JP2000279915A - Supercritical water treatment of water-insoluble organic solid matter and supercritical water reactor for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supercritical water treatment process, by which incineration fly ash or the like can stably be treated over a long period through supercritical water reaction and also to provide a supercritical water reactor. SOLUTION: This supercritical water reactor has a supply system of water to be treated 40, an air supply system, a preheater, a reaction vessel and an outflow system placed downstream from the reaction vessel, all of which, except the supply system of water to be treated 40, are the same as those of a conventional supercritical water reactor, wherein the supply system of water to be treated 40 is provided with a neutralization tank 44 having an agitator 42, a cyclone 46 and a dilution tank 50 having an agitator 48.When water-insoluble organic solid matter such as dioxins in fly ash are subjected to supercritical water treatment using the reactor, this process involves: neutralizing water to be treated 40 which consists of an aqueous slurry of fly ash, in the neutralization vessel 44; and subjecting the neutralized water to be treated 40 to solid matter separation, to obtain first treated water which has a high solid matter concentration and a low salt concentration; and feeding the first treated water to the reaction vessel. Thus, when the aqueous slurry of fly ash is fed to the reaction vessel, salts liable to cause troubles such as salt deposition on a pipe wall or pipe plugging by salts, are removed from the slurry beforehand.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating supercritical water of water-insoluble organic solids and a supercritical water reactor for carrying out the method. The present invention relates to a supercritical water treatment method and a supercritical water reactor for water-insoluble organic solids, which can stably continue the treatment without any troubles such as the above.

[0002]

2. Description of the Related Art With increasing awareness of environmental issues,
Attention has been paid to attempts to decompose and detoxify environmental pollutants by utilizing supercritical water reaction, which has high ability to oxidize and decompose organic substances. That is, harmful and hardly decomposable organic substances, such as PCB (polychlorinated biphenyl), dioxin, and organic chlorinated compounds, which were difficult to decompose in the related art by supercritical water reaction utilizing high reactivity of supercritical water. It is an attempt to decompose a solvent or the like and convert it into harmless products such as carbon dioxide, nitrogen, water, and inorganic salts. As one of the attempts, recently, research on treating incinerated fly ash (hereinafter simply referred to as fly ash) containing such harmful organic compounds discharged from garbage incinerators etc. by supercritical water reaction A supercritical water reactor for processing fly ash has also been developed.

[0003] A supercritical water reactor is a device that decomposes organic substances by using high reactivity of supercritical water. For example, harmful organic substances that are hardly decomposable are decomposed and harmless carbon dioxide and water are decomposed. Is converted to Supercritical water is water in a supercritical state,
That is, water that is beyond the critical point of water, specifically, at a temperature of 374.1 ° C. or higher and 22.04MPa
Water under a pressure of a or more. Supercritical water has a high ability to dissolve organic substances and can completely dissolve non-polar substances, which are abundant in organic compounds, but has a very low ability to dissolve inorganic substances such as metals and salts. Also,
Supercritical water can be mixed with a gas such as oxygen or nitrogen at any ratio to form a single phase.

Referring to FIG. 3, a configuration of a conventional supercritical water reactor for treating water slurries of fly ash will be described.
FIG. 3 is a flow sheet showing the configuration of a conventional supercritical water reactor for treating water slurries of fly ash. The supercritical water reactor 10 is a device for treating water to be treated consisting of a water slurry of fly ash by a supercritical water reaction, and as shown in FIG. A closed vessel-shaped pressure-resistant reactor 12 is provided. A preheater 14 for preheating a reactant is provided upstream of the reactor 12, and a heat exchanger 16 and a cooler 18 for cooling reaction products are provided downstream of the reactor 12. It has. When the content of fly ash in the water to be treated is high, a tubular pressure-resistant closed reactor is often used. Further, the supercritical water reactor 10 has a pressure control valve 20 for controlling the pressure in the reactor 12 downstream of the cooler 18 and a gas-liquid separator 22 for gas-liquid separation of the reaction product into gas and slurry. A solid-liquid separator 24 is provided downstream of the pressure control valve 20 and separates a solid reaction product from the reaction product by solid-liquid separation of a slurry-like reaction product. Solid-liquid separator 24
The inorganic solid separated in the above is mainly contained in the reaction product and did not contribute to the reaction, and may further contain a salt generated by the supercritical hydroxylation reaction.

