Metallurgical apparatus – Linings – With specific lining enclosing structure
Reexamination Certificate
2000-12-28
2003-06-10
Kastler, Scott (Department: 1742)
Metallurgical apparatus
Linings
With specific lining enclosing structure
C210S090000
Reexamination Certificate
active
06576185
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains generally to methods and systems for the hydrothermal treatment of a feed stream to destruct waste, recovery heat, or produce beneficial chemicals. More specifically, the present invention pertains to methods and systems for the hydrothermal treatment of organics which contain inorganic compounds such as salts or oxides or which will generate these inorganic compounds. The present invention is particularly, but not exclusively, useful as a method and system for the hydrothermal treatment of organics under supercritical temperature and pressure conditions, or at supercritical temperatures and elevated, yet subcritical pressures.
BACKGROUND OF THE INVENTION
It is well known that a broad spectrum of materials can be chemically treated in an aqueous media at either supercritical temperature and pressure conditions, or at supercritical temperatures and elevated, yet subcritical pressures. In supercritical water oxidation (“SCWO”), the oxidation reaction occurs substantially entirely at conditions which are supercritical in both temperature (>374° C.) and pressure (>about 3,200 psi or 220 bar). Specifically, at temperatures of about five hundred degrees Celsius to six hundred fifty degrees Celsius (500° C.-650° C.) and pressures of about 250 bar, rapid and complete oxidation of virtually any organic compound can be obtained in an aqueous media in a matter of seconds. A process related to SCWO known as supercritical temperature water oxidation (“STWO”) can provide similar oxidation effectiveness for certain feedstocks but at pressures as low as 25 bar. In both of these processes, the temperature and pressure can be varied to accommodate the type of feedstream and the desired result. For example, these processes can be used to combust materials of high thermal value for energy recovery; to convert hazardous waste materials into more benign materials; or to produce beneficial chemicals for later use. In general, these processes involve combining water, a reactant, and an oxidizer such as air or oxygen, at elevated temperatures and pressures. The resultant chemical reaction is generally exothermic and occurs directly within the aqueous phase. The energy released by the reaction can often be used to maintain the high temperatures and pressures required in the reactor vessel. By continuously feeding the reactants while withdrawing the reaction products, the energy released from the reaction can be used to heat the incoming feedstream. Batch type processing is generally inefficient in these processes due to the large amount of energy that would be needed to heat and pressurize each batch.
The various processes for oxidation in an aqueous media at temperatures above about three hundred seventy-four degrees Celsius and pressures above about 25 bar are referred to collectively as hydrothermal treatment. In addition to the increased reaction rates as described above, other reaction features distinguish hydrothermal treatment from reactions conducted at standard temperatures and pressures (STP), which are generally considered to be 25 degrees Celsius and 1.013 bar. For example, most inorganic salts have high solubility's in water at STP. In stark contrast, under hydrothermal treatment conditions, most inorganic salts are insoluble in the aqueous media. Consequently, inorganic salts that are present in the feedstreams precipitate from the aqueous media and create solids. These solids can be problematic because they often buildup on the surfaces of process equipment such as the walls of the pressure vessel used to contain the reaction. In continuous feed processes, the buildup of solids often progresses until the reactor vessel becomes plugged. Once the reactor vessel is plugged, the continuous reaction must be interrupted to clean out the reactor vessel, wasting valuable time and energy.
Further complicating hydrothermal treatment is the fact that corrosion rates generally increase with increasing temperature. Feedstreams used for hydrothermal treatment often generate corrosive acids such as hydrochloric acid and sulfuric acid, resulting in corrosive attack on the process vessel that is so severe that alkali is often added to neutralize the acids. Unfortunately, this addition of alkali creates insoluble salts which aggravate the vessel plugging problem described above. Further, stress considerations often dictate that the reactor vessel have a relatively narrow diameter and long length to thereby withstand the high pressures and corrosion rates generating in the reactor, yet reactor vessel's with narrow diameters further aggravate the plugging problem.
The extreme temperatures, pressures, corrosives and insoluble salts present in the hydrothermal reactor vessel present what can only be characterized as a harsh environment to the pressure bearing wall of the reactor vessel. To alleviate the effects of this environment on the pressure bearing wall, liners have been heretofore suggested to separate the reactor chamber from the pressure bearing wall. For example, U.S. Pat. No. 5,591,415 which issued to Dassel et al. entitled “Reactor for Supercritical Water Oxidation of Waste” discloses a reactor enclosed in a pressure vessel in a manner that the walls of the pressure vessel are thermally insulated and chemically isolated from the harsh environment of the reaction zone. Unfortunately, the liner disclosed by Dassel et al. fails to adequately address the problem associated with insoluble salt buildup and reactor plugging. Similarly, U.S. Pat. No. 3,472,632 which issued on Oct. 14, 1969 to Hervert et al. entitled “Internally Lined Reactor for High Temperatures and Pressures and Leakage Monitoring Means Therefore” discloses a liner having a porous layer for a high temperature reactor. Hervert et al., however, does not disclose the use of the liner for hydrothermal treatment environments, and consequently, the disclosed liner lacks several very important features necessary for using a liner in hydrothermal treatment. For instance, the liner disclosed by Hervert et al. is not a suitable mechanism for relieving the effects of insoluble salt buildup and reactor plugging, it is not easily replaceable, and there is no thermal barrier.
In light of the above, it is an object of the present invention to provide a liner to protect the pressure bearing wall of a hydrothermal treatment reactor wherein the liner includes a system for leak detection that is operable during the hydrothermal reaction which allows for reactor shutdown before a severe attack on the pressure bearing wall occurs. Another object of the present invention is to provide a liner to protect the pressure bearing wall of a hydrothermal treatment reactor wherein the liner incorporates a mechanism for pre-heating the reaction chamber before steady state treatment conditions are achieved. Yet another object of the present invention is to provide a liner to protect the pressure bearing wall of a hydrothermal treatment reactor wherein the liner incorporates a mechanism for passing a heat exchange fluid near the reactor chamber to allow heat to be recovered from the reaction. Still another object of the present invention is to provide a liner to protect the pressure bearing wall of a hydrothermal treatment reactor incorporating a mechanism to control the liner temperature and thereby prevent the buildup of insoluble salts on the liner. Yet another object of the present invention is to provide a system and method for accomplishing hydrothermal treatment which is easy to implement, simple to use, and cost effective.
SUMMARY OF THE PREFERRED EMBODIMENTS
In accordance with the present invention, a system for performing hydrothermal treatment at temperatures above approximately three hundred seventy-four degrees Celsius (374° C.) and pressures above about 25 bars, includes a reactor vessel that is formed with a pressure bearing wall which surrounds a reactor chamber. An inlet is provided at one end of the reactor vessel to introduce the feed material into the reactor chamber and an outlet
General Atomics
Kastler Scott
Nydegger & Associates
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