JPS62198798A - Refrigerator for radioactive gas waste processor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a refrigerator for a radioactive gaseous waste treatment equipment in a nuclear power plant.

[Technical background of the invention and its problems] Examples of radioactive gas waste treatment equipment in nuclear power plants include those that treat exhaust gas pushed out from the main condenser in boiling water nuclear power plants, or pressurized water nuclear power plants. There are various types of equipment, including those that treat exhaust gas extracted from primary cooling water in plants. As an example, a method for processing exhaust gas extracted from the main condenser of a boiling water nuclear power plant will be described below.

The steam generated in a nuclear reactor contains hydrogen gas produced by the radiolysis of water and radioactive elements such as r, Xe, etc., but these are not condensed in the main condenser and remain as non-condensable gases. Radioactive gaseous waste treatment equipment is designed to reduce this waste to a safe radioactive concentration and release it into the atmosphere through a stack.

As shown in Fig. 3, the conventional radioactive gas waste treatment equipment draws radioactive exhaust gas from the main condenser 1 through the steam air extractor 2, and removes the aforementioned hydrogen gas through an oxyhydrogen recombination reaction. A preheater 3 for preheating the exhaust gas to a temperature necessary for starting the recombination reaction, and a recombiner 4 filled with a catalyst for promoting the oxyhydrogen recombination reaction are provided.

Since the gas flowing out from the recombiner 4 is high-temperature superheated steam, the steam is condensed in the condenser 5 and the temperature is lowered to about 50'C in consideration of the influence on downstream equipment.

The downstream side of the condenser 5 is a treatment step for reducing the radioactive concentration of l(r, xe).

This treatment process is a process in which Kr and Xe are retained for a certain period of time using the adsorption capacity of activated carbon to reduce radioactivity.In order to increase the adsorption capacity of activated carbon, the dew point is lowered to -20°C in the first stage.
It is necessary to perform sufficient dehumidification treatment by lowering the humidity to a low level.

That is, first, the exhaust gas is made into saturated air at about 10° C. using the precoolers 6a, 6b, and most of the moisture is removed, and then the exhaust gas is connected to the exhaust gas valves 7a, 7b, 7c through the dehumidifiers 8a, 8b,
8c and this dehumidifier 3a 13b.

After cooling (dehumidifying) at 8C to about -20'C, the exhaust gas passes through outlet valves 9a, 9b, and 9C to activated carbon towers 10...10'.
Then, Xe is held for a certain predetermined time to reach a safe radioactive concentration, and then a particle filter (HEPA filter) 11,
It is discharged into the atmosphere from the stack 13 via the vacuum pump 12.

Here, the gaseous waste treatment system includes a preheater 3, a recombiner 4, a condenser 5, and a precooler 6a in order to improve the reliability of the treatment system.
, 6b has a spare aircraft (2 series).
The valves are omitted in the figure for clarity. ) On the other hand, since the dehumidifiers 8a, 8b, and 8C cool the exhaust gas to below 0°C, frost will adhere to the heat transfer tubes, so a switching operation is periodically performed to alternately operate the two units and defrost. ,
There are three series installed, including a backup machine.

Therefore, the precoolers 6a, 6b and the dehumidifiers 8a, 8b, 8C
The precoolers 6a, 6b cover the capacity of the dehumidifiers 8a, 8b, 8C, and the dehumidifiers 8a, 8b
, 8C and precoolers 6a, 6b.
By removing most of the moisture with the dehumidifiers 8a, 8
b, reduce frost generated in 8C, dehumidifiers 8a, 8b, 8
This is to lengthen the operating time of C.

The precoolers 6a and 6b are paired with coolers 14a and 14b, and the dehumidifiers 8a, 8b, and 8C are paired with refrigeration filters 15a, 15b, and 15C, respectively, to form a refrigeration system.

