JP2004181427A - Hydrothermal reaction method and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrothermal reaction method capable of recovering the energy from a reaction fluid produced in a hydrothermal reaction and efficiently condensing a liquid to be treated of a low organic concentration, thereby realizing an efficient and inexpensive hydrothermal oxidation reaction, and to provide an apparatus therefor. <P>SOLUTION: In the hydrothermal reaction method, the liquid to be treated is condensed by a steam compression type condenser 2, the condensed liquid is fed to a hydrothermal reactor 7, and compressed air from an air compressor 8 is fed to the hydrothermal reactor 7 to perform the hydrothermal oxidation reaction in the supercritical or subcritical state of water. The reaction fluid discharged from the hydrothermal reactor 7 is cooled by a cooler 13, a high-pressure gas separated by vapor-liquid separation in a vapor-liquid separator 14 is fed to a turbine 6 as a steam compressed motive force source of the condenser 2, and a steam compressor 5 is driven to continue condensation in the condenser 2. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydrothermal reaction method and apparatus for concentrating a liquid to be treated and oxidatively decomposing organic substances in a supercritical or subcritical state of water.
[0002]
[Prior art]
As a method for treating a liquid to be treated containing an organic substance such as an organic waste liquid, a hydrothermal reaction in which a water is subjected to a hydrothermal oxidation in a supercritical or subcritical state in the presence of water and an oxidizing agent to oxidatively decompose the organic substance is used. is there. This hydrothermal reaction can decompose organic effluents to a high level in a short time, and can also efficiently process high-concentration effluents in a short time. In such a hydrothermal reaction, since the calorific value increases as the concentration of the organic substance increases, when the liquid to be treated containing a low concentration of the organic substance is treated, the liquid to be treated is concentrated and then the hydrothermal reaction is performed.
[0003]
In order to concentrate the liquid to be treated, a concentration method by evaporation is widely used. As the evaporative concentration method, a method is generally used in which steam is generated by a boiler and the liquid to be treated is concentrated with the generated steam (for example, in Patent Document 1, concentration is performed using a multi-stage evaporator). However, in order to generate steam by such a method, heating is required. In the hydrothermal reaction, the reaction is performed in a supercritical or subcritical state of water, so a high-temperature reaction fluid is generated, but heat is recovered because the total calorific value is not enough to concentrate the liquid to be treated. Even in such cases, external heat input is required.
[0004]
As a result of studying other evaporative concentration methods for concentrating the liquid to be treated, when concentration is performed using a vapor compression concentrator, energy is recovered from the reaction fluid generated by the hydrothermal reaction, and the liquid to be treated is efficiently collected. It was found that it could be concentrated.
[0005]
[Patent Document 1]
JP-A-11-77089 [0015], [0017], [0023]
[0006]
[Problems to be solved by the invention]
An object of the present invention is to recover water from a reaction fluid generated by a hydrothermal reaction and efficiently concentrate a liquid to be treated having a low organic substance concentration, thereby enabling water to efficiently perform a hydrothermal oxidation reaction at low cost. It is to obtain a thermal reaction method and apparatus.
[0007]
[Means for Solving the Problems]
The present invention is the following hydrothermal reaction method and apparatus.
(1) a concentration step of condensing the liquid to be treated with a vapor compression concentrator;
A concentrate supply step of supplying the concentrated concentrate to the hydrothermal reactor,
In the presence of water and an oxidizing agent in a hydrothermal reactor, a hydrothermal oxidation reaction in a supercritical or subcritical state of water, and a hydrothermal reaction step of oxidatively decomposing organic substances,
A high-pressure gas supply step of supplying a high-pressure gas discharged from the hydrothermal reaction step as a vapor compression power source of the concentrator.
(2) The method according to the above (1), wherein the concentrator compresses the steam by a turbine powered by a high-pressure gas as a heating source to concentrate the liquid to be treated.
(3) The method according to the above (1) or (2), wherein air is used under pressure as an oxidizing agent.
