JP2002273195A - Hydrothermal reaction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hydrothermal reaction method capable of efficiently performing hydrothermal reaction while simply and certainly controlling reaction temperature, and also capable of preventing the contamination of piping or a supply port. SOLUTION: In the hydrothermal reaction method for subjecting an organic substance to be reacted and an oxidizing agent to hydrothermal reaction in a supercritical or sub-critical state of water in a reactor, an organic compound with a solubility parameter of 11 or less and a specific inductivity of 15 or more is supplied to the reactor as auxiliary fuel to perform reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for oxidatively decomposing or hydrolyzing an organic reactant by a hydrothermal reaction in a supercritical or subcritical state of water in the presence of an oxidizing agent. The present invention relates to a hydrothermal reaction method capable of stably controlling a reaction.

[0002]

2. Description of the Related Art Hitherto, in the decomposition of waste, generation of energy, production of chemical substances, etc., a method of oxidatively decomposing or hydrolyzing an object to be treated by using a hydrothermal reaction has been widely used. In particular, in recent years, a hydrothermal reaction method capable of substantially decomposing organic substances in an object to be treated in a short time by reacting the object to be treated and water containing an oxidizing agent in a supercritical state of water or a subcritical state close to the same has been developed. Attention has been paid. The organic matter in the object to be processed becomes a high-temperature and high-pressure reaction product composed of water and carbon dioxide by an oxidation reaction including combustion. The reaction product is
Energy is recovered or cooled and decompressed to separate gas and liquid components.

[0003] When a hydrothermal reaction is performed in a supercritical or subcritical state of water as described above, heat of reaction is generated by an oxidation reaction, and the temperature in a device such as a reactor rises. Therefore, by controlling the concentration of the reactants in the reactor with water or cooling the reactor by adding water, the temperature in the reactor and other equipment is controlled so that it does not exceed the allowable temperature of the equipment materials. Have been. Conversely, if the amount of heat in the reactor is too low, it is necessary to obtain the reaction temperature necessary for the decomposition of organic substances.Therefore, measures to increase the temperature in the reactor by adding heat from the outside or adding an auxiliary fuel are required. Is being done. Kerosene, isopropyl alcohol, and methanol are known as auxiliary fuels. However, it is sometimes difficult to maintain an appropriate temperature for efficiently and reliably decomposing organic substances in the reactor only by using the above-mentioned temperature adjusting means.

In the above-mentioned hydrothermal reaction, an object to be treated, an oxidizing agent, an auxiliary fuel, etc., which are previously mixed or mixed in a pipe, are supplied into the reactor from a reactant supply port.
A hydrothermal reaction takes place in the reactor. When these reactants are supplied, the reactants often adhere to the pipes and supply ports, thereby contaminating the pipes and supply ports. For example, when performing a continuous hydrothermal reaction process, even if the concentration of each reactant is accurately measured and injected into the reactor, it may adhere to pipes and supply ports, The concentration of the reactants in the reactor changes. Further, when the contamination becomes severe, the supply port may be blocked. As a result, the temperature inside the reactor becomes unstable, and it becomes difficult to control the temperature and pressure inside the apparatus, and an emergency stop of the reaction treatment has occurred.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to control a reaction temperature easily and reliably by using a specific auxiliary fuel to efficiently perform a hydrothermal reaction. It is to propose a hydrothermal reaction method that can prevent mouth pollution.

[0006]

The present invention is the following hydrothermal reaction method. (1) A hydrothermal reaction method in which an organic reactant and an oxidizing agent are hydrothermally reacted in a supercritical or subcritical state of water in a reactor. A hydrothermal reaction method in which an organic compound having a dielectric constant of 15 or more is supplied to a reactor to perform a reaction. (2) The method according to the above (1), wherein the auxiliary fuel is at least one organic compound selected from the group consisting of acetone, 2-butanol and acetaldehyde.

The present inventors have conducted intensive studies on the above-mentioned conventional problems in the hydrothermal reaction. As a result, if the compatibility of the reactants such as the reactant and the auxiliary fuel is poor, phase separation occurs in the subject, It was found that the reaction temperature was not stable. For example, when kerosene conventionally used as an auxiliary fuel is used, kerosene hardly dissolves in water, so if the substance to be treated is a highly polar substance, phase separation occurs in the reactant injected into the reactor. As a result, it was found that the mixing of the reactants tended to be uneven. Similarly, when isopropyl alcohol or methanol is used as an auxiliary fuel, phase separation also occurs in the reactants injected into the reactor due to insufficient compatibility with low-polarity substances to be treated. Was. As a result of such phase separation, the reaction temperature is not stable. Regarding contamination of pipes and supply ports, when reactants that easily cause phase separation from each other are introduced into the reactor, phase separation occurs at the pipes and supply ports, and low-polarity reactants such as kerosene cause the pipes and supply ports to react. It was found that it easily adhered to the supply port.

