JP3836270B2 - Method for shutting down supercritical water reactor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for shutting down a supercritical water reactor equipped with a pressure balance type reactor comprising a pressure vessel and a reaction cartridge communicating with each other as a reactor, and more particularly, the pressure of the pressure balance type reactor. The present invention relates to a method for stopping the operation of a supercritical water reactor without corroding the vessel.
[0002]
[Prior art]
With increasing awareness of environmental issues, attention has been paid to attempts to decompose and detoxify environmental pollutants using supercritical water reactions with high oxidation and decomposition capabilities of organic matter. That is, due to the supercritical water reaction utilizing the high reactivity of supercritical water, harmful and hardly decomposable organic substances that have been difficult to be decomposed by the prior art, such as PCB (polychlorinated biphenyl), dioxin, and organic chlorine It is an attempt to decompose solvents and convert them into harmless products such as carbon dioxide, nitrogen, water and inorganic salts.
[0003]
A supercritical water reactor is a device that decomposes organic substances using the high reactivity of supercritical water. For example, it decomposes harmful organic substances that are difficult to decompose and converts them into harmless carbon dioxide and water. In order to decompose difficult-to-decompose high-molecular compounds and convert them into useful low-molecular compounds, their practical application is currently being actively studied.
Supercritical water refers to water in a supercritical state, that is, water in a state exceeding the critical point of water, and more specifically, at a temperature of 374.1 ° C. or higher and a pressure of 22.04 MPa or higher. Says water in a certain 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 oxygen or nitrogen at an arbitrary ratio to form a single phase.
[0004]
Here, with reference to FIG.1 and FIG.2, the basic structure of a supercritical water reaction apparatus is demonstrated. FIG. 1 is a flow sheet showing the basic configuration of a supercritical water reactor. FIG. 2 is a cross-sectional view showing the configuration of the pressure balance reactor.
The supercritical water reaction apparatus 10 is an apparatus 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. 1, a reactor that performs a supercritical water reaction. , A vertical pressure-resistant sealed reactor 12, a processing liquid pipe 14 for flowing the processing liquid out of the reactor 12, a cooler 16 for cooling the processing liquid, and a pressure control for controlling the pressure in the reactor 12. A valve 18 and a gas-liquid separator 20 for separating the processing liquid into gas and liquid are provided.
The vertical reaction vessel is usually suitable for processing a liquid to be processed having a low solid content, and a pipe-shaped tube for processing a liquid to be processed having a high solid content. Rahler reactors may be used.
[0005]
The supercritical water reactor 10 serves as a supply system for supplying a reactant to be subjected to a supercritical water reaction to the reactor 12, and is supplied with a liquid to be treated containing an organic substance to the reactor 12 via a liquid pipe 22 to be treated. A treatment liquid pump 24 and an air compressor 28 for feeding air as an oxidant into the reactor 12 via an air feed pipe 26 are provided.
Further, the supercritical water reaction apparatus 10 includes an auxiliary fuel pipe 30 for sending auxiliary fuel to the reactor 12 as a heat energy source necessary for maintaining the supercritical water reaction in the reactor 12 as necessary. In addition, an alkaline agent feed pipe 31 that feeds into the reactor 12 an alkaline agent that neutralizes chlorine generated from organic substances in the treatment liquid by supercritical water reaction in the reactor 12 is joined to the liquid pipe 22 to be treated. Yes. When the supercritical water state cannot be maintained with the water in the liquid to be treated, a make-up water pipe (not shown) may be connected to the liquid pipe 22 to be treated to replenish the make-up water.
[0006]
The liquid tube 22 to be treated and the air inlet tube 26 are connected to the reactor 12 via a two-fluid nozzle 34.
In addition, the supercritical water reactor 10 includes, for example, a liquid pipe 22 to be treated, an air inlet pipe 26, a treatment liquid, and a pipe around the reactor 12 in order to urgently shut off the reactor 12 when the apparatus is urgently stopped. Each of the pipes 14 and the like is provided with an emergency shut-off valve (not shown).