(4) The method according to any one of (1) to (3) above, wherein the high-pressure gas is obtained by cooling the hydrothermal reaction fluid and performing gas-liquid separation.
(5) a vapor compression concentrator for condensing the liquid to be treated;
Concentrate supply means for supplying the concentrated concentrate to the hydrothermal reactor,
In the presence of water and an oxidizing agent, a hydrothermal oxidation reaction in a supercritical or subcritical state of water, and a hydrothermal reactor that oxidatively decomposes organic matter,
A high-pressure gas supply means for supplying high-pressure gas discharged from the hydrothermal reactor as a vapor compression power source of the concentrator.
(6) The apparatus according to the above (5), wherein the concentrator compresses steam as a heating source by using a turbine driven by high-pressure gas as a power source to concentrate the liquid to be treated.
(7) The apparatus according to the above (5) or (6), further comprising a compressor that pressurizes air as an oxidant and supplies the compressed air to a hydrothermal reactor.
(8) The apparatus according to any one of the above (5) to (7), wherein the high-pressure gas is obtained by cooling the hydrothermal reaction fluid and performing gas-liquid separation.
[0008]
The target liquid to be treated in the present invention is a liquid containing an organic substance that can be converted into a harmless substance by a hydrothermal oxidation reaction such as an organic waste liquid, and particularly, a target liquid containing a low-concentration organic substance is treated. Suitable as a target. Such liquids to be treated include, but are not limited to, food production waste liquids, industrial waste liquids containing organic substances, sewage, human waste, and other organic substance-containing waste liquids. The concentration of the organic substance in the liquid to be treated is generally 0.1 to 20% by weight, preferably 0.5 to 10% by weight, which is suitable for the treatment.
[0009]
In the present invention, such a liquid to be treated is concentrated by a vapor compression concentrator in the concentration step. The concentration of organic substances in the concentrated liquid is generally 2 to 30% by weight, preferably 5 to 20% by weight, suitable for the hydrothermal reaction. The vapor compression concentrator generates steam by heating and / or decompression, compresses the generated steam to increase the temperature, and heats the liquid to be treated with the compressed steam having the increased temperature to generate steam. This is a method of further compressing and heating to concentrate the liquid to be treated. In this method, power for driving the compressor is required. However, in the present invention, a high-pressure gas is recovered from a reaction fluid generated by a hydrothermal reaction described later, and the compressor is driven to thereby obtain a low organic matter concentration. Concentrate the processing solution efficiently. The vapor compression concentrator is preferably one that compresses steam by a turbine using a high-pressure gas as a power source, uses it as a heating source, and concentrates the liquid to be treated.
[0010]
In the concentrated liquid supply step of the present invention, the concentrated liquid supply means is configured to supply the concentrated liquid concentrated by the vapor compression concentrator in the concentration step to the hydrothermal reactor. Since the hydrothermal reactor is maintained at a high temperature and a high pressure, the concentrate supply means is configured to pressurize the concentrate, and in some cases, heat and supply the concentrate to the hydrothermal reactor. In this case, for example, air may be pressurized as an oxidant and supplied to the hydrothermal reactor together with the waste liquid.
[0011]
In the hydrothermal reaction step, the concentrated liquid supplied by the concentrated liquid supply means is subjected to a hydrothermal oxidation reaction in a supercritical or subcritical state of water in the presence of water and an oxidizing agent in a hydrothermal reactor to form a concentrated liquid. The organic matter contained is oxidatively decomposed. The hydrothermal reactor is configured to perform a hydrothermal oxidation reaction by maintaining the waste liquid in a supercritical or subcritical state of water in the presence of an oxidizing agent. Here, the hydrothermal oxidation reaction is a reaction in which a concentrated solution is oxidatively decomposed by an oxidation reaction in the presence of supercritical or subcritical high-temperature and high-pressure water and an oxidizing agent. The supercritical state is a state of 374 ° C. or higher and 22 MPa or higher. The subcritical state refers to, for example, a state of 374 ° C. or more, 2.5 MPa or more and less than 22 MPa, or a state of 374 ° C. or less, 22 MPa or more, or a high temperature and high pressure state of less than 374 ° C. or less than 22 MPa close to a critical point.
