JPH033200B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention mainly relates to radioactive gas waste treatment equipment for boiling water nuclear power plants, and is concerned with the removal of hydrogen and oxygen produced by radiolysis of reactor water. The present invention relates to an exhaust gas recombination device used in

[Conventional technology]

The flow of the radioactive gas waste treatment system in a boiling water nuclear power plant is shown in Figure 1.

Hydrogen and oxygen gas generated by radiolysis of reactor water are extracted from the main condenser by the air extractor 3 along with the leaked air from the main condenser 2, and the driving steam of the air extractor causes an explosion. After being diluted to below the gas limit, the exhaust gas preheater 4 adjusts the temperature using in-house steam so that the temperature is about 30° C. higher than the saturation temperature of the process gas. The treated gas that has exited the exhaust gas preheater is turned into water vapor by the catalyst in the exhaust gas recombiner 5. The water vapor is condensed and removed together with the driving steam by the exhaust gas condenser 6. Radioactive exhaust gas from which hydrogen, oxygen, and water vapor have been removed has a long half-life.
After the Kr and Xe are attenuated by the carbon adsorption tower 7, they are released into the atmosphere from the exhaust stack 8.

The catalyst charged in the exhaust gas recombiner has the disadvantage that the recombination reaction deteriorates when moisture flows into it. The heated air heats the piping between the exhaust gas preheater and the exhaust gas recombiner to prevent condensate from flowing into the exhaust gas recombiner.

Note that the technology related to the present invention is disclosed in Japanese Patent Application Laid-Open No.
-There is one described in Publication No. 158600.

[Problem that the invention seeks to solve]

However, since it is not possible to flow a large amount of air through processing vessels such as downstream coal adsorption towers, the flow rate is approximately 1/200 of the rated value even through an exhaust gas preheater, resulting in poor heat exchange and increasing the temperature of the piping. The drawback is that it takes a very long time and the temperature cannot be raised sufficiently. In addition, the exhaust gas preheater, exhaust gas recombiner, and exhaust gas condenser are composed of two systems with 100% capacity, and one system is operated.
One system is on standby. When switching the operating system to the standby side, there is air leakage from the main condenser.
Due to the capacity of the charcoal adsorption tower, it is not possible to flow much air to raise the temperature. Therefore, when switching to the standby side, the temperature of the piping between the exhaust gas preheater and exhaust gas recombination cannot be raised, so some of the water vapor condenses and flows into the recombiner, causing temporary The disadvantage is that performance deteriorates.

The object of the present invention is to provide a method that overcomes the drawbacks of the prior art described above.

[Means for solving problems]

In order to achieve the above object, the present invention has an exhaust gas recombination device configured as follows.

That is, exhaust gas containing hydrogen gas and oxygen gas,
A preheater that preheats to a temperature higher than the saturation temperature is connected to the preheater via piping, the exhaust gas discharged from the preheater is introduced, and the hydrogen gas and the oxygen gas are supplied with a catalyst filled inside, An exhaust gas recombination device comprising: a recombiner for recombining water vapor; a heater installed in the piping between the preheater and the recombiner; and a temperature detector installed in the piping. , based on the output of the temperature detector, the lower limit of the heating temperature of the pipe is higher than the saturation temperature of steam during normal operation, and the upper limit of the heating temperature of the pipe is the exhaust gas discharged from the preheater during normal operation. and a control means for controlling the heating temperature of the heater so that the heating temperature is lower than the temperature of the heater.

[Effect]

The catalytic type Condensate does not flow into the recombination of the catalyst, and the recombination reaction of the catalyst can be prevented from deteriorating. Further, since the upper limit temperature of the tube by adjusting the temperature of the heater is set lower than the gas temperature at the outlet of the exhaust gas preheater, heating by the heater during normal operation becomes unnecessary.

〔Example〕

The details of the present invention will be explained with reference to the embodiment shown in FIG.

A heater 11 is attached to the outer surface of the pipe 10 between the exhaust gas preheater and the exhaust gas recombiner, and a temperature detector is provided on the pipe wall, and the heater is regulated by this thermometer. Insulating material 15 around the heater
is wrapped around it.

Before the process gas flows into the exhaust gas recombination device, the heater is turned on to raise the temperature of the piping. The temperature of the pipe surface is detected and controlled so that this temperature is equal to or higher than the saturation temperature of the steam when the processing gas is flowing.

Note that two systems are provided in parallel on the downstream side of the air extractor 3 in FIG. Any of these systems can be used as a regular system or a standby system.

According to the present invention, the temperature of the piping can be easily raised within a short time, and no condensed water is generated even when the process gas is vented, so that the performance of the catalyst does not deteriorate.

The temperature of the process gas containing oxygen and hydrogen gas is controlled by the exhaust gas preheater, which is heated by the in-house steam to a temperature several tens of degrees higher than the saturation temperature of the steam. By setting the temperature lower than the outlet gas temperature, the heater does not need to be energized during normal operation.

〔Effect of the invention〕

According to the present invention, it is possible to obtain an exhaust gas recombination device that can be easily activated and switched to the standby side without deteriorating the performance of the catalyst in the recombiner.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram of a radioactive gas waste treatment system which is the main subject of the present invention, FIG. 2 is an explanatory diagram of an embodiment of the present invention, and FIG. 3 is a detailed diagram of the present invention. 3...Air extractor, 4...Exhaust gas preheater, 5...
...Exhaust gas recombiner, 10...Piping, 11...Heater, 12...Power source, 13...Temperature detector, 14...
...Switch, 15...Heat insulation material, 16...Temperature detector, 17...Temperature adjustment valve.

Claims (1)

[Claims] 1. A preheater that preheats exhaust gas containing hydrogen gas and oxygen gas to a temperature equal to or higher than the saturation temperature; and a preheater connected to the preheater via piping to introduce the exhaust gas discharged from the preheater, and In an exhaust gas recombination device comprising a recombiner that recombines gas into water vapor using a catalyst filled inside, the exhaust gas recombination device includes a heater provided in the piping between the preheater and the recombiner; , based on a temperature detector installed in the piping and the output of the temperature detector, the lower limit of the heating temperature of the piping is higher than the saturation temperature of steam during normal operation, and the upper limit of the heating temperature of the piping is normally An exhaust gas recombination device comprising: control means for controlling the heating temperature of the heater so that the temperature is lower than the temperature of the exhaust gas discharged from the preheater during operation.