JPH10314769A - Supercritical water oxidizing method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish a process in which when supercritical water oxidation is effected using a vessel type reactor, a device can be protected against acid corrosion and improved safety and durability can be provided. SOLUTION: In a supercritical water oxidation process in which objects to be decomposed are continuously fed into a vertical type reactor 1 in a supercritical water atmosphere and a fluid generated by oxidation in the presence of supercritical water is continuously discharged from a discharge pipe 5 connected to the upper part of the reactor 1 so that acid contained in the fluid is neutralized by neutralizing agents, the interior of the reactor 1 is held at high temperatures to prevent the reactor from being corroded by acid and neutralizing agents 6 are added to the fluid discharged from the pipe 5, and the temperature of the fluid at the time of adding the agents or immediately after adding the agents is so held that corrosion due to acid can be avoided and salt produced by neutralization can be sufficiently dissolved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for supercritical water oxidation, for example, a method for converting an acid into a fluid produced by a decomposition reaction of a hardly decomposable waste or waste liquid or a waste or waste liquid containing toxic substances. The present invention relates to a supercritical water oxidation method suitably 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 a problem when discharged into the environment, such as hardly decomposable wastes and waste liquids and wastes and waste liquids containing harmful substances, and disposing them as safe substances. There has been proposed a supercritical water oxidation method suitable for completely decomposing these wastes and waste liquids (for example, Japanese Patent Publication No. 1-38532).

[0003] 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, for example, due to insufficient decomposition due to the partial generation of a low-temperature portion. In addition, while there is a problem that harmful substances are diffused because the combustion gas is released into the atmosphere, the supercritical water oxidation treatment is performed under the supercritical condition of water (at a temperature of 374 ° C. or more and a pressure of 22 MPa or more). ) Is a method that can completely decompose the organic matter to be decomposed into water and carbon dioxide by using supercritical water as a medium for the decomposition reaction. This is because not only can it achieve a very high reaction rate, but also it can be completely decomposed in a closed system.

In the supercritical water oxidation method, the critical conditions of water, namely, a critical temperature of 374 ° C. and a critical pressure of 22 MPa are used.
Water (supercritical water) under the conditions exceeding the temperature can control the polarity by temperature and pressure, and can dissolve non-polar substances such as paraffin hydrocarbons and benzene. It shows excellent properties as a reaction solvent for oxidative decomposition of organic substances, which is mixed in a single phase at a ratio. If the decomposition target has a carbon content of several percent, it can be heated to a critical temperature or higher just by heat of oxidation. Therefore, it is extremely excellent in terms of thermal energy, and in particular, it can completely decompose most hardly decomposable organic substances and hazardous organic wastes in supercritical water by properly controlling the hydrolysis reaction and thermal decomposition reaction. It is extremely suitable for the decomposition treatment of harmful organic substances in that it has an extremely excellent action and that the treatment can be performed in a closed system.

[0005] As a proposal of such a supercritical water oxidation treatment technique, for example, Japanese Patent Publication No. 1-38532 discloses the principle and basic flow. 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 an air compressor is introduced as an oxidizing agent to perform oxidative decomposition.
Part of the supercritical water after treatment is recirculated to the ejector,
The rest is used for energy recovery. However, this document does not show details of the reactor, but merely mentions that a tubular, cylindrical or fluidized bed type can be adopted.

Japanese Unexamined Patent Publication (Kokai) No. 3-500264 discloses that a reactor used for supercritical water oxidation has a tubular shape as a reactor type suitable for decomposing waste liquid not containing inorganic salts or inorganic salt-forming substances. The use of a reactor is disclosed, and
As a reactor type suitable for a case where an organic waste liquid containing an inorganic salt or generating an inorganic salt after the reaction through the addition of a neutralizing agent is to be decomposed, a vertical cylinder type so-called Vessel type is used. A reactor is disclosed.

[0007] By the way, one of the main decomposed substances to be treated by supercritical water oxidation is a hardly decomposable organic substance or a harmful organic substance. Most of these substances contain chlorine, sulfur, nitrogen, or phosphorus. When these substances are subjected to supercritical water oxidation treatment, acids (hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid) are often generated, so that these acids are neutralized with an alkali as a measure against acid corrosion in order to protect the reactor materials. It is proposed to perform the operation. However, it is known that the inorganic salt such as NaCl generated by this neutralization operation hardly dissolves in supercritical water and has high adhesion to a pipe wall surface or the like.

[0008] 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 required to prevent acid corrosion. Nevertheless, it means that there is a need for a solution to the problem that the neutralized salt resulting from the neutralization treatment causes a blockage of the reactor or discharge line. In order to solve this problem, Japanese Patent Application Laid-Open No. 3-500264 proposes a method for supplying and discharging subcritical water at the bottom of a vessel of a vessel type, which is formed by the reaction of supercritical water oxidation. The resulting acid is neutralized with an alkali to form a salt, and the salt is dropped into the subcritical water using the heavy specific gravity of the salt to separate it from the light fluid (supercritical water, volatile gas, etc.) It proposes a method of discharging by.

