JP3437408B2 - Supercritical water oxidation method and apparatus - Google Patents

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 method and apparatus, for example, an acid in a fluid generated by a decomposition reaction of hardly decomposable waste / waste liquid or waste / waste liquid containing harmful substances. The present invention relates to a supercritical water oxidation method preferably used when a substance to be contained is to be decomposed and a supercritical water oxidation apparatus used for the method.

[0002]

2. Description of the Related Art Conventionally, there has been a technology for completely decomposing substances that cause problems when discharged into the environment, such as hardly decomposable wastes / liquids and wastes / liquids containing harmful substances, and disposing as safe substances. A supercritical water oxidation method that has been sought and is suitable for completely decomposing these wastes and waste liquids has been proposed (for example, Japanese Patent Publication No. 1-38532).

This is because, in the conventional combustion method performed in an incinerator, there is a possibility that a highly toxic substance such as dioxin may be generated in the decomposition of a chlorine compound due to insufficient decomposition due to generation of a partial low temperature part. However, while there is a problem that harmful substances diffuse because the combustion gas is released to the atmosphere, supercritical water oxidation is performed under supercritical water conditions (temperature of 374 ° C or higher and pressure of 22 MPa or higher). ) Is a method of completely decomposing organic matter to be decomposed into water and carbon dioxide by using supercritical water as a medium for the decomposition reaction, and thermal decomposition, hydrolysis and oxidative decomposition proceed at the same time. This is because it is excellent not only in achieving a large reaction rate, but also in being able to completely decompose in a closed system.

That is, in the supercritical water oxidation method, the critical condition of water is, that is, the critical temperature is 374 ° C. and the critical pressure is 22 MPa.
Water under supercritical conditions (supercritical water) can have its polarity controlled by temperature and pressure, and can also dissolve non-polar substances such as paraffinic hydrocarbons and benzene, and can be used with any gas such as oxygen. It exhibits extremely excellent characteristics as a reaction solvent for oxidative decomposition of organic substances, which is mixed in a single phase in proportion, and if the carbon content of the decomposition target is several%, it is possible to raise the temperature above the critical temperature only by heat of oxidation. Therefore, it is extremely excellent in terms of thermal energy, and in particular, most hardly decomposable organic substances and harmful organic wastes can be completely decomposed by appropriately controlling the hydrolysis reaction or thermal decomposition reaction in supercritical water. It is extremely suitable for the decomposition treatment of harmful organic substances because it has an extremely excellent action and can be treated in a closed system.

As a proposal of such a supercritical water oxidation treatment technique, for example, Japanese Patent Publication No. 1-38532, which discloses the principle and basic flow, is known. In the method disclosed therein, the decomposition target is pressurized by a feed pump, mixed with supercritical water by an ejector, and heated,
It is introduced into the reactor. In the reactor, high-pressure air from the air compressor is introduced as an oxidant to carry out oxidative decomposition.
Part of the treated supercritical water is recycled to the ejector,
The remaining part is used for energy recovery. However, the details of the reactor are not shown in this document, and there is only a description that tubular, cylindrical, and fluidized beds can be adopted.

In Japanese Patent Publication No. 3-500264, a reactor used for supercritical water oxidation is a tubular type as a reactor type suitable for decomposition of waste liquid containing no inorganic salt or inorganic salt-producing substance. The use of a reactor is disclosed, and also
As a reactor type suitable for decomposing an organic waste liquid containing an inorganic salt or mediating the addition of a neutralizing agent to produce an inorganic salt after the reaction, a so-called vessel type vertical cylinder type A reactor is disclosed.

By the way, one of the main decomposition products to be treated by supercritical water oxidation is persistent organic substances and harmful organic substances, and most of them contain chlorine, sulfur, nitrogen or phosphorus. , When these substances are supercritically hydroxylated, they often produce acids (hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid), so neutralize these acids with alkali as a measure against acid corrosion to protect the reactor materials. It is suggested to do the operation. However, it is known that an inorganic salt such as NaCl generated by this neutralization operation is hardly dissolved in supercritical water and has high adhesion to the wall surface of the pipe.

This means that when a substance containing a high concentration of atoms such as chlorine, sulfur, nitrogen and phosphorus is treated by the supercritical water oxidation method, a neutralization treatment is necessary to prevent acid corrosion. However, this means that a solution of the problem that the neutralized salt produced as a result of the neutralization treatment causes blockage of the reactor or discharge system pipeline is required. Therefore, as a method of solving this problem, in the proposal of the above-mentioned Japanese Patent Publication No. 3-500264, a means for supplying / discharging subcritical water is provided at the bottom of the vessel of the vessel type to generate it by the reaction of supercritical water oxidation. The acid is neutralized with an alkali to form a salt, and by taking advantage of the heavy specific gravity of this salt, it is dropped into the above-mentioned subcritical water to separate it from a fluid with a low specific gravity (supercritical water, volatile gas, etc.) We propose a method of discharging in.

As described above, in the vessel type reactor, a supercritical zone is formed in the upper part of the vessel reactor and a subcritical zone is formed in the lower part of the vessel reactor, and the particles are deposited in the reactor and moved downward due to the difference in density. Since it is a method of dissolving the inorganic salt in water for salt transfer in the subcritical zone and discharging it, the discharge system from the reactor has a decomposition product fluid (water from the upper part of the reactor and a volatile gas) There are two discharge systems, one for the supercritical water, a mixture of excess oxygen, carbon dioxide and nitrogen) and one for the brine stream (water for salt transfer containing inorganic salts such as sodium chloride) from the bottom of the reactor. Heat recovery, cooling, and depressurization steps are required for each discharge system, which complicates the apparatus configuration and increases equipment investment. In addition, there is a problem in that control and maintenance are more complicated than when a tubular reactor is used.