[0005] The reactor 12 has a supercritical water region in which supercritical water is retained throughout the reactor. The reactant preheated to the reaction temperature enters the reactor 12 from the reactor inlet near the preheater 14, is supercritically hydroxylated, and flows out of the bottom reactor outlet as a reaction product. In the present supercritical water reactor 10 using fly ash slurry as the water to be treated, the preheater 14, the heat exchanger 16, and the cooler 18 are configured as a double-pipe heat exchanger through which the fly ash slurry flows through the inner tube. Have been. The heat exchanger 16 through which the heat medium flows and the outer pipe of the preheater 14 are connected by a heat medium pipe 25.

The supercritical water reactor 10 supplies a reactant fluid supply system with a feed pump 26 for feeding fly ash water slurry to the reactor 12 as water to be treated, and air as an oxidant. And an air compressor 28 for supplying water to be treated through a water pipe 30 to be treated and an air supply pipe 32, respectively.
Then, air is sent to the preheater 14 and then to the reactor 12 together with the water to be treated via the water pipe 30 to be treated. Further, the supercritical water reactor 10 is provided with a neutralizing agent for neutralizing an acid component such as chlorine generated from organic matter in the water to be treated by the supercritical water reaction in the reactor 12 or an alkali component in the water to be treated. 1
And an auxiliary fuel such as a petroleum hydrocarbon oil as a heat energy source necessary for maintaining the supercritical water reaction in the reactor 12 if necessary. An auxiliary fuel pipe (not shown) for feeding the reactor 12 and a supercritical water pipe (not shown) for feeding make-up water of supercritical water necessary for the supercritical water reaction in the reactor 12 to the reactor 12. Are joined to the water pipe 30 to be treated.

The water to be treated is preheated together with air to the reaction temperature of the supercritical hydroxylation reaction in the preheater 14, then enters the reactor 12, and flows through the reactor 12 from the inlet to the outlet. Organic substances therein, for example, dioxins are mainly converted to water, nitrogen and carbon dioxide by a supercritical water reaction, and flow out of the reactor 12 as a reaction product. The reaction product enters the heat exchanger 16, heats the heating medium, lowers its own temperature, then flows into the cooler 18, and is cooled by a cooling medium, for example, cooling water, and flows out. Cooler 1
The outlet of 8 is connected to a reaction product line 36, which is connected to the gas-liquid separator 22 via the pressure control valve 20.
In the gas-liquid separator 22, the reaction product is subjected to gas-liquid separation to be separated into a gaseous reaction product and a slurry-like reaction product. The gaseous reaction product is released to the atmosphere or goes to the next processing step, and the slurry-like reaction product is collected in the solid-liquid separator 2.
4 is introduced. The reaction product in the form of a slurry is solid-liquid separated into a liquid processing liquid and an inorganic solid by a solid-liquid separator 24,
Each is sent out.

[0008]

However, the water slurry of the incinerated fly ash is sent to the above-mentioned conventional supercritical water reactor as water to be treated to treat dioxins and the like contained in the incinerated fly ash. If this is attempted, problems such as blockage at the water pipe to be treated, the heat transfer tube of the preheater, or the inlet of the reactor, and local heating in the heating device will occur in the high-temperature area of the preheater and the reactor. It was difficult to operate the supercritical water reactor stably.

Accordingly, an object of the present invention is to provide a treatment method and a supercritical water reactor capable of stably treating incinerated fly ash and the like by a supercritical water reaction for a long period of time.

