Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – With means applying electromagnetic wave energy or...
Reexamination Certificate
1999-12-27
2004-06-15
Tran, Hien (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
With means applying electromagnetic wave energy or...
C422S105000, C422S112000, C422S232000, C422S242000, C422S296000
Reexamination Certificate
active
06749816
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-pressure treatment apparatus for reacting and treating an object to be treated such as organic radioactive waste such as, for instance, ion exchange resin used at atomic power plants with a medium such as, for instance, water, oxygen or the like under high-pressure. To be more specific, the present invention relates to a high-pressure treatment apparatus using a medium in a sub-critical or super-critical state. In particular, the present invention relates to, in the aforementioned apparatus, a high-pressure reactor for reacting therein an object to be treated and a medium under a high-pressure, a feeder for feeding the object to the high-pressure reactor and a feeding method thereof, and a method for protecting the high-pressure reactor.
2. Description of the Related Art
In recent years, a technology for reacting in water under high pressure and high temperature exceeding the critical point of water (temperature: 374° C., pressure: 22 MPa), a technology for reacting in carbon dioxide under high pressure and high temperature exceeding the critical point of carbon dioxide (temperature: 31° C., pressure: 7.38 MPa) and a technology for reacting in hydrocarbons under high-pressures exceeding critical points of various kinds of hydrocarbons are well known. By making use of such super-critical fluids, the following effects can be obtained (for instance, Caruana, C. M.: Chem. Eng. Prog., 4, 10 (1995), Erickson, J. C., P. Schyns, and C. L. Cooney: AlChE J., 36, 299 (1990), and Jezko, J., D. Gray, and J. R. Kershaw: Fuel Processing Technology, 5, 229-239 (1982)).
(1) With only a small pressure change, a large density change can be obtained. In general, solubility of substance varies in proportion to the density thereof. Accordingly, a large difference of solubility can be obtained by changing pressure only. This property can be applied in extraction and separation.
(2) Super-critical fluid, though the density thereof is similar to that of liquid, is low in viscosity thereof and high in diffusion thereof. Accordingly, the super-critical fluid is more advantageous than liquid from a viewpoint of mass transfer, resulting in a large rate of reaction.
(3) Thermal conduction of super-critical fluid is remarkably high. Accordingly, reaction temperatures can be controlled with ease.
Recently, an apparatus of decomposing organic waste and inorganic waste by use of such sub-critical fluid or super-critical fluid, in particular, super-critical water as a reaction medium is attracting attention. According to this method, in spite of relatively high cost thereof, compared with the case of incinerating, there are advantages that reaction products can be completely decomposed to non-hazardous substances and incineration ashes are prevented from dispersing. Accordingly, this method is considered to apply in decomposition of hazardous organic materials and radioactive wastes.
When processing such substances, safety of an apparatus is the most important problem. It is presumed that high-pressure reactors are not subjected to damage such as corrosion. In addition, the treatment object, in feeding to the apparatus, is required to prevent from leaking outside of the apparatus.
A high-pressure reactor, generally considering corrosion-resistance to reaction media and reaction products, is designed as a pressure vessel having thickness of strength capable of enduring the pressure thereof. Austenite system stainless steel and Ni based alloy that have high-temperature strength and are corrosion-resistant are used in large as typical materials for high-temperature and high-pressure reactors. However, under such an oxidizing condition that the super-critical water contains Cl
−
or SO
4
2−
, it is reported that these are not sufficiently corrosion-resistant and tend to be subjected to corrosion (for instance, D. A. Hazlebeck, K. W. Doeney, J. P. Elliot and M. H. Spritzer, Proc. First Int. Workshop on Super-critical Water oxidation).
As highly corrosion-resistant metallic materials in such an environment, noble metals such as Pt, Au or the like, Ti, Ti alloys, Ta, Ta alloys or ceramics can be considered. However, these materials are expensive compared with generally used steel for pressure-vessel. In addition, some of these are highly corrosion-resistant but too low in strength to be a pressure-vessel by itself. In such cases, they can be used only as covering materials for such as lining and coating.
As a means to these ends, a structure is disclosed in which a high-pressure vessel is built into a double-vessel structure, inside of an exterior pressure vessel a high-pressure vessel as a high pressure reactor is installed, and the pressure within the high-pressure vessel and that of the gap portion therebetween is made equal to be balanced. Thereby, the high-pressure vessel is alleviated from being pressurized too much (for instance, WPI Acc No. 98-057323/199806: Supercritical water oxidation processing (ORGANO CORP)).
In this method, the high-pressure vessel is not required to be highly pressure-resistant but is required only to be corrosion-resistant. Accordingly, a vessel of thin-walled structure can be adopted. As a result of this, the cost of a vessel can be reduced. In addition, the exterior pressure vessel is not required to be highly corrosion-resistant but required only to be pressure-resistant. Accordingly, various kinds of materials can be adopted to result in cost reduction.
However, it is difficult to foresee completely local damages such as pitting and stress-corrosion cracking. Once such a damage happened, hazardous materials within the high-pressure vessel diffuse into the gap to be likely to contaminate even the exterior pressure vessel.
When it is necessary to heat the high-pressure vessel due to insufficient generation of heat of reaction, ordinarily a heating unit such a heater or the like is arranged outside of the high-pressure vessel. Therewith, the inside of the vessel is heated by making use of the vessel wall as heat conduction medium. However, when there is likelihood of contaminating even the exterior pressure vessel as mentioned above, though the heating unit is necessary to be arranged outside of the exterior pressure vessel, due to existence of pressure-holding medium between the exterior pressure vessel and the high-pressure vessel, heating efficiency becomes extremely low.
In order to make a treatment object react efficiently, it is desirable that feeding amount and feeding speed of the object to the high-pressure vessel can be controlled with ease. From a viewpoint of safety too, such a control is necessary. However, when the treatment objects are solid materials, it is difficult to feed them into the high-pressure reactor of high temperature and high pressure. In particular, it is difficult to feed them continuously.
Within super-critical fluids or sub-critical fluids, reactions of substance proceed faster. Accordingly, if super-critical fluid or sub-critical fluid within the high-pressure vessel penetrates into feeding system in the treatment apparatus, it is likely for the reaction to occur inside of the feeding system.
Such a problem is common not only in the case of feeding solid materials into super-critical fluid but also in the case of feeding into highly pressurized fluid.
Accordingly, it is of great importance to prevent the fluid within a high-pressure vessel from the back flow into a feeding system of an object to be treated.
In
FIGS. 17 and 18
, conventional feeding systems of feeding solid materials into a high-pressure vessel are shown.
FIG. 17
shows an example of system diagrams, where organic material prepared in slurry are fed into a high-pressure reactor by use of a feed-pump (see U.S. Pat. No. 4,338,199: Processing Method for the Oxidation of Organics in Supercritical Water).
Organic materials fed into a feed slurry tank
11
are mixed with water for adjusting to form slurry. This slurry is fed by use of a feed-pump
15
into an oxidizing reactor
19
thr
Abe Yumiko
Akai Yoshie
Hasegawa Hiroko
Hasegawa Yutaka
Matsubayashi Yoshikazu
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Hasegawa Hiroko
Kabushiki Kaisha Toshiba
Leung Jennifer A.
Tran Hien
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