JPH11271483A - Treatment method of nuclear fusion furnace exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To positively deal with intermittent exhaust gas supply, and efficiently collect fuel constituent with less amount of a reaction object, by using an electrochemical reaction device for continuously performing oxidation reaction and reduction reaction. SOLUTION: For a process for collecting a hydrogen isotope that is a fuel constituent from the exhaust gas of a nuclear fusion furnace, for example, a solid electrolyte tube with oxygen ion permeability is provided, and an electrochemical reaction device 2 is used, where the electrochemical reaction device simultaneously performs oxidation reaction for supplying oxygen to a reaction object and reduction reaction for eliminating the oxygen from it. In this process, for example, when methane and vapor are supplied from an inlet 1, the mixture gas of hydrogen and carbon dioxide is discharged from the outlet of the electrochemical reaction device 2. The gas is sent to a palladium hydrogen permeation device 3 for separating into the hydrogen and non-permeation gas containing no hydrogen. When a reaction rate is insufficient, retreatment can be made. In that case, a tank for preventing mixture is used, thus improving collection efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the recovery of hydrogen isotopes from compounds, and is used in a process for treating a fusion reactor exhaust gas to recover a fuel component. In addition, it can be applied to a hydrogen production process.

[0002]

2. Description of the Related Art The exhaust gas of a fusion reactor utilizing the fusion reaction of deuterium and tritium contains a compound of oxygen and carbon as fuel components, that is, water and hydrocarbons, which are decomposed and used as fuel. It must be recovered in the form of reusable hydrogen. For this purpose, conventionally, this compound component was once oxidized by a catalyst and recovered as water, and then electrolyzed to obtain hydrogen. However, this method has the disadvantage that the form of water and the amount of tritium adsorbed by the catalyst and staying in the apparatus are large, and the operation is complicated because several chemical apparatuses are connected and operated.

FIG. 1 shows an example of a conventional method for treating a fusion reactor exhaust gas to recover a fuel component. In the figure,
A process for obtaining hydrogen gas as a product using methane and steam as raw materials will be described. The raw material is supplied from the inlet 1 and oxidized in the catalyst tower 2 to convert the hydrocarbon components into water and carbon dioxide.
While the fuel component is collected as water by the water adsorption device 3, carbon dioxide containing no fuel flows out as exhaust gas. A plurality (3, 4) of moisture adsorbers are used. In contrast to the moisture adsorber 3 used for collecting water, the moisture adsorber 4 regenerates the collected water by heating or the like, and sends the collected water to the electrolytic cell 5 to transmit the water vapor. Is reduced to recover hydrogen as a fuel component from 6, while oxygen is extracted from 7 as a by-product from the opposite side of the electrolyte. Since hydrogen is mixed with other gases, the palladium permeation device 8 recovers the fuel components to 9 by permeation, while discharging the exhaust gas from 10 or recovering the remaining fuel components from the process inlet 11 to recover the remaining fuel components. Return to

[0004] Since a compound containing a fuel component is separately treated in an oxidation treatment and a reduction treatment, and these treatments are not used at the same time, a large number of such apparatuses are used. Further, there is a problem that a relatively large amount of fuel (tritium) component is adsorbed and always remains in the catalyst tower 2 and the water adsorption devices 3 and 4. Further, due to problems in the process operation such as supply of oxygen for oxidation in the catalyst tower 2 and regeneration cycle of the adsorption devices 3 and 4, it is necessary to cope with the amount, concentration and composition of the fluctuating exhaust gas from 1. It was difficult.

[0005]

An object of the present invention is to provide a method for obtaining hydrogen gas by decomposing water and hydrocarbons.
Catalytic and adsorption reactions, which were inevitable in the past, are eliminated.The amount of fuel components that accumulate due to the generation of water by the oxidation reaction is extremely reduced.Moreover, the number of chemical devices used is reduced to facilitate operation. It is an object of the present invention to provide a method suitable for treating exhaust gas that is supplied in a specific manner.

That is, the present invention relates to a method for recovering fuel components by treating the exhaust gas of a nuclear fusion reactor. The present invention relates to a method for isolating water and hydrogen in an electrochemical reactor for continuously performing an oxidation reaction and a reduction reaction. An object of the present invention is to obtain an operation method suitable for treating an intermittently supplied exhaust gas with high efficiency and a small amount of retained reactant by combining an exchange reaction column for performing a body exchange reaction.

