, entitled "Waste Processing" by Rolf Hesbol and Lars E. Holst, both of which applications being also assigned to the assignee of the present invention.
Reacting organic compounds with near-critical or supercritical aqueous phases can dramatically transform the organic compounds over short time periods (on the order of minutes to hours). The reductive process is conducted in anaerobic or near-anaerobic conditions. The process works with a wide range of organic compounds and biomass sources, including cellulose, chitin, starches, lipids, proteins, lignin, and whole cells. Disposal of waste biomass is currently expensive, and can create environmental problems. The present invention allows the conversion of waste lipids (for example) into a hydrocarbon mixture similar to a sweet crude petroleum, along with volatile alkane and alkene gases (C.sub.2 to C.sub.5). This conversion allows the generation of a burnable fuel, as well as the generation of feed streams for reforming and distillation. The environmental and other costs associated with fossil fuel extraction are reduced. Reactions in accordance with the present invention may be conducted in continuous, batch, or semi-batch mode. To date, we have used both batch and stop-flow reactors to transform biomass in near-critical (320-390.degree. C., 200-420 bar) and supercritical water (400-500.degree. C., 400-550 bar).
An apparatus and method for processing hazardous wastes directly from 55-gallon drums through the use of pyrolysis and steam reforming. The method is based on a pyrolyzer using heat to vaporize organics that are present in the hazardous wastes. The waste is heated in the original drums to avoid the bulk handling of alpha radionuclides and to ensure criticality control. At pyrolysis temperatures, all liquids and organics in the drums will evaporate and volatize. The resulting waste in the drums is a dry, inert, inorganic matrix with carbon char containing radioactive metals. The off-gas produced by pyrolysis mainly consists of water vapor, volatized organics, and acid gases from the decomposition of various plastics and other organics present in the waste drums. The off-gas produced by the pyrolysis is then collected and fed into an off-gas treatment system that is in fluid communication with pyrolyzer operated under oxidizing conditions.
A process for the treatment of radioactive graphite which includes the following steps: (i) reacting the radioactive graphite at a temperature in the range of from 250.degree. C. to 900.degree. C. with superheated steam or gases containing water vapor to form hydrogen and carbon monoxide; (ii) reacting the hydrogen and carbon monoxide from step (i) to form water and carbon dioxide; and (iii) reacting the carbon dioxide of step (ii) with metal oxides to for carbonate salts. The process enables radioactive graphite, such as graphite moderator, to be treated either in-situ or externally of a decommissioned nuclear reactor.
A system and method is described having a single reaction vessel (12) using superheated stream optionally augmented by oxygen for reducing nitrogen oxides present in a wide variety of organic compounds. Reduction takes place quickly when a stream/oxygen mixture is injected into a fluidized bed (22) of ceramic beads. Reducing additives are metered into the reaction vessel (12) and/or provide energy input to reduce nitrates to nitrogen. The speed of the fluidizing gas mixture agitates the beads that then help to break up solid wastes and to allow self-cleaning through abrasion thereby eliminating agglomerates, and the oxygen, when used, allows for some oxidation of waste by-products and provides an additional offset for thermal requirements of operation.
A system and method using superheated steam optionally augmented by oxygen for the reduction of nitrogen oxides present for reducing nitrogen oxides present in a wide variety of organic compounds. The system includes a single reaction vessel, or optionally, multiple reaction vessels in operational communication. Reduction takes place quickly when a steam/oxygen mixture is injected into the reaction vessel or vessels. Reducing additives are metered into the reaction vessel or vessels and/or provide energy input to reduce nitrates to nitrogen. The oxygen, when used, allows for some oxidation of waste by-products and provides an additional offset for thermal requirements of operation.
