JP2003236363A - Process for hydrothermal oxidation reaction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose a process for a hydrothermal oxidation reaction, with which a safe and long-term operation is attained by reducing corrosion of a hydrothermal reactor and a low-cost operation is attained by reducing the amount of a neutralizing agent used. <P>SOLUTION: A mixed waste liquid 13 is prepared by introducing an alkaline waste liquid through a route 11 and an organic substance through a route 12 into a mixing vessel 1 and mixing them. In this case, the organic substance is added so as to generate excessive carbon dioxide with respect to Z value expressed by an equation, Z=([Na]+[K]+[Mg]×2+[Ca]×2)-([F]+[Cl]+[Br]+[P]×3+[S]×2) (here [Na], [K]... represent molar concentrations (mol/l) of each atom contained in a liquid to be treated). The mixed waste liquid 13 is delivered to a supplying apparatus 2a of the hydrothermal reactor 2 and is mixed with an oxidizing agent. The mixed stream is supplied to the hydrothermal reactor 2 in a downward stream and the hydrothermal oxidation reaction is carried out. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hydrothermal oxidation reaction method for carrying out a hydrothermal reaction under supercritical or subcritical conditions of water, and more particularly to a hydrothermal oxidation reaction method suitable for decomposing wastes. Is.

[0002]

2. Description of the Related Art Hydrothermal oxidation reaction treatment, in which an oxidation reaction is carried out under supercritical or subcritical conditions of water, has been attracting attention as a technology capable of oxidatively decomposing organic matter in waste liquid to a high level in a short time. By performing the hydrothermal oxidation reaction, the organic components in the liquid to be treated are decomposed into carbon dioxide, and the nitrogen components are decomposed into nitrogen gas (ammonia and nitrate nitrogen are also generated depending on the conditions). Heteroatoms such as phosphorus and sulfur are also oxidized to phosphate ions and sulfate ions, respectively.

As a major issue for practical application of hydrothermal oxidation reaction,
Corrosion of the material of the processing equipment. Generally, corrosion by an acid contained in the liquid to be treated or an acid generated by a hydrothermal oxidation reaction is large, but corrosion by an alkali is also reported. In the conventional hydrothermal oxidation reaction method, the liquid to be treated is analyzed in advance to obtain an estimated acid production amount, and a sufficient amount of a neutralizing agent for neutralizing the estimated acid production amount is supplied before the reactor is supplied (see Table 3
500264) or a method of supplying the reaction fluid after the reaction (JP-A-10-314770, JP-A-11-156186). The amount of the neutralizing agent added is such that after the reaction is completed, the hydrothermally treated water is cooled and decompressed to obtain a pH, and the pH is an appropriate value (usually pH
It was dealt with by adjusting so as to be 3 to 11).

When corrosion due to alkali is a problem, N
Since hydroxide alkali such as aOH is separated from the fluid in the reactor and adheres to the wall of the reactor, it is necessary to mix it with the neutralizing agent before supplying the reactor. However, the selection of the appropriate neutralizing agent causes another problem. For example, when a halogen-containing acid such as hydrochloric acid is used as a neutralizing agent, corrosion may occur due to the salt produced. The use of other acids may alleviate the corrosion problem somewhat, but adds to the cost of the neutralizing agent added.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to reduce corrosion of a hydrothermal reactor to enable safe and long-term operation, and to reduce the amount of neutralizing agent used. It is to propose a hydrothermal oxidation reaction method that can be operated at a cost.

[0006]

Means for Solving the Problems As a result of studying means for solving the above problems, the present inventor has found that carbon dioxide produced during the decomposition of organic matter has a neutralizing effect, and that the alkali generated in the hydrothermal reactor is It has been found that by adjusting the concentration of organic substances in the liquid to be treated so that excess carbon dioxide is generated, corrosion due to alkali can be greatly reduced.

That is, the present invention is the following hydrothermal oxidation reaction method. (1) A hydrothermal oxidation reaction method in which a liquid to be treated containing salts and an organic substance is hydrothermally reacted in a supercritical or subcritical state of water to oxidize and decompose the organic substance, which comprises cations and anions in the liquid to be treated. The concentration of ions is converted into the concentration of monovalent cation and the concentration of monovalent anion, respectively, and the difference in the cation content is large. A hydrothermal oxidation reaction method in which a hydrothermal oxidation reaction is carried out in the state of generation. (2) A hydrothermal oxidation reaction method in which a liquid to be treated containing salts and organic matter is hydrothermally reacted in a supercritical or subcritical state of water to oxidize and decompose organic substances, and each element contained in the liquid to be treated The value of Z represented by the following mathematical formula (1) showing the relationship of the concentration of 0 is 0 <Z, and hydrothermal oxidation is performed in a state where excess carbon dioxide is generated with respect to the molar concentration of cations corresponding to the Z value. A hydrothermal oxidation reaction method for carrying out the reaction.