Further, in the vessel-type reactor, there is a problem that an inorganic salt such as sodium chloride adheres to the inner wall of the reactor, so that an additional device such as a scraper for scraping it off must be provided.

[0011]

As described above, the technique of supercritical water oxidation is an effective technique for the decomposition treatment of organic substances, but mainly the acid represented by hardly decomposable organic substances and harmful organic substances is used. Oxidative decomposition treatment of the decomposition target including the generated substance,
There is a further problem to be solved in order to be able to carry out the process on an industrial scale in consideration of cost and durability of the device.

The inventors of the present invention have made earnest researches in view of the above-mentioned circumstances, and completed the present invention.

That is, one of the objects of the present invention is to ensure the neutralization of the acid generated by supercritical water oxidation, so that the equipment can be protected from acid corrosion and the treatment excellent in safety and durability can be performed. An object is to provide a supercritical water oxidation method that can be realized and an apparatus used therefor.

Another object of the present invention is to prevent the above-mentioned problem of acid corrosion of the equipment by the reliable neutralization and to solve the problem that the salt produced by the neutralization adheres to the inner wall of the reactor or the discharge system pipeline. It is an object to provide a supercritical water oxidation method and an apparatus used therefor.

Still another object of the present invention is to prevent the salt formed by the neutralization reaction from adhering to the wall surface of the reactor or the discharge system pipeline, thereby making it possible to produce an acid-producing organic substance, particularly a difficult-to-decompose substance. It is an object of the present invention to provide a supercritical water oxidation method capable of efficiently decomposing volatile organic substances and harmful organic substances at low cost, and an apparatus used therefor.

[0016]

The above-mentioned objects can be achieved by the inventions of the respective claims described in the claims of the present application.

The invention of the supercritical water oxidation method according to claim 1 of the present invention continuously supplies the decomposition target into a vertical cylindrical reactor in which a supercritical water atmosphere having a temperature and pressure above the critical point of water is formed. The acid generated by oxidative decomposition in the presence of supercritical water
In a supercritical water oxidation treatment in which a fluid containing chemical decomposition products is continuously discharged from a discharge pipe connected to the vertical tubular reactor, and an acid group contained in the fluid is neutralized with a neutralizing agent, the discharge is performed. tube
In the road, the criticality of water , where there is virtually no acid corrosion due to acid groups
Contains decomposition products while maintaining a high temperature above the temperature
Neutralizer is added to the fluid, and during or immediately after the addition
In the temperature range where the neutralization salt is sufficiently dissolved.
Characterized in that was.

[0018]

[0019]

The present inventors arrived at each of these inventions as follows. That is, in the conventional supercritical water oxidation treatment involving the generation of acid, the neutralizing agent was supplied from the starting end of the reactor together with the decomposition target and supercritical water.
This is because in the supercritical water oxidation reaction in which an acid is produced by the reaction, it is considered necessary to perform neutralization in the reaction region in order to protect the reactor.

However, when the inventors of the present invention repeated the research with variously changing the conditions of supercritical water oxidation, it was found that pinholes were generated not in the reactor but in the discharge system pipeline of the fluid produced by decomposition. Further observation and analysis of the situation revealed that the problem of acid corrosion is different from the conventional technical understanding that the temperature of the fluid produced by supercritical water oxidation occurs at the cooling stage rather than in the reactor. ， I found a phenomenon. It was presumed that this phenomenon occurred based on the following reaction mechanism. In other words, the acid groups (for example, halogens) in the product fluid decomposed by supercritical water oxidation are free in supercritical water and have no or extremely weak action of corroding the wall surface of the reactor as an acid. When the decomposition product fluid is cooled and supercritical water undergoes a phase transition to liquid (water), its free acid groups are rapidly dissolved in the liquid to locally increase the acid concentration, causing the action of high-concentration acid. Therefore, it is considered that the walls of the reactor are corroded. Therefore, the present inventors have re-examined the neutralization operation of the generated acid from a viewpoint different from the conventional technical understanding that the reactor was considered to be in the most severe acid corrosive environment. Since the addition is in order to prevent corrosion due to acid, based on the fact that the present inventors have found, if the acid group is dissolved in the liquid to cause a problem of acid corrosion, if the neutralization reaction is performed. It is often understood that the neutralization reaction in the reactor is not always essential. On the other hand, the neutralization salt is generally insoluble in high-temperature supercritical water and has strong adhesiveness. Therefore, the salt produced by the neutralization reaction can be sufficiently dissolved, and the acid formed by the acid group If the neutralization reaction can be performed without corrosion problems,
In addition to preventing corrosion due to acid, the problem of salt adhesion leading to blockage of the pipeline can be effectively eliminated. The inventors of the present invention have made the above-described inventions by repeating tests that technically demonstrate such points of interest.

In each of the above inventions, it is important to maintain the inside of the vertical cylinder type reactor in a supercritical atmosphere to sufficiently supercritically oxidize an object to be decomposed, and as a result of the reaction, it is decomposed. After discharging the produced fluid to the discharge line, it is important to add the neutralizing agent in the middle of the discharge line.