As described above, in the Bessel type reactor, a supercritical zone is formed in the upper part and a subcritical zone is formed in the lower part in the Bessel reactor, and precipitated and moved downward due to a density difference in the reactor. In this method, the inorganic salt is dissolved in water for transporting the salt in the subcritical zone and then discharged. Therefore, the discharge system from the reactor is provided with a decomposition product fluid (water and volatile gas from the upper part of the reactor). There are two systems, a discharge system for supercritical water, excess oxygen, a mixture of carbon dioxide and nitrogen), and a discharge system for brine flow (water for salt transfer containing inorganic salts such as sodium chloride) from the lower part of the reactor. Heat recovery, cooling and decompression steps are required for each discharge system, which complicates the structure of the apparatus and increases capital investment. In addition, there is a problem that control and maintenance are complicated as compared with the case where a tubular reactor is used.

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

[0011]

As described above, the supercritical water oxidation technique is an effective technique for the decomposition treatment of organic substances, but mainly uses acids represented by hardly decomposable organic substances and toxic organic substances. The oxidative decomposition treatment of the decomposition target containing the generated substance,
There are further problems to be solved in order to be able to implement the method on an industrial scale in consideration of the cost and the durability of the apparatus.

The present inventors have conducted intensive research in view of such a current situation, and have accomplished the present invention.

[0013] That is, one of the objects of the present invention is to ensure the neutralization of the acid generated by supercritical water oxidation, thereby protecting the apparatus from acid corrosion and providing a treatment excellent in safety and durability. An object of the present invention is to provide a supercritical water oxidation method that can be realized and an apparatus used for the method.

Another object of the present invention is to protect the apparatus from acid corrosion by the above-mentioned reliable neutralization and to solve the problem that the salt formed by the neutralization adheres to the inner wall of the reactor or the discharge line. It is an object of the present invention to provide a supercritical water oxidation method and an apparatus used for the method.

Still another object of the present invention is to prevent the salt generated by the neutralization reaction from adhering to the walls of the reactor and the discharge line, thereby enabling organic substances which generate acids, especially hardly decomposable substances. It is an object of the present invention to provide a supercritical water oxidation method capable of efficiently decomposing toxic organic substances and harmful organic substances at low cost and an apparatus used for the method.

[0016]

The above objects can be attained by the inventions set forth in the claims of the present application.

According to the first aspect of the present invention, a decomposition target is continuously supplied into a vertical cylindrical reactor having a supercritical water atmosphere at a temperature and a pressure higher than a critical point of water. The fluid generated by oxidative decomposition in the presence of water is continuously discharged from a discharge line connected to the vertical cylindrical reactor, and the acid groups contained in the fluid are neutralized with a neutralizing agent. In the treatment, the inside of the vertical cylindrical reactor is maintained at a high temperature substantially free of acid corrosion by the acid group, and a neutralizing agent is added to the fluid discharged to the discharge line, The fluid is characterized in that the temperature of the fluid at the time of or immediately after the addition is such that there is substantially no acid corrosion by the acid groups and the neutralized salt is sufficiently dissolved.

According to a second aspect of the present invention, in the supercritical water oxidation treatment, the inside of the vertical cylindrical reactor is maintained at a high temperature substantially free from an acid corrosion action due to an acid group. A neutralizing agent is added to the discharged high-temperature fluid having a low solubility of the neutralized salt, and the temperature of the fluid immediately after the addition of the neutralizing agent is cooled to a temperature range in which the neutralized salt is sufficiently dissolved. It is characterized by the following.

According to a third aspect of the present invention, in the supercritical water oxidation treatment, the inside of the vertical cylindrical reactor is maintained at a high temperature substantially free of an acid corrosion action due to an acid group, and is provided to the discharge pipe. It is characterized in that a neutralizing agent is added to the fluid discharged and having a temperature higher than the critical temperature of water and in a temperature range in which the neutralized product salt is sufficiently dissolved.

The inventor of the present invention has made the following inventions. That is, in the conventional supercritical water oxidation treatment involving generation of an acid, the neutralizing agent is supplied from the starting end of the reactor together with the decomposition target, supercritical water, and the like.
This is because in a supercritical hydroxylation reaction in which an acid is generated by the reaction, it is considered necessary to perform neutralization in the reaction zone in order to protect the reactor.