[0010]

SUMMARY OF THE INVENTION The present inventor has found that the above-mentioned blockage trouble is mainly caused by the accumulation of inorganic salts. For example, as shown in Table 1, incineration fly ash contains a high content of alkali metals, alkaline earth metals, and halogen elements that generate inorganic salts by neutralization. Thus, the ion concentration in the water slurry of the incinerated fly ash is extremely high. In a high-temperature environment of the supercritical water reaction, these metals easily generate inorganic salts and adhere to the pipe wall of the water pipe to be treated and the pipe wall of the heat transfer pipe of the preheater to cause blockage. Fly ash concentration in Table 2 1%, 1
The fly ash slurry of 0% and 25% is obtained by converting the fly ash of Table 1 into a water slurry.

[Table 1]

[Table 2]

The inventor of the present invention has focused on the fact that dioxins are water-insoluble organic solids at room temperature when the object to be treated in incineration fly ash is, for example, dioxins. The idea was to neutralize the earth metals in advance, dissolve them in a water slurry, and then perform solid-liquid separation to selectively remove those metals. For example, the ion concentration in the fly ash water slurry shown in Table 2 is, as shown in Table 3, when neutralized, the concentrations of Ca ions and Cl ions that form inorganic salts attached to the tube wall are increased in the fly ash water slurry. Increased significantly. That is, after solid-liquid separation, these Ca ions, Cl ions, etc. migrated to the liquid side to be removed, and in the fly ash water slurry subjected to supercritical water treatment, the concentration of ions for forming inorganic salts was significantly reduced. The present inventors have conducted further experiments based on the results of these experiments and completed the present invention.

[Table 3]

In order to achieve the above object, a method for treating a water-insoluble organic solid by a supercritical water reaction according to the present invention comprises:
A slurry-like water to be treated containing a water-insoluble organic solid material to be treated and at least one of a water-soluble inorganic salt and a metal that forms a water-soluble inorganic salt by neutralization is introduced into the reactor, and is subjected to supercritical In a method of treating water to be treated by a supercritical water reaction in the presence of water, a neutralization step of neutralizing the water to be treated, and subjecting the neutralized water to be treated to a solid separation process to obtain a solid concentration And a separation step of separating the first treated water into a second treated water having a lower solid matter concentration than the first treated water, and feeding the first treated water to the reactor. It is characterized by doing.

The process of the present invention is characterized in that the concentration of the slurry-like water to be treated, which contains water-insoluble organic solids and precipitates inorganic salts when heated to a high temperature, for example, fly ash accompanying dioxins, is 1 to 30% by mass. Is treated by a supercritical water reaction. When the solid concentration of the first water to be treated is high, a dilution step of diluting the first water to be treated with a diluent is provided, and the diluted first water to be treated is sent to the reactor. good. As the diluent, water or alcohols used as an auxiliary fuel is used.

In the method of the present invention, preferably,
A solid substance separation treatment is performed on the second treated water, and a third treated water having a solid concentration higher than the second treated water and a fourth treated solid having a solid concentration lower than the second treated water. A step of separating the first water to be treated and the third water to be treated with or without adding a diluent to prepare a fifth water to be treated; And supplying the fifth treated water to the reactor.

In the method of the present invention, the water to be treated is neutralized to dissolve the water-soluble inorganic salts and the metals that form the water-soluble inorganic salts upon neutralization, and then to solid-liquid separation to form a water-insoluble organic solid. By preparing the first water to be treated having a high concentration and a low concentration of the water-soluble inorganic salts, and treating the first water to be treated, water such as dioxin can be obtained without causing a trouble of clogging by the water-soluble inorganic salts. The insoluble organic solid is treated by a supercritical water reaction. When the concentration of the water-insoluble organic solid in the second water to be treated is high, a solid-liquid separation treatment such as membrane separation is further performed to separate the water-insoluble organic solid from the second water to be treated, Third with insoluble organic solids
Of water to be treated is treated by a supercritical water reaction together with the first water to be treated. This makes it possible to reduce the concentration of the water-insoluble organic solid of the fourth water to be treated to an allowable concentration that can be discharged as it is.