By the way, the refrigeration system of the dehumidifier is explained with reference to FIG. 4. Exhaust gas flows in from the inlet nozzles 20 of the dehumidifiers 8a, 8b, and 8C, and is indirectly cooled with a refrigerant in the cooling section 22 while being sent from the outlet nozzle 21 to downstream equipment. be done. The flow of refrigerant forms a typical basic refrigeration cycle.

The gaseous refrigerant returned from the dehumidifiers 8a, 8b, and 8C flows into the compressor 24 through the return refrigerant pipe 23, and is compressed into a high-temperature, high-pressure gas state. The compressed gas is gas line 3
2 and check valve 28 to flow into the condenser 25, where it is liquefied to a predetermined condensation temperature for the refrigerated recycle. The liquefied liquid is adiabatically expanded by the expansion valve 26 and turned into a whit gas state, which is sent through the liquid refrigerant pipe 27 to the dehumidifiers 8a, 8b, and 8C for heat exchange, and the whit gas turns into dry gas.

Note that, as a special feature of this refrigeration cycle, the variation ratio of the heat load is i:ioo. Therefore, a part of the high temperature gas that has flowed out of the compressor 23 is transferred to the liquid refrigerant pipe 27 that has flowed out of the expansion valve 26.
A control method is adopted in which the compressor 24 is mixed in (flows due to pressure fluctuations on the secondary side) to give a pseudo thermal load so that the load on the compressor 24 is always constant. Therefore, a hot gas bypass line 29 and a capacity control valve 30 are provided which branch from the upstream side of the check valve 28 and connect to the cooling section 22.

The refrigerant is compressed into a high-temperature, high-pressure gas, but depending on the type of refrigerant, the refrigerating machine oil (which is contained in the refrigerant and circulates) may deteriorate, so the temperature is set so that it does not exceed the operating temperature. For this purpose, a fan 3 is mounted on the head of the compressor 24.
1 is installed to cool the head portion of the compressor 24. The outlet temperature of this compressor 24 is determined by a temperature sensor 33 in the gas line 32.
A signal from the temperature sensor 33 is inputted from a temperature switch 34 to a control panel 35, and interlocked with the operation of the compressor 24 via the control panel 35.

However, if the temperature of the atmosphere in which the compressor 24 is installed is high, forced ventilation by the fan 3 may cause the compressor 24 to
4, the outlet temperature exceeds the set value. Furthermore, as the load fluctuates, a method is adopted in which a pseudo load is applied by partially bypassing the hot gas, which makes control difficult and takes a long time to adjust.

When the atmospheric humidity at the installation location of the compressor a24 is high, the outlet gas temperature of the compressor 24 becomes high, causing problems such as tripping to prevent deterioration of the refrigerating machine oil.

[Object of the Invention] The present invention has been made to solve the above problems, and it prevents the outlet temperature of the compressor from becoming higher than the set value even if the ambient temperature of the compressor becomes high, and also prevents the entire system from rising above the set value. It is an object of the present invention to provide a refrigerator for a radioactive gas waste processing equipment that can reduce the load fluctuation width of the equipment and thereby improve the stability of control.

[Summary of the Invention] In the present invention, refrigerant gas compressed from the outlet of the compressor flows into the condenser through gas piping and becomes liquid refrigerant, and this liquid refrigerant flows into the dehumidifier through the expansion valve to perform heat exchange. a refrigeration cycle in which the refrigerant is vaporized and gasified from the outlet of the dehumidifier, and the refrigerant gas flows into the compressor through a return pipe; and the outlet of the dehumidifier is branched from between the condenser and the expansion valve. a bypass line having a constant flow valve connected to a side return pipe; an evaporator connected to the outlet side of the constant flow valve and disposed on the gas inlet side of the compressor; and a fan attached to the evaporator. , a first temperature sensor installed on the upstream side of the bypass line branch of the return piping, a control panel for inputting the output signal of the first temperature sensor via a converter, and a control panel installed on the gas line. The refrigerator for a radioactive gaseous waste processing apparatus is characterized in that it includes a temperature switch that receives an output signal from the second temperature sensor and sends the output signal to the control panel.