However, the inventors of the present invention have repeated studies with various conditions of supercritical water oxidation, and found that pinholes are generated not in the reactor but in the discharge line of the fluid generated by decomposition. When the situation was further observed and analyzed, the fact that the acid corrosion problem occurred in the stage of cooling the fluid produced by supercritical water oxidation rather than in the reactor differs from the conventional technical understanding that , I found a phenomenon. This phenomenon was presumed to be based on the following reaction mechanism. In other words, the acid groups (eg, halogens) in the product fluid decomposed by supercritical water oxidation are free in supercritical water and have no or very weak action as an acid to corrode the walls of the reactor, etc. When the decomposition product fluid is cooled and the supercritical water undergoes a phase transition to liquid (water), its free acid radicals rapidly dissolve in the liquid and locally increase the acid concentration, causing the action of a high concentration of acid. It is thought that the wall of the reactor etc. is corroded. Therefore, the present inventors reexamined the neutralizing operation of the generated acid from a viewpoint different from the conventional technical understanding that the inside of the reactor was considered to be in the most severe acid corrosion environment. Since the addition is in order to prevent corrosion by the acid, the neutralization reaction is carried out at the stage where the acid group is dissolved in the liquid to cause the problem of the acid corrosion, based on the fact that the present inventors have found. It is well understood that a neutralization reaction in the reactor is not necessarily required. On the other hand, the neutralized product salt is generally hardly soluble in high-temperature supercritical water and has strong adhesiveness. Therefore, the salt generated by the neutralization reaction can be sufficiently dissolved, and the acid generated by the acid group If the neutralization reaction can be performed without corrosion problems,
In addition to preventing corrosion by acid, it is possible to effectively solve the problem of salt adhesion leading to blockage of the pipeline. The present inventors have conducted tests for technically verifying such a point of interest, and have reached the above-described inventions.

In each of the above-mentioned inventions, it is important to maintain the inside of the vertical cylindrical reactor in a supercritical atmosphere to sufficiently supercritically oxidize the decomposition object. After discharging the generated 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 present invention, the addition fluid causes the produced fluid to be "at a temperature at which substantially no acid corrosion due to acid groups is caused and the neutralized product salt is sufficiently dissolved".
To be. In the present specification, the term "acid group" does not constitute a so-called acid group by its atoms alone in addition to halogen such as chlorine which generates hydrochloric acid, etc., but may generate an acid such as sulfuric acid, nitric acid or phosphoric acid. Sulfur, nitrogen, phosphorus, etc.

Representative organic substances to be decomposed containing such substances are persistent organic pollutants (POPs: Persistent O.P.).
rganic pollutants) or persistent toxic bio-accumlatives (PTBs). Representative substances are PCBs, trichlorethylene, tetrachloroethylene, and organic pesticides such as waste pesticides, which are designated as harmful substances in environmental standards. These are generally hardly decomposable substances. In addition to these, halogen compounds such as organic bromine compounds, sulfur compounds, nitrogen compounds, phosphorus compounds and the like can also be mentioned.

The above "state of a temperature substantially free of acid corrosion" refers to a temperature range exceeding a critical temperature (374 ° C.) at which supercritical water undergoes a phase transition to a liquid (water). Considering the temperature fluctuation at
C. or higher, preferably 450 ° C. or higher.
The "temperature at which the neutralized product salt is sufficiently dissolved" cannot be uniformly determined as the temperature limit because it is not the same depending on the type of the salt to be produced. The solubility in supercritical water at 25 MPa is about 100 ppm, whereas the solubility in supercritical water below 450 ° C. is on the order of several percent. Therefore, when a neutralizing agent that generates sodium chloride is used as a salt, the temperature 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 so. "Sufficiently dissolved" means that salt can be prevented from adhering to a wall surface or the like to cause a problem of clogging. When another type of salt is produced, the temperature at which the salt sufficiently dissolves 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. In addition, as a neutralizing agent which can be used in the present invention, an alkali hydroxide such as sodium hydroxide or potassium hydroxide can be typically exemplified, but it is not limited thereto. The addition is generally preferably effected in the form of an aqueous solution.

The second aspect of the present invention is basically the same as the first aspect of the present invention, except that the addition of the neutralizing agent has a low solubility (almost no solubility) of the salt formed in the neutralization reaction.
One of the features is that the process is performed on a high-temperature fluid (a decomposition product fluid). For example, when the generated salt is sodium chloride, the reaction temperature (for example, 500 ° C. or higher) to 450 ° C.
The addition of the neutralizing agent is performed within the range. The addition of the neutralizing agent is performed in the discharge line so as not to affect the complete decomposition of the decomposition target by supercritical water oxidation. Another feature of the present invention is that the temperature of the decomposition product fluid immediately after the addition of the neutralizing agent is cooled to a temperature at which the salt generated by the neutralization reaction can be sufficiently dissolved. And For this cooling, a method of lowering the temperature of the generated 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 the reduction may be higher or lower than the critical temperature.