Therefore, in the hydrothermal reaction method of the present invention,
Regardless of the polarity of the reactant involved in the hydrothermal reaction, an organic compound having a solubility parameter of 11 or less and a relative dielectric constant of 15 or more is used as an auxiliary fuel as a compatible organic compound. As a result, it has been possible to provide a stable hydrothermal reaction by preventing phase separation and stabilizing the reaction temperature of the hydrothermal reaction, and preventing contamination of the piping and the reactor.

The reactant to be treated in the present invention is an organic reactant and contains an organic substance which can be oxidatively decomposed by a hydrothermal reaction. Specific examples include waste liquid, waste, waste solvent, sludge, human waste, sewage, bacteria, plastic waste, membrane, adsorption resin, ion exchange resin, activated carbon, and the like. The object to be processed may include an inorganic substance in addition to the organic substance.

In the present invention, such a reactant is oxidatively decomposed by a hydrothermal reaction in a supercritical or subcritical state of water in the presence of an oxidizing agent. Supercritical state is 374 ° C or higher, 22MPa
This is the state described above. The subcritical state is, for example, 374 ° C.
More than 2.5MPa and less than 22MPa or 374
C. or lower and 22 MPa or higher, or 374 ° C. or lower and lower than 22 MPa, a high-temperature and high-pressure state close to a critical point. The oxidizing agent is not particularly limited, and examples thereof include air, oxygen-enriched air, oxygen, liquid oxygen, hydrogen peroxide, and nitrate. When the calorie of the reactant is insufficient in such a hydrothermal reaction, an auxiliary fuel is supplied to the reactor to perform the reaction. The auxiliary fuel is an organic compound having a solubility parameter of 11 or less and a relative dielectric constant of 15 or more.

A solubility parameter (solubility coefficient: solubili)
The ty parameter) is a temperature-dependent material constant that is a measure of the mixing property of molecules, and substances having similar solubility parameter values are easily mixed. For example, non-polar substances readily mix with substances having low solubility parameters. The solubility parameter is a value σ represented by the following equation (1). σ = (E / V) ^1/2 (1) (In the above equation (1), E is the evaporation energy (cal
/ Mol) and V are molecular volumes (cc / Mol), each of which is a value at 25 ° C. )

The relative permittivity is a material constant indicating the polarity of a substance. The larger the value, the higher the polarity. The dielectric constant is a value epsilon _s represented by the following formula (2). ε _s = ε ₁ / ε ₀ (2) (In the above formula (2), ε ₁ is a dielectric constant in a substance, and ε ₀ is a dielectric constant in a vacuum. In the present invention,
The relative permittivity is the relative permittivity of a liquid at 25 ° C. unless otherwise indicated. )

The organic compounds used as auxiliary fuels include:
The solubility parameter is 11 or less, preferably 11 to 9,
And, it is not particularly limited as long as it is an organic compound having a relative dielectric constant of 15 or more, preferably 15 to 38, among which acetone (solubility parameter = 9.9, relative dielectric constant = 20.7),
It is at least one organic compound selected from the group consisting of 2-butanol (solubility parameter = 10.5, relative permittivity = 16.56) and acetaldehyde (solubility parameter = 10.3, relative permittivity = 21.1). Is preferred. The organic compound as the auxiliary fuel does not need to be a pure substance, and may be, for example, a waste solvent containing another organic substance, inorganic substance, moisture, or the like.

As described above, by using an organic compound having a solubility parameter of 11 or less as an auxiliary fuel,
Phase separation is less likely to occur with respect to the reactant having a low polarity. Further, by using an organic compound having a relative dielectric constant of 15 or more as an auxiliary fuel, it becomes difficult to cause phase separation for a highly polar reactant or the like. Therefore, the solubility parameter is 11 or less and the relative dielectric constant is 1
The five or more organic compounds are compatible with both the polar reactant and the non-polar or low-polar reactant. By using such an organic compound as an auxiliary fuel, phase separation is unlikely to occur without regard to the polarity of the reactant even if the reactant has a variation in polarity. As a result, the reaction temperature is stabilized in the hydrothermal reaction.