[Equation 3] (In the formula (1), [Na], [K], [Mg], and [C]
a], [F], [Cl], [Br], [P] and [S] are molar concentrations (mol) of each atom contained in the liquid to be treated.
/ L). (3) A hydrothermal oxidation reaction method in which a liquid to be treated containing salts and an organic substance is hydrothermally reacted in a supercritical or subcritical state of water to oxidize and decompose the organic substance, each of which is contained in the liquid to be treated. The value of Z represented by the mathematical formula (1) showing the relation of the content of elements is 0 <Z, and 10 times or more molar concentration of carbon dioxide is generated with respect to the molar concentration of the cation corresponding to the Z value. A hydrothermal oxidation reaction method in which the TOC concentration in the liquid to be treated is adjusted to carry out the hydrothermal oxidation reaction. (4) The hydrothermal oxidation reaction method according to the above (2) or (3), wherein an organic substance or an organic substance-containing waste liquid is added to the liquid to be treated so that carbon dioxide having a molar concentration of 10 times or more is produced.

Specific examples of the liquid to be treated in the present invention include alkaline waste liquid containing organic substances discharged from factories, waste liquid containing organic substances discharged from factories, etc. Examples include waste liquids that become alkaline with the progress of the reaction.

The method of the present invention is a method of neutralizing an alkali with carbon dioxide, and utilizes an organic substance in the liquid to be treated as a source of the carbon dioxide. The amount of carbon dioxide used for neutralization is determined so as to be an excess molar concentration, preferably a large excess concentration, with respect to the cation excess molar concentration in the liquid to be treated, which is determined according to the above mathematical formula (1). The reason for making carbon dioxide excessive is that the reaction between carbon dioxide and a cation (such as an alkali metal) is a reaction between a gas phase and a liquid / solid phase, and the reaction rate is slow.

As a specific amount of carbon dioxide used for neutralization, the value of Z represented by the above equation (1) showing the relationship of the concentration of each element contained in the liquid to be treated is 0 <Z. hand,
The molar concentration is more than 2-fold, preferably 10-fold or higher, and more preferably 50-500-fold the molar concentration of the cation corresponding to the Z value.

Specific examples of the atom serving as a cation include alkali metals such as Na and K, alkaline earth metals such as Ca and Mg, and metal atoms such as aluminum and iron. The concentration obtained by converting the content of cations into monovalent cations is the value obtained by multiplying the actual concentration of cations having a valence of 2 or more by the ionic valence number. For example, in the case of a divalent cation, the value is twice the actual concentration. In the case of monovalent cations, the actual concentration and the converted concentration have the same value.

Specific examples of atoms constituting the anion include F, Cl, Br, P and S. The concentration obtained by converting the anion concentration into a monovalent anion is a value obtained by multiplying the actual concentration of the anion having a divalent or higher valence by the ionic valence number. For example, in the case of a divalent anion, it is a value obtained by doubling the actual concentration. In the case of monovalent anions, the actual concentration and the converted concentration have the same value.

Carbon dioxide is generated in the hydrothermal reactor by hydrothermally oxidizing an organic substance. When the content of the organic substance in the liquid to be treated is sufficient, it is not necessary to add a new carbon dioxide source, but when it is insufficient, the organic substance serving as the carbon dioxide source is added. It is desirable that the organic substance to be added be inexpensive, harmless, and easily decomposable. Hydrocarbons, alcohols and the like, which are usually used as a combustion improver for hydrothermal oxidation reaction, are suitable as a carbon dioxide source, and thus they can be added to the liquid to be treated. It is also effective to mix and treat another organic waste. Further, another waste liquid having a relatively low cation content and a relatively high organic matter content can be mixed. Since the combustion improver is necessary to maintain the temperature of the hydrothermal oxidation reaction and will eventually treat other organic wastes and waste liquids, it is not necessary to add an expensive neutralizing agent. Even if it does, it can be greatly reduced and can be processed at low cost. Organic substances, combustion improvers, other waste liquids, etc. can be supplied to the hydrothermal reactor in a state of being mixed with the liquid to be treated in advance, or can be supplied separately to the hydrothermal reactor.

