JP3280797B2 - Apparatus for supercritical water oxidation of harmful organic substances and operating method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for supercritical water oxidation of harmful organic substances and a method for operating the apparatus.

[0002]

2. Description of the Related Art Conventionally, regarding the decomposition treatment of organic substances, the decomposition treatment by microorganisms has been generally carried out by taking human waste treatment as a typical example. However, the large amount of sludge generated due to the treatment is problematic. Therefore, a method for reducing it has been studied. The typical method is 200-3
A method called a wet oxidation method in which air or oxygen is forcibly sent as an oxidizing agent under a hot water condition of about 100 ° C. and about 100 atm to cause oxidative decomposition,
This method has no particular problem in the case of general organic substances such as night soil, but is not harmful to humans and animals.
It has been said that there is a problem in the level of decomposition when applied to wastewater containing CB and Freon.

In order to further improve such a problem relating to the degree of decomposition, supercritical water (temperature 374) is used.
Supercritical water oxidation, in which an oxidizing agent is allowed to act at a temperature and pressure of 220 ° C. or more to cause decomposition, has recently attracted attention and has been actively researched and developed. There is a technique disclosed in Japanese Patent Publication No. 4225 (Japanese Patent Publication No. 1-38532).

That is, water under supercritical conditions can dissolve organic substances which are difficult to dissolve under normal pressure due to the change in polarization characteristics (thus, it becomes an excellent solvent), and water When an oxidizing agent such as oxygen or aqueous hydrogen peroxide coexists, these are also uniformly dispersed, and oxidative heat (combustion) of the organic substance occurs, and the decomposition reaction proceeds without additional input of combustion energy.

The degree of the decomposition is said to be, for example, 99.99% or more in the case of PCB, which is close to complete decomposition,
Also, since the reaction conditions are milder than the combustion conditions, no secondary harmful substances such as dioxin are generated, and the treatment of harmful organic substances has become a problem. This is a very promising processing technology.

The basic flow (Process) is shown in FIG.
As shown in FIG. 2, an organic substance-containing fluid (water) as an object to be treated is sent from a tank 1 through a shut-off valve 2 to a high-pressure pump 3 through a check valve 5 under pressure, and an oxidant fluid (as an example) Hydrogen peroxide solution is supplied from the tank 9 to the shut-off valve 10
Are sent under pressure via a check valve 13 by means of a high-pressure pump 11 as well, which merge into a preheater 6
Then, heating is performed by the heater 33 to reach the supercritical condition of water. As a result, the mixed fluid entering the high-pressure reactor 7 heats up due to the oxidation reaction of organic substances,
During this time, organic matter is mainly decomposed into water and carbon dioxide gas. Next, these decomposed products are cooled by the cooler 8 and separated by the gas-liquid separator 20.
Where it is separated into a gas and a liquid, and the gas is released from the pressure reducing valve 21 through the shutoff valve 22 to the atmosphere, while the liquid is discharged from the pressure reducing valve 23 through the shutoff valve 24 to complete a series of processes. .

[0007]

That is, although the basic flow of the supercritical water oxidation treatment method is disclosed as described above, its operation is described only in a steady state, and particularly in the treatment of harmful organic substances. In fact, hard and soft countermeasures against the abnormalities of the above system are hardly presented, and there is a risk that the gas-liquid separated liquid may be released to the environment without being decomposed.

Accordingly, the present invention is to provide a new pressurized fluid supply to the system when an abnormality occurs in the system by detecting the flow ratio of the fluid supplied to the system under pressure, the temperature and the pressure in the reaction vessel. An object of the present invention is to provide an apparatus for supercritical water oxidation of harmful organic substances having high safety by circulating an undecomposed fluid due to an abnormality, and a method of operating the same.

[0009]

The present invention comprises a preheater 6,
A reactor 7 for decomposing harmful organic substances with an oxygen-containing fluid under supercritical conditions of water, and a gas-liquid separator 20 for gas-liquid separation of decomposition products decomposed in the reactor 7 In the equipped supercritical water oxidation treatment equipment for harmful organic substances,
The following technical measures have been taken to achieve the above objectives.

That is, the device of the present invention according to claim 1 is:
A shut-off valve 19 is provided in front of the gas-liquid separator 20 so that the flow path to the gas-liquid separator 20 can be closed, and the flow path before the shut-off valve 19 and the preheater 6 A branch flow path for communicating with the inlet side flow path;
A safety stop circuit C provided with a branch shutoff valve 27 and a pump 28 for returning undecomposed harmful organic substances to the inlet side flow path of the preheater 6.
It is characterized by having.