In the hydrothermal reaction, a reactant, an oxidizing agent, an auxiliary fuel, and if necessary, water are supplied from a supply port into the reactor, and the reactor is maintained in a supercritical or subcritical state of water. Perform oxidative decomposition. The reactor for performing the hydrothermal reaction may be of any type as long as the reaction can be performed safely and stably. For example, a reactor of a tube type, a vessel type, a cylinder type, or the like can be used.
A vertical tube type reactor as shown in No. 56186 and a tubular type reactor as shown in Japanese Patent No. 3036077 can also be used. The reactor is formed of a heat-resistant and pressure-resistant material so that a hydrothermal reaction can be performed in a supercritical or subcritical state. For example, a corrosion-resistant material such as Hastelloy, Inconel, or stainless steel is preferable. If the supercritical or subcritical state is not reached only by the heat of reaction, an external heating means can be provided outside the reactor.

The supply of the reactants and the like to the reactor is not particularly limited, and any supply may be used. For example, a reactant supply pipe, an oxidant supply pipe, an auxiliary fuel supply pipe, and a water supply pipe are connected as necessary, and they are mixed immediately before being supplied to the reactor, respectively. May be supplied. Alternatively, the reactant, auxiliary fuel, and water may be preliminarily mixed, an oxidant may be added to the mixture supply pipe, and the mixture may be supplied to the reactor from the supply port. When the reactant is a liquid, a high-pressure pump or the like is used, and when the reactant is a gas, a gas compressor such as an air compressor or a booster is used. In the present invention, the auxiliary fuel does not adhere to the supply pipe or the supply port at the time of supply, and further has the effect of cleaning the inner surface of the supply pipe or the supply port. Contamination due to the adhesion of water can be prevented.

At the start of the hydrothermal reaction, the reactor is usually preheated to around a predetermined reaction temperature, and the reactants such as reactants supplied into the reactor are also preheated. Preheating of the reactants can be performed by providing a heating device in a reactor, a reactant supply passage, an oxidant supply passage, and the like. Usually, water or an oxidizing agent is supplied to the reactor, and the reactor is pressurized to a predetermined pressure by a normally provided pressure regulating valve. Predetermined temperature,
After the pressure is adjusted, the fluid containing the reactant is supplied to start the hydrothermal reaction.

The reaction temperature and pressure in the hydrothermal reaction are as follows:
The temperature and pressure are set so as to bring the water into a supercritical or subcritical state, but it is preferable to set the reaction temperature to a predetermined temperature in order to stably and surely decompose the object to be treated. For example, 500-700 for general organic matter decomposition
By controlling the temperature to 550 ° C., preferably 550 to 650 ° C., decomposition into carbon dioxide and water is possible. 550 to 700 when containing ammonia nitrogen or organic nitrogen
C., preferably 600 to 650.degree. C., enables decomposition into nitrogen gas. Since the reaction temperature fluctuates due to fluctuations in the total calorific value of the reactants, it is preferable to control the temperature while monitoring the reaction temperature of the hydrothermal oxidation reaction. In the present invention, since the reaction temperature can be prevented from becoming unstable due to phase separation, the reaction temperature can be easily and simply controlled by adjusting the concentration, flow rate, etc. of the reactants, oxidizing agent, auxiliary fuel, etc. supplied to the reactor. It can be done reliably. For the flow rate control, a monitoring unit may be provided in each supply unit. If the reactant contains sufficient water, it is not necessary to supply water.However, if the amount of water is insufficient or the amount of heat is too high and the temperature becomes too high, supply water to supplement the amount of water. , Can be diluted.

The reaction pressure in the hydrothermal reaction does not have to be particularly taken into consideration because it does not greatly affect the properties of the treated material as much as the reaction temperature, but it is desirable to maintain a constant level for stable control.

When the hydrothermal reaction is carried out in the supercritical or subcritical state of water in the reactor as described above, the organic matter to be reacted is oxidized by an oxidizing agent and finally decomposed into water and carbon dioxide. Alternatively, the molecular weight is reduced by hydrolysis, and the inorganic substance is separated in a solid or molten state. The reaction product is discharged from the outlet, cooled, depressurized, and separated into a gas component and a liquid component. At this time, it is preferable that the solid is separated.

As a cooling method for discharging the reaction product from the outlet, for example, water may be introduced into the reactor to cool it. In this case, the inorganic salt is dissolved to promote the discharge. Can be. The reactor may be cooled by introducing water containing an acid or an alkali into the reactor. In this case, the alkali or the acid can be neutralized. If the solids in the reaction product are significantly attached, mechanical removal may be performed to remove the solids attached to the inner wall of the reactor. To remove the reaction product, the pressure in the reactor may be used, and a means for lowering the temperature by a cooler or reducing the pressure by a pressure reducing valve may be employed.

Separating solids, for example, inorganic salts, in the reaction fluid discharged from the hydrothermal reactor facilitates reuse of the treated water. The method for separating the solid matter is not particularly limited, and a conventionally known method can be employed. The solid separation may be performed in a cooling or depressurizing step or before the cooling step.