The supercritical water reactor according to the present invention is provided with a reactor containing supercritical water, and comprises a treatment object comprising a water-insoluble organic solid, a water-soluble inorganic salt, and a water-soluble inorganic salt by neutralization. In a supercritical water reactor for introducing a slurry-like water to be treated containing at least one of the metals that form the water into a reactor and treating the water to be treated by a supercritical water reaction in the presence of supercritical water, A neutralization tank for neutralizing the treated water, a solid matter separation treatment for the neutralized treated water, a first treated water having a high solid matter concentration, and a solid matter concentration higher than the first treated water. And a solid separation means for separating the first treated water from the first treated water into the reactor.

Further, a diluting tank for diluting the first water to be treated with a diluting liquid may be provided, and the diluted first water to be treated may be fed into the reactor. Preferably, a solid substance separation treatment is performed on the second treated water, and a third treated water having a solid concentration higher than the second treated water, and a solid substance concentration higher than the second treated water. A second solid separation means for separating into low fourth water to be treated, a first water to be treated and a third water to be treated mixed with or without a diluent; And a preparation means for preparing the fifth water to be treated, and feeding the fifth water to the reactor.

The solid substance separation means used in the present invention comprises a first treated water having a high solid substance concentration and a second treated water having a lower solid substance concentration than the first treated water. As long as it can be separated, there are no restrictions on the type of the filter. use. Also, the second
The solid substance separation means includes a third substance water having a higher solid substance concentration than the second substance water and a fourth substance water having a lower solid substance concentration than the second substance water. As long as the water to be treated can be separated, the type thereof is not limited. Use

In the method of the present invention, when a solid containing a large amount of inorganic salts or a solid which becomes acidic or alkaline when slurried, for example, a fly ash water slurry is treated with supercritical water,
After neutralization in a water slurry state, solid-liquid separation is performed to dissolve and remove inorganic salts in water. Thereafter, a solid having a low inorganic salt concentration after solid-liquid separation is mixed with water to adjust the slurry to an appropriate concentration. When incinerated fly ash containing dioxins is slurried and subjected to supercritical water treatment, dioxins are insoluble in water, so if the method of the present invention is applied, only salts can be dissolved in water and separated. Also, unlike the conventional case, there is no occurrence of blockage of the pipe and local heating by the heating device. The supercritical water reactor according to the present invention is most suitable for treating a water-insoluble organic solid such as dioxin by a supercritical water reaction.

[0020]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 of Supercritical Water Reactor This embodiment is an example of an embodiment of a supercritical water reactor according to the present invention, and is an apparatus for treating a fly ash water slurry described below with supercritical water. . FIG. 1 is a flow sheet showing the configuration of the main part of the supercritical water reactor of the present embodiment. The supercritical water reactor of the present embodiment is an air supply system having the same configuration as a conventional supercritical water reactor, except for a supply system of water to be treated, a preheater 14, a reactor 12, and reactors 12 and subsequent. It has an outflow system. As shown in FIG. 1, the supercritical water reactor of this embodiment includes a neutralization tank 44 having a stirrer 42 and a cyclone 46 as a supply system 40 of the water to be treated.
And a dilution tank 50 having a stirrer 48.

The neutralization tank 44 is provided by adding a neutralizing agent to water to be treated, which is a water slurry of fly ash, and neutralizing the water to be treated or by mixing fly ash, water and a neutralizing agent. A water to be treated comprising a neutralized water slurry is prepared. Cyclone 46 is used for neutralization tank 4
The water to be treated neutralized in step 4 is separated into solids to separate the first to-be-treated water having a high solid matter concentration and the second to-be-treated water having a solid matter concentration lower than the first to-be-treated water. The dilution tank 50 dilutes the first treated water flowing out of the cyclone 46 to a predetermined solid concentration with water.