[0012]
Such a hydrothermal oxidation reaction is performed in a hydrothermal reactor in a state where the concentrate is mixed with an oxidizing agent, and the mixture undergoes a hydrothermal reaction inside the reactor. As the oxidizing agent, air, oxygen, liquid oxygen, aqueous hydrogen peroxide, nitric acid, nitrous acid, nitrate, nitrite, and the like can be used. Preferably, air is supplied under pressure. The oxidizing agent may be supplied after being mixed with the concentrated liquid, or may be supplied as a multi-layer flow by using a double tube nozzle as a supply port. If necessary, a catalyst, a neutralizing agent, and the like may be added. These may be mixed with the concentrated solution or separately supplied to the reactor.
[0013]
The hydrothermal reactor used in the present invention performs a hydrothermal reaction in a supercritical or subcritical state. Formed in a container. When the supercritical or subcritical state is not reached only by the heat of reaction, an external heating means can be provided. A cylindrical, elliptical, or polygonal cylindrical reactor can be used as the shape of the cylindrical reactor, and the lower end portion can have a cone shape. As the above-mentioned hydrothermal reactor, those conventionally used in hydrothermal oxidation reactions can be used as they are.
[0014]
The material of the hydrothermal reactor is not limited, but is preferably a corrosion-resistant material such as Hastelloy, Inconel, or stainless steel. Preferably, the hydrothermal reactor is 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 can be used.
[0015]
The hydrothermal reactor can be provided with cooling means for cooling the reaction mixture before discharging it from the outlet. The cooling means is not particularly limited, but quenching water can be introduced into the reactor to cool it, and the inorganic salt can be dissolved to facilitate its discharge. In addition, water containing an acid or an alkali can be introduced into the reactor and cooled to neutralize the alkali or the acid. If the solid is very sticky, a mechanical removal device for removing the solid attached to the inner wall of the reactor can be provided. The mechanical removal device for removing solids is not particularly limited, but a substantially cylindrical scraper including a cutout window is preferable.
[0016]
Separation means for separating solids in the reaction fluid discharged from the hydrothermal reactor can be provided. In particular, since the inorganic salts are not dissolved but contained as a solid in the reaction fluid in a supercritical state, the reuse of the treated water is facilitated by separating the insolubilized inorganic substances. The solid matter separation means is not particularly limited, and a container provided with an inlet for introducing a reaction fluid from a hydrothermal reactor and an outlet for discharging a fluid from which solids have been removed, and a container provided in the container and having the reaction fluid One provided with a means for removing and discharging the solid contained therein can be used. In the step of cooling and depressurizing the reaction fluid discharged from the hydrothermal reactor, means for solid separation or gas-liquid separation may be provided.
[0017]
In the present invention, in the hydrothermal reaction step, the hydrothermal reaction is performed in a supercritical or subcritical state by the above-described hydrothermal reactor. The means for initiating 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 performed by providing a heating device in the reactor or by introducing a heating fuel such as kerosene with water or an oxidizing agent. Further, 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. After the temperature and pressure are adjusted to the predetermined values, the fluid containing the concentrated liquid as the reactant is supplied to start the hydrothermal reaction.
[0018]
Organic matter is decomposed by the hydrothermal reaction, and heat of reaction is generated. At this time, in the hydrothermal reaction step, the organic matter in the concentrated liquid is oxidized by the oxidizing agent and is finally decomposed into water and carbon dioxide, and the inorganic matter is separated in a solid state, a dissolved state or a molten state. The reaction fluid is water, carbon dioxide, and inorganic substances generated by the above-described hydrothermal reaction, unreacted components in the concentrated solution and the oxidizing agent, such as water in the concentrated solution, and nitrogen gas when air is used as the oxidizing agent. Is included.
