JP4508766B2 - Hydrothermal reactor shutdown method - Google Patents

Description

  The present invention relates to an operation stop method in the event of an emergency stop of a hydrothermal reactor, and more particularly to an operation stop method suitable for a hydrothermal reactor using a pressure balance reactor.

  In recent years, attention has been paid to attempts to decompose and detoxify environmental pollutants using a hydrothermal oxidation reaction in the presence of high-temperature and high-pressure water, particularly supercritical water. In particular, due to supercritical water oxidation utilizing the high reactivity of supercritical water, harmful and hardly decomposable organic substances, such as PCB (polychlorinated biphenyl), dioxin, and organic chlorine, which were difficult to be decomposed by the prior art. Attempts have been focused on decomposing organic substances and converting them into harmless products such as carbon dioxide, nitrogen, water and inorganic salts. The supercritical water means water in a supercritical state, that is, water in a state exceeding the critical point of water. Specifically, it is at a temperature of 374.1 ° C. or higher and under a pressure of 22.04 MPa or higher. Says water in a state. Supercritical water has a high ability to dissolve organic substances, and can completely dissolve non-polar substances that are abundant in organic compounds. Conversely, the ability to dissolve inorganic substances such as metals and salts is extremely low. Supercritical water can be mixed with a gas such as air, oxygen, or nitrogen at an arbitrary ratio to form a single phase. When a pressure balance type reactor is applied to a hydrothermal reaction including supercritical water oxidation using such supercritical water, particularly a hydrothermal reaction using high-temperature high-pressure water having a temperature of 180 ° C. or higher and a pressure of 1 MPa or higher, A desired hydrothermal reactor can be configured at low cost.

  This pressure-balanced reactor is a reactor that performs a reaction under high pressure, and is provided with a reactor in a pressure vessel to form a double vessel structure. The pressure in the reactor and the pressure between the pressure vessel and the reactor In order to prevent a large internal / external differential pressure from being applied to the reactor itself. In such a structure, since a large deformation force or the like is not applied to the reactor itself, a relatively thin wall structure can be adopted, and the material cost can be reduced even when an expensive corrosion-resistant material is required, On the other hand, the pressure vessel needs only to have a structure that can satisfy only the pressure resistance performance, so that relatively inexpensive materials can be selected, the entire device can be configured at low cost, and sufficiently high required performance can be easily achieved for each part of the device. It becomes possible to have.

In the hydrothermal reaction apparatus having such a pressure balance type reactor, when stopping during steady operation, for example, in case of emergency stop, while maintaining the balance between the pressure in the reactor and the pressure between the pressure vessel and the reactor, In order to prevent the corrosive reaction fluid remaining in the reactor from flowing out between the pressure vessel and the reactor and corroding the inner wall of the pressure vessel, (1) air supplied as an oxidant There has been proposed an operation stopping method in which supply devices other than the above are stopped and supply of air is continued until the reactor temperature decreases in order to prevent corrosion of piping and the like (Patent Document 1).
JP 2000-279790 A

  However, the following problem may occur in the operation stop method according to the above proposal. That is, when the object to be processed has, for example, halogen (for example, when the object to be processed is PCB), acid is generated by decomposition. If an emergency stop occurs in this state, the acid remains in the reactor and the reactor may be corroded. Furthermore, if the acid remaining in the reactor flows to the reactor outlet in the normal line due to air supply, since the supply other than air is stopped, the neutralizing agent is not supplied, and the reactor outlet Subsequent piping may be corroded.

  Therefore, the object of the present invention is to pay attention to such a problem, and when the hydrothermal reactor using supercritical water is stopped, it is possible to surely prevent the corrosion of the reactor, and in addition, after the reactor outlet. It is an object of the present invention to provide a hydrothermal reactor operation stop method that can prevent corrosion of pipes and the like, and can stop the operation of the device under desirable conditions.

In order to solve the above-mentioned problem, the hydrothermal reactor operation stop method according to the present invention is a hydrothermal reactor operation stop method in which a liquid to be treated and supercritical water are supplied to perform a hydrothermal reaction in the reactor. And when you stop driving,
Continuing the supply of the liquid to be treated and the supercritical water, but continuing the air supply and the supply of the neutralizing agent to the reactor outlet side until the temperature in the reactor falls below the critical point of water;
Supplying a neutralizing agent into the reactor after the reactor temperature has dropped below the critical point of water;
After stopping the supply of the neutralizing agent into the reactor, pure water is supplied into the reactor to wash the neutralizing agent in the reactor, and at the outlet side of the reactor, pure water is supplied from the neutralizing agent supply. Switching to the feed and washing the neutralizer after the reactor;
A step of stopping the supply of the pure water and air after confirming that the washing of the neutralizing agent has been completed by a pH meter provided in a subsequent stage;
It consists of the method characterized by having.

