JP2000279790A - Operation stopping method of supercritical water reaction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a countermeasure to prevent the generation of corrosion on the inside surface of a pressure vessel of a pressure balance type reactor. SOLUTION: The operation of the super critical water reaction device 10 is stopped so as to prevent the generation of corrosion on the inside wall of the pressure vessel. At the time of stopping the operation of the supercritical water reaction device 10, stop valves provided in a pipe 22 for a liquid to be treated, an alkali feeding pipe 31 and an assistant fuel pipe 30 are closed while continuing the operation of an air compressor 28 to supply air from a two fluid nozzle 34 into a reaction cartridge of the reactor 12 and from an air feed nozzle to a circular part 46 and a stop valve provided in a treated liquid pipe 14 is left as it is opened. At a point of time that the temp. of the reactor 12 is decreased to equal to or below the critical temp., preferably <=300 deg.C, the stop valve provided in the air feed pipe 26 is closed to stop the supply of air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stopping the operation of a supercritical water reactor equipped with a pressure balanced reactor comprising a pressure vessel and a reaction cartridge communicating with each other as a reactor. The present invention relates to a method for stopping the operation of a supercritical water reactor without corroding a pressure vessel of a pressure balanced reactor.

[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.

[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. In order to convert the hard-to-decompose high-molecular compounds into useful low-molecular compounds,
Its practical application is being actively studied. Supercritical water refers to water that is in a supercritical state, that is, water that is in a state beyond the critical point of water, and specifically, at a temperature of 374.1 ° C. or more and a pressure of 22.04 MPa or more. A state of water. 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. The supercritical water can be mixed with a gas such as oxygen or nitrogen at an arbitrary ratio to form a single phase.

Here, a basic configuration of a supercritical water reactor will be described with reference to FIGS. 1 and 2. FIG. 1 is a flow sheet showing a basic configuration of the supercritical water reactor. FIG.
FIG. 2 is a cross-sectional view illustrating a configuration of a pressure balanced reactor. The supercritical water reactor 10 is a device for treating a liquid to be treated containing an organic substance by a supercritical water reaction in the presence of supercritical water, and as shown in FIG. A vertical pressure-resistant closed type reactor 12, a processing solution pipe 14 through which a processing solution flows out of the reactor 12, a cooling device 16 for sequentially cooling the processing solution, and a pressure control for controlling the pressure in the reactor 12. The apparatus includes a valve 18 and a gas-liquid separator 20 that separates the processing liquid into gas and liquid. The vertical reaction vessel is usually suitable for treating a liquid to be treated having a low solid content, and a pipe-shaped tube is preferably used for treating a liquid to be treated having a high solid content. Sometimes a reactor is used.

[0005] The supercritical water reactor 10 has a supply system for supplying a reactant to be used for the supercritical water reaction to the reactor 12.
A liquid pump 24 for feeding a liquid to be treated containing an organic substance into the reactor 12 through the liquid pipe 22 for treatment, and an air inlet pipe 26
And an air compressor 28 for feeding air as an oxidant to the reactor 12 through the air compressor. Further, the supercritical water reactor 1
0 is an auxiliary fuel pipe 30 that feeds an auxiliary fuel into the reactor 12 as a heat energy source necessary for maintaining a supercritical water reaction in the reactor 12, and a supercritical An alkali agent feed pipe 31 for feeding an alkali agent for neutralizing chlorine and the like generated from organic matter in the processing liquid by the water reaction into the reactor 12 is joined to the liquid pipe 22 to be processed. When the supercritical water state cannot be maintained due to the moisture in the liquid to be treated, a supplementary water pipe (not shown) may be connected to the liquid to be treated pipe 22 to supply supplementary water.

The liquid pipe 22 to be treated and the air inlet pipe 26 are connected to the reactor 12 via a two-fluid nozzle 34.
Further, the supercritical water reactor 10 includes, for example, a liquid pipe 22 to be treated, an air inlet pipe 26, An emergency shutoff valve (not shown) is provided in each of the pipes 14 and the like.