[0019]
The reaction fluid exiting the hydrothermal reactor is cooled and gas-liquid separated without or after separating solids. After gas-liquid separation, the gas is depressurized to an intermediate pressure, and a part of the gas is used as a high-pressure gas and used as a power source for the concentration step. The remaining gas is released to the outside after further reducing the pressure to atmospheric pressure. After confirming that the liquid does not contain harmful substances, discharge it out of the system.
[0020]
The high-pressure gas to be separated here is preferably cooled and depressurized so as to have a pressure of 0.5 to 2 MPa. The high-pressure gas from which the liquid has been separated mainly contains carbon dioxide and unreacted components in the oxidizing agent. For example, when air is used as the oxidizing agent, nitrogen gas is a main component, which includes carbon dioxide and other gases.
[0021]
The high-pressure gas supply means is configured to supply the high-pressure gas separated from the hydrothermal reaction step to the vapor compression concentrator as a vapor compression power source in the high-pressure gas supply step. If the steam compression concentrator has a structure in which steam is compressed by a turbine powered by high-pressure gas and used as a heating source, the high-pressure gas shall be supplied to the turbine and used as the power source for the steam compressor. Can be.
[0022]
By operating the vapor compression concentrator using the high-pressure gas separated from the hydrothermal reaction step as a vapor compression power source, energy can be recovered from the reaction fluid and the liquid to be treated having a low organic substance concentration can be efficiently concentrated. . In this case, after the reaction fluid is cooled and the liquid component is separated, the depressurized high-pressure gas has a pressure suitable as a power source of a compressor of a general vapor compression concentrator. It is suitable when driven by a turbine as a power source and when air is used under pressure as an oxidizing agent.
[0023]
As described above, when the heat is recovered from the reaction fluid and the liquid to be treated is concentrated by evaporating the liquid to be treated, the amount of recovered heat is insufficient, but the high-pressure gas is recovered as a power source, and the liquid to be treated is concentrated by a vapor compression concentrator. , The necessary concentration can be performed by the recovered energy. In this case, as the enrichment ratio is increased, the power required for enrichment gradually increases, but the amount of high-pressure gas discharged decreases in inverse proportion to the enrichment ratio. In general, when the enrichment ratio is about 3 times or less, the power required for enrichment can be sufficiently provided by the recovered energy alone, but when it exceeds 3 times, it is necessary to supply external energy such as electric power and steam. Sometimes.
[0024]
【The invention's effect】
According to the present invention, the liquid to be treated is concentrated in a vapor compression concentrator and supplied to a hydrothermal reactor, where organic substances are oxidized and decomposed by a hydrothermal oxidation reaction, and the high-pressure gas discharged from the hydrothermal reaction step is concentrated. Since it is supplied as a vapor compression power source for the vessel, energy can be recovered from the reaction fluid generated by the hydrothermal reaction and the liquid to be treated having a low organic substance concentration can be efficiently concentrated. An oxidation reaction can be performed.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart of the hydrothermal reactor of the embodiment.
[0026]
In FIG. 1, reference numeral 1 denotes a liquid tank to be treated, 2 denotes a concentrator, which is a vapor compression type concentrator, and has a heating chamber 4 surrounding a heating tube 3. Reference numeral 5 denotes a vapor compressor which is driven by a turbine 6. 7 is a hydrothermal reactor, 8 is an air compressor, 9 is a fuel tank, 11 is a concentrate tank, 12 is a water tank, 13 is a cooler, 14 is a gas-liquid separator, 15 is a pressure regulator, L1, L2,. ... are lines, P1, P2 ... are pumps, V1, V2 ... are pressure reducing valves.