In addition, the hydrothermal reactor operation stop method according to the present invention, as a more specific form, shuts down the hydrothermal reactor that supplies the liquid to be treated and supercritical water and performs the hydrothermal reaction in the reactor. When stopping operation,
The supply of the liquid to be treated and the supercritical water is stopped, but the air supply through the air supply line as the oxidant of the hydrothermal reaction and the neutralizer supply line connected to the reactor outlet side Continuing the supply of neutralizing agent;
Waiting until the inside of the reactor is cooled to a temperature below the critical point of water by the air supply;
Supplying a neutralizing agent into the reactor via the air supply line after the temperature in the reactor drops below the critical point of water;
After stopping the supply of the neutralizing agent into the reactor, supplying pure water into the reactor via the same line, and washing the neutralizing agent in the reactor;
Along with the neutralizing agent cleaning step in the reactor, the supply of the neutralizing agent through the neutralizing agent supply line on the outlet side of the reactor is stopped, and pure water is supplied through the neutralizing agent supply line. Washing the neutralizer after the reactor;
A step of stopping the supply of the pure water and air after confirming that the washing of the neutralizing agent has been completed by a pH meter provided in a subsequent stage;
It consists of the method characterized by having.

  Such a hydrothermal reaction apparatus shutdown method according to the present invention is applicable to any hydrothermal reaction apparatus using supercritical water regardless of the form of the reactor. When using a pressure balance type reactor having a double vessel structure in which a reactor is provided in a pressure vessel and balancing the pressure in the reactor and the pressure between the pressure vessel and the reactor, This is a preferred method for stopping operation.

  In the method for shutting down the hydrothermal reaction apparatus according to the present invention, after the apparatus is stopped (for example, after an emergency stop), the supply of air is continued and the reactor is cooled to a temperature below the critical point of water. In addition, the supply of the neutralizing agent to the reactor outlet side is continued, and corrosion of piping and the like after the reactor outlet is prevented. Then, after the temperature in the reactor is lowered, a neutralizing agent is supplied into the reactor to neutralize the acid remaining in the reactor, and after neutralization, pure water is supplied and washed. At the same time, pure water is also supplied to the reactor outlet side line, and the piping and the like after the reactor outlet are washed. Therefore, substantially all the lines after the reactor including the reactor are neutralized and washed, and corrosion of the reactor and subsequent piping and equipment is prevented. In addition, since the residue in the reactor is neutralized, even if the residue leaks between the pressure vessel and the reactor in the pressure balanced reactor, corrosion of the inner wall of the pressure vessel is prevented. Will be.

  Therefore, according to the operation stop method of the hydrothermal reactor according to the present invention, it is possible to prevent the reactor and subsequent piping / equipment from being corroded due to an emergency stop or the like. Become.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an overall schematic configuration of a hydrothermal reactor for carrying out an operation stop method according to an embodiment of the present invention, and particularly shows a case where a pressure balance type reactor is used as a reactor. Yes. In FIG. 1, 1 shows the whole hydrothermal reactor, and it has a double container structure in which a reactor 3 is provided in a pressure vessel 2 as a reactor, and the pressure in the reactor 3 and the pressure vessel 2 A pressure balance type reactor 4 that balances the pressure between the reactors 3 is used. In this embodiment, the waste liquid 5 as the liquid to be treated is introduced into the reactor 3 together with the supercritical water 6, and the air 7 as the reaction oxidant is introduced into the reactor 3 through the air supply line 8, A hydrothermal oxidation reaction is performed in the reactor 3 under supercritical water oxidation conditions, and organic substances contained in the waste liquid 5 are decomposed. In the early stage of the reaction, the auxiliary combustor 9 can be supplied as necessary to raise the reaction temperature to a predetermined temperature. The air supplied as the reaction fluid is also supplied between the pressure vessel 2 and the reactor 3 through the branch line, and the pressure between the pressure in the reactor 3 and the pressure between the pressure vessel 2 and the reactor 3. It is also used as a balancing fluid for balancing. During the pressure balance, the inside of the reactor 3 communicates between the pressure vessel 2 and the reactor 3 through the nozzle gap 10 so that the pressure inside and outside the reactor 3 is maintained at substantially the same pressure. It has become.

  The fluid after the reaction in the reactor 3 is discharged from the outlet line 11 as a processing fluid, cooled by the cooler 12, and then separated into the exhaust gas 14 and the treated water 15 by the gas-liquid separator 13. It has become. A pH meter 16 is installed in the treated water 15 line. On the outlet side of the reactor 3, a neutralizing agent supply line 17 is connected to the outlet line 11, and a neutralizing agent 18 (for example, an alkali agent) can be supplied through the neutralizing agent supply line 17. ing. Further, pure water 19 for cleaning can be supplied using the neutralizing agent supply line 17.

  In this embodiment, the air supply line 8 is used to supply the neutralizer 20 (for example, the same alkaline agent as described above) and the pure water 21 for cleaning into the reactor 3. It has become.