[0007]
In addition, a heat exchanger (not shown) that heat-recovers the process liquid by heat-exchanging the process liquid and the process liquid and raising the temperature of the process liquid to recover the heat is disposed upstream of the cooler 16. 14 or a preheater for preheating the liquid to be treated may be provided in the liquid pipe 22 to be treated upstream of the reactor 12.
Furthermore, a subcritical water region may be provided in the lower part of the reactor 12, and a mechanism may be provided for causing the inorganic salts generated in the reactor 12 to settle and remove in the subcritical water region.
[0008]
By the way, when an organic substance containing halogen such as chlorine, for example, PCBs, is treated in supercritical water, hydrochloric acid or the like is generated from chlorine atoms contained in the PCB, and the treatment liquid has a very high corrosivity.
Therefore, as the reactor 12, a pressure balance type reactor described below is used.
[0009]
As shown in FIG. 2, the pressure balance type reactor 12 is formed as a double cylinder of 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 supercritical water reaction. In addition, an annular portion 46 that communicates with the inside of the reaction cartridge 42 is formed between the pressure vessel 40 and the reaction cartridge 42 via the communication hole 44, and the pressure between the annular portion 46 and the reaction cartridge 42 is maintained. Balanced. In other words, the reaction cartridge 42 functions as a corrosion-resistant partition wall that partitions the reaction zone so as not to receive the internal pressure of the reactor 12.
The pressure vessel 40 is formed as a thick-walled high-strength steel pressure-resistant cylindrical vessel to counter the internal pressure of the reactor 12, while the reaction cartridge 42 is formed as a thin-walled covered cylinder with high corrosion resistance. The lower end of the pressure vessel 40 is tightly fixed to the bottom of the pressure vessel 40. Note that the reaction cartridge 42 may also be provided with a bottom, and the bottom of the pressure vessel 40 may be provided close to the bottom of the reaction cartridge 42.
[0010]
The reactor 12 includes a two-fluid nozzle 34 that passes through the pressure vessel 40 and the reaction cartridge 42 and protrudes into the reaction cartridge 42, and a treatment liquid that passes through the reaction cartridge 42 and the pressure vessel 40 from the inside of the reaction cartridge 42. A conduit 48 and an air feed nozzle 50 for feeding air into the annular portion 46 are provided. In this example, a 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.
Two-fluid nozzle 34, the inner tube 52 and outer tube 54, respectively, are connected to the treated liquid pipe 22 and the air inlet tube 26, the liquid to be treated the atomizing Lee ing to the reaction cartridge 42 in atomized by the air Has been introduced.
The processing liquid conduit 48 is connected to the processing liquid pipe 14. The air inlet nozzle 50 is connected to an air inlet branch pipe 56 (see FIG. 1) branched from the air inlet pipe 26, introduces air into the annular portion 46, and then passes through the communication hole 44 to the reaction cartridge 42. Let it flow into the interior and become part of the oxidant.
[0011]
In the pressure balance type reactor 12, air having the same pressure as the air flowing into the reaction cartridge 42 through the two-fluid nozzle 34 is introduced into the annular portion 46, so that there is almost no pressure difference inside and outside the reaction cartridge 42. The reason why air is introduced into the annular portion 46 is that air is a non-corrosive fluid.
In this example, a two-fluid nozzle is used to allow the liquid to be processed and air to flow into the pressure balance type reactor 12, but instead of the two-fluid nozzle, the pressure vessel 40 and the reaction cartridge 42 are used. There may be a separate inflow nozzle that passes through the.
[0012]
[Problems to be solved by the invention]
However, during operation of the supercritical water reactor using the above-described pressure balanced reactor as a reactor, corrosion has occurred on the inner wall of the pressure vessel 40 of the pressure balanced reactor. understood. 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 proceeds under high pressure and high temperature, even if extremely small corrosion holes are generated in the reactor wall, it may lead to an unexpected dangerous situation due to stress concentration. is there.
[0013]
Therefore, an object of the present invention is to provide a measure for preventing corrosion from occurring on the inner wall of the pressure vessel of the pressure balanced reactor.
[0014]
[Means for Solving the Problems]
As a result of pursuing the cause of corrosion on the inner wall of the pressure vessel, the present inventor has found the following.