The third aspect of the invention is basically the same as the first aspect of the invention, except that the addition of the neutralizing agent is carried out at a temperature at which the solubility of the salt formed in the neutralization reaction is high, In addition, it is performed on a fluid (decomposition generated fluid) in a temperature range higher than the critical temperature. When the salt to be produced is sodium chloride, it is generally carried out on a decomposition product fluid at a temperature of 600 to 450 ° C, preferably 500 to 450 ° C. The temperature after the reduction may be higher or lower than the critical temperature.

In the above-mentioned structure of the invention according to claims 1 to 3, the supercritical water atmosphere is usually prepared by reacting an organic substance to be decomposed, supercritical water and an oxidizing agent under a pressure higher than the critical pressure (22 MPa). And the organic matter to be decomposed is formed at a critical temperature (374 ° C.) or higher, which is performed by using a conventionally known technique of a supercritical water oxidation method using a so-called Bessel type reactor. Can be. However, in the present invention, the inside of the reactor is maintained in a supercritical atmosphere over the entire region. The supercritical water can be supplied separately from the decomposition target, or can be supplied as a mixture. If the decomposition target contains a necessary amount of water and the supercritical water atmosphere can be maintained by the self-combustion of the decomposition target, supercritical water may be supplied only at the beginning of the reaction. The supercritical water atmosphere is
It can also be formed by a method without supplying supercritical water to the reactor.

As this method, for example, there can be mentioned 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 reactor is supplied with an organic substance which is an object to be decomposed, an oxidizing agent, and water when the required amount of water is not contained in the object to be decomposed, and is installed around the reactor. The inside of the reactor can be heated by transferring heat from the heated heating element to make the inside of the reactor a supercritical water atmosphere.
If supercritical water oxidation can be maintained by the self-combustion of the decomposition target, heat may be supplied only from the heating element at the beginning of the reaction, and the heat supply from the heating element may be interrupted after the self-combustion is sufficiently continued. it can. The organic matter to be decomposed can be supplied after being preheated as necessary. As the oxidizing agent, a liquid phase oxidizing agent such as hydrogen peroxide solution can be used in addition to air and oxygen gas.

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

The operation of adding the neutralizing agent to the fluid flowing through the discharge line includes, for example, connecting an aqueous solution of the neutralizing agent pressurized to a supercritical pressure set for the reaction to the discharge line. It can be performed by injecting through a filled injection pipe.

In the supercritical water oxidation method of the present invention, the critical pressure and critical temperature (22
(MPa, 374 ° C.), but any method can be applied without limitation. Conditions for the treatment are, generally, a temperature of 400 ° C. or higher, preferably around 600 to 650 ° C.,
Reaction pressure is 22-50MPa, preferably 22-25M
It is often appropriate to set it to around Pa. The reaction time is about 1 to 10 minutes, preferably about 1 to 2 minutes.

According to each of the above-mentioned inventions, the salt formed after the injection (addition) of the neutralizing agent is sufficiently dissolved in supercritical water or water, so that there is no danger that the salt will adhere to the wall of the discharge pipe. Therefore, it is possible to substantially eliminate the possibility that the pipe is blocked, and there is no possibility that the reactor may be corroded by acid.

According to a fourth aspect of the present invention, in the second aspect of the present invention, the salt formed by adding the neutralizing agent is sodium chloride, and the temperature of the fluid flowing through the discharge line at the time of adding the neutralizing agent is 450. In a fifth aspect of the present invention, the salt formed by the addition of the neutralizing agent is sodium chloride, and the neutralizing agent for the fluid flowing through the discharge pipe is provided. The temperature at the time of addition is 450 ° C. or lower.

According to these inventions, the operation of the neutralization reaction can be carried out using sodium hydroxide, which is the most representative as a neutralizing agent, and in the latter invention, the temperature exceeds 450 ° C. It can cope with the case where critical water oxidation is performed.

A sixth aspect of the present invention is characterized in that, in each of the above-mentioned inventions, the neutralizing agent to be added is an aqueous solution at a low temperature (for example, normal temperature).

According to the present invention, the temperature of the decomposition product fluid can be lowered by adding the aqueous solution of the neutralizing agent, 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 reduced to the temperature, and other cooling means such as a heat exchanger can be omitted.

The invention of claim 7 is characterized in that, in each of the above-mentioned inventions, after the neutralization reaction, the decomposition product fluid is cooled to a critical temperature of water or lower.

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

The invention of a supercritical water oxidation apparatus according to claim 8 provides a reactor for a supercritical water oxidation reaction comprising a vertical cylindrical pressure-resistant container, and a continuous supply of a substance to be decomposed and an oxidizing agent into the reactor. Supply means for supplying the decomposition object and the oxidizing agent to be decomposed, a discharge pipe connected to discharge the fluid decomposed and generated by the reaction of supercritical hydroxylation from the reactor to the outside of the reactor, and a discharge pipe inside the discharge pipe. And a neutralizing agent adding means provided in the middle of the discharge conduit to neutralize the acid groups contained in the fluid flowing through.