The actual pH of the treated water is determined by the influence of elements other than the elements shown in the above equation (1), but this equation is effective for obtaining a rough pH value. That is, Z>
At 0, the treated water has a large number of moles of cations such as Na ⁺ and K ⁺ , and the treated water is considered to be alkaline. For example, in the case of Z = + 0.001, the molar concentration of cations such as Na ⁺ and K ⁺ is 0.001 mol / L excess, so the estimated pH is about 0.01 mol / L sodium hydroxide added to water. That is, pH = 11.

In addition to the elements shown in the formula (1), various heavy metal ions, carbonate ions, nitrogen-containing ions (NH ₄ ⁺ ,
NO ₂ ^-, NO ₃ ^- but the like), or they are less likely to be included, either only be included, or under hydrothermal reaction is decomposed, or a gas-liquid separation of the process fluid It is an element that migrates to the gas side later and in most cases does not significantly affect the neutralization reaction. However, it is considered that the pH value may greatly differ from the approximate value due to these ionic species and other factors. Therefore, even when utilizing the above formula (1), it is desirable to use a means for monitoring the pH of the treated water during treatment and adding a neutralizing agent if necessary.

It should be noted that mixing of a plurality of waste liquids may be normally carried out in one storage tank, but if there is some inconvenience (for example, generation of odor, phase separation, precipitation of solids, etc.) due to mixing. , Mix in suitable places (eg
Each of them may be fed and mixed near the inlet of the reactor).

By neutralizing the alkali with carbon dioxide, a carbonate as a neutralizing salt may be produced in the hydrothermal reactor and may be deposited in the reactor. Therefore, it is desirable to use a salt accumulation preventing means and a discharging means in combination in the hydrothermal reactor. As a specific method, means for dissolving and discharging salt by providing a water layer in the lower part of the hydrothermal reactor (patent 2726293) and means for mechanically scraping salt (USP 5,100,56)
0, JP-A-10-15566, JP-A-11-25378.
6), a known method such as a means for ejecting a fluid from the surface of the reactor to prevent adhesion (Japanese Patent Laid-Open No. 9-299966) can be adopted.

In the hydrothermal oxidation reaction, the liquid to be treated is introduced into a hydrothermal reactor to oxidize and decompose organic substances. The hydrothermal reactor is configured to oxidatively decompose organic matter by a hydrothermal oxidation reaction in the presence of an oxidant in a supercritical or subcritical state of water. Here, the hydrothermal oxidation reaction is a reaction of oxidatively decomposing an organic substance in the presence of water at high temperature and high pressure in a supercritical or subcritical state and an oxidizing agent. Supercritical state is 374 ° C or higher, 22 MPa
The above is the state. The subcritical state is, for example, 374 ° C.
Or more, 2.5 MPa or more and less than 22 MPa or 374
A state of less than 0 ° C., 22 MPa or more, or a state of 374 ° C. or less, less than 22 MPa, high temperature and high pressure close to the critical point.

Such a hydrothermal oxidation reaction is carried out in a hydrothermal reactor in a state where an organic substance is mixed with an oxidant, and these mixtures react inside the reactor. Air, oxygen, liquid oxygen, ozone, hydrogen peroxide solution, nitric acid, nitrous acid, nitrate, nitrite and the like can be used as the oxidizing agent. The oxidant may be supplied by being mixed with the liquid to be treated, or may be supplied as a multi-layered flow by using a double-tube nozzle as a supply port.
If necessary, a catalyst, a neutralizing agent and the like may be added, and these can be mixed with the liquid to be treated or supplied separately to the reactor.

The hydrothermal reactor used in the present invention has heat resistance, so that the hydrothermal oxidation reaction is performed in a supercritical or subcritical state.
It is made of a material having at least one of pressure resistance and corrosion resistance. Usually, the temperature required for the reaction is covered by the heat of oxidation reaction of the liquid to be treated itself, but when the reaction heat is insufficient, a combustion improver is added, the liquid to be treated is preheated, and the reactor is externally heated. The reaction temperature is maintained by heating or the like. The shape of the reactor is not particularly limited, but in a reactor having a small inner diameter such as a tube type, salt clogging is likely to occur, which is not suitable for application to the present invention. A tubular reactor having an inner diameter of 50 mm or more and arranged substantially vertically is preferable. The reactor may have a cylindrical shape, an elliptic cylindrical shape, or a polygonal cylindrical shape, and the lower end thereof may have a cone shape.