When the supercritical water reactor is shut down urgently, the piping around the reactor, for example, the emergency shut-off valve provided in the liquid pipe to be treated, the air inlet pipe, the processing liquid pipe, etc. is closed. Although the liquid to be processed and air do not flow in and the processing liquid does not flow out, the reaction fluid in the reaction cartridge is hot for a while, so it flows toward the upper part of the reaction cartridge due to the convection phenomenon and communicates. It flows into the annular part 46 through the 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.
[0015]
The phenomenon described above occurs not only when the supercritical water reactor is stopped urgently but also when it is normally shut down. In use, it is important to note the above-mentioned corrosion.
Therefore, the inventor must (1) 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) If all the organic substances in the liquid to be treated in the reactor are oxidized, even if air is fed in, the supercritical water reaction will not proceed and become abnormal. At the time of normal equipment stop, of course, even during an emergency stop, the idea was to keep the pressure balance by sending air into the reaction cartridge and the annular part of the reactor. It came to completion.
[0016]
In order to achieve the above object, based on the above knowledge, the present invention provides a method for shutting down the supercritical water reactor shown in the following (1) to (3).
(1) It is formed as a double cylinder composed of a pressure vessel and a reaction cartridge communicating with each other, and includes a pressure balance type reactor containing supercritical water, and a liquid to be treated and an oxygen-containing gas as an oxidant Is supplied into the reaction cartridge, and an oxygen-containing gas as a pressure balancing gas is supplied between the pressure vessel and the reaction cartridge, so that the organic substance and oxygen in the liquid to be treated are present in the presence of supercritical water. A method for stopping the operation of a supercritical water reactor that performs a supercritical water reaction.
Stopping the supply of the liquid to be processed while supplying the oxygen-containing gas;
And a step of stopping the supply of the oxygen-containing gas when the temperature of the reactor falls below a predetermined temperature.
(2) As a fluid to be supplied to the reactor, in addition to the liquid to be treated, an oxygen-containing gas as an oxidizing agent, and an oxygen-containing gas as a pressure balance gas, auxiliary fuel, supercritical water, neutralizing agent, and subcritical water When at least one of them is supplied into the reaction cartridge and the operation is stopped,
Stopping the supply of fluids excluding the oxygen-containing gas among the fluids supplied to the reactor sequentially or at a time while supplying the oxygen-containing gas;
And (2) stopping the operation of the supercritical water reactor, wherein the supply of the oxygen-containing gas is stopped when the temperature of the reactor falls below a predetermined temperature.
(3) The method for shutting down the supercritical water reactor according to (1) or (2), wherein the liquid to be treated and an oxygen-containing gas as an oxidant are allowed to flow into the reaction cartridge as a mixed fluid.
[0017]
The fluid supplied to the reactor means, for example, a liquid to be treated, auxiliary fuel, supercritical water, neutralizing agent, subcritical water and the like. The fluid flowing out from the reactor means, for example, a treatment liquid, subcritical waste water, or the like. Normally, air is used as the oxygen-containing gas.
In the method of the present invention, the operation stop is a concept including an emergency operation stop and other normal operation stop.
There are no restrictions on the method of flowing the liquid to be processed and the oxygen-containing gas into the reaction cartridge of the pressure balance type reactor, and a two-fluid nozzle or a separate inflow nozzle may be used. A mixed fluid of liquid and oxygen-containing gas may be allowed to flow.
In the method of the present invention, the predetermined temperature is a critical temperature, preferably 300 ° C.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described specifically and in detail with reference to FIGS. 1 and 2 of the accompanying drawings.
Embodiment 1
The present 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 is supplied from the two-fluid nozzle 34 through the air inlet pipe 26 while the air compressor 28 is kept moving. 12 reaction cartridge 42 of, also, while through the air inlet tube 26 and the air feed Nyueda pipe 56 is supplied from the air infeed nozzles 50 air annulus 46, the treated liquid pipe 22, an alkaline agent The on-off valve (not shown) provided on the feed pipe 31 and the auxiliary fuel pipe 30 is closed, and the on-off valve (not shown) provided on the processing liquid pipe 14 remains open.
