JPH07275871A - Supercritical water oxidation treatment method of harmful substance and apparatus therefor - Google Patents

Abstract

PURPOSE:To efficiently perform the supercritical water oxidation treatment of a harmful substance by performing the mixing of the harmful substance with an aq. soln. at the inlet of a reactor. CONSTITUTION:In the supercrifical water oxidation treatment of a harmful substance performing the decomposition treatment of the harmful substance under a supercritical condition of water using a supercritical water oxidation treatment apparatus equipped with a preheater 5, a reactor 6, a cooler 7 and a gas-liquid separator 25 and performing the gas-liquid separation of a decomposition product in the gas-liquid separator 25, an aq. soln. containing water as a main component is supplied to the preheater 5 to preheat the same to a supercritical state and the preheated aq. soln. and the harmful substance are mixed at the inlet of the reactor 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supercritical water oxidation treatment method and treatment apparatus for decomposing and detoxifying harmful substances, for example, harmful organic substances such as CFCs and PCBs, mainly by water under supercritical conditions. It is a thing.

[0002]

2. Description of the Related Art Conventionally, with regard to the decomposition treatment of organic substances, a decomposition treatment by microorganisms has been generally performed as a typical example of human waste treatment, but a large amount of sludge generated by the treatment is a problem. Therefore, methods have been studied to reduce it. The typical method is 200 to 3
Under the temperature of about 00 ° C and the hot water condition of about 100 atm,
Forcibly sending in air or oxygen as an oxidant,
This method is called a wet oxidation method that causes oxidative decomposition. This method has no particular problem in the case of general organic substances such as human waste, but harmful organic substances such as PCB
It has been said that there is a problem with the level of decomposition when applied to wastewater containing water.

As a means for further improving the problem relating to the degree of decomposition, supercritical water conditions (temperature: 374 °) are used.
The supercritical water oxidation method, in which an oxidant is caused to act at a temperature and pressure of 220 Cm or more) to cause decomposition, has been attracting attention in recent years and is being actively researched and developed, and one example thereof is JP-A-57- There is a technique disclosed in Japanese Patent No. 4225 (Japanese Patent Publication No. 1-358532).

That is, water under supercritical conditions can dissolve organic substances, which were difficult to dissolve under normal pressure, by virtue of the change in polarization characteristics (and thus become excellent solvents). When an oxidizing agent such as oxygen or hydrogen peroxide is allowed to coexist, these are also uniformly dispersed to generate an exothermic heat (combustion) of the organic matter, and the decomposition reaction proceeds without additional input of combustion energy.

The degree of decomposition is said to be 99.99% or more in the case of PCB, for example, which is close to complete decomposition.
In addition, since the reaction conditions are milder than combustion, the generation of secondary harmful substances such as dioxins does not occur, 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 (4), the organic substance-containing fluid (water) that is the object to be processed is delivered from the tank 61 to the preheater 5 under pressure by the high pressure pump 63 via the stop valve 62 and the check valve 64.
On the other hand, the oxidant fluid (hydrogen peroxide solution as an example) is sent from the tank 12 to the preheater 5 under pressure by the high pressure pump 14 via the stop valve 13 and also via the check valve 15, and these are heated by the preheater 5. While merging, here is the heater 65
Heating is performed to reach the supercritical condition of water. However, the mixed fluid that has entered the high-pressure reactor 6 heats up due to the oxidation reaction of the organic matter, and during this time, the organic matter mainly decomposes into water and carbon dioxide. These decomposed products are then cooled by the cooler 7.
The liquid is cooled in the gas-liquid separator 25, and is separated into gas and liquid, and the gas is released from the pressure reducing valve 26 to the atmosphere through the stop valve 27, while the liquid is released from the pressure reducing valve 28 to the stop valve 29.
After being discharged, a series of processing is completed.

[0007]

Regarding the supercritical water oxidation treatment method, the basic flow is disclosed as described above, but when decomposing harmful substances such as Freon and PCB, the decomposition reaction is performed. It is hard to say that the system configuration for mixing the reaction system at the reactor inlet for efficient promotion and heat exchange efficiency for effectively recovering energy has been disclosed so far. Is.