According to the first aspect of the invention, this addition causes the produced fluid to be "at a temperature at which there is substantially no acid corrosion due to an acid group and the neutralized product salt is sufficiently dissolved."
To be done. In the present specification, the term "acid group" does not constitute a so-called acid group by its atom alone in addition to halogen such as chlorine which produces hydrochloric acid, but it produces an acid such as sulfuric acid, nitric acid or phosphoric acid. It contains sulfur, nitrogen, phosphorus, etc.

Typical organic substances to be decomposed containing such substances are persistent organic pollutants (POPs: Persistent O 2).
rganic Pollutants) or Persistent Toxic Bio-accumlatives (PTBs. These are generally persistent substances. In addition to these, halogen compounds such as organic bromine compounds, sulfur compounds, nitrogen compounds, phosphorus compounds and the like are also included.

The above-mentioned "state of temperature at which there is substantially no acid corrosion" refers to a temperature range above the critical temperature (374 ° C.) at which supercritical water undergoes a phase transition to liquid (water). In consideration of temperature fluctuations in
It is preferable that the temperature is not lower than ° C, preferably not lower than 450 ° C.
The "state of temperature at which the salt produced by neutralization is sufficiently dissolved" is not the same depending on the type of salt produced, and therefore cannot be uniformly set as the temperature limit. For example, when the salt is sodium chloride, 500 ° C, The solubility in supercritical water of 25 MPa is about 100 ppm, while the solubility in supercritical water below about 450 ° C. is on the order of several%. Therefore, when a neutralizing agent that produces sodium chloride is used as a salt, the temperature state of the decomposition product fluid to which the neutralizing agent is added is generally 374 to 450 ° C, preferably 400 to 450 ° C. It is often appropriate to do this. "Sufficiently dissolved" means that salt can be prevented from adhering to the wall surface or the like and causing the problem of clogging. When another type of salt is produced, the temperature at which the salt is sufficiently dissolved is set as the upper limit of the temperature state (range) as described above.
The temperature range in which such other types of salts are sufficiently dissolved can be determined by conducting tests as necessary. As the neutralizing agent that can be used in the present invention, alkali hydroxides such as sodium hydroxide and potassium hydroxide can be typically mentioned, but the neutralizing agent is not limited thereto. It is generally preferred to make the addition in the form of an aqueous solution.

The invention described in claim 1, the addition of Neutralization agents,
One of the features is that it is performed on a high temperature fluid (decomposition product fluid) in which the solubility of the salt produced by the neutralization reaction is low (almost not dissolved). For example, when the salt formed is sodium chloride, the reaction temperature (for example, 500 ° C. or higher) to 4
The neutralizing agent is added within the range of 50 ° C. The addition of the neutralizing agent is carried out in the discharge pipe line so as not to affect the complete decomposition of the decomposition object by the supercritical water oxidation. Further, the temperature of the decomposition product fluid immediately after addition of the Neutralization agent, and another wherein the cooling to the salt produced by the neutralization reaction at a temperature that can sufficiently dissolve. For this cooling, a method of lowering the temperature of the produced fluid by using a low temperature aqueous solution as a neutralizing agent to be added or a method of lowering the temperature by using a cooling means is exemplified. The temperature after lowering may be higher or lower than the critical temperature.

Furthermore feature of the invention of claim 1, the addition of Neutralization agent, a temperature is high solubility of the salt produced in the neutralization reaction, and the fluid (decomposition products in the temperature range higher than the critical temperature Fluid) .

In the above-mentioned structure of the invention of claim 1, in the supercritical water atmosphere, the organic substance, which is usually an object of decomposition, the supercritical water and the oxidizing agent are supplied to the reactor under a pressure higher than the critical pressure (22 MPa). By doing so, the organic substance to be decomposed is formed at a critical temperature (374 ° C.) or higher, and this can be performed by using a conventionally known technique of a supercritical water oxidation method using a so-called Bessel type reactor. . However, in the present invention, a supercritical atmosphere is maintained throughout the reactor. The supercritical water may be supplied separately from the decomposition target or may be mixed and supplied. When the decomposition target contains a required amount of water and the supercritical water atmosphere can be maintained by self-combustion of the decomposition target, supercritical water may be supplied only at the beginning of the reaction. The supercritical water atmosphere can also be formed by a method in which supercritical water is not supplied to the reactor.

Examples of this method include a method in which a heating element such as an electric heating coil is arranged around a vertical cylindrical reactor, and heating is performed from around the reactor to apply heat to the inside of the reactor.

According to this method, the organic substance which is the decomposition target, the oxidant, and water when the decomposition target does not contain the required amount of water are supplied to the reactor and installed around the reactor. It is possible to heat the inside of the reactor by transmitting heat from the heating element, and to make the inside of the reactor a supercritical water atmosphere.
If supercritical water oxidation can be maintained by self-combustion of the decomposition object, heat is applied from the heating element only at the beginning of the reaction, and heat supply from the heating element may be interrupted after the self-combustion is sufficiently continued. it can. The decomposition target organic matter and the like can be preheated and supplied as necessary. As the oxidant, in addition to air and oxygen gas, a liquid phase oxidant such as hydrogen peroxide solution can be used.

The apparatus type for carrying out each of the above inventions may be a vertical cylinder type so-called Bessel type reactor,
Generally, a system of supplying the decomposition target, supercritical water and an oxidant from the upper center of the container is used, but a system of installing a heating element as described above may be used.