The device according to the second aspect of the present invention is characterized in that the branch passage 26 of the safety stop circuit C is provided with a positive displacement pressure regulator 32 for adjusting the pressure of the passage. . The present invention according to claim 3 further comprises a preheater 6, a reactor 7 for decomposing harmful organic substances with an oxygen-containing fluid under water supercritical conditions, and a decomposer which is decomposed by the reactor 7. A gas-liquid separator 20 for gas-liquid separation of a product, and a shut-off valve 19 provided in front of the gas-liquid separator 20 to form a gas-liquid separator 20
And a branch flow path 26 that connects the flow path before the shut-off valve 19 and the inlet flow path of the preheater 6 is provided. A supercritical water oxidation treatment system for harmful organic substances (system) having a safety stop circuit C having a branch shutoff valve 27 and a pump 28 for returning undecomposed harmful organic substances to the inlet side flow path of the preheater 6. An operation method, in order to achieve the above object, a flow ratio of an oxygen-containing fluid and a harmful organic substance-containing fluid or a harmful organic substance to be fed under pressure to the system, and an inlet part, an intermediate part, and the reaction vessel 7, At least a part of the temperature of the outlet and the pressure of the system including the reaction vessel 7 are detected, and when any of them is reduced below a predetermined value,
The pressurized supply of new fluid to the system is stopped, the shut-off valve 19 reaching the gas-liquid separator 20 is closed, and the branch shut-off valve 27 is opened to preheat undecomposed harmful organic substances by the pump 28. It is characterized by refluxing to the inlet flow path of the vessel 6.

[0012]

The basic steady state operation of the present invention will be described with reference to FIG. 1. An aqueous solution containing a harmful organic substance (PCB as an example) to be treated passes through a shutoff valve 2 to a first aqueous solution.
It is pressurized by the pump 3 and is sent to the preheater 6 via the flow meter 4 and the check valve 5.

On the other hand, an oxidizing agent (for example, aqueous hydrogen peroxide) used for an oxidation reaction under supercritical water conditions is stored in a tank 9.
The pressure is increased by a second pump 11 via a shut-off valve 10 and supplied to a preheater 6 via a flow meter 12 and a check valve 13. In the preheater 6, a heat transfer medium for performing heat exchange with a cooler 8 described below is provided by a third pump 14.
Circulates from the pipe 15 through the pipe 16. A preheater 17 is provided in the pipe 16, and when the system is started, the heat transfer medium is heated by the preheater 17, and thus the preheater 6. Is heated so that the temperature of the mixed fluid flowing into the preheater 6 reaches the supercritical condition of water (374 ° C.), and the pressure thereof is controlled by the pressure reducing valve described later. Pressure).

The mixed fluid flows into the high-pressure reactor 7 while forming the above reaction temperature and pressure fields, and the harmful organic substances are oxidized by the oxidizing agent in the reactor 7 in a homogeneously dispersed state in a supercritical water solvent. A decomposition reaction occurs, and then flows into the cooler 8 to be radiated and cooled by the heat transfer medium described above.
8. The gas flows into the gas-liquid separator 20 through the closing valve 19. If the decomposition of harmful organic substances is carried out under insufficient conditions during the steady operation described above, it is discharged into the environment and causes a serious problem. A basic factor related to realization of the condition, that is, the temperature of the reactor 7 is detected by the thermometer 30 or 30A or 30B at the inlet, intermediate, or outlet of the reactor. Is detected by the pressure gauge 31 at the low temperature section (the pressure does not depend much on the detection location, and may be detected by the gas-liquid separator 20). Either of these temperature conditions or pressure conditions, or any of the flow ratios of the oxygen-containing fluid and the harmful organic-containing fluid (the flow ratios of the flow meters 12 and 4), which define the decomposition reaction of organic substances, have fallen below a predetermined value. At this point, the first and second pumps 3 and 11 are stopped to stop the pressurized supply of new fluid to the system, and the shut-off valve 19 (normally open) reaching the gas-liquid separator 20 is closed. On the other hand, by opening the branch closing valve 27 (normally closed),
By operating the pump 28, the undecomposed fluid is removed from the preheater 6,
It is circulated back to the system including the reactor 7 and the cooler 8, so that undecomposed harmful organic substances do not enter the gas-liquid separator 20 and are discharged to the environment.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below with reference to the drawings. In FIG. 1 showing the first embodiment, the main structure of the apparatus of the present invention is that a preheater 6, a reactor 7, a cooler 8 and a gas-liquid separator 20 are arranged in series and connected by a flow path. Have been.