A heat exchanger (not shown) for exchanging heat between the liquid to be processed and the processing liquid to cool the processing liquid and raise the temperature of the liquid to be processed to recover heat is provided upstream of the cooler 16. A preheater for preheating the liquid to be treated is provided in the reactor 12
May be provided in the liquid pipe 22 to be processed, which is located upstream of the pipe. Furthermore,
A subcritical water region may be provided in the lower part of the reactor 12, and a mechanism may be provided to settle and remove inorganic salts generated in the reactor 12 in the subcritical water region.

By the way, when an organic substance containing halogen such as chlorine is treated in supercritical water, for example, PCBs, hydrochloric acid is generated from chlorine atoms contained in the PCB, and the treatment liquid has an extremely high corrosive property. there were. Therefore, a pressure balanced reactor described below is used as the reactor 12.

As shown in FIG. 2, the pressure balanced reactor 12 includes a pressure vessel 40 provided as an outer cylinder and a reaction cartridge 42 provided as an inner cylinder in the pressure vessel 40.
The inside 43 of the reaction cartridge 42 is configured as a reaction zone for the supercritical water reaction. Further, between the pressure vessel 40 and the reaction cartridge 42, an annular portion 46 communicating with the inside of the reaction cartridge 42 through a communication hole 44 is formed, and a pressure is applied between the annular portion 46 and the inside of the reaction cartridge 42. Balanced.
In other words, the reaction cartridge 42 functions as a corrosion-resistant partition that partitions the reaction zone by not receiving the internal pressure of the reactor 12. The pressure vessel 40 includes the reactor 12
In order to oppose the internal pressure of the reaction cartridge 42, it is formed as a thick-walled high-strength steel pressure-resistant cylindrical container.
Is formed as a thin-walled cylindrical body with high corrosion resistance,
The lower end is tightly fixed to the bottom of the pressure vessel 40. The reaction cartridge 42 is also provided with a bottom, and the pressure vessel 4
The bottom of the reaction cartridge 42 may be provided close to the bottom of the zero.

The reactor 12 includes a two-fluid nozzle 34 penetrating the pressure vessel 40 and the reaction cartridge 42 and projecting into the reaction cartridge 42,
The processing liquid conduit 48 penetrates the reaction cartridge 42 and the pressure vessel 40 from the inside of the container 2, and an air supply nozzle 50 for supplying air to the annular portion 46. The communication hole 44 for communicating the annular portion 46 with the inside of the reaction cartridge 42 is formed around the two-fluid nozzle 34 in this example. In the two-fluid nozzle 34, the inner pipe 52 and the outer pipe 54 are connected to the liquid pipe 22 and the air inlet pipe 26, respectively, and the liquid to be processed is atomized by air and introduced into the reaction cartridge 42 in the form of a spray. are doing. The processing liquid conduit 48 is connected to the processing liquid pipe 14. In addition, the air inlet nozzle 5
Numeral 0 is connected to an air inlet branch pipe 56 (see FIG. 1) branched from the air inlet pipe 26 to introduce air into the annular portion 46 and then flow into the reaction cartridge 42 through the communication hole 44 to oxidize the air. Part of the drug.

In the pressure balanced type reactor 12, air having the same pressure as the air flowing into the reaction cartridge 42 via the two-fluid nozzle 34 is introduced into the annular portion 46, so that the pressure difference between the inside and outside of the reaction cartridge 42 is almost zero. Does not occur.
The air is introduced into the annular portion 46 because the air is a non-corrosive fluid. In addition, in this example, in order to make a to-be-processed liquid and air flow into the pressure balance type reactor 12,
Although a two-fluid nozzle is used, a pressure vessel 40 and a reaction cartridge 42 are used instead of the two-fluid nozzle, respectively.
May be provided with a separate inflow nozzle.

[0012]

However, during operation of the supercritical water reactor using the above-described pressure-balanced reactor as a reactor, the inner wall of the pressure vessel 40 of the pressure-balanced reactor is operated. It was found that corrosion had occurred.
In particular, as shown in FIG. 3, it was confirmed that the upper wall of the pressure vessel 40 was significantly corroded. Since the supercritical water reactor promotes the reaction under high pressure and high temperature, even if extremely small corrosion holes are generated on the reactor wall,
This can lead to unexpected and dangerous situations.