The operation of adding the neutralizing agent to the fluid flowing through the discharge pipeline is carried out by, for example, connecting the neutralizing agent aqueous solution pressurized to the supercritical pressure set for the reaction to the discharge pipeline. It can be performed by injecting through the injection pipe.

The supercritical water oxidation method of the present invention uses the critical pressure and the critical temperature (22) for completely decomposing an object in a supercritical water atmosphere.
MPa, 374 ° C.). However applied without being limited as long even for the Ru is carried out at conditions beyond, decomposing the hardly decomposable substance present invention method is particularly preferably applied by supercritical water oxidation In general, the conditions are as follows:
It is often appropriate that the reaction pressure is 0 ° C or higher, preferably 600 to 650 ° C, and the reaction pressure is 22 to 50 MPa, preferably 22 to 25 MPa. Reaction time is 1 to 1
It is 0 minutes, preferably about 1 to 2 minutes.

According to each of the above inventions, since the salt formed after the injection (addition) of the neutralizing agent is sufficiently dissolved in supercritical water or water, there is no risk of sticking to the wall surface of the discharge pipeline. Therefore, it is possible to substantially eliminate the risk of blockage of the pipeline, and there is no risk of acid corrosion of the reactor.

According to a second aspect of the present invention, in the above-mentioned first aspect , the salt produced by the addition of the neutralizing agent is sodium chloride, and the temperature of the fluid flowing through the discharge pipe at the time of adding the neutralizing agent is 450. ℃ characterized in that or more, of the invention of claim 3, in the invention described in claim 1, a salt generated by addition of a neutralizing agent is sodium chloride, neutralizer fluid flowing in the discharge pipe The temperature at the time of addition is 450 ° C. or less.

According to these inventions, the most representative sodium hydroxide can be used as the neutralizing agent to carry out the operation of the neutralization reaction. It can be applied when performing critical water oxidation.

The invention of claim 4 is characterized in that, in each of the above inventions, the neutralizing agent to be added is an aqueous solution at a low temperature (for example, room temperature).

According to the present invention, the temperature of the decomposition product fluid can be lowered by adding the neutralizing agent aqueous solution, and the salt is sufficiently dissolved depending on the addition position and the temperature of the fluid before the addition. In some cases, the temperature of the fluid can be lowered to the temperature, and other cooling means such as a heat exchanger can be omitted.

The invention of claim 5 is characterized in that, in each of the above inventions, the decomposition product fluid is cooled to below the critical temperature of water after the neutralization reaction.

According to the present invention, the temperature of the decomposition product fluid is lowered to the critical temperature or lower after the acid is surely converted to the salt by the neutralization reaction, so that the cause of the corrosion near the critical temperature is removed.

The invention of the supercritical water oxidation apparatus of claim 6 is a contract
A device for use in the method of claim 1, comprising a reactor for a supercritical water oxidation reaction , which comprises a vertical cylindrical pressure-resistant container, and a decomposition target and a decomposition target for continuously supplying an oxidant into the reactor. A means for supplying an oxidant, a discharge pipe line connected to discharge the fluid decomposed and produced by the reaction of supercritical water oxidation from the reactor to the outside of the reactor, and a fluid flowing in the discharge pipe line. And a neutralizing agent addition means provided in the middle of the discharge pipe line for neutralizing the acid groups contained in.

In the above-mentioned structure, the reactor can desirably be composed of, for example, an acid-corrosion-resistant alloy (for example, Inconel or the like having excellent oxidation resistance at high temperature).
The neutralizing agent adding means is provided by connecting the discharge system pipeline to the peripheral wall of the tube so as not to adversely affect the reaction of supercritical water oxidation. The neutralizing agent is preferably used in the form of an aqueous solution, but is not limited thereto. For example, a pressurizing system such as a high-pressure press-fitting pump is used to press the neutralizing agent into the reactor from the neutralizing agent tank, or the reaction vessel. It can be press-fitted from a tank pressurized to a pressure higher than the inside. An on-off valve, a flow rate control valve, etc. may be provided in the system path to which the neutralizing agent is added, and a concentration adjusting device for the neutralizing agent may be provided.

The organic substance to be decomposed, the oxidant, etc. are usually supplied from the central part of the reactor using a nozzle or the like, and the supply system for the substance to be decomposed excluding the neutralizing agent addition means, the decomposition product fluid. The exhaust system and the like can be configured in the same manner as the conventionally known supercritical water oxidation apparatus.

According to the present invention, the treatment by supercritical water oxidation of a hardly decomposable substance, which is accompanied by the formation of salt, can be carried out without causing problems such as clogging of the discharge pipe line and acid corrosion.

According to a seventh aspect of the present invention, the position of the neutralizing agent addition means provided in the middle of the discharge pipe line in the above invention of the apparatus is the flow rate.
Acid corrosion by acid groups contained in the body, characterized in that a substantially such have position.

According to the present invention, the neutralizing agent adding means can be provided at an appropriate position in the temperature distribution determined along the distance from the starting end of the discharge pipe according to the setting of the decomposition target and the processing operation. It

According to an eighth aspect of the invention, in the invention of the sixth aspect , the position of the neutralizing agent addition means provided in the middle of the discharge pipe line is
Water with low solubility of the neutralization salt (almost insoluble)
A neutralizing agent added at a position where a fluid having a temperature equal to or higher than the critical temperature flows, and the neutralizing agent to be added is a low temperature aqueous solution capable of cooling the temperature of the fluid to a temperature at which the salt for neutralization is sufficiently dissolved. Characterize.