When a hydrothermal reaction is carried out in a supercritical or subcritical state by such a hydrothermal reactor, organic substances react with an oxidizing agent to be oxidized, and finally decomposed into at least water and carbon dioxide. Cations or anions contained in the liquid to be treated or generated by the hydrothermal oxidation reaction form an inorganic salt, and are separated in a solid or molten state. The inorganic salts also include carbonate ions produced by decomposition of organic substances and neutralized with cations. The reaction product is cooled, gas-liquid separated, decompressed, and the like, and then released as a treated gas and treated water. If necessary, a solid separating means can be provided between the reactor outlet and the treated water discharge part. This is properly used according to various purposes such as clogging and wear due to solids, or reduction of SS in treated water.

As the above-mentioned hydrothermal reactor, the one conventionally used for the hydrothermal reaction can be used as it is, but as shown in JP-A-11-156186, a mixed reaction accompanied by a reverse flow in the upper part. In the upper and lower parts of the reactor, a mixed flow of the liquid to be treated and the oxidant is supplied in a downward flow from a supply device installed in the upper part to a substantially vertical reactor forming a plug flow reaction region in the upper part. A structure is preferred in which a mixed flow accompanied by backflow is formed in the reaction zone for hydrothermal reaction, and a parallel downward plug flow is formed in the lower plug flow reaction zone for additional hydrothermal reaction. This is because the mixed reaction zone with backflow promotes the reaction between carbon dioxide and cations.

The material of the hydrothermal reactor is not limited, but is preferably a corrosion resistant material such as Hastelloy, Inconel or stainless steel. The hydrothermal reactor is preferably provided with a corrosion resistant liner. The corrosion-resistant liner is not particularly limited, and a corrosion-resistant liner having a gap between the corrosion-resistant liner and the pressure load wall as disclosed in JP-A-11-156186 can be used.

The hydrothermal reactor may be provided with means for dissolving the inorganic salt before discharging the reaction mixture from the outlet. This means is not particularly limited, but for example, by introducing water into the lower part of the reactor, the inorganic salt can be dissolved and its discharge can be promoted. Also, by introducing water containing an acid or an alkali into the lower part of the reactor, the alkali or the acid can be neutralized. When the adherence of solids is significant, a mechanical removal device for removing solids adhering to the inner wall of the reactor can be provided. The mechanical removing device for removing solids is not particularly limited, but is disclosed in Japanese Patent Laid-Open No. 11-15618.
A substantially cylindrical scraper including a notched window portion as disclosed in No. 6 is suitable.

The means for starting the reaction by the hydrothermal reactor is not particularly limited. Usually, the reactor is preheated to around a predetermined reaction temperature at the start of the reaction. Preheating can be carried out by providing a heating device in the reactor or by introducing water or air heated in the liquid to be treated and / or the oxidant supply passage. Also, normally, supplying water and an oxidant to the reactor,
It is pressurized to a predetermined pressure by a pressure adjusting valve that is usually provided. After the temperature and pressure are adjusted to predetermined values, a fluid containing the liquid to be treated is supplied to start the hydrothermal reaction. Organic substances are decomposed by the reaction, and heat of reaction is generated. When a mixing reaction zone involving backflow is provided in the upper part of the hydrothermal reactor, the organic substance, the oxidant, the contents of the reactor and the like are sufficiently mixed by the mixing action involving backflow, so that the temperature of the fluid rises. As a result, the supplied organic substance promptly starts the hydrothermal reaction, and the stable reaction is continued. The reaction fluid moves downward in the reactor, continuously reacts in the plug flow reaction region, and is then discharged from the discharge port. Reactor length: diameter ratio of 1: 1
~ 100: 1 is preferred.

In the present invention, the alkali is neutralized by the carbon dioxide produced from the organic matter as the hydrothermal oxidation reaction progresses. Therefore, the amount of the neutralizing agent used is saved to prevent the corrosion of the reactor. Will be able to. INDUSTRIAL APPLICABILITY The present invention is useful as a simple and inexpensive corrosion inhibition method in actual hydrothermal oxidation reaction.