[0027]
A line L1 having a pump P1 for supplying the liquid to be treated from the liquid tank 1 to be treated is connected to the concentrator 2. A line L2 for sending steam from the upper part of the concentrator 2 communicates with the steam compressor 5, and a line L3 for sending compressed steam from the steam compressor 5 communicates with the heating chamber 4 of the concentrator 2. A line L4 for sending a condensate from the heating chamber 4 of the concentrator 2 communicates with the outside of the system. A line L5 for sending a concentrate from the lower part of the concentrator 2 is connected to the concentrate tank 11. Lines L6, L7, L8 for sending compressed air, fuel, and concentrate from the air compressor 8, the fuel tank 9, and the concentrate tank 11, respectively, communicate with the upper part of the hydrothermal reactor 7. A line L9 for sending quench water from the water tank 12 communicates with a lower portion of the hydrothermal reactor 7.
[0028]
A line 11 for sending a reaction fluid from the lower part of the hydrothermal reactor 7 communicates with the cooler 13, and a line L12 from the cooler 13 communicates with the gas-liquid separator 14. The cooling water passage L13 communicates with the cooler 13. A gas discharge line L14 having the pressure reducing valves V1 and V2 and a liquid discharge line L15 having the pressure reducing valve V3 are connected to the outside of the system from the gas-liquid separator 14. A line L16 for sending high-pressure gas from the line L14 between the pressure reducing valves V1 and V2 via the pressure regulator 15 is connected to the turbine 6. A line L17 for sending exhaust gas from the turbine 6 communicates with the outside of the system.
[0029]
In the above-described hydrothermal reactor, the liquid to be treated is supplied from the liquid tank 1 to be treated to the concentrator 2 by the pump P1 through the line L1 for concentration. In the concentrator 2, the vapor generated from the liquid to be treated passing through the heating pipe 3 enters the vapor compressor 5 from the line L2 and is compressed, and the compressed vapor whose temperature has increased enters the heating chamber 4 of the concentrator 2 from the line L3. The operation of heating and evaporating the liquid to be treated passing through the heating tube 3 is continuously performed. The condensed liquid condensed in the heating chamber 4 is taken out of the system from the line L4 as distilled water, and the concentrated liquid concentrate is sent to the concentrated liquid tank 11 from the line L5.
[0030]
The concentrate in the concentrate tank 11 is sent from the line L8 to the hydrothermal reactor 7 by the high-pressure pump P3, where it is mixed with compressed air as an oxidant sent from the air compressor 8 through the line L6, and The hydrothermal reaction is performed by supplying the reactor 7 in a downward flow. At this time, if necessary, fuel is supplied from the fuel tank 9 to the hydrothermal reactor 7 through the line L7. The mixed stream supplied to the hydrothermal reactor 7 undergoes a hydrothermal oxidation reaction in a supercritical or subcritical state of water in the reactor 7, whereby organic substances are oxidized and decomposed to generate water and carbon dioxide.
[0031]
Although the salt is dissolved in the concentrated solution, it does not dissolve in the supercritical state and is released in a salt state. In addition, there are cases where the substance is released without being partially dissolved in the subcritical state. When quench water is supplied from the water tank 12 through the line L9 in these states, a part of the supercritical or subcritical water becomes liquid, and undissolved salts are dissolved. The reaction fluid of the hydrothermal reactor 7 is introduced into the cooler 13 from the line L11 and is cooled by cooling water supplied from the cooling water passage L13 to liquefy steam in the reaction fluid. It is preferable to use the liquid to be supplied to the liquid tank 1 as the cooling water to be supplied to the cooling water passage L13, since the heat generated in the hydrothermal reactor 7 can be recovered.
[0032]
The reaction fluid containing the liquid liquefied by the cooler 13 is introduced into the gas-liquid separator 14 from the line L12 to separate gas and liquid. The liquid containing solids is discharged through the system. The liquid component containing the solid is further separated into solid and liquid, and the solid is discharged as valuables or sludge, and the liquid is discharged out of the system as treated water. Here, the pressure of the gas to be separated is reduced by the pressure reducing valve V1 so as to be a high-pressure gas having a pressure of 0.5 to 2 MPa.