According to the present invention, as in the case of the above-mentioned claim 7 , the neutralizing agent adding means can be provided at an appropriate position of the temperature distribution determined along the distance from the starting end of the discharge pipeline. Simultaneously with or immediately after the addition of the low temperature neutralizing agent aqueous solution, the salt reaches a temperature at which it can be sufficiently dissolved. The position is the start end of the discharge pipe or the end of the discharge pipe. When the salt produced is sodium chloride, the temperature of the decomposition product fluid is generally the reaction temperature to 450 ° C., preferably 500. ~ 450
The position is ℃.

According to a ninth aspect of the present invention, the vertical cylindrical reactor of each of the above inventions has a supply port for the decomposition target and the oxidant as a supply part, and a discharge part as a result of a supercritical water oxidation reaction. It is characterized by having only one discharge port for discharging the generated fluid to the discharge pipe line.

According to the present invention, since the conventional salt transfer water supply path and salt discharge water path are not provided, the structure of the apparatus is simplified and the control is facilitated.

According to a tenth aspect of the present invention, in each of the above-mentioned apparatus inventions, a cooling means for cooling the flowing fluid is provided at the position where the neutralizing agent adding means is provided or at the subsequent discharge pipe line. Characteristically, according to the present invention, the decomposition product fluid is cooled by the cooling means to ensure the neutralization of the acid and the dissolution of the produced salt in water.

[0052]

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1 FIG. 1 shows a schematic configuration of an apparatus for carrying out the method of the present invention, in which 1 is a so-called Bessel type reactor,
The vertical cylindrical pressure-resistant container is made of a high-temperature and acid-resistant material. A double pipe nozzle 2 is attached to the center of the ceiling of the reactor 1, and an object to be decomposed such as an organic waste liquid pressurized from the waste liquid supply pipe 3 to a critical pressure (22 MPa) or higher of water. Is blown into the reactor 1 through the inner tube of the double tube nozzle 2, and a mixed fluid of supercritical water and air as an oxidant from the supercritical water supply tube 4 passes through the outer tube of the double tube nozzle 2. It is designed to be blown into the reactor 1. As a result, the liquid (waste liquid + supercritical water + air) blown from the double pipe nozzle 2 becomes a mixed fluid under a supercritical pressure of 22 to 25 MPa, and at 600 to 650 ° C., for example, due to the oxidation of organic matter in the waste liquid. Continue supercritical hydroxylation reaction. If the organic waste liquid contains a necessary amount of water and the supercritical water atmosphere can be maintained by the heat of oxidation of the organic matter in the waste liquid, supercritical water is supplied only at the beginning of the reaction, and thereafter, the supercritical water is supplied. It does not have to be supplied. Further, the waste liquid supply pipe 3 may be provided with a preheater (not shown) for heating the supplied fluid (waste liquid) to a predetermined temperature (for example, about 400 ° C.) in advance. The fluid supplied from each of the supply pipes 3 and 4 is pressurized using an appropriate device (not shown).

Reference numeral 5 is a discharge pipe for discharging from the reactor 1 a fluid generated by decomposition in the supercritical water oxidation reaction (hereinafter referred to as "treatment fluid"), which is made of an acid resistant material, for example, in the reactor 1. The processing fluid, which is connected to the ceiling from the ceiling and is completely decomposed by the supercritical water oxidation reaction in the reactor 1, is discharged to the outside of the reactor 1 through the discharge pipe 5.

In the middle of the discharge pipe 5, a neutralizer supply pipe 6 from a neutralizer tank and a pressurizing means (neither is shown) is used to discharge the neutralizer such as sodium hydroxide. 5 is connected so as to inject (add) to the processing fluid flowing through the inside of the processing fluid 5, whereby a neutralizing agent is injected and added to the processing fluid, so that the acid group contained in the processing fluid is The sum is done.

The temperature of the treatment fluid in the portion to which the neutralizing agent is added needs to be a temperature above which the acid group does not cause a corrosive action as an acid, and theoretically, above the critical temperature of water, Considering the temperature fluctuation of the apparatus, the temperature is set to 400 ° C or higher, which is higher than the critical temperature to some extent, and when the inorganic salt generated by the addition of the neutralizing agent is sodium chloride, the reaction temperature may be set to 450 ° C. it can. When the temperature of the treatment fluid after the addition of the neutralizing agent exceeds 450 ° C., immediately after the addition of the neutralizing agent, the temperature of the treatment fluid is adjusted to 450 ° C. or lower which is a temperature range in which the solubility of sodium chloride is high. . To lower (cool) the temperature of such a treatment fluid, a cooling means such as a heat exchanger can be used, but the simplest is to use a low temperature aqueous solution as a neutralizing agent and add a predetermined amount of this. As a result, the temperature of the processing fluid may be lowered.

As described above, the neutralization of the acid groups is already completed at the time when the temperature of the treatment fluid is lowered to around the critical temperature of water, whereby the water undergoes a phase transition from supercritical water to liquid. It is possible to prevent generation of a high concentration of acid due to rapid dissolution of the acid group in water.