[0007]

In order to achieve this object, the present inventor has proposed that an electrochemical reaction apparatus for continuously performing an oxidation reaction and a reduction reaction uses a hydrocarbon component requiring an oxidation treatment and a water component requiring a reduction treatment. As a result of focusing on the fact that can be simultaneously processed in a single device, a method for achieving the above object with a simple process configuration has been devised. That is, (1) the fusion reactor exhaust gas is led to an electrochemical reaction device that continuously performs an oxidation reaction and a reduction reaction, and the hydrocarbons in the exhaust gas are oxidized to water and carbon dioxide, and then the nuclear reactor in the same device. Hydrogen is obtained by reducing water in the fusion reactor exhaust gas and water generated by the oxidation of the hydrocarbon.

[0008] The excess or deficiency of the amount of oxygen in the apparatus is automatically adjusted by the oxygen balance control ability of the electrochemical reaction apparatus, so that the oxidation of hydrocarbons is always performed regardless of the concentration of steam and hydrocarbons and their ratio. And the water is completely reduced.

(2) Hydrogen generated by the reaction in the electrochemical reaction device is purified and recovered by permeation by a device having a hydrogen permeable membrane provided downstream thereof, and is reused as a fuel component. Since the gas at the outlet of the electrochemical reactor such as carbon dioxide that does not permeate contains almost no fuel component,
It is sent to an exhaust gas treatment system.

Thus, the fuel component contained as a compound in the fusion exhaust gas is almost completely reused as a fuel, while He, which is undesirable to be contained in the fuel,
Elements such as C and O are discharged in the form of a fuel-free air flow. Experimental recovery of this process is 99.9%
Has been confirmed to reach.

(3) Depending on the recovery rate of the fuel component, the gas at the outlet of the electrochemical reaction device such as carbon dioxide which does not permeate the hydrogen permeable membrane is returned to the inlet for another treatment, and is again returned to the electrochemical reaction device. By performing the treatment, the recovery efficiency of the fuel component can be improved. Thus, in the process for treating a fusion reactor exhaust gas according to the present invention, one of the fuel components
It is possible to select and operate a 99.9% recovery per pass or recovery with a once-through process with lower efficiency or a higher recovery efficiency with two or more processes. Such a circulation process is suitable for the intermittent supply of the exhaust gas.

In the above-described electrochemical reaction apparatus that simultaneously performs oxidation and reduction, the reaction cannot be completed unless the compounds in the exhaust gas are ideally in an appropriate ratio. For example, in a reaction system of methane and steam, CH ₄ ┼2H ₂ O → 4
Since the reaction becomes H ₂ ┼CO _2, the reaction is completed without excess or deficiency of oxygen when the exhaust gas composition is methane: steam = 1: 2. On the other hand, under conditions where there is a large amount of water (steam), oxygen generated by the decomposition of water (steam) is accumulated and the reaction cannot be continued.

As an example of solving this problem, a new solid electrolyte tube permeable to oxygen ions is installed in an electrochemical reactor to control the supply amount of oxygen, and a reaction compound is passed through one side of the electrolyte tube. The oxygen concentration is controlled by supplying or removing oxygen by passing oxygen through a gas having a known oxygen concentration on the other side.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (One Embodiment of the Present Invention) A method for treating fusion reactor exhaust gas according to the present invention will be described with reference to FIG. The figure shows a process for obtaining hydrogen gas as a product using methane and steam as raw materials.

A raw material gas is supplied from an inlet 1, undergoes an oxidation-reduction process in an electrochemical reactor 2, and is discharged as a mixed gas of hydrogen and carbon dioxide from an outlet. This gas is sent to a palladium hydrogen permeator 3 where hydrogen is recovered from 4 as a pure fuel component, while unpermeated fuel-free gas is discharged from 5. If the conversion is not sufficient, the exhaust gas returns from 6 to the inlet for reprocessing.

In this series of processes, a large number of devices are not required as in the conventional method, and the same effect can be obtained with only two devices. Further, since there is no catalyst tower or water adsorption device as in the conventional method, the fuel (tritium) component is not adsorbed or condensed and remains, so that the amount of retained fuel is extremely small. In a fusion reactor, the retention of tritium fuel is an important problem in terms of safety and fuel economy, and the present invention is excellent in this respect. Further, in the electrochemical reactor 2, the excess or deficiency of the oxygen amount is automatically adjusted by the oxygen balance control ability, so that there is no need to control the supply of oxygen for oxidation. No driving problems. Therefore, even if the amount, concentration, and composition of the fusion reactor exhaust gas supplied from 1 fluctuate, it is easy to cope with it, and it is particularly suitable for intermittent exhaust gas supply.