That is, many harmful substances such as CFCs are insoluble in water or hardly soluble in water. Further, when treating a gaseous toxic substance or performing an oxygen reaction in supercritical water using air or oxygen, the solubility in water is not sufficiently high. Therefore, when water, a gaseous or liquid harmful substance, and further a gas such as oxygen are supplied from the inlet of the preheater as in the prior art, the solubility of these substances in water is limited. Due to this, the mixing is not sufficiently performed, and the flow inside the preheater becomes a two-phase flow of gas-liquid or a mixed-phase flow of three phases of gas-liquid, and the flow is difficult to stabilize. There is a problem in that the efficiency of heat exchange to be performed becomes poor and, eventually, the stability during steady operation is impaired.

Therefore, an object of the present invention is to provide a more efficient supercritical water oxidation treatment method and treatment apparatus for harmful substances by mixing these substances at the entrance of the reactor.

[0010]

The present invention uses a supercritical water oxidation treatment apparatus equipped with a preheater 5, a reactor 6 and a cooler 7, and a gas-liquid separator 25 to superconduct water under supercritical conditions. In order to achieve the above-mentioned object, in the supercritical water oxidation treatment method for harmful substances, in which the harmful substances are decomposed and then the decomposition products are separated into gas and liquid in the gas-liquid separator 25, the following technical methods are provided. I am taking steps.

In the method of the present invention according to claim 1, an aqueous solution containing water as a main component is fed to the preheater 5 to be preheated to a supercritical state by the preheater 5, and the preheated aqueous solution and harmful substances are added. Are mixed at the inlet of the reactor 6. The method of the present invention according to claim 2 is characterized in that an oxygen-containing fluid is mixed with a harmful substance in the preheated aqueous solution at the inlet of the reactor 6.

The method of the present invention according to claim 3 is characterized in that the harmful substance is a gas. The method of the present invention according to claim 4 is characterized in that the oxygen-containing fluid is air or oxygen. The method of the present invention according to claim 5 is characterized in that the harmful substance which is the gas and / or the air or oxygen is preheated by direct heating.

The method of the present invention according to claim 6 is characterized in that the liquid after gas-liquid separation is circulated to the preheater. Further, the present invention includes a preheater 5, a reactor 6 and a cooler 7.
In addition, in the supercritical water oxidation treatment apparatus equipped with the gas-liquid separator 25, the following technical measures are taken to achieve the above-mentioned object.

The apparatus of the present invention according to claim 7 is provided with first feeding means A for feeding an aqueous solution containing water as a main component to the preheater 5 to preheat it to a supercritical state, and preheats it. The present invention is characterized by comprising a second feeding means B for feeding the harmful substance in order to mix the aqueous solution and the harmful substance at the entrance of the reactor 6. The device of the present invention according to claim 8 is characterized in that it is provided with a first circulation feeding means C for circulating a heat transfer medium for heat exchange between the preheater 5 and the cooler 7. Is.

The apparatus of the present invention according to claim 9 comprises a third feeding means D for the oxygen-containing fluid for mixing the oxygen-containing fluid together with harmful substances in the preheated aqueous solution at the inlet of the reactor 6. It is characterized by being present. The apparatus of the present invention according to claim 10 is characterized in that it is provided with a second circulation feeding means E that circulates the gas-liquid separated liquid to the preheater 5.

[0016]

According to the present invention, only water is supplied to the preheater 5 by the first feeding means A, while harmful substances and oxidizers (after being preheated by another system, if necessary) react with each other. The water is fed to the inlet of the vessel 6 by the second feeding means B, preheated to a supercritical state, and mixed with water discharged from the preheater 5.
In this supercritical state, water is a good solvent for many substances, and since it has a low viscosity and a large diffusion coefficient, these substances practically rapidly become a one-phase state near the entrance of the reactor 6, Moreover, it is in a sufficiently mixed state. In this state, the supercritical fluid mixture becomes homogeneous and the decomposition reaction proceeds. This makes it possible to suppress an undesirable phenomenon such as a change in the decomposition rate due to the uneven distribution of the concentration.
Moreover, since only water passes through the preheater 5, heat exchange with the cooler 7 can be stably and efficiently performed.

Further, when the harmful substance or the oxidizing agent is a gas, it can be preheated by direct heating by a heating element of an electric heating type instead of an external heating type, which is also preferable in terms of thermal efficiency.