[Embodiment of the Invention] Hereinafter, an embodiment of a refrigerator for a radioactive gas waste treatment apparatus according to the present invention will be described with reference to FIG.

In FIG. 1, the outlet side of the compressor 24 is connected to a gas line 32.
The condenser 25 is connected to a dehumidifier 8a via a liquid refrigerant pipe 27 having an expansion valve 26.
, 8b, and 8c.

The dehumidifiers 8a, 8b, 8C are connected to a compressor 24 by a return refrigerant pipe 23. A bypass line 41 is connected between the upstream liquid refrigerant pipe 27 of the expansion valve 26 and the outlet return refrigerant pipe 23 of the dehumidifiers 8a, 8b, and 8C, and this bypass line 41 is connected to the upper part of the compressor 24. It passes through the disposed evaporator 40 and has a constant flow valve 45. The evaporator 40 is provided with cold air radiation fins 42, and the head portion of the compressor 24 is cooled by a fin 71 provided on the evaporator 40. A second temperature sensor 33 is provided in the gas line 32 near the discharge side of the compressor 24, and the output of the temperature sensor 33 is connected to the temperature switch 3.
4 is input. The output of the temperature switch 34 is connected to the signal line 46
The output of the control panel 35 is input to the motor of the compressor 24 through an output signal line 47.

Further, a first temperature sensor 43 is provided in the return refrigerant pipe 23 on the upstream side of the branch to which the bypass line 41 is connected, that is, on the compressor 24 side. The output of this first temperature sensor 43 is input to a converter 44, and the output of the converter 44 is input to the control panel 35 through a signal line 48.

Next, the operation of the above embodiment will be explained.

The heat load on dehumidifiers 8a, 8b, and 8C is approximately 1 at maximum flow rate.
000 kcaβ/h and the minimum load is approximately 10 kcaβ/h at the lowest flow rate. Therefore, the load variation ratio is 1:100. Therefore, this fluctuation range is within the range that can be controlled by the inverter (approximately 30 to 40%).
Shrink it to After the refrigerant is liquefied in the condenser 25, one part passes through the expansion valve 26 and enters the dehumidifier, but the liquid refrigerant pipe 27
It is branched from the evaporator 40 and guided to the evaporator 40. The evaporator 40 cools the air surrounding the compression Ia 24 and ventilates it to the compressor 24, and the amount of heat is approximately 1500 kca, which is equivalent to lowering the ambient temperature of air at a maximum of 35°C to 20'C.
β/h.

Therefore, the maximum heat load for both the dehumidifier and evaporator 40 is 250
0 kcaβ/h, and the compressor 24 is also selected to have a capacity of 1 to cover it.

Capacity control when the heat load inside the dehumidifier fluctuates will now be explained. As mentioned above, if a stable amount of refrigerant was flowing to the dehumidifier and evaporator 40, but the load was reduced, the temperature at the first temperature sensor 43 would decrease because the liquid would not completely gasify in the dehumidifier. descend. The amount of change is converted into an electric signal by the converter 44, converted into a frequency change amount by the control panel 35, and the signal is sent to the compressor 24 to reduce the rotation speed.

Therefore, the amount of liquid refrigerant flowing in the frozen cell changes.

Since the constant flow valve 45 is provided to control the amount of refrigerant flowing into the refrigerant bypass line 41, the amount of refrigerant does not change, and the heat load can be adjusted by changing only the amount of refrigerant flowing toward the dehumidifier. . The air cooled by the cooling section attached to the upper part of the compressor 24 is forced into the air by a fan 31, and is then sent to the compressor 24.
The temperature of the gas line at the outlet is above 125°C (below 125°C)
Avoid becoming. In the unlikely event that the above-mentioned temperature exceeds the set value, the temperature sensor 32 and temperature switch 33 cause the compressor 24 to trip via the control panel 35, causing the compressor of another machine to operate.