An object of the present invention is to provide a countermeasure for preventing the corrosion of the inner wall of the pressure vessel of the pressure balanced reactor.

[0014]

The present inventor has found the following as a result of pursuing the cause of the corrosion of the inner wall of the pressure vessel. When the supercritical water reactor is shut down urgently,
The piping around the reactor, for example, the liquid pipe to be processed, the air inlet pipe, the emergency shutoff valve provided in the processing liquid pipe, etc. is closed, so the reactor is shut off from around, the liquid to be processed, air does not flow in, Although the processing liquid does not flow out, the reaction fluid in the reaction cartridge has a high temperature for a while, so that it flows toward the upper part of the reaction cartridge by a convection phenomenon and flows into the annular portion 46 through the communication hole 44. Since the pressure vessel is made of a steel plate having a relatively low corrosion resistance, the upper wall of the pressure vessel is corroded by an acid substance such as hydrochloric acid in the reaction fluid flowing into the annular portion 46.

The above phenomenon occurs not only when the supercritical water reactor is stopped in an emergency but also when the normal operation is stopped, and the phenomenon occurs to a greater or lesser extent, but to a greater or lesser degree.
It is important to note the above-mentioned corrosion when using a pressure balanced reactor. Therefore, the present inventor
(1) It is essential to maintain the pressure balance of the reactor even when the apparatus is stopped so that the reaction fluid in the reaction cartridge does not flow out to the annular portion. (2) The liquid to be treated in the reactor Once all of the organic matter has been oxidized,
Considering that the supercritical water reaction does not proceed to an abnormal state even if air is supplied, air is usually supplied to the With the idea of maintaining the pressure balance in the reaction cartridge and in the annular portion, the present invention was completed as a result of research.

In order to achieve the above object, based on the above findings, a method for shutting down the operation of a supercritical water reactor according to the present invention is described as a double cylinder comprising a pressure vessel and a reaction cartridge communicating with each other. A pressure-balanced reactor formed and containing supercritical water is provided, and a liquid to be treated and an oxygen-containing gas as an oxidizing agent are supplied into a reaction cartridge, and
A supercritical water reactor that supplies an oxygen-containing gas as a pressure balancing gas between a pressure vessel and a reaction cartridge to perform a supercritical water reaction between an organic substance in a liquid to be treated and oxygen in the presence of supercritical water. A method of stopping the operation of, when stopping the operation, while supplying the oxygen-containing gas, stopping the supply of the fluid excluding the oxygen-containing gas in the fluid to be supplied to the reactor sequentially or at once. And stopping the supply of the oxygen-containing gas when the temperature of the reactor has dropped to a predetermined temperature or lower.

The fluid supplied to the reactor refers to, for example, a liquid to be treated, an auxiliary fuel, supercritical water, a neutralizing agent, subcritical water and the like.
The fluid flowing out of the reactor refers to, for example, a treatment liquid, subcritical wastewater, and the like. Air is usually used as the oxygen-containing gas. In the method of the present invention, the shutdown is a concept including an emergency shutdown and other normal shutdowns. There is no restriction on the method of flowing the liquid to be treated and the oxygen-containing gas into the reaction cartridge of the pressure balanced reactor, and a two-fluid nozzle or a separate inflow nozzle may be used.
Further, a mixed fluid of the liquid to be treated and the oxygen-containing gas may be flowed. In the method of the present invention, the predetermined temperature is a critical temperature, preferably 300 ° C.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below specifically and in detail with reference to FIGS. 1 and 2 of the accompanying drawings. Embodiment 1 This embodiment is an example of an embodiment in which the method for stopping the operation of the supercritical water reactor according to the present invention is applied to the normal operation stop of the supercritical water reactor 10 described above. When the operation of the supercritical water reactor 10 is normally stopped, as in the normal operation, the air inlet pipe 2
6 from the two-fluid nozzle 34 into the reaction cartridge 42 of the reactor 12 and from the air inlet nozzle 50 via the air inlet pipe 26 and the air inlet branch pipe 56 to the While supplying the liquid to the processing liquid pipe 46, the on-off valves (not shown) provided on the liquid pipe 22, the alkali inlet pipe 31, and the auxiliary fuel pipe 30 are closed, and the on-off valve (not shown) provided on the processing liquid pipe 14. (Not shown) are left open.