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

The organic matter to be decomposed, the oxidizing agent, and the like are usually supplied from the center of the reactor using a nozzle or the like, and a supply system for the decomposition object, excluding the neutralizing agent adding means, and a fluid generated by decomposition. The discharge system and the like can be configured similarly to a conventionally known supercritical water oxidation apparatus.

According to the present invention, the treatment by supercritical hydroxylation of mainly a hardly decomposable substance accompanied by the formation of a salt can be carried out without causing a problem of blockage of an exhaust pipe and acid corrosion.

According to the ninth aspect of the present invention, the position of the neutralizing agent adding means provided in the middle of the discharge pipe in the above-described apparatus invention is substantially free from acid corrosion due to acid groups and the neutralized salt is sufficiently reduced. It is characterized in that it is located at a position where a fluid at a temperature for dissolving flows.

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 object and the processing operation. . In the case where the salt to be produced is sodium chloride, the position is generally a position where the temperature of the decomposition product fluid is 600 to 450 ° C, preferably 500 to 450 ° C.

According to a tenth aspect of the present invention, in the eighth aspect of the present invention, the position of the neutralizing agent adding means provided in the middle of the discharge pipe is such that the solubility of the neutralized salt is low (almost insoluble).
It is a low-temperature aqueous solution at a position where a high-temperature fluid flows, and wherein the neutralizing agent to be added can be cooled to a temperature at which the neutralized product salt can be sufficiently dissolved by addition. I do.

According to the present invention, as in the case of the ninth aspect, 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 pipe, Simultaneously with or immediately after the addition of the low temperature aqueous solution of the neutralizing agent, the salt is brought to a temperature at which it can be sufficiently dissolved. The position may be at the beginning of the discharge line or at the end of the discharge line. When the salt formed is sodium chloride, the temperature of the decomposition product fluid is generally from the reaction temperature to 450 ° C., preferably 500 ° C. ~ 450
° C.

According to an eleventh aspect of the present invention, the vertical cylindrical reactor of each of the above-described apparatus inventions has a supply port for a decomposition target and an oxidizing agent as a supply unit and a supercritical water oxidation reaction as a discharge unit. It is characterized in that it has only one outlet for discharging the generated fluid to the discharge line.

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

According to a twelfth aspect of the present invention, in each of the above-described apparatus inventions, a cooling means for cooling a flowing fluid is provided at a position where the neutralizing agent adding means is provided or at a discharge pipe at a subsequent stage. According to the present invention, the decomposition product fluid is cooled by the cooling means, so that neutralization of the acid and dissolution of the generated salt in water are reliably performed.

[0052]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. 1 shows an outline of the configuration of an apparatus for carrying out the method of the present invention, and 1 is a so-called Bessel type reactor,
It is made of a high temperature and acid resistant material as a vertical cylindrical pressure vessel. A double pipe nozzle 2 is attached to the center of the ceiling of the reactor 1, and a decomposition target such as an organic waste liquid or the like pressurized from a waste liquid supply pipe 3 to a pressure higher than the critical pressure of water (22 MPa). Is blown into the reactor 1 through the inner pipe of the double pipe nozzle 2, and a mixed fluid of supercritical water and air as an oxidant is supplied from the supercritical water supply pipe 4 through the outer pipe of the double pipe nozzle 2. It is blown into the reactor 1. Thereby, the (waste liquid + supercritical water + air) blown from the double pipe nozzle 2 becomes a fluid mixed under a supercritical pressure of 22 to 25 MPa, and is oxidized at a temperature of, for example, 600 to 650 ° C. by oxidation of organic matter in the waste liquid. Continue supercritical water oxidation reaction continuously. 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 is not necessary to supply. Further, the waste liquid supply pipe 3 may be provided with a preheater (not shown) for heating the fluid (waste liquid) to be supplied 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) as appropriate.

Reference numeral 5 denotes a discharge pipe for discharging a fluid (hereinafter, referred to as a “processing fluid”) generated by the decomposition in the supercritical hydroxylation reaction from the reactor 1, which is made of an acid-resistant material. The processing fluid which is connected to open from the ceiling to the inside and is completely decomposed by the supercritical hydroxylation 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 neutralizing agent supply pipe 6 from a neutralizing agent tank and pressurizing means (neither is shown) discharges a neutralizing agent such as sodium hydroxide. 5 is connected so as to be injected (added) to the processing fluid flowing through the inside, whereby a neutralizing agent is injected and added to the processing fluid, so that the acid group contained in the processing fluid is removed. Sum is done.