[0019]
Then, the temperature is the predetermined temperature of the reactor 12, for example, below the critical temperature, preferably at the time when the temperature was lowered under 300 ° C. or less, and closed-off valve provided in the air inlet tube 26 (not shown), the air Stop supplying.
[0020]
Embodiment 2
The present embodiment is an example of an embodiment in which the method for shutting down the supercritical water reactor according to the present invention is applied to the emergency shutdown 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 moved as in the normal operation. While continuing, air is supplied from the two-fluid nozzle 34 through the air inlet pipe 26 into the reaction cartridge 42 of the reactor 12, and also through the air inlet pipe 26 and the air inlet branch pipe 56. While supplying air from the nozzle 50 to the annular portion 46, the emergency shutoff valve (not shown) provided in the liquid pipe 22 to be processed, the alkaline agent inlet pipe 31, and the auxiliary fuel pipe 30 is closed, and the processing liquid The on-off valve (not shown) provided in the pipe 14 remains open.
[0021]
Next, when the temperature of the reactor 12 falls 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 is closed to supply air. To stop.
[0022]
【The invention's effect】
According to the method of the present invention, during the operation stop of the supercritical water reactor, it stops supply of the fluids other than the oxygen-containing gas, and oxygen-containing gas and the reaction cartridge of the pressure balance reactor and the annular portion since continue to supply, Ki out to maintain the pressure balance between the reaction cartridge and the annular portion, as in the prior art, upon shutdown of the supercritical water reactor, corrosive reaction fluid in the annulus from the reaction cartridge There will be no situation of spilling and corroding the inner wall of the pressure vessel.
[Brief description of the drawings]
FIG. 1 is a flow sheet showing the configuration of a supercritical water reactor equipped with a pressure balance type reactor as a reactor.
FIG. 2 is a cross-sectional view showing a configuration of a pressure balance type reactor.
FIG. 3 is a cross-sectional view showing a corrosion region of a pressure balanced reactor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Supercritical water reactor 12 Reactor 14 Process liquid pipe 16 Cooler 18 Pressure control valve 20 Gas-liquid separator 22 Process liquid pipe 24 Process liquid pump 26 Air inlet pipe 28 Air compressor 30 Auxiliary fuel pipe 31 Alkali Agent feeding pipe 34 Two-fluid nozzle 40 Pressure vessel 42 Reaction cartridge 44 Communication hole 46 Annular portion 48 Treatment liquid conduit 50 Air feeding nozzle 52 Two-fluid nozzle inner pipe 54 Two-fluid nozzle outer pipe 56 Air feeding branch pipe

Claims (3)

A reaction cartridge that is formed as a double cylinder composed of a pressure vessel and a reaction cartridge that communicate with each other, includes a pressure balance type reactor that contains supercritical water, and contains a liquid to be treated and an oxygen-containing gas as an oxidizing agent. And supplying an oxygen-containing gas as a pressure balancing gas between the pressure vessel and the reaction cartridge, and supercritical water of organic matter and oxygen in the liquid to be treated in the presence of supercritical water. It is a method of stopping the operation of the supercritical water reactor that performs the reaction, and when stopping the operation,
Stopping the supply of the liquid to be processed while supplying the oxygen-containing gas;
And a step of stopping the supply of the oxygen-containing gas when the temperature of the reactor falls below a predetermined temperature. As a fluid to be supplied to the reactor, in addition to the liquid to be treated, an oxygen-containing gas as an oxidant, and an oxygen-containing gas as a pressure balance gas, at least one of auxiliary fuel, supercritical water, neutralizing agent, and subcritical water When one is supplied into the reaction cartridge and the operation is stopped,
  Stopping the supply of fluids excluding the oxygen-containing gas among the fluids supplied to the reactor sequentially or at a time while supplying the oxygen-containing gas;
  The method of stopping the operation of the supercritical water reactor according to claim 1, further comprising the step of stopping the supply of the oxygen-containing gas when the temperature of the reactor falls below a predetermined temperature. The method for stopping operation of a supercritical water reactor according to claim 1 or 2, wherein the liquid to be treated and an oxygen-containing gas as an oxidant are allowed to flow into the reaction cartridge as a mixed fluid.

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