The preheater 6 has harmful organic substances to be treated,
For example, a first pressurizing and feeding means A for pressurizing and feeding an aqueous solution containing PCB, chlorofluorocarbon, etc. is connected,
The pressurized feeding means A includes a first storage tank 1 and a first shut-off valve 2.
, A first pump 3, a first flow meter 4, and a first check valve 5 in series with the flow path. Further, the preheater 6 is connected to a second pressurizing and feeding means B for pressurizing and feeding an oxidizing agent used for an oxidation reaction under supercritical water conditions. Storage tank 9 for an oxidizing agent, for example, hydrogen peroxide, a second shut-off valve 10, and a second pump 11
, A second flow meter 12 and a second check valve 13 in series in the flow path.

Preferably, the first and second pumps 3 and 11 are high-pressure pumps.
When a gas such as air or oxygen is used as an oxidizing agent, a method of temporarily accumulating the pressure in an accumulator from a gas cylinder by a booster pump and then reducing the pressure by a pressure reducing valve can be adopted. In the preheater 6, a heat transfer medium for performing heat exchange between the preheater 6 and the cooler 8 is circulated by the third pump 14 from the pipe 15 through the pipe 16. Is provided with a pre-heater 17 so that the pre-heater 1
7 heats the heat transfer medium and, consequently, the preheater 6, so that the temperature of the mixed fluid flowing into the preheater 6 reaches near the supercritical condition of water (374 ° C.). The pressure is set by a pressure reducing valve described later so as to maintain the supercritical condition of water (220 atm).

The mixed fluid flows into the high-pressure reactor 7 while forming the above-mentioned reaction temperature and pressure fields, and harmful organic substances are oxidized by the oxidizing agent in the reactor 7 in a homogeneously dispersed state under a supercritical water solvent. A decomposition reaction occurs, and then flows into the cooler 8 and is radiated and cooled by the heat transfer medium described above (after reaching a steady state, the radiated heat is used for heating the preheater 6 and the preheater 17 does not need to operate. And cooler 1
8. The gas flows into the gas-liquid separator 20 via the third closing valve 19.

In the gas-liquid separator 20, gas (mainly carbon dioxide), which is a main product of decomposition, and liquid (mainly water) are separated, and the gas passes through the first pressure reducing valve 21 and the fourth closing valve 22. The liquid is also discharged to the storage tank 25 through the second pressure reducing valve 23 and the fifth shutoff valve 24 (in the case where the harmful organic substance contains chlorine such as PCB, for example, the liquid is particularly illustrated. However, an alkaline solution (eg, caustic soda) is added to the system under pressure to convert it into salt and water, and the salt can be removed from the gas-liquid separator 20 as a solid content and is desirable. In the configuration described above, a pipe 26 is further provided in a branch from a position short of the third shut-off valve 19, and the pipe 26 is connected to a high-pressure fourth pump 2 through a sixth shut-off valve 27.
8, a safety stop circuit C is provided so as to be recirculated before the preheater 6 through the third check valve 29.

However, if the decomposition of harmful organic substances is carried out under insufficient conditions, they are discharged into the environment and cause a serious problem. The basic factor involved in the realization, namely the temperature of the high-pressure reactor 7 is that the thermometer 30 or 30A at the inlet, middle or outlet of the reactor.
Alternatively, the pressure is detected by 30B, and the pressure is further detected by the pressure gauge 31 in the low-temperature portion before the preheater (the pressure does not depend much on the detection location, and may be detected by the gas-liquid separator 20). Either of these temperature conditions or pressure conditions, or any of the flow ratios of the oxygen-containing fluid and the harmful organic-containing fluid (the flow ratios of the flow meters 12 and 4), which define the decomposition reaction of organic substances, have fallen below a predetermined value. At the time, the first pump 3 and the second pump 1
1 to stop pressurized supply of new fluid to the system, and a third shut-off valve 1 reaching the gas-liquid separator 20.
9 (normally open) is closed, while branch closing valve 27 (normally closed)
And the high-pressure fourth pump 28 is operated to recirculate the undecomposed fluid to the system including the preheater 6, the high-pressure reactor 7, and the cooler 8, where undecomposed harmful organic substances are vaporized. It does not enter the liquid separator and is not discharged to the environment.

FIG. 2 shows a second embodiment in which harmful organic substances are supplied under pressure separately from water as a solvent. Water is supplied from a tank 1A to a shutoff valve 2A, a high-pressure pump 3A,
In the system of the check valve 5A, harmful organic substances are removed from the tank 1B through the shut-off valve 2B, the high-pressure pump 3B, the flow system 4B, the check valve 5B.
The system is supplied to the preheater 6 and the flow rate ratio between the oxygen-containing fluid and the harmful organic substance (the ratio between the flow meters 12 and 4B) is applied to the operation of the safety stop circuit.