[0023]

According to the hydrothermal reaction method of the present invention, an organic compound having a solubility parameter of 11 or less and a relative dielectric constant of 15 or more is used as an auxiliary fuel, and the auxiliary fuel has various polarities. Since it has good compatibility with, for example, the material to be treated and the like, phase separation hardly occurs and the reaction temperature in the reactor is stabilized. In addition, the auxiliary fuel does not adhere to the supply pipe or the supply port and does not cause contamination. Further, the supply pipe or the supply port can be cleaned by passing the auxiliary fuel, so that the contamination due to the adhesion of the processing object or the like can be achieved. Can also be prevented. Therefore, the concentration of each substance in the reactor becomes close to the set value, and the hydrothermal reaction control can be easily and reliably controlled.

[0024]

Embodiments of the present invention will be described below. Example 1 A hydrothermal reaction was performed using waste emulsion (TOC: 27000 ppm) as a reactant and acetone (solubility parameter = 9.9, relative dielectric constant = 20.7) as an auxiliary fuel.
A stainless tube having an inner diameter of 9.45 mm and a length of 600 mm was used as a reactor. The reaction was started with acetone as an auxiliary fuel at 0.25 ml / m 2 using a high pressure pump from the supply port.
Pressed in. A 35% hydrogen peroxide solution was used as an oxidizing agent, and pressure was injected at 3 ml / min using a high-pressure pump.
Hydrogen peroxide was preheated to 370 ° C. by an external heat source in the pipe section, and then injected into the pipe just before the supply port and mixed. After the stabilization, the supply amount of the auxiliary fuel was reduced by half, and the reactant was supplied at 2 ml / min. The reactant and the auxiliary fuel were mixed in a pipe before the oxidant was injected. The temperature of the reaction fluid was set to 650 by a ceramic heater provided outside the reactor and a thermocouple provided inside.
° C. The pressure is controlled by a pressure regulating valve provided at the outlet.
It was adjusted to MPa.

The hydrothermal reaction continued stably for 1 hour or more.
After the reaction, the reaction fluid is cooled by a double tube cooler and then decompressed,
Further, gas-liquid separation was performed to obtain a processing gas and a processing liquid. The treatment liquid was colorless and transparent, TOC was 10 ppm, and organic matter was almost completely decomposed.

Example 2 Except that 2-butanol (solubility parameter = 10.5, relative permittivity = 16.56) was used as an auxiliary fuel,
A hydrothermal reaction was performed in the same manner as in Example 1. The hydrothermal reaction continues stably for 1 hour or more, the treatment liquid is colorless and transparent, and the TOC is 10
In ppm, organic matter was almost completely decomposed.

Comparative Example 1 Isopropyl alcohol (solubility parameter = 11.
5, relative permittivity = 19.92) was used as the auxiliary fuel, and a hydrothermal reaction was performed in the same manner as in Example 1. But,
Five minutes after the start of the supply of the liquid to be treated, the inlet was closed, and the reaction could not be continued. When the supply port was decomposed, a waste emulsion component was deposited and the supply port was closed.

Comparative Example 2 Kerosene (solubility parameter = 7.9, relative permittivity = 1.
A hydrothermal reaction was performed in the same manner as in Example 1 except that 9) was used as an auxiliary fuel. However, the temperature of the reaction fluid was not stable, and the temperature exceeded the preset allowable temperature (670 ° C.) 15 minutes after the start of the reaction, so that the reaction could not be continued.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) B09B 3/00 304Z (71) Applicant 598124412 General Atmix Inc. San Diego, California, USA General Atomics Coat 3550 (72) Inventor Masaaki Wakita 3-4-7 Nishi-Shinjuku, Shinjuku-ku, Tokyo F-term (reference) 4K004 AA02 AA07 AA47 AC04 CA39 CC01 CC02 CC03 CC11 CC15 DA03 DA20 4D050 AA12 AA15 AA20 AB07 BB01 BB08 BB09 BC01 BC02 BC10 BD02 BD03 BD08 4D059 AA00 AA01 BC01 DA44 DA47 DA70 DB01 DB02

Claims (2)

[Claims] 1. A hydrothermal reaction method in which an organic reactant and an oxidant are hydrothermally reacted in a supercritical or subcritical state of water in a reactor, wherein the auxiliary fuel has a solubility parameter of 11 or less. A hydrothermal reaction method in which an organic compound having a relative dielectric constant of 15 or more is supplied to a reactor to perform a reaction. 2. The method according to claim 1, wherein the auxiliary fuel is at least one organic compound selected from the group consisting of acetone, 2-butanol and acetaldehyde.