The water supply system 40 further includes a water supply pump 52 for supplying the water to be treated to the cyclone 46 from the neutralization tank 44, and a first water diluted from a dilution tank 50 through the water pipe 30 to be treated. And a press-in pump 54 for injecting the water to be treated into the reactor 12 (see FIG. 3).

The supercritical water treatment method for water-insoluble organic solids
First Embodiment Next, a method of treating dioxin (water-insoluble organic solids) in fly ash with supercritical water using the supply system 40 of the water to be treated will be described with reference to FIG. First, the neutralization tank 42
In, mix fly ash, water and neutralizer, fly ash concentration is 1-20%
A neutral slurry having a concentration is prepared as the water to be treated. By neutralization, NaOH and Ca (OH) contained in fly ash
Alkaline components such as ₂ can be dissolved in water as inorganic salts. Next, the prepared water to be treated is supplied to the water pump 52.
To separate into a high-concentration fly ash slurry (first treated water) and a salt solution (second treated water). Here, since the dioxins to be treated are hardly soluble in water, most of them are contained in the high-concentration fly ash slurry.

Thereafter, the high-concentration fly ash slurry is added to the dilution tank 50.
To prepare diluted water to be treated having a predetermined slurry concentration. The diluted water to be treated is fed into the reactor 12 via the preheater 14 via the water pipe 30 to be treated by the injection pump 54. Dioxins are decomposed by supercritical water treatment and can render fly ash harmless.

In the method of the present embodiment, when the fly ash water slurry is fed into the reactor 12 as the water to be treated, salts which adhere to the pipe wall or the like and cause troubles such as clogging are previously removed. , So that troubles such as blockage and local heating as in the related art do not occur. Therefore, the supercritical water treatment of the fly ash slurry can be continued stably for a long time.

Embodiment 2 of Supercritical Water Reactor This embodiment is another example of the embodiment of the supercritical water reactor according to the present invention. FIG. 2 shows the supercritical water of this embodiment. 3 is a flow sheet showing a configuration of a main part of the reaction apparatus. Supply system 60 of the water to be treated in the supercritical water reactor of the present embodiment
Has a membrane separation device 62 provided with a UF membrane or an MF membrane as a second solid matter separation means in addition to the configuration of the supply system 40 of the water to be treated in the first embodiment.

The supercritical water treatment method for water-insoluble organic solids
Second Embodiment Since the supply system 60 of the water to be treated of the second embodiment includes the membrane separation device 62 provided with the UF membrane or the MF membrane, for example, the supply system 40 of the water to be treated of the first embodiment is provided. Water-insoluble organic solids in the salt-dissolved water discharged from the cyclone 46,
For example, it is optimal when the concentration of dioxins is high.
That is, the salt-dissolved water flowing out of the cyclone 46 is separated into solids by the membrane separation device 62, and the obtained solids such as dioxins are introduced into the dilution tank 50 and mixed with the first water to be treated from the cyclone 46. Then, if necessary, the mixture is diluted with water and pressed into the reactor 12. On the other hand, the content of dioxins in the salt-dissolved water permeated through the separation membrane of the membrane separation device 62 is extremely low and is below the permissible concentration. can do.

[0028]

According to the present invention, the water to be treated containing water-insoluble organic solids such as dioxin is neutralized, and the neutralized water to be treated is subjected to a solids separation treatment to obtain a solid matter concentration (dioxin). Concentration), the first water to be treated having a low salt concentration is separated, and the first water to be treated is fed into the reactor.
Blockage of pipes, heat transfer tubes, and the like due to attachment of salts and local heating of a heating device can be prevented, and stable supercritical water treatment of water-insoluble organic solids can be performed. Further, the supercritical water reactor according to the present invention realizes a device for smoothly performing the method for treating supercritical water of a water-insoluble organic solid according to the present invention.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing a configuration of a main part (a supply system of water to be treated) of a supercritical water reactor of a first embodiment.