Next, when the temperature of the reactor 12 drops to a predetermined temperature, for example, a critical temperature or lower, preferably 300 ° C. or lower, an on-off valve (not shown) provided in the air inlet pipe 26.
And shut off the air supply.

Embodiment 2 This embodiment is an example of an embodiment in which the method for stopping the operation of the supercritical water reactor according to the present invention is applied to the emergency stop of the supercritical water reactor 10 described above. When the operation of the supercritical water reactor 10 is continued, for example, when the temperature in the reactor 12 becomes higher than the set temperature and the emergency stop is performed, the air compressor 28 is operated as in the normal operation. While continuing, air is supplied from the two-fluid nozzle 34 into the reaction cartridge 42 of the reactor 12 via the air supply pipe 26 and air is supplied via the air supply pipe 26 and the air supply branch 56. While supplying air from the nozzle 50 to the annular portion 46, the emergency shutoff valves (not shown) provided in the liquid pipe 22, the alkali feed pipe 31, and the auxiliary fuel pipe 30 are closed, and the processing liquid pipe is closed. The on-off valve (not shown) provided at 14 is kept open.

Next, when the temperature of the reactor 12 drops to a predetermined temperature, a critical temperature or lower, preferably 300 ° C. or lower, an on-off valve (not shown) provided in the air inlet pipe 26 is closed to allow air to flow. Stop supplying.

[0022]

According to the method of the present invention, when the operation of the supercritical water reactor is stopped, the supply of the fluid other than the oxygen-containing gas and the outflow of the fluid from the reactor are stopped, and the pressure balanced type reaction is stopped. Since the oxygen-containing gas is continuously supplied to the inside of the reaction cartridge and the annular portion of the reactor, the pressure balance between the inside of the reaction cartridge and the annular portion can be maintained. At this time, a situation in which the corrosive reaction fluid flows out of the reaction cartridge into the annular portion and corrodes the inner wall of the pressure vessel does not occur.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing a configuration of a supercritical water reactor equipped with a pressure balanced reactor as a reactor.

FIG. 2 is a cross-sectional view illustrating a configuration of a pressure balanced reactor.

FIG. 3 is a sectional view showing a corroded area of the pressure balanced reactor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 supercritical water reactor 12 reactor 14 treatment liquid pipe 16 cooler 18 pressure control valve 20 gas-liquid separator 22 liquid liquid to be treated 24 liquid to be treated pump 26 air inlet pipe 28 air compressor 30 auxiliary fuel pipe 31 alkali Agent supply pipe 34 Two-fluid nozzle 40 Pressure vessel 42 Reaction cartridge 44 Communication hole 46 Annular part 48 Treatment liquid conduit 50 Air supply nozzle 52 Inner pipe of two-fluid nozzle 54 Outer pipe of two-fluid nozzle 56 Air supply branch pipe

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akira Suzuki 1-2-2-8 Shinsuna, Koto-ku, Tokyo Organo Corporation F-term (reference) 4D050 AA13 AB19 BB01 BC01 BC02 BC10 BD02 BD03 BD06 BD08 CA13

Claims (1)

[Claims] A pressure-balanced reactor formed of a pressure vessel and a reaction cartridge communicating with each other and containing supercritical water; a liquid to be treated; and an oxygen-containing gas as an oxidizing agent. Is supplied into the reaction cartridge, and an oxygen-containing gas is supplied as a pressure-balancing gas between the pressure vessel and the reaction cartridge, so that the organic substance and oxygen in the liquid to be treated are mixed with each other in the presence of supercritical water. A method for stopping the operation of a supercritical water reactor for performing a supercritical water reaction, wherein, when the operation is stopped, while supplying an oxygen-containing gas, a fluid excluding an oxygen-containing gas in a fluid supplied to the reactor is supplied. Operation of a supercritical water reactor characterized by having a step of stopping the supply sequentially or at once, and a step of stopping the supply of the oxygen-containing gas when the temperature of the reactor falls below a predetermined temperature. Stop method.