Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Organic component
Utility Patent
1998-02-17
2001-01-02
Dunn, Tom (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Organic component
C423S210000, C423S235000, C423S238000, C423S24000R, C423S242100, C423S243010, C423S245100, C423S245200, C588S253000, C588S253000, C588S253000, C588S253000, C588S253000, C588S253000, C588S253000, C588S253000, C588S253000, C588S253000, C588S253000, C588S253000, C588S249000, C588S249000, C588S249000
Utility Patent
active
06168771
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an oxidation processing method of converting dangerous substances to be processed to highly safe waste by using an active oxidation reaction medium, such as high pressure and high temperature water in a supercritical state, and an apparatus and a reaction vessel for containing the substances to be processed, which use the method.
An example of a supercritical reaction processing apparatus applied to fluid extraction is disclosed in Japanese Patent Laid-Open 296662/1993.
In a supercritical oxidation processing apparatus using active oxidation of water at a supercritical state, an opening/closing type pressure vessel for generating a supercritical state (autoclave) is used as a process vessel. After substances to be processed are enclosed in the autoclave together with water or a hydrogen peroxide aqueous solution, the autoclave is sealed up tightly with flanges, and the temperature in the autoclave is increased by directly heating an outer wall of the autoclave with a heater. If the water or the hydrogen peroxide aqueous solution, in an amount adequate for the amount of enclosed substances to be processed, is enclosed in the autoclave, the internal pressure of the autoclave increases to more than 250 atm when the temperature in the autoclave is increased to the 600° C., and the organic material in the substances is oxidized within a short period of several minutes and is converted to a highly safe material, such as acid, nitrogen gas, carbon dioxide gas, salt, and so on. If the amount of oxygen is insufficient, oxidation is promoted by injecting oxygen into the autoclave at a higher pressure than the internal pressure of the autoclave.
However, one of the factors in a conventional supercritical oxidation processing is that if the substances to be processed are inflammable or if the toxic, or substances change to an inflammable or toxic material in the intermediate process on the way to a supercritical state or at a supercritical state, the danger of harming human beings could possibly occur in case of a leakage of the dangerous substances from the autoclave or occurrence of a fire in the oxidation processing apparatus. Since the temperature and the pressure in the autoclave highly increase to 600° C. and 250 atm, respectively, the leakage of substances to be processed, from the autoclave, can be caused by a sealing deficiency occurring at a joint of bolt clamping flanges using a metal packing as a sealing part, where a micro-crack may be generated in a wall of the autoclave by oxidization corrosion during operations, are break of the oxidation processing apparatus may be is brought by the earthquake, etc.,.
Furthermore, even if a power source of an electrical heater is turned off, the temperature of the electrical heater directly heating an autoclave does not decrease immediately. Therefore, it is possible for a part of the substances to be processed, which are leaking from the autoclave, to contact a surface of the electrical heater at a high temperature so that oxidation reaction of the substances progresses, causing the leaking substances to continue to change to flammable or toxic material, which may cause a fire at the processing apparatus or severe trouble to the health of an operator in the vicinity.
Further, a conventional supercritical pressure oxidation processing apparatus has the following problem. That is, since solid material (salt) tends to deposit on an inner wall of the autoclave, it is necessary to clean the inner wall every time after oxidation processing, which degrades the operational efficiency of the processing apparatus.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an oxidation processing method and a processing apparatus using the method which are capable of preventing substances to be processed from leaking to the outside atmosphere.
Another object of the present invention is to provide an oxidation processing method and a processing apparatus using the method which do not cause a fire to occur at the processing apparatus or undesirably affect the health of an operator in the vicinity even if the substances to be processed leak from a process vessel.
Still another object of the present invention is to provide an oxidation processing method and a processing apparatus using the method which do not cause a fire to occur at the processing apparatus and protect an operator from the bad influence of a substances to be processed which may leak from a process vessel.
Yet another object of the present invention is to provide an oxidation processing method and a processing apparatus using the method which can make it easier to process solid substances separated on an inner wall of a process vessel and to improve the operational efficiency of the processing apparatus.
A further object of the present invention is to provide a process vessel which is adequate to perform oxidation processing of substances to be processed safely and efficiently.
The present invention provides a method of performing oxidation processing of substances to be processed by enclosing substances to be processed in a reaction vessel together with oxygen and a reaction medium, sealing up the reaction vessel, and heating the sealed-up reaction vessel to a high-temperature and high-pressure state, the method comprising the steps: of enclosing the substance to be processed in a first vessel (process vessel) together with oxygen and a first reaction medium and sealing up the first vessel; enclosing the sealed-up first vessel in a second vessel (pressure vessel=autoclave) together with a second reaction medium and sealing up the second vessel; and oxidizing the substances to be processed by changing the state inside the sealed-up first vessel to a high temperature and high pressure state, such as a supercritical state, by heating the sealed-up second vessel which indirectly heats the sealed-up first vessel; whereby the substance to be processed does not leak from the oxidation processing apparatus even if the substance to be processed leaks from the first vessel. Further, by performing the injection of the substance to be processed, oxygen and the first reaction medium into the first vessel, inside an isolation container, the substance to be processed is prevented from leaking to the air.
Also any substances to be processed which leak from the first vessel can be oxidized by heating the second reaction medium enclosed in the second vessel to a high temperature and high pressure. Oxidation processing of the leaking substance to be processed is positively promoted by injecting oxygen into the second vessel.
The second vessel covered with an insulation material that is absorbent so as to absorb the leaking substance to be processed, is contained in a protection container, and a pressure inside the protection container is decreased to a pressure less than atmospheric pressure, so that even if the substance to be processed leaks from the second vessel, the leaking substance does not leak from the oxidation processing apparatus.
The processed substances in the first vessel are discharged and abandoned by taking out the first vessel which was set into the second vessel and which was subjected to the heating process, and opening the first vessel.
By using a nozzle formed at the first vessel, the substance to be processed is enclosed into the first vessel together with oxygen and the first reaction medium, after which the first vessel is sealed up, and the first vessel is opened after the oxidation processing is finished, after which the processed substance is discharged.
Moreover, a hydrogen peroxide aqueous solution is used for generating oxygen and the first medium to be enclosed into the first vessel. In order to abandon sulfuric acid, hydrochloric acid, hydrofluoric acid, heavy metal (arsenic), etc., at stable forms, a material (for example, Zn) to react on hydrofluoric acid and change it to a stable material, ferrous salt to change heavy metal (for example, arsenic) to an iron eutectic alloy, or a neutra
Isogami Hisashi
Morita Minoru
Saho Norihide
Shibano Yoshiki
Antonelli Terry Stout & Kraus LLP
Dunn Tom
Hitachi , Ltd.
Nave Eileen E.
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