[0018]

EXAMPLE An example of the present invention will be described below with reference to the drawings. In FIG. 1 showing the first example, the supercritical water oxidation treatment apparatus of the present invention comprises a flow type preheater 5 and It is mainly configured by connecting the high-pressure reactor 6 with the cooler 7 and the gas-liquid separator 25 in series by a pipe line.

A first feeding means A is connected to the preheater 5, and the means A comprises a storage tank 1, a shutoff valve 2 and a high pressure first means.
The pump 3 and the check valve 4 are provided, and the water in the storage tank 1 is pressurized by the first pump 3 via the stop valve 2 and then passes through the check valve 4 and the preheater 5 Will be sent to. Auxiliary feeding means A for the first feeding means A
1, the means A1 comprises a storage tank 8 for alkaline aqueous solution, a shutoff valve 9, a second pump 10 and a check valve 11.
And the like, and the alkaline aqueous solution in the storage tank 8 passes through the shutoff valve 9 like the water and the second pump 1
It is pressurized by 0 and sent to the preheater 5 via the check valve 11. This alkaline aqueous solution is used for the purpose of neutralizing acidic substances generated in the decomposition products.

In the preheater 5, a heat transfer medium for exchanging heat with the cooler 7 is circulated by the pump 20 from the conduit 21 to the conduit 22.
A pre-heater 23 is provided in the conduit 22 of the first circulation feeding means C.
Is provided, the heat transfer medium is heated by the preheater 23 at the time of system startup, and the preheater 5 is heated, and the temperature of the mixed fluid flowing into the preheater 5 along with it is close to the critical temperature of water. And the pressure is set by the pressure reducing valve described later so as to maintain the supercritical pressure condition of water. Reaction temperature and pressure field above (374 °
The fluid flows into the inlet of the high pressure reactor 6 while forming (C, 220 atm).

On the other hand, a second feeding means B for harmful substances is connected to the inlet of the reactor 6, and the means B is a storage tank 16, a shutoff valve 17, a third pump 18, a check valve. 1
9 is provided in the conduit. Therefore, harmful substances in the storage tank 16, such as CFCs and PCBs, are pressurized by the third pump 18 via the stop valve 17, and the check valve 1
It is fed to the inlet of the reactor 6 via 9 where the preheater 5
Is mixed with the water and / or alkaline aqueous solution that has come out. Inside the reactor 6, the harmful substance undergoes a decomposition reaction in a uniformly dispersed state in a supercritical water solvent, then flows into the cooler 7, and is radiatively cooled to the heat transfer medium described above (after reaching a steady state. Is used to heat the preheater 5 and the preheater 23 does not need to be operated), and the cooler 24
And then flows into the gas-liquid separator 25.

In the gas-liquid separator 25, the main components of decomposition are gas (mainly carbon dioxide) and liquid (mainly water).
The gas is discharged to the atmosphere through the pressure reducing valve 26 and the stop valve 27, while the liquid is discharged through the pressure reducing valve 28 and the stop valve 29. FIG. 2 shows a second embodiment of the present invention in which an oxidant is used for decomposing harmful substances, and for this purpose a storage tank 12, a shutoff valve 13, a pump 14, a check valve 15 and the like are provided. The third feeding means D is connected to the inlet of the reactor 6, and the other parts are common to those in FIG.

In this second embodiment, the oxidizer is pressurized from the storage tank 12 via the shut-off valve 13 by the third pump 14 and is fed to the inlet of the reactor 6 via the check valve 15. Here, in the same manner, the harmful substances supplied to the reactor 6 are mixed with the water and / or the alkaline aqueous solution coming out of the preheater 5. The harmful substance is decomposed and rendered harmless by the oxidation reaction in a uniformly dispersed state in the supercritical water solvent inside the reactor 6.