[0027]

The hydrothermal oxidation reaction method of the present invention converts the concentrations of cations and anions in the liquid to be treated into monovalent cation and monovalent anion concentrations, respectively, and calculates the difference between the two values. The concentration of cations is high, the alkali is neutralized by performing a hydrothermal oxidation reaction in a state in which excess carbon dioxide is generated with respect to the difference in concentration, the corrosion of the hydrothermal reactor is reduced, and it is safe, In addition to enabling long-term operation, it is possible to operate at low cost by reducing the amount of the neutralizing agent used.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of a hydrothermal reaction apparatus of an embodiment for carrying out the hydrothermal oxidation reaction method of the present invention, where 1 is a mixing tank, 2 is a hydrothermal reactor, 3 is an oxidant tank, 5 is gas-liquid separation. It is a vessel.

The hydrothermal reaction treatment by the apparatus of FIG. 1 is performed as follows. First, an alkaline waste liquid is introduced into the mixing tank 1 from the system path 11, and an organic substance is introduced from the system path 12 and mixed to prepare a mixed waste solution 13. In this case, an excess with respect to the molar concentration of the cation corresponding to the value of Z represented by the formula (1),
Organic substances are preferably added so that carbon dioxide of 10 times or more molar concentration is produced.

The mixed waste liquid 13 is sent by the high-pressure pump P1 through the system 14 to the supply device 2a of the hydrothermal reactor 2, where the oxidant (eg air, sent from the oxidizer tank 3 by the high-pressure pump P2 is sent through the system 15). (Hydrogen peroxide water), and the mixed flow is supplied to the hydrothermal reactor 2 in a downward flow to perform the hydrothermal reaction. In the hydrothermal reactor 2, heating is performed by a preheater (not shown) provided in the system passage 14 or 15 at the time of starting the reaction, and the hydrothermal reaction is performed while maintaining the supercritical or subcritical state.

The mixed flow supplied from the supply device 2a forms a mixed reaction zone accompanied by a reverse flow in the upper part of the hydrothermal reactor 2, oxidative decomposition of organic substances is carried out, and the turbulent flow is eliminated in the lower part to form a plug-like flow. A reaction zone is formed to carry out an additional reaction. By such a hydrothermal reaction, carbon dioxide is produced from the organic matter. The mixed waste liquid 13 processed in the hydrothermal reactor 2 is neutralized by the generated carbon dioxide because the organic substance is added so that excess carbon dioxide is generated, and corrosion of the hydrothermal reactor 2 by alkali is prevented. To be done.

The reaction fluid of the hydrothermal reactor 2 is introduced into the cooler 19 from the system passage 16, cooled by the cooling water supplied from the cooling water passage 21, and introduced into the gas-liquid separator 5 from the system passage 22 to be vaporized. The liquid is separated, the gas is discharged from the gas discharge path 23 through the valve V1, and the treated water is discharged from the liquid discharge path 24 through the valve V2. The treated water obtained is of high quality in which organic substances, ammonia, and other substances to be reacted are decomposed, and can be recovered and used.

Although organic substances are added to the waste liquid in FIG. 1,
It is also possible to prepare a mixed waste liquid by adding other organic waste or a waste liquid containing the organic substance in a relatively high concentration in place of the organic substance. When the organic matter and the organic waste do not mix well with the waste liquid and are separated, they can be separately supplied to the hydrothermal reactor 2. In FIG. 1, the high pressure pump P2
A compressor can be used instead of.

[0034]

EXAMPLES Examples 1 and 2 and Comparative Example 1 0.022 mol / L solution of sodium acetate (Sample 1,
Comparative Example 1), which was prepared by adding methanol as a carbon dioxide source so as to be 1.40 mol / L (Sample 2,
In Example 1), a solution obtained by adding methanol to a 0.05 mol / L solution of sodium acetate to a concentration of 0.40 mol / L (Sample 3, Example 2) was used. I went there.

Sample preheated to 300 ° C. and oxidizer (35%
Hydrogen peroxide solution diluted 5 times) was mixed in front of the reactor, and the mixture was supplied into the reactor through a nozzle (tube diameter 1 mmφ). An external heater was attached to the reactor, and the reaction conditions were adjusted to 650 ° C. and 24 MPa. A test rod (1.6
mmφ) can be attached. Water and an oxidizing agent were supplied to the reactor, and the inside of the reactor was adjusted by heating with an external heater so that the reaction temperature was set. When the reaction temperature reached the set value, the water and the sample were gradually switched to carry out the hydrothermal reaction in the supercritical or subcritical state of water. The reaction was continued for 4 hours after the water and the sample were completely switched, the sample was gradually switched to water, and then the heater was turned off to end the test. In order to minimize corrosion during cooling, the reactor was cooled by flowing only air after turning off the heater. After the test, the test rod was taken out and several sections were observed to determine the maximum corrosion depth. In Example 1, a tube having an inner diameter of 5 mm was used, and in Example 2, a vertical tube reactor having an inner diameter of 50 mm was used and a supply nozzle having an inner diameter of 1 mm was used. The results are shown in Table 1.