It is necessary that the temperature of the processing fluid at the portion where the neutralizing agent is added is not lower than the temperature at which the acid group does not cause corrosive action as an acid. In consideration of temperature fluctuations of the apparatus, the temperature is set to 400 ° C. or higher, which is somewhat higher than the critical temperature, and when the inorganic salt generated by adding the neutralizing agent is sodium chloride, the reaction temperature may be set to 450 ° C. it can. When the temperature of the processing fluid after the addition of the neutralizing agent exceeds 450 ° C., immediately after the addition of the neutralizing agent, the temperature of the processing fluid is set to 450 ° C. or lower, which is a temperature range in which the solubility of sodium chloride is high. . In order to lower (cool) the temperature of the processing fluid, for example, a cooling means such as a heat exchanger can be used. Thus, there can be mentioned a method in which the temperature of the processing fluid is reduced.

As described above, the neutralization of the acid groups has already been completed when the temperature of the processing fluid has dropped to near the critical temperature of water, so that water undergoes a phase transition from supercritical water to liquid. The generation of a high-concentration acid due to rapid dissolution of the acid group in water can be prevented.

The processing fluid having undergone the acid group neutralization reaction is subjected to necessary processing such as cooling, decompression, gas-liquid separation and the like, and is discharged out of the apparatus.

[0058]

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

Example 1 Using a supercritical water oxidation apparatus having the vessel-type reactor 1 shown in FIG. 1 described above, a substance consisting of the components shown in Table 1 below including a substance that produces a salt with supercritical water oxidation. Is a sample of an object to be decomposed, and a discharge pipe 5 for discharging a processing fluid from the reactor 1
From a predetermined position (between TC-6 and TC-7 in FIG. 2), a supercritical water oxidation treatment was carried out by adding a neutralizing agent (aqueous sodium hydroxide solution).

[0060]

[Table 1]

The conditions for supercritical water oxidation are as follows.

(Test conditions) Temperature and pressure: 650 ° C., 25 MPa Oxidizing agent: Air Reactor: Bessel 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 to decompose 100% of a sample to be decomposed).

(Test Results) (1) The test was performed under the above test conditions for 600 minutes, but the pressure in the reactor 1 did not increase, and a continuous test could be performed. Further, the reactor 1 and the discharge pipe 5
Was examined, and the measurement points and temperatures are shown in FIG. The temperature distribution was measured by inserting a thermocouple into each reactor.

(2) The temperature of the processing fluid before the addition of the neutralizing agent aqueous solution is 621 ° C. at the position of TC-6,
At the position of TC-7 after the addition, the temperature is 288 ° C. By this, there is no acid-corrosion action of the acid group, and the solubility of the salt is low, the processing fluid is rapidly lowered to the critical temperature of water by adding the neutralizing agent aqueous solution to the high-temperature processing fluid, and It can be seen from (3) that the salt was dissolved in water and discharged without causing salt to adhere to the inner wall of the tube. In addition, even when the test was repeated, no pinhole was generated in the pipe near TC-6 to TC-7, and it was confirmed that acid corrosion 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 using ion chromatography DX-AQ (manufactured by Nippon Dionex) and found to be as shown in Table 2 below.

[0066]

[Table 2]

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

The pH calculated from the Cl ^- ion concentration of the processing solution is 2.9, whereas the pH of the processing solution is 6.1, and the hydrochloric acid generated by supercritical water oxidation is sodium hydroxide. Was confirmed to be neutralized. The reason why the pH of the treatment liquid is 6.1 is due to the dissolution of carbon dioxide.

Next, from the Na ⁺ ion concentration in the processing solution, the recovery rate of Na ⁺ ions was determined by the following equation.

[0070]

(Equation 1)

As a result of this calculation, the recovery of Na ⁺ ions was 101%, indicating that the Na ⁺ ions that did not contribute to the neutralization reaction flowed together with the processing liquid (decomposition fluid). It was confirmed that no precipitation of salt occurred in the vessel and the discharge line.

COMPARATIVE EXAMPLE 1 Next, for comparison, as shown in FIG. 3, a configuration for supplying and discharging subcritical water for transferring the salt to the bottom of the vessel type reactor 101, that is, a pure water supply pipe 107 and A treatment liquid (brine) drain pipe 108 is connected, and respective supply lines of a waste liquid supply pipe 103, a supercritical water supply pipe 104, and an air supply pipe 109 are connected to the double pipe nozzle 102 of the reactor 101.
The neutralizing agent was subjected to supercritical water oxidation using a conventional supercritical water oxidation apparatus in which supercritical water was mixed and supplied.

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

The conditions for supercritical water oxidation are as follows.

(Test conditions) Temperature and pressure: 650 ° C., 25 MPa Oxidizing agent: Air Reactor: Bessel type reactor shown in FIG. 3; Inner diameter 50 mm × Height 1050 mm Neutralizer: Sodium hydroxide aqueous solution (trichloroethylene completely Cl occurs when disassembled ^- feed flow ions and an equal molar amount) were mixed in a supercritical water (SCW): 0.99 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 to decompose 100% of a sample to be decomposed).