The treatment fluid which has undergone the neutralization reaction of the acid groups is subjected to necessary treatments such as cooling, decompression and gas-liquid separation, and then discharged to the outside of the apparatus.

[0058]

EXAMPLES Examples and comparative examples conducted to confirm the effects of the present invention will be described below.

Example 1 Using the supercritical water oxidation apparatus having the vessel-type reactor 1 of FIG. 1 described above, the materials consisting of the components shown in the following Table 1 including the materials that produce salts with supercritical water oxidation A discharge pipe 5 for discharging the processing fluid from the reactor 1
The supercritical water oxidation was carried out by a method of adding a neutralizing agent (sodium hydroxide aqueous solution) from a predetermined position (between TC-6 and TC-7 in FIG. 2).

[0060]

[Table 1]

The conditions for supercritical water oxidation are as follows.

(Test conditions) Temperature / pressure: 650 ° C., 25 MPa Oxidizing agent: Air reactor: Vessel type reactor shown in FIG. 1; Inner diameter 50 mm × height 1050 mm Neutralizer: Sodium hydroxide aqueous solution, concentration 530
ppm (about 1.2 times the molar amount of Cl ⁻ ions generated when trichlorethylene is completely decomposed), temperature 20 ° C., addition amount 9.6 ml / min Flow rate (SCW): 8 ml / min (sample): 2 ml / min ( Air): 1.6 Nm ³ / hr (1.8 times the theoretical amount required for 100% decomposition of the decomposition target of the sample).

(Test Results) (1) The test was carried out for 600 minutes under the above test conditions, but the pressure inside the reactor 1 did not rise, and continuous tests could be carried out. Also, the reactor 1 and the discharge pipe 5
The temperature distribution was investigated and the measurement points and temperatures are shown in FIG. The temperature distribution was measured by inserting thermocouples into the reactor.

(2) While the temperature of the treatment fluid before the addition of the neutralizing agent aqueous solution is 621 ° C. at the TC-6 position,
It is 288 ° C. at the position of TC-7 after the addition. As a result, by adding the neutralizing agent aqueous solution to the treatment fluid in a high temperature state where the acid group does not have an acid corrosive action and the solubility of the salt is low, the treatment fluid is rapidly lowered to below the critical temperature of water. It can be seen from (3) that salt was dissolved in water and discharged without adhering to the inner wall of the pipe. Further, it was confirmed that no pinhole was formed in the pipe in the vicinity of TC-6 to TC-7 even after repeating the test, and the corrosion by the acid was sufficiently prevented.

[0065] (3) the component contained in the reactor is discharged from the process fluid (treatment solution), was determined by gas chromatography GC-311 (HNU SYSTEMS Co., photoionization detector), also, Cl ^- , Na ⁺ ions were measured by using ion chromatography DX-AQ (manufactured by Nippon Dionex Co., Ltd.) and the results are shown in Table 2 below.

[0066]

[Table 2]

As can be seen from the results shown in Table 2, trichlorethylene in the sample (decomposition object) was substantially completely decomposed.

Further, the pH calculated from the Cl ⁻ ion concentration of the treatment liquid is 2.9, whereas the pH of the treatment liquid is 6.1, and the hydrochloric acid produced by supercritical water oxidation is sodium hydroxide. It was confirmed that it was neutralized by. It should be noted that the treatment liquid having a pH of 6.1 is due to the dissolution of carbon dioxide.

Next, the recovery rate of Na ⁺ ions was determined from the Na ⁺ ion concentration in the treatment liquid by the following formula.

[0070]

[Equation 1]

As a result of this calculation, the recovery rate of Na ⁺ ions was 101%, which means that Na ⁺ ions that did not contribute to the neutralization reaction flowed together with the treatment liquid (decomposition product fluid). It was confirmed that precipitation of salt did not occur in the vessel and discharge system pipeline.

Comparative Example 1 Next, for comparison, as shown in FIG. 3, a structure in which subcritical water for salt transfer is supplied to and discharged from the bottom of the vessel-type reactor 101, that is, a pure water supply pipe 107. A treatment liquid (brine) drain pipe 108 is connected, each supply line of a waste liquid supply pipe 103, a supercritical water supply pipe 104, and an air supply pipe 109 is connected to a double pipe nozzle 102 of a reactor 101, and
The neutralizing agent was subjected to supercritical water oxidation by a conventional supercritical water oxidation apparatus which was mixed with supercritical water and supplied.

The sample of the decomposition object used in the test is
The same trichlorethylene (TCE) as in Example 1 was dissolved in a water-isopropyl alcohol (IPA) mixed solution and supplied at 135 g / hr.

The conditions for supercritical water oxidation are as follows.

(Test conditions) Temperature / pressure: 650 ° C., 25 MPa Oxidizing agent: Air reactor: Vessel type reactor shown in FIG. 3; Inner diameter 50 mm × height 1050 mm Neutralizer: Sodium hydroxide aqueous solution (trichloroethylene is completely (Molecular amount equivalent to Cl ⁻ ion generated upon decomposition) is mixed with supercritical water, and supply flow rate (SCW): 150 liters / hr Flow rate (IPA): 41.5 liters / hr IPA concentration: 20.4% ( Air): 1.5 Nm ³ / hr (1.5 times the theoretical amount required for 100% decomposition of the decomposition target of the sample).