[0036]

[Table 1]

As can be seen from the results in Table 1, in Example 2 in which methanol was added so that carbon dioxide having a 10-fold molar concentration was produced, the amount of corrosion was significantly reduced as compared with Comparative Example 1 having a 2-fold molar concentration. did it. It is considered that this is because the carbon dioxide neutralization effect was sufficiently exerted.

[Brief description of drawings]

FIG. 1 is a system diagram of a hydrothermal reaction apparatus of an embodiment for carrying out the hydrothermal oxidation reaction method of the present invention.

[Explanation of symbols]

1 mixing tank 2 Hydrothermal reactor 3 oxidizer tank 5 gas-liquid separator 11, 12, 14, 15, 16, 22 Route 13 Mixed waste liquid 19 Cooler 21 Cooling channel 23 Gas discharge path 24 Liquid discharge path

Continued front page    (71) Applicant 598124412             General Atomix Incorporated             Itted             United States of America California Sun             Diego General Atomics Co             3550 (72) Inventor Hiroshi Obuse             Kurita, 3-4-3 Nishi-Shinjuku, Shinjuku-ku, Tokyo             Industry Co., Ltd. (72) Inventor Kiyoyuki Kitano             1200 Manda, Hiratsuka-shi, Kanagawa Made by Komatsu Ltd.             Sakusho Central Research Institute (72) Inventor Yasuhiko Hatake             1200 Manda, Hiratsuka-shi, Kanagawa Made by Komatsu Ltd.             Sakusho Central Research Institute F term (reference) 4D050 AA13 AB07 BB01 BB02 BB08                       BB09 BC01 BC02 BC06 BD02                       BD03 CA03

Claims (4)

[Claims] 1. A hydrothermal oxidation reaction method in which a liquid to be treated containing salts and an organic substance is hydrothermally reacted in a supercritical or subcritical state of water to oxidize and decompose the organic substance, wherein cations in the liquid to be treated are contained. And the concentration of anions are converted into the concentration of monovalent cations and monovalent anions, respectively,
A hydrothermal oxidation reaction method in which the hydrothermal oxidation reaction is carried out in a state in which the cation content is large due to the difference between the two and carbon dioxide in excess of twice the molar concentration with respect to the difference is produced. 2. A hydrothermal oxidation reaction method in which a liquid to be treated containing salts and an organic substance is hydrothermally reacted in a supercritical or subcritical state of water to oxidize and decompose the organic substance, which is contained in the liquid to be treated. The value of Z represented by the following mathematical formula (1) showing the relationship of the concentration of each element is 0 <Z, and water is produced in a state where excess carbon dioxide is generated with respect to the molar concentration of cations corresponding to the Z value. A hydrothermal oxidation reaction method for performing a thermal oxidation reaction. [Equation 1] (In the formula (1), [Na], [K], [Mg], and [C]
a], [F], [Cl], [Br], [P] and [S] are molar concentrations (mol) of each atom contained in the liquid to be treated.
/ L). ) 3. A hydrothermal oxidation reaction method in which a liquid to be treated containing salts and an organic substance is hydrothermally reacted in a supercritical or subcritical state of water to oxidize and decompose the organic substance, which is contained in the liquid to be treated. The value of Z represented by the following mathematical formula (1) showing the relation of the content of each element is 0 <Z, and carbon dioxide in a molar concentration 10 times or more the molar concentration of the cation corresponding to the Z value is generated. TOC in the liquid to be treated so as to generate
A hydrothermal oxidation reaction method in which the concentration is adjusted to perform a hydrothermal oxidation reaction. [Equation 2] (In the formula (1), [Na], [K], [Mg], and [C]
a], [F], [Cl], [Br], [P] and [S] are molar concentrations (mol) of each atom contained in the liquid to be treated.
/ L). ) 4. The hydrothermal oxidation reaction method according to claim 2, wherein an organic substance or an organic substance-containing waste liquid is added to the liquid to be treated so that carbon dioxide having a molar concentration of 10 times or more is produced.