(Test Results) (1) The test was performed for 360 minutes under the above conditions, but the pressure in the reactor 1 did not rise, and a continuous test could be performed. Further, the temperature distribution of the reactor 1 and the discharge pipe 5 was examined, and the measurement points and temperatures 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,
In addition, a high-temperature processing fluid is discharged to the discharge pipe, which indicates that the temperature distribution in the reactor is not uniform.

(2) The temperature of the processing fluid is 450 ° C. at a position TC-5 near the subcritical zone of the supercritical zone,
Since the temperature is 125 ° C. at the position TC-6 of the subcritical zone,
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 liquid) discharged from the reactor were measured by gas chromatography GC-311 (manufactured by HNU SYSTEMS, photoionization detector: supra). , Cl ^-, Na
^{The +} ion was measured using ion chromatography DX-AQ (manufactured by Nippon Dionex), and was as shown in Table 3 below.

[0079]

[Table 3]

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

Next, from the Na ⁺ ion concentration in the processing solution, the recovery rate of Na ⁺ ions was determined by the following equation.

[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 precipitated in the reactor 101 or the discharge pipe 105 and remained. It indicates that.

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

Comparative Example 2 Further, for comparison, supercritical water oxidation was carried out using a device for performing supercritical water oxidation provided with a tubular reactor extended in a swirl shape as shown in FIG.

In the test, a substance consisting of the components shown in Table 4 below including a substance that forms a salt was used as a sample of a substance to be decomposed, and supercritical water oxidation was performed 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 to decompose 100% of a sample to be decomposed).

(Test Results) (1) A test was conducted for 720 minutes as described above.
FIG. 4 shows the temperature distribution of the tubular reactor at that time.

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

[0092]

[Table 5]

[0093] As can be seen from the results shown in Table 5, the organic chlorine compounds of the sample (decomposition targets) has been substantially completely degraded, Cl processing liquid ^- high ion concentration, pH
Was 3.1, and it was confirmed that hydrochloric acid was generated by supercritical water oxidation.

(3) A pinhole was formed on the peripheral wall of the reactor at about 120 m from the beginning of the reactor over a width of about 2 m. This situation is shown in FIG.

In the vicinity of 120 m from the starting end, as can be seen from the temperature distribution diagram of FIG.
The temperature range was in the vicinity of ° C.

This comparative test confirmed that the problem of acid corrosion of the reactor or the pipeline through which the processing fluid flows occurred near the critical temperature of water.

[0097]

As described above, according to the present invention,
The substance to be decomposed 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 treatment fluid discharge pipe. As a result, it is possible to protect the equipment from acid corrosion, and it is possible to achieve safe and durable treatment, and the salt generated by the neutralization reaction adheres to the walls of the reactor and the discharge line. This can eliminate the possibility of clogging of the reactor and the pipeline, so that continuous processing of organic substances that generate acids such as hardly decomposable organic substances and toxic organic substances can be suitably realized.

Further, since the above-described prevention of corrosion by the acid and prevention of the adhesion of the neutralized salt can be achieved at the same time, there is no need to provide a structure for supplying and discharging the salt transfer water in the vessel type reactor, and the control is easy. In addition, it is extremely excellent as an industrial-scale implementation device using a supercritical water oxidation facility with low equipment cost.

[Brief description of the drawings]

FIG. 1 is a flow chart showing an outline of the configuration of an apparatus according to a first embodiment used to carry out the supercritical water oxidation method of the present invention.

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

FIG. 3 is a diagram showing an operation outline of Comparative Example 1 in which supercritical water oxidation treatment is performed using the conventional vessel reactor of FIG. 3, and a temperature distribution.

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

FIG. 5 is a diagram showing a state of a pinhole generated when the processing of Comparative Example 2 is performed.

[Explanation of symbols]

1 ... Vessel 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 ・ ・ ・
Neutralizing agent supply pipe, 101: Bessel type reactor, 10
2 ... double pipe nozzle, 103 ... waste liquid (decomposition target) supply pipe, 104 ... supercritical water supply pipe, 105 ...
・ Treatment liquid (main) discharge pipe, 107 ... pure water supply pipe,
108 ... processing 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.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 1/66 540 C02F 1/66 540H (72) Inventor Taro Oe 1-4-9 Kawagishi, Toda City, Saitama Prefecture Organo Corporation Within the Research Institute (72) Inventor Shinichiro Kawasaki 1-4-9 Kawagishi, Toda City, Saitama Prefecture Organo Research Institute

Claims (12)