(Other Embodiments of the Present Invention) In the above-described process of treating the exhaust gas of a fusion reactor to recover a fuel component, the exhaust gas is temporarily recovered by a container of a type for preventing the mixing thereof, and then supplied. By recirculating the gas after fuel recovery, the recovery efficiency of the fuel component can be improved.

FIGS. 3 (a) and 3 (b) show the recirculation process of FIG. 2 performed by a conventional tank 7 and a tank 7 of a type for preventing mixing, respectively. While the flow in the container is completely mixed in (a),
In (b), a plug flow occurs, and no mixing occurs in the container.

When the recovery rate of the fuel component at this time is η, the capacity of the tank is V, the flow rate of the loop is F, and the concentration and initial concentration of the fuel component are C and C ₀ , respectively, the component concentration in the tank is represented. , (A), the change in density is represented by C = C ₀ exp (−ηVt / F). Given that V = Ft, that is, the concentration at each circulating time, the concentration is 1 / ηe each time.
Becomes

For the sake of simplicity, ignoring the volume of the portion other than the tank and assuming that η = 0.99, (a) becomes about 1/3 every time, while (b) becomes ( 0.9
9) It becomes ⁿ , and the recovery of the fuel component can be completed very quickly. Therefore, the fuel component can be recovered with higher efficiency in the same operation time, and the loss of the fuel component in the exhaust gas can be reduced. For example, if the supply of the raw material gas from 1 is intermittent and the gas is discharged after processing two rounds each, the recovery rate in (a) is less than 99.87%, b) is 99.99%, and there is a difference of about 13 times in the loss of the fuel component.

[0021]

As can be seen from this example, a large number of devices are not required as in the conventional method, and similar effects can be obtained with only two devices. In the present invention,
Since the amount of retained fuel (tritium) components is extremely small, this is excellent in terms of safety of the apparatus and fuel economy.

Furthermore, in the electrochemical reaction apparatus of the present invention, the excess or deficiency of the oxygen amount is automatically adjusted by the ability to control the oxygen balance, so that there is no need to control the supply of oxygen for oxidation, and the regeneration of the adsorption apparatus is not required. There is no problem in the process operation of the cycle or switching. Therefore, the amount, concentration,
Even if the composition fluctuates, it is easy to cope with it, and particularly excellent in coping with intermittent supply.

[Brief description of the drawings]

FIG. 1 is a view showing a conventional method for treating a fusion reactor exhaust gas.

FIG. 2 is a view showing a method for treating a fusion reactor exhaust gas according to the present invention.

FIG. 3 shows processing by recirculation in the processing method of FIG. 2;
It is a figure which shows what was performed by the tank of (a) conventional method and the tank of the type which prevents (b) mixing, respectively.

[Explanation of symbols]

In FIG. 1, 1 fusion reactor exhaust gas inlet 2 catalyst tower 3 moisture adsorption device (during adsorption) 4 moisture absorption device (during regeneration) 5 electrolytic tank 6 electrolytic tank outlet gas 7 electrolytic tank by-product outlet 8 palladium permeation device 9 recovered fuel Outlet 10 Exhaust gas outlet 11 Exhaust gas return flow In FIG. 2, 1 Fusion reactor exhaust gas inlet 2 Electrochemical reactor 3 Palladium permeation device 4 Recovered fuel outlet 5 Exhaust gas outlet 6 Exhaust gas return flow. In Fig. 3, 1 fusion reactor exhaust gas inlet 2 electrochemical reactor 3 palladium permeation device 4 recovered fuel outlet 5 exhaust gas outlet 6 exhaust gas return flow 7 (a) is a complete mixing tank, (b) is a plug flow tank

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kawanori Nomura 2-4, Shirane, Shirakata, Tokai-mura, Naka-gun, Ibaraki Pref. Japan Atomic Energy Research Institute Tokai Research Institute (72) Inventor Yasunori Iwai, Tokai-mura, Naka-gun, Ibaraki (2) Inventor Masataka Nishi 2-4, Shirane, Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki Pref.

Claims (2)

[Claims] 1. An electrochemical reaction apparatus for continuously performing an oxidation reaction and a reduction reaction in a process for treating a compound in an exhaust gas of a fusion reactor utilizing a nuclear fusion reaction between deuterium and tritium to recover a fuel component. And converting the fuel component in the compound into reusable hydrogen. 2. In the above-mentioned process of treating the exhaust gas of a fusion reactor and recovering a fuel component, the exhaust gas after the fuel recovery is temporarily recovered in a container of a type for preventing mixing, and then recovered into the exhaust gas of the fusion reactor. 2. The processing method according to claim 1, wherein the supply of the fuel improves the recovery efficiency of the fuel component by recirculating the gas after the fuel recovery.