JPH0379623B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cryogenic liquefaction refrigeration system, and particularly relates to an operating method suitable for a cryogenic liquefaction refrigeration system that requires various operating modes such as liquefaction operation, refrigeration operation, and liquefaction + refrigeration operation. It is.

Cryogenic liquefaction refrigeration equipment, especially helium liquefaction refrigeration equipment, is a development of various applied technologies that utilize the superconducting phenomenon in which the electrical resistance of certain materials becomes zero when they are cooled to a temperature close to absolute zero (-273°C). With,
It has become necessary for a single device to be able to operate not only as a general liquefier but also in various operating modes such as liquefaction operation, refrigeration operation, and liquefaction + refrigeration operation.

FIG. 1 shows an example of a helium liquefaction refrigerator system flow for cooling a superconducting magnet. The helium gas compressed by the compressor 1 is guided to the cryogenic liquefaction refrigerator 10 and then passed through the first heat exchanger 11.
A is cooled with low-temperature return gas (liquid nitrogen or the like may be used as an auxiliary cold source), and some of the gas is guided to the first expansion turbine 13A that generates cold through isentropic expansion. After the temperature drops, it is further cooled by the return gas in the third heat exchanger 11C, and then enters the second expansion turbine 13B, where the temperature drops due to isentropic expansion and the conduit 2
0 and joins the return gas. First heat exchanger 1
The remaining gas cooled at 1A is transferred to the second heat exchanger 1.
1B, third heat exchanger 11C, fourth heat exchanger 11
D, the fifth heat exchanger 11E sequentially cools down to below the reversal temperature, expands to almost atmospheric pressure at the J-T valve 14, becomes a gas-liquid mixed phase state, and passes through the gas-liquid separator 15.
guided by.

The gas in a gas-liquid multiphase state led to the gas-liquid separator 15 is separated into gas and liquid, and the liquid is transferred to the refrigerated transfer pipe 2.
4A, it is sent to the cryostat 30 containing a superconducting magnet 32, enters the cryostat inner tank 31, absorbs the heat load, and is gasified. A part of the gasified part is used to cool the power supply line (power lead) of the superconducting magnet 32, and after the temperature has recovered to room temperature, it passes through the conduit 25 and returns to the suction side of the compressor 1. The remaining gas passes through the cryogenic transfer pipe 24B and returns to the cryogenic liquefaction refrigerator 10, and then passes through the gas-liquid separator 15.
The gas separated into gas and liquid is joined with the fifth heat exchanger 11.
The cold is recovered by exchanging heat with E, and is combined with the outlet gas of the second expansion turbine 13B to be transferred to the fourth heat exchanger 11D, the third heat exchanger 11C, the second heat exchanger 11B, and the first The heat exchanger 11A sequentially recovers the cold and returns to the suction side of the compressor 1 after returning to room temperature. The intermediate pressure tank 2 is used for cushioning the gas within the system, and the pressures of the high pressure line 5 and the low pressure line 6 are controlled by control valves 3 and 4.

In the case of the above example, the liquid helium produced by the cryogenic liquefaction refrigerator 10 absorbs the heat load,
A part of the gasified low-temperature gas is transferred to cryogenic liquefaction refrigerator 1.
0, but the gas used to cool the power reed returns to room temperature and returns directly to the compressor 1. In this case, the former, that is, the liquid produced in the cryogenic refrigerator 10, The operation in which the superconducting magnet 32 is cooled with helium and the low-temperature gas that has been gasified by absorbing the heat load is returned to the cryogenic liquefaction refrigerator 10 corresponds to the freezing operation, and the latter, that is, the cryogenic refrigerator 10 The superconducting magnet 32 is cooled by liquid helium produced by
An operation in which low-temperature gas that has been gasified by absorbing a heat load is recovered to room temperature and returned directly to the compressor 1 without passing through the cryogenic liquefaction refrigerator 10. In this case, the power lead is cooled to return it to room temperature. The operation that recovers the temperature and returns it corresponds to the liquefaction operation. The helium liquefaction refrigeration system shown in FIG. 1 operates in combination with these refrigeration operations and liquefaction operations.

The conditions of the cryogenic liquefaction refrigerator differ greatly between liquefaction operation and refrigeration operation. That is, during refrigeration operation, since there is low-temperature return gas, the amount of liquid helium that can be produced is approximately four times greater than during liquefaction operation, and the amount of refrigeration that must be generated by the expansion turbine can be reduced. In addition, in liquefaction operation, since there is no low-temperature return gas that returns to the cryogenic liquefaction refrigerator, the amount of gas to the expansion turbine is increased to increase the amount of cooling that should be generated, and the amount of high-pressure gas for liquefaction is conversely reduced. It is necessary to ensure sufficient cooling. In order to achieve such a comprehensive balance, the expansion turbine and J
-The ratio of the amount of gas flowing to the T valve also needs to be changed significantly between liquefaction operation and refrigeration operation. During liquefaction operation, approximately 75% of the total flow rate of the compressor flows to the expansion turbine and approximately 25% to the J-T valve. On the other hand, during refrigeration operation, approximately 55% of the compressor's total flow goes to the expansion turbine, and approximately 45% goes to the J
-Flows into the T-valve.