In the hydrothermal reactor 1 having such a configuration, when the operation is stopped, for example, when an emergency stop is performed, the method according to the present invention is performed as follows.
First, when a stop command is issued, the supply of the waste liquid 5 and the supercritical water 6 is stopped, the supply of air 7 through the air supply line 8 and the neutralizer supply line 17 on the reactor outlet side. The supply of the neutralizing agent 18 is continued. By supplying air, the temperature in the reactor 3 is lowered and eventually cooled to a temperature below the critical point of water. When the temperature in the reactor 3 decreases to a temperature below the critical point of water, the neutralizing agent 20 is newly supplied into the reactor 3 using the air supply line 8. As the supply amount, an amount equivalent to the internal volume of the reactor 3 is preferable, so that the neutralizer 20 is filled in the reactor 3 and the acid remaining in the reactor 3 is completely neutralized. it can.

  After supplying the neutralizing agent 20 into the reactor 3, pure water 21 is supplied into the reactor 3 using the same air supply line 8, and the neutralizing agent in the supply line 8 and the reactor 3 is supplied. And is discharged from the outlet line 11. At the same time, on the outlet side of the reactor 3, the supply of the neutralizing agent 18 via the neutralizing agent supply line 17 is stopped, and the pure water 19 is also supplied using the line 17. That is, the piping / equipment after the outlet of the reactor 3 is washed. Then, it is confirmed by the pH meter 16 provided in the latter stage that the neutralizing agent has been washed, and after the confirmation, the operation of the apparatus is completely stopped.

  By the above method, all the piping and equipment in the reactor 3 and after the reactor 3 were neutralized by the neutralizing agent, and the neutralizing agent was washed, and remained in the reactor 3. It is efficiently prevented that the acid causes corrosion. In particular, since the remaining acid is reliably neutralized and removed in the reactor 3, the remaining acid is reliably prevented from causing corrosion of the inner wall of the pressure vessel 2. As a result, the entire apparatus is safely stopped.

  The hydrothermal reactor shutdown method according to the present invention can be applied to any hydrothermal reactor shutdown, particularly for hydrothermal reactor shutdown using a pressure balanced reactor having a double vessel structure. Is preferred.

It is a schematic equipment diagram of a hydrothermal reaction device for carrying out an operation stop method concerning one embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydrothermal reactor 2 Pressure-resistant container 3 Reactor 4 Pressure balance type reactor 5 Waste liquid as liquid to be treated 6 Supercritical water 7 Air as reaction oxidant and balance fluid 8 Air supply line 9 Auxiliary agent 10 Nozzle gap 11 Outlet line 12 Cooler 13 Gas-liquid separator 14 Exhaust gas 15 Treated water 16 pH meter 17 Neutralizer supply line 18 Neutralizer 19 Pure water 20 Neutralizer 21 Pure water

Claims (3)

A method for shutting down a hydrothermal reactor in which a liquid to be treated and supercritical water are supplied to perform a hydrothermal reaction in a reactor, and when the operation is stopped,
Continuing the supply of the liquid to be treated and the supercritical water, but continuing the air supply and the supply of the neutralizing agent to the reactor outlet side until the temperature in the reactor falls below the critical point of water;
Supplying a neutralizing agent into the reactor after the reactor temperature has dropped below the critical point of water;
After stopping the supply of the neutralizing agent into the reactor, pure water is supplied into the reactor to wash the neutralizing agent in the reactor, and at the outlet side of the reactor, pure water is supplied from the neutralizing agent supply. Switching to the feed and washing the neutralizer after the reactor;
A step of stopping the supply of the pure water and air after confirming that the washing of the neutralizing agent has been completed by a pH meter provided in a subsequent stage;
A method for shutting down a hydrothermal reactor characterized by comprising: A method for shutting down a hydrothermal reactor in which a liquid to be treated and supercritical water are supplied to perform a hydrothermal reaction in a reactor, and when the operation is stopped,
The supply of the liquid to be treated and the supercritical water is stopped, but the air supply through the air supply line as the oxidant of the hydrothermal reaction and the neutralizer supply line connected to the reactor outlet side Continuing the supply of neutralizing agent;
Waiting until the inside of the reactor is cooled to a temperature below the critical point of water by the air supply;
Supplying a neutralizing agent into the reactor via the air supply line after the temperature in the reactor drops below the critical point of water;
After stopping the supply of the neutralizing agent into the reactor, supplying pure water into the reactor via the same line, and washing the neutralizing agent in the reactor;
Along with the neutralizing agent cleaning step in the reactor, the supply of the neutralizing agent through the neutralizing agent supply line on the outlet side of the reactor is stopped, and pure water is supplied through the neutralizing agent supply line. Washing the neutralizer after the reactor;
A step of stopping the supply of the pure water and air after confirming that the washing of the neutralizing agent has been completed by a pH meter provided in a subsequent stage;
A method for shutting down a hydrothermal reactor characterized by comprising:   As the reactor, a pressure balance type reactor having a double vessel structure in which a reactor is provided in a pressure vessel and balancing the pressure in the reactor and the pressure between the pressure vessel and the reactor. The method for stopping the operation of the hydrothermal reactor according to claim 1 or 2 to be used.

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