FIG. 3 shows a third example of the case where oxygen or air is used as an oxidant and a gaseous harmful substance is treated.
This is an embodiment, and the other components and functions are the same as those described above, so common reference numerals are given. In FIG. 3, oxygen or air is pressurized from a gas cylinder 40 via a valve 41 by a booster pump 42, and is temporarily accumulated via a check valve 43 in an accumulator 44 whose inside is insulated by a heat insulating member. Here, since oxygen or air is a gas, it can be directly heated by the heating element 54 by electric heating, and therefore the thermal efficiency for temperature rise is also good, and further, the water and / or the alkali discharged from the preheater 5 can be used. There is no excessive decrease in temperature when mixed with an aqueous solution. Then, oxygen or air heated to a predetermined temperature is supplied to the high pressure reactor 6 through the pressure reducing valve 45 and the check valve 46. The gaseous toxic substance in the gas cylinder 47 is similarly supplied to the reactor 6. Further, in FIG. 3, the liquid separated by the gas-liquid separator 25 passes through the filter 35, and is returned by the high-pressure pump 36 to the outlet of the discharge-side check valve 4 of the water high-pressure pump 3 through the check valve 37. The conduit 31 is also shown. That is, the second circulation feeding means E is provided.
This reduces the amount of fluid discharged to the outside, thus reducing the flow rate of the high-pressure pressure reducing valve 28, improving the life of the pressure reducing valve 28, and is also preferable in terms of heat recovery of the system.

[0025]

As described above, according to the present invention, when detoxifying harmful substances such as CFCs and harmful organic substances with water under supercritical conditions to render them harmless, it is possible to effectively mix the substances before the reaction. In addition, it is possible to perform heat exchange between the preheater and the cooler more effectively.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a first embodiment of the present invention.

FIG. 2 is an overall configuration diagram showing a second embodiment of the present invention.

FIG. 3 is an overall configuration diagram showing a third embodiment of the present invention.

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

[Explanation of symbols]

 5 Preheater 6 Reactor 7 Cooler 25 Gas-Liquid Separator A First Feeding Means B Second Feeding Means C First Circulating Feeding Means D Third Feeding Means E Second Circulating Feeding Means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B01D 53/70 C02F 11/08 ZAB (72) Inventor Satoshi Furuta 1 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo 5th-5th Kobe Steel Works, Ltd. Kobe Research Institute

Claims (10)

[Claims] 1. A supercritical water oxidation treatment apparatus equipped with a preheater (5), a reactor (6) and a cooler (7), and a gas-liquid separator (25) is used to supercritical water conditions. In the method for supercritical water oxidation of harmful substances, in which the harmful substances are decomposed and then the decomposition products are separated in the gas-liquid separator (25), the aqueous solution containing water as a main component is preheated. A hazardous substance characterized by being fed to a reactor (5) and preheated to a supercritical state by the preheater (5), and the preheated aqueous solution and a hazardous substance being mixed at the inlet of the reactor (6). Supercritical water oxidation method. 2. The method for supercritical water oxidation of harmful substances according to claim 1, wherein an oxygen-containing fluid is mixed with the harmful substances in the preheated aqueous solution at the inlet of the reactor (6). 3. The method for supercritical water oxidation of harmful substances according to claim 1, wherein the harmful substance is gas. 4. The supercritical water oxidation treatment method for harmful substances according to claim 2, wherein the oxygen-containing fluid is air or oxygen. 5. The method for supercritical water oxidation of a harmful substance according to claim 3, wherein the harmful substance that is the gas and / or the air or oxygen is preheated by direct heating. 6. The method for supercritical water oxidation of harmful substances according to claim 1, wherein the liquid after gas-liquid separation is circulated in a preheater. 7. A supercritical water oxidation treatment apparatus comprising a preheater (5), a reactor (6) and a cooler (7), and a gas-liquid separator (25), wherein an aqueous solution containing water as a main component is added. The reactor (6) is provided with a first feeding means (A) for feeding the preheater (5) to preheat it to a supercritical state.
And a second feeding means (B) for feeding the harmful substance for mixing at the entrance of the supercritical water oxidation device for harmful substance. 8. A first circulation feeding means (C) for circulating a heat transfer medium for heat exchange between the preheater (5) and the cooler (7). The supercritical water oxidation apparatus for harmful substances according to claim 7. 9. A third feed means (D) for the oxygen-containing fluid for mixing the oxygen-containing fluid with harmful substances in the preheated aqueous solution at the inlet of the reactor (6). The supercritical water oxidation treatment apparatus for harmful substances according to any one of claims 7 and 8. 10. The second circulation feeding means (E) for circulating the gas-liquid separated liquid to the preheater (5), according to any one of claims 7 to 9. Supercritical water oxidation equipment for harmful substances.