FIG. 2 is a flow sheet showing a configuration of a main part (supply system of water to be treated) of a supercritical water reactor of a second embodiment.

FIG. 3 is a flow sheet showing a configuration of a conventional supercritical water reactor.

[Explanation of symbols]

10 Conventional Supercritical Water Reactor 12 Reactor 14 Preheater 16 Heat Exchanger 18 Cooler 20 Pressure Control Valve 22 Gas-Liquid Separator 24 Solid-Liquid Separator 25 Heat Medium Pipe 26 Feed Pump 28 Air Compressor 30 Treatment Water pipe 32 Air supply pipe 34 Alkaline agent feed pipe 36 Reaction product line 40 Supply system of water to be treated in supercritical water reactor of Embodiment 1 42 Stirrer 44 Neutralization tank 46 Cyclone 48 Stirrer 50 Dilution tank 52 Water pump 54 Press-fit pump

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D004 AA37 AB07 CA10 CA13 CA34 CA39 CB04 CB31 CC03 DA02 DA06 DA07 4D059 AA18 BC01 BE31 BE37 BE42 BE53 BF13

Claims (6)

[Claims] 1. A slurry-like water to be treated containing an object to be treated comprising a water-insoluble organic solid and at least one of a water-soluble inorganic salt and a metal which forms a water-soluble inorganic salt by neutralization, is placed in a reactor. In the method of introducing and treating the water to be treated by a supercritical water reaction in the presence of supercritical water, a neutralization step for neutralizing the water to be treated and a solids separation treatment to the neutralized water to be treated And a separation step of separating the first treated water into a first treated water having a higher solid matter concentration and a second treated water having a lower solid matter concentration than the first treated water. A supercritical water treatment method for a water-insoluble organic solid, which is fed into a reactor. 2. The water-insoluble water according to claim 1, further comprising a dilution step of diluting the first water to be treated with a diluting liquid, and feeding the diluted first water to be treated into a reactor. Supercritical water treatment method for organic solids. 3. A process for subjecting the second treated water to a solid separation process, wherein the third treated water has a higher solid content than the second treated water, and the solid content is higher than the second treated water. Separating the first water to be treated and the third water to be treated with or without adding a diluent to the fifth water to be treated. The method for treating super-critical water of a water-insoluble organic solid according to claim 1, further comprising a step of preparing water to be treated, wherein the fifth water to be treated is fed into the reactor. 4. A reactor containing supercritical water, comprising: a treatment target comprising a water-insoluble organic solid; and a water-soluble inorganic salt and / or a metal which forms a water-soluble inorganic salt by neutralization. A neutralization tank that neutralizes the water to be treated in a supercritical water reactor that introduces slurry-like water to be treated into the reactor and treats the water to be treated by supercritical water reaction in the presence of supercritical water Subjecting the neutralized water to be treated to a solid separation treatment to obtain a first water to be treated having a high solid concentration and a second water to be treated having a solid concentration lower than the first water to be treated. A supercritical water reactor, comprising: a solid separation means for separating the first water to be treated into the reactor. 5. The supercritical system according to claim 4, further comprising a diluting tank for diluting the first water to be treated with a diluent, and feeding the diluted first water to be treated into the reactor. Water reactor. 6. A process for solid-solid separation of the second water to be treated, a third water to be treated having a higher solid concentration than the second water to be treated, and a solid concentration to be higher than the second water to be treated. A second solid separation means for separating the first water to be treated and the third water to be treated, with or without adding a diluent, The supercritical water reactor according to claim 5, further comprising a preparation means for preparing a fifth water to be treated by mixing, wherein the fifth water to be treated is fed into the reactor.