In the case where the system is normalized after the safety stop is performed once, especially when the amount of the oxygen-containing fluid is short and the system is stopped, the same fluid is additionally supplied by operating the high-pressure pump 11 and the above-mentioned operation is performed. Although it is necessary to restart while performing the circulation recirculation operation, it is necessary to adjust the pressure of the closed circulation recirculation system by using a positive displacement (piston type) pressure as shown in FIG. According to the third embodiment in which the regulator 32 is installed, the pressure regulator monitors the pressure of the system with the pressure gauge 31 and is used for pressurizing to a supercritical pressure condition, or is closed during the safety stop. It can also be used for pressure reduction for avoiding excessive pressure rise in the circulation system, which is desirable.

The safety stop circuit and the safety stop method using the same according to the present invention exert a special effect on the oxidative decomposition of harmful organic substances under supercritical water conditions. Needless to say, the present invention can be similarly applied to the case where hydrolysis is carried out without using the method, or to the oxidative decomposition under subcritical water.

[0024]

According to the apparatus and method according to the present invention described above, during the oxidative decomposition treatment of harmful organic substances under supercritical water conditions, the discharge of hazardous substances to the environment due to inadequate decomposition conditions is prevented. And since it can be implemented safely including restarting, it is possible to respond to society's request to reduce harmful substances by promoting the application of supercritical water oxidation treatment to decompose harmful organic substances. Is extremely large.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing a first embodiment.

FIG. 2 is an overall configuration diagram showing a second embodiment.

FIG. 3 is an overall configuration diagram showing a third embodiment.

FIG. 4 is an overall configuration diagram of a conventional example.

[Explanation of symbols]

 6 Preheater 7 Reactor 8 Cooler 19 Shut-off valve 20 Gas-liquid processor 28 Pump 30 Thermometer 31 Pressure gauge

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Taku Aogata 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Inside Kobe Steel, Ltd.Kobe Research Institute (72) Inventor Satoshi Furuta Kobe, Hyogo Prefecture 1-5-5 Takatsukadai, Nishi-ku, Kobe Kobe Steel, Ltd. Kobe Institute of Technology (56) References JP-B Hei 1-38532 (JP, B2) JP-B 57-33320 (JP, B1) Hei 5-504093 (JP, A) WO 89/2874 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) A62D 3/00 B01J 3/00 B09B 3/00 C02F 1 / 74 C02F 11/08

Claims (3)

(57) [Claims] 1. A preheater (6) and under water supercritical conditions,
A reactor (7) for decomposing harmful organic substances with an oxygen-containing fluid; and a gas-liquid separator (20) for gas-liquid separation of decomposition products decomposed in the reactor (7). A supercritical water oxidation treatment apparatus for harmful organic substances, wherein a shutoff valve (19) is provided in front of the gas-liquid separator (20) so that a flow path to the gas-liquid separator (20) can be closed. And a branch flow path (26) connecting the flow path before the shut-off valve (19) and the input flow path of the preheater (6).
A safety shut-off circuit (C) provided with a branch shut-off valve (27) and a pump (28) in the branch flow path (26) to return undecomposed harmful organic substances to the inlet flow path of the preheater (6). A supercritical water oxidation treatment device for harmful organic substances, comprising: 2. A branch flow path (26) of a safety stop circuit (C).
And a positive pressure regulator (32) for adjusting the pressure of the flow path.
The supercritical water oxidation treatment apparatus for harmful organic substances according to claim 1, further comprising: 3. A preheater (6) and, under supercritical conditions of water,
A reactor (7) for decomposing harmful organic substances with an oxygen-containing fluid, a gas-liquid separator (20) for gas-liquid separation of decomposition products decomposed in the reactor (7), A shutoff valve (19) is provided in front of the separator (20) so as to close the flow path to the gas-liquid separator (20). The preheater (6)
A branch flow path (26) communicating with the inlet side flow path of the pump is provided in the branch flow path (26).
8) A method for operating a harmful organic matter supercritical water oxidation treatment system (system) equipped with a safety stop circuit (C) having a safety stop circuit (C) for refluxing undecomposed harmful organic matter to the inlet flow path of the preheater (6). And the flow ratio of the oxygen-containing fluid and the harmful organic substance-containing fluid or harmful organic substance to be pressure-fed to the system, and the temperature of at least a part of the inlet, the middle, and the outlet of the reaction vessel (7); The pressure of the system including the reaction vessel (7) is detected, and when any one of them falls below a predetermined value, the pressurized supply of a new fluid to the system is stopped and the gas-liquid separator is stopped. The shutoff valve (19) reaching (20) is closed, and the branch shutoff valve (27) is opened to return undecomposed harmful organic substances to the inlet flow path of the preheater (6) by the pump (28). Harmful organic matter How to operate the interfacial hydroxylation treatment equipment.