[Claims] An apparatus for continuously decomposing a substance to be decomposed into a vertical cylindrical reactor having a supercritical water atmosphere at a temperature and pressure higher than a critical point of water, and oxidizing and decomposing in the presence of supercritical water. In a supercritical water oxidation treatment in which the generated fluid is continuously discharged from a discharge pipe connected to the vertical cylinder type reactor and an acid group contained in the fluid is neutralized with a neutralizing agent, the vertical cylinder The reactor is maintained at a high temperature in which there is substantially no acid corrosion by the acid groups, and a neutralizing agent is added to the fluid discharged to the discharge pipe, and at the time of or immediately after the addition. A supercritical water oxidation method, characterized in that the temperature of the fluid is set to a temperature at which there is substantially no acid-corrosion action by the acid groups and the neutralization formed salt is sufficiently dissolved. 2. A method for continuously supplying an object to be decomposed into a vertical cylindrical reactor having a supercritical water atmosphere at a temperature and pressure higher than a critical point of water, and oxidative decomposition in the presence of supercritical water. In a supercritical water oxidation treatment in which the generated fluid is continuously discharged from a discharge pipe connected to the vertical cylinder type reactor and an acid group contained in the fluid is neutralized with a neutralizing agent, the vertical cylinder The reactor is maintained at a high temperature in which there is substantially no acid corrosion by the acid groups, and a neutralizing agent is added to the high-temperature fluid having a low solubility of the neutralized product salt discharged into the discharge pipe. Along with
A supercritical water oxidation method, wherein the temperature of the fluid immediately after the addition of the neutralizing agent is cooled to a temperature range in which the neutralized salt is sufficiently dissolved. 3. A decomposition target is continuously supplied into a vertical cylindrical reactor having a supercritical water atmosphere at a temperature and pressure higher than a critical point of water, and oxidative decomposition is performed in the presence of supercritical water. In a supercritical water oxidation treatment in which the generated fluid is continuously discharged from a discharge pipe connected to the vertical cylinder type reactor and an acid group contained in the fluid is neutralized with a neutralizing agent, the vertical cylinder The reactor is maintained at a high temperature in which there is substantially no acid corrosion due to acid groups, and is discharged to the discharge pipe and is at a temperature higher than the critical temperature of water, so that the neutralized salt is sufficiently dissolved. A supercritical water oxidation method comprising adding a neutralizing agent to a fluid within a temperature range of the supercritical water. 4. The method according to claim 2, wherein the salt formed by adding the neutralizing agent is sodium chloride, and the temperature of the fluid flowing through the discharge line at the time of adding the neutralizing agent is 450 ° C. or higher. Supercritical water oxidation method. 5. The method according to claim 3, wherein the salt formed by adding the neutralizing agent is sodium chloride, and the temperature of the fluid flowing through the discharge line at the time of adding the neutralizing agent is 450 ° C. or less. Supercritical water oxidation method. 6. The method according to claim 1, wherein
A supercritical water oxidation method, wherein the neutralizing agent to be added is a low-temperature aqueous solution. 7. The method according to claim 1, wherein
A supercritical water oxidation method comprising cooling a decomposition product fluid to a temperature below the critical temperature of water after the neutralization reaction. 8. A reactor for a supercritical water oxidation reaction comprising a vertical cylindrical pressure-resistant container, a decomposition object and an oxidant supply means for continuously supplying a decomposition object and an oxidant into the reactor. A discharge line connected to discharge the fluid decomposed by the supercritical water oxidation reaction from the reactor to the outside of the reactor,
A supercritical water oxidation apparatus comprising: a neutralizing agent adding means provided in the middle of the discharge line for neutralizing acid groups contained in the fluid flowing through the discharge line. . 9. The method according to claim 8, wherein the position of the neutralizing agent adding means provided in the middle of the discharge line is a temperature at which acid corrosion by the acid group is substantially absent and the neutralized product salt is sufficiently dissolved. A supercritical water oxidation apparatus, which is located at a position where a fluid flows. 10. The method according to claim 8, wherein the position of the neutralizing agent adding means provided in the middle of the discharge pipe is a position where a high-temperature fluid having a low solubility of the neutralized product salt flows, and A supercritical water oxidation apparatus, wherein the wetting agent is a low-temperature aqueous solution capable of cooling the temperature of the fluid by addition to a temperature at which the neutralized salt is sufficiently dissolved. 11. The vertical cylindrical reactor according to any one of claims 8 to 10, wherein the vertical cylinder type reactor is provided with a decomposition target,
A supercritical water oxidation apparatus having a supply port for an oxidizing agent and having, as a discharge section, only one discharge port for discharging a fluid generated by the reaction of supercritical water oxidation to a discharge pipe. 12. The method according to claim 8, wherein a cooling means for cooling the flowing fluid is provided at a position where the neutralizing agent adding means is provided or at a discharge pipe at a subsequent stage. Supercritical water oxidation equipment.