At this time, high-pressure gas is supplied to the turbine 6 from the line L16 through the pressure regulator 15 to rotate the turbine 6, and the rotating force rotates the steam compressor 5 to compress steam, and exhaust gas is discharged out of the system from the line L17. I do. As a result, energy can be recovered from the high-pressure gas and the concentrator 2 can be operated to concentrate the liquid to be treated. By setting the concentration ratio of the concentrator 2 to about 3 times or less, the power required for the concentration can be sufficiently provided by the recovered energy alone. If the concentration ratio exceeds 3 times, energy can be replenished as necessary by rotating the vapor compressor 5 with a motor or supplying steam from outside to the heating chamber 4.
[0034]
In the above embodiment, the vapor compression type concentrator having the heating chamber 4 so as to surround the heating tube 3 is shown as the concentrator 2, but the heating type may be another type. The turbine 6 may be integrated with the concentrator 2. Also, the hydrothermal reactor 7 is shown as having a cylindrical reactor, but a reactor having another type of reactor, such as a tube type, may be used.
[0035]
【Example】
Hereinafter, examples of the present invention will be described.
Example 1
In the processing apparatus of FIG. 1, the vapor compression type concentrator 2 consumes about 32 kW of vapor compression power to concentrate the organic waste liquid of 60 t / day 2.5 times. On the other hand, in the hydrothermal reactor 7, when a 24 t / day organic waste liquid is treated by a hydrothermal reaction, a high-pressure gas of 23.5 MPa and 50 ° C. is generated. When this pressure is reduced to 1 MPa and used as a power source of the vapor compressor 5, a power of 32 kW can be obtained assuming that thermal efficiency × mechanical efficiency = 20%. When each apparatus was actually operated under these conditions, it was found that evaporation and concentration by the concentrator 2 was possible without supplying external energy for evaporation and concentration.
[Brief description of the drawings]
FIG. 1 shows a liquid tank to be treated 2 a condenser 3 a heating pipe 4 a heating chamber 5 a steam compressor 6 a turbine 7 a hydrothermal reactor 8 an air compressor 9 a fuel tank 11 a concentrated liquid tank 12 a water tank 13 a cooler 14 a gas-liquid separator. 15 Pressure regulator

Claims (8)

A concentration step of condensing the liquid to be treated with a vapor compression concentrator,
A concentrate supply step of supplying the concentrated concentrate to the hydrothermal reactor,
In a hydrothermal reactor, in the presence of water and an oxidizing agent, perform a hydrothermal oxidation reaction in a supercritical or subcritical state of water, and a hydrothermal reaction step of oxidatively decomposing organic substances,
A high-pressure gas supply step of supplying a high-pressure gas discharged from the hydrothermal reaction step as a vapor compression power source of the concentrator. 2. The method according to claim 1, wherein the concentrator compresses the steam by a turbine powered by a high-pressure gas as a heating source to concentrate the liquid to be treated. 3. The method according to claim 1, wherein air is used under pressure as the oxidizing agent. The method according to any one of claims 1 to 3, wherein the high-pressure gas is obtained by cooling the hydrothermal reaction fluid and performing gas-liquid separation. A vapor compression concentrator for condensing the liquid to be treated,
Concentrate supply means for supplying the concentrated concentrate to the hydrothermal reactor,
In the presence of water and an oxidizing agent, a hydrothermal oxidation reaction in a supercritical or subcritical state of water, and a hydrothermal reactor that oxidatively decomposes organic matter,
A high-pressure gas supply means for supplying high-pressure gas discharged from the hydrothermal reactor as a vapor compression power source of the concentrator. 6. The apparatus according to claim 5, wherein the concentrator compresses the steam by a turbine powered by a high-pressure gas as a heating source to concentrate the liquid to be treated. The apparatus according to claim 5 or 6, further comprising a compressor that pressurizes air as an oxidant and supplies the air to a hydrothermal reactor. The apparatus according to any one of claims 5 to 7, wherein the high-pressure gas is obtained by cooling the hydrothermal reaction fluid and performing gas-liquid separation.

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