(Test Results) (1) The test was carried out under the above conditions for 360 minutes, but the pressure inside the reactor 1 did not rise, and continuous tests could be carried out. Further, the temperature distributions of the reactor 1 and the discharge pipe 5 were examined, and the measurement points and temperatures thereof are shown in FIG. As can be seen from this temperature distribution diagram, the temperature in the reactor 101 is distributed over a wide range from the reaction temperature to a temperature below the critical temperature,
Further, it can be seen that the high temperature processing fluid is discharged to the discharge pipe, and the temperature distribution in the reactor is not uniform.

(2) The temperature of the processing fluid is 450 ° C. at the position TC-5 near the subcritical zone of the supercritical zone,
At position TC-6 in the subcritical zone, the temperature is 125 ° C, so
It can be seen that there is a temperature distribution including the critical temperature between TC-5 and TC-6.

(3) The components contained in the processing fluid (processing solution) discharged from the reactor were measured by gas chromatography GC-311 (manufactured by HNU SYSTEMS, photoionization detector: mentioned above), and , Cl ^-, Na
^{The +} ion was as shown in Table 3 below when measured using ion chromatography DX-AQ (manufactured by Nippon Dionex).

[0079]

[Table 3]

The pH of the treatment liquid (main) is 2.8,
The pH of the treatment liquid (brine) was 5.9.

Next, the recovery rate of Na ⁺ ions was calculated from the Na ⁺ ion concentration in the treatment liquid by the following formula.

[0082]

[Equation 2]

As a result of this calculation, the recovery rate of Na ⁺ ions was 30%, which means that salt (NaCl) or sodium hydroxide (NaOH) was deposited and remained in the reactor 101 or the discharge pipe 105. It indicates that

Therefore, in the method of supplying the neutralizing agent of Comparative Example 1 together with the supercritical water, it was judged that salt or sodium hydroxide was deposited in the reactor or the pipe and the neutralization was not sufficiently performed. It

Comparative Example 2 Further, for comparison, a supercritical water oxidation treatment was carried out by using an apparatus for performing a supercritical water oxidation treatment equipped with a tubular reactor extending in a swirl shape in FIG.

In the test, a substance consisting of the components shown in Table 4 below including a substance which produces a salt was used as a sample of a substance to be decomposed, and supercritical water oxidation was carried out without adding a neutralizing agent.

[0087]

[Table 4]

The conditions for supercritical water oxidation are as follows.

(Test conditions) Temperature / pressure: 650 ° C., 25 MPa Oxidizing agent: Air reactor: Tubular reactor (coil type reactor) shown in FIG. 4; Inner diameter 5 mm × 130 m Flow rate (SCW): 8 ml / min (Sample) ): 2 ml / min (air): 1.6 Nm ³ / hr (1.8 times the theoretical amount required for 100% decomposition of the decomposition target of the sample).

(Test Results) (1) By the above, a test was conducted for 720 minutes,
The temperature distribution in the tubular reactor at that time was investigated and the result is shown in FIG.

(2) The components contained in the treatment fluid (treatment liquid) discharged from the reactor and the Cl ⁻ ions were measured in the same manner as in Example 1, and the results are shown in Table 5 below.

[0092]

[Table 5]

As can be seen from the results shown in Table 5, the organochlorine compound in the sample (decomposition target) was substantially completely decomposed, but the Cl ^- ion concentration of the treatment liquid was high, and the pH was low.
In 3.1, it was confirmed that hydrochloric acid was generated by supercritical water oxidation.

(3) A pinhole was generated in a width of about 2 m on the peripheral wall of the reactor about 120 m from the starting end of the reactor. This situation is shown in FIG.

As can be seen from the temperature distribution diagram of FIG. 4, the temperature in the reactor, that is, the temperature of the treatment liquid, which is a decomposition product fluid, in the vicinity of 120 m from the start end is the critical temperature of water 374
The temperature range was in the vicinity of ° C.

By this comparative test, it was confirmed that the problem of acid corrosion of the reactor or the pipeline through which the treatment fluid flows occurs near the critical temperature of water.

[0097]

As described above, according to the present invention,
The decomposition target can be sufficiently decomposed by supercritical water oxidation in a vessel type (vertical cylinder type) reaction vessel, and the acid generated by the reaction can be reliably neutralized in the middle of the discharge pipe of the processing fluid. As a result, the equipment can be protected from acid corrosion, and the treatment with excellent safety and durability can be achieved, and the salt generated by the neutralization reaction adheres to the wall surface of the reactor and the discharge system pipeline. Since the above problem can be solved and there is no fear of clogging of the reactor or the pipeline, continuous treatment of organic substances that generate acids such as hardly decomposable organic substances and harmful organic substances can be suitably realized.

Further, since it is possible to simultaneously prevent the corrosion by the above-mentioned acid and the adhesion of the neutralized salt, it is not necessary to provide the vessel type reactor with a structure for supplying / discharging the salt transfer water, and the control is easy. Moreover, the equipment cost is extremely excellent as an industrial scale implementation device using a supercritical water oxidation equipment.

[Brief description of drawings]

FIG. 1 is a flowchart showing a schematic configuration of an apparatus of Embodiment 1 used for carrying out a supercritical water oxidation method of the present invention.

FIG. 2 is a diagram showing an operation outline and temperature distribution of Example 1 in which supercritical water oxidation was performed using the apparatus of FIG.

FIG. 3 is a diagram showing an operation outline and temperature distribution of Comparative Example 1 in which supercritical water oxidation was performed using the conventional Bessel-type reactor of FIG.