According to the above embodiment, the heat load variation ratio is 1:100→
1: 1.56, which is extremely narrow, making it possible to change from the conventional hot gas bypass system to compressor rotation speed control. As a result, hot gas escapes in a chaotic manner,
Differences in performance due to variations in capacity control valves and abnormal hunting due to troubles are eliminated.

Previously, a considerable amount of time was spent on adjustment tests. This is because the full width needs to automatically follow the fluctuation ratio of 100 to 1000 kcaβ/h, so it was necessary to find one point. In contrast, in the present invention, the rotation of the compressor is changed even if the load changes, so no particular time is required for adjustment.

Furthermore, when the performance of the refrigeration cycle is plotted on a Mollier diagram as shown in FIG. 2, the compressor outlet temperature 50, condenser outlet 51, expansion valve inlet 52, and compressor population 53 are shown as solid lines. On the other hand, in the present invention, the point 50 → 50
'Point 53→53', the compressor outlet temperature is 1
The temperature can be as low as 15℃ or less. The Mollier diagram has enthalpy on the horizontal axis, pressure on the vertical axis, and a saturated liquid line 54, a saturated gas line 55, and an isothermal curve 56.

However, when the heat load inside the dehumidifiers 8a, 8b, and 8C is stable (maximum load), the temperature of the return refrigerant pipe 23 is stable at a certain degree of superheat, but if the heat load changes, the temperature The sensor 43 changes and controls F! through the converter 44! E,
35, the rotation speed of the compressor 24 changes.

Although the amount of refrigerant in the frozen Nicle changes as a result, the amount of refrigerant flowing into the evaporator 40 does not change due to the constant flow valve 45 provided in the liquid bypass line 41. Then, only the amount of refrigerant flowing to the dehumidifier changes, corresponding to the reduction in load. In this way, not only can cold air be delivered to cool the compressor, but also the compressor power can be varied.

[Effects of the Invention] According to the present invention, even if the ambient temperature at the location where the compressor is installed increases, the refrigerant temperature from the outlet of the compressor can be prevented from increasing, and the load fluctuation range of the entire system can be reduced. The stability of control can be measured by reducing the

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an embodiment of a refrigerator for radioactive gas waste treatment equipment according to the present invention, Fig. 2 is a Mollier diagram for explaining the effects of the present invention and the conventional example; Figure 3 shows the radioactive gas waste disposal site]! I! FIG. 4 is a system diagram showing the refrigerator in FIG. 3. 8a, 3b, 8c... Dehumidifier 22... Cooling section 23... Return refrigerant piping 24... Compressor 25... ......Condenser 26...Expansion valve 27...Liquid refrigerant piping 31...Fan 32... ...Gas line 33...Second temperature sensor 34...
...Temperature switch 35 ... Control panel 40 ... Evaporator 41 ... Liquid bypass line 42 ...
...Fin 43...First temperature sensor 44...
...Converter 46, 47, 48...Signal line Applicant Toshiba Corporation Representative Patent attorney Sasu Suyama - Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) The compressed refrigerant gas from the outlet of the compressor flows into the condenser through the gas pipe and becomes liquid refrigerant, and this liquid refrigerant flows into the dehumidifier through the expansion valve, where it exchanges heat and vaporizes, dehumidifying it. A refrigeration cycle in which refrigerant is gasified from the outlet of the container and the refrigerant gas flows into the compressor through a return pipe, and a refrigeration cycle is branched from between the condenser and the expansion valve and connected to the return pipe on the outlet side of the dehumidifier. a bypass line having a constant flow valve; an evaporator connected to the outlet side of the constant flow valve and disposed on the gas inlet side of the compressor; a fan attached to the evaporator; A first temperature sensor provided on the upstream side of the bypass line branch, a control panel into which the output signal of the first temperature sensor is input via a converter, and a second temperature sensor provided in the gas line. A refrigerator for a radioactive gaseous waste processing apparatus, comprising a temperature switch that receives an output signal and sends the output signal to the control panel.