4 is a diagram showing an operation outline and temperature distribution of Comparative Example 2 in which supercritical water oxidation was carried out using the tubular reactor of FIG.

FIG. 5 is a diagram showing a situation of pinholes generated when the process of Comparative Example 2 is performed.

[Explanation of symbols]

1 ... Bessel type reactor, 2 ... double tube nozzle,
3 ... Waste liquid (decomposition target) supply pipe, 4 ... Supercritical water supply pipe, 5 ... Treatment liquid (treatment fluid) discharge pipe, 6 ...
Neutralizer supply pipe, 101 ... Vessel type reactor, 10
2 ... Double pipe nozzle, 103 ... Waste liquid (decomposition target) supply pipe, 104 ... Supercritical water supply pipe, 105 ...
・ Processing liquid (main) discharge pipe, 107 ... Pure water supply pipe,
108 ... Treatment liquid (brine) discharge pipe, 109 ...
Air supply pipe, 201 ... Tubular reactor, 203 ... Waste liquid (decomposition target) supply pipe, 204 ... Supercritical water supply pipe, 205 ... Treatment liquid discharge pipe, 209 ... Air supply tube.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C02F 1/66 540 C02F 1/66 540H (72) Inventor Taro Oe 1-4-9 Kawagishi, Toda City, Saitama Organo Co., Ltd. Research Institute (72) Inventor Shinichiro Kawasaki 1-4-9 Kawagishi, Toda City, Saitama Organo Research Institute (56) Reference JP-A-7-258772 (JP, A) JP-A-9-85075 (JP, A) JP-A-8-38853 (JP, A) JP-B 1-338532 (JP, B2) JP-A-5-504093 (JP, A) US Pat. No. 5591415 (US, A) US Pat. US, A) US Patent 5571424 (US, A) US Patent 5571423 (US, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 1/74 C02F 1/66 B01J 3 / 00,19 / 00

Claims (10)

(57) [Claims] 1. An object to be decomposed is continuously supplied into a vertical cylindrical reactor in which a supercritical water atmosphere having a temperature and pressure higher than the critical point of water is formed, and oxidative decomposition is performed in the presence of supercritical water. and,
A fluid containing the produced oxidative decomposition product is continuously discharged from a discharge pipe connected to the vertical cylindrical reactor, and in a supercritical water oxidation treatment of neutralizing an acid group contained in the fluid with a neutralizing agent,
In the above-mentioned discharge pipeline, decomposition products are generated while maintaining a high temperature above the critical temperature of water , where there is virtually no acid corrosion effect due to acid groups.
The neutralizing agent is added to the fluid containing the product, and
Immediately after the addition, the neutralization product salt is in a temperature range where it is sufficiently dissolved.
Supercritical water method characterized by the so that. 2. The salt according to claim 1, wherein the salt produced by the addition of the neutralizing agent is sodium chloride, and the temperature of the fluid flowing through the discharge pipeline at the time of adding the neutralizing agent is 450 ° C. or higher. Supercritical water oxidation method. 3. The supercritical water according to claim 1, wherein the salt produced by the addition of the neutralizing agent is sodium chloride, and the temperature of the fluid flowing through the discharge pipe at the time of adding the neutralizing agent is 450 ° C. or lower.
A supercritical water oxidation method characterized by being in the range of water temperature . 4. The method according to any one of claims 1 to 3 ,
A supercritical water oxidation method in which the neutralizing agent to be added is a low temperature aqueous solution. 5. The method according to any one of claims 1 to 4 ,
A supercritical water oxidation method comprising cooling a fluid containing decomposition products to a temperature below the critical temperature of water after the neutralization reaction. 6. A reactor for a supercritical water oxidation reaction, which comprises a vertical cylindrical pressure-resistant container, and a means for supplying a decomposition target and an oxidizer for continuously supplying a decomposition target and an oxidizer into the reactor. A discharge pipe connected so as to discharge the fluid decomposed and produced by the reaction of supercritical water oxidation from the reactor to the outside of the reactor,
The method according to claim 1, further comprising: a neutralizing agent addition means provided in the middle of the discharge pipeline for neutralizing acid groups contained in the fluid flowing in the discharge pipeline. used <br/> supercritical water oxidation unit. 7. The method of claim 6, and wherein the position of the neutralizing agent adding means provided in the middle of the discharge line is, acid corrosive action by acid groups contained in the fluid is substantially a have positions Supercritical water oxidation equipment. 8. The position of the neutralizing agent addition means provided in the middle of the discharge pipe line according to claim 6 , is a position where a fluid having a low solubility of the neutralization salt is above the critical temperature of water , Further, the neutralizing agent to be added is a supercritical water oxidation apparatus characterized by being a low temperature aqueous solution capable of cooling the temperature of the fluid to a temperature at which the neutralization salt is sufficiently dissolved by the addition. 9. In any of the claims 6 to 8,
The above-mentioned vertical cylinder type reactor has a supply port for a decomposition target and an oxidizing agent as a supply part, and as a discharge part, discharges a fluid containing an oxidative decomposition product generated by a reaction of supercritical water oxidation to a discharge pipeline. A supercritical water oxidation apparatus having only one outlet. 10. In any of the claims 6 to 9, and characterized in that the discharge line position to the subsequent stage is provided a neutralizing agent addition means and a cooling means for cooling the fluid flowing Supercritical water oxidation equipment.