In conventional liquefaction refrigeration equipment, in order to maintain a balance between liquefaction operation and refrigeration operation as described above, the inlet valves 12 of the first and second expansion turbines 13A and 13B are fully opened during liquefaction operation, and the J-T valve 14 is fully opened during refrigeration operation.
The opening degree of the inlet valve 12 was lowered at the same time as the opening degree of the inlet valve 12 was increased. In such an operation, the inlet pressure of the first expansion turbine 13A during refrigeration operation becomes approximately 70% of that during liquefaction operation (16 atm during liquefaction operation, approximately 12 atm during refrigeration operation), and the pressure is increased by the compressor 1. The disadvantage was that the pressure energy was wasted.

An object of the present invention is to provide an operating method that increases energy efficiency in a cryogenic liquefaction refrigeration system that requires various operating modes such as liquefaction operation, refrigeration operation, and liquefaction + refrigeration operation.

In each operation mode of liquefaction operation, refrigeration operation, and liquefaction + refrigeration operation, the ratio of the flow rate of the compressor to the expansion turbine that generates cold and the J-T valve (liquefaction line) is different, and the distribution of this gas is Maximum capacity cannot be achieved unless the process is carried out in a prescribed manner.In this gas distribution, the liquefaction line flow rate can be controlled by a J-T valve, but in the case of an expansion turbine, it is controlled by a mechanically fixed inlet nozzle. Automatically determined by inlet temperature and pressure. Therefore, under a constant compressor flow rate, an inlet valve has conventionally been used to reduce the expansion turbine flow rate in the refrigeration mode of operation.

The present invention provides conditions that meet the expansion turbine flow rate, which were conventionally adjusted by the inlet valve of the expansion turbine, that is, the expansion turbine inlet pressure is high during liquefaction operation, and the expansion turbine inlet pressure is low during refrigeration operation.
By adjusting the compressor discharge pressure to a pressure that is intermediate between these during liquefaction + refrigeration operation, cryogenic liquefaction can be achieved under the conditions of various operation modes such as liquefaction operation, refrigeration operation, and liquefaction + refrigeration operation. This is designed to increase energy efficiency when operating the refrigeration equipment.

FIG. 2 is a T-S diagram (temperature-entropy diagram) showing the energy balance of the cryogenic liquefaction refrigerator. An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

During liquefaction operation, the high-pressure gas compressed by the compressor 1 is guided to the cryogenic liquefaction refrigerator 10, and is passed through the first heat exchanger 11A along the isobar line 50B on the high-pressure side.
The gas is cooled from 16A to 18A in the first expansion turbine 13A, distributed to the first and second expansion turbines 13A and 13B and the J-T valve 14, and led to the first and second expansion turbines 13A and 13B.
A, the second expansion turbine B performs isentropic expansion from 19A to 20A, generates cold, and moves from 20A to 6A along the low-pressure side isobars 50A to the fourth heat exchanger 11D, the third heat exchanger 11C, and the second heat exchanger 11D. After being cooled and recovered by the heat exchanger 11B and the first heat exchanger 11A, it returns to the suction side of the compressor 1. On the other hand, the gas for the J-T valve 14 further flows from 16A to 2 along the isobar line 50B.
1A second heat exchanger 11B, third heat exchanger 11
C, cooled by the fourth heat exchanger 11D and the fifth heat exchanger 11E, and isoenthalpy line 55 by the J-T valve 14.
The gas expands along the line until it reaches the pressure on the low pressure side of the vapor-liquid equilibrium curve 51, and becomes a gas-liquid mixed phase.

On the other hand, during refrigeration operation, the first and second expansion turbines 1
In order to reduce the flow rates of 3A and 13B, conventionally the inlet valve 1 was
2, the pressure was reduced to 16 A', whereas in the present invention, the discharge pressure of the compressor 1 is reduced from 5 A to 5 A'. Therefore, the high pressure gas introduced into the cryogenic liquefaction refrigerator 10 will be cooled from 5A' to 16A' along the new isobar line 50B'.
There is almost no need to reduce the pressure at the inlet valve 12, and the pressure energy compressed by the compressor 1 can be used effectively, so that the power consumption of the compressor 1 can be reduced.

Note that even during refrigeration operation in which the discharge pressure of the compressor 1 is lowered from 5 A to 5 A', there is no problem in performing isentropic expansion with the J-T valve 14. That is, the isentropic expansion in the J-T valve 14 is performed along the isentropic line 55, and at which point on the isentropic line 55 (in this case, the isobar line 50
Even if it expands from point 21' along B', the final liquefaction rate 53 does not change. Furthermore, in this case,
As in the case of liquefaction operation, the isentropic line 55
Since the temperature rises upward from the point 21A above, and then the temperature does not drop and liquefy, no unnecessary load is placed on the fifth heat exchanger 11E.

In addition, during liquefaction + refrigeration operation, between the conditions of these liquefaction operation and refrigeration operation, that is, isobar line 5
The pressure may be adjusted between A and 5A'.

Next, a device for controlling the optimum conditions for each of the operation modes of liquefaction operation, refrigeration operation, and liquefaction + refrigeration operation will be explained with reference to FIG. A load condition is set by the load condition setting device 40, and according to this load condition, the controller 42 controls the discharge pressure of the compressor 1 to the previously specified high pressure condition, and also controls the control valve of the high pressure line. 3 is changed, and the opening degree of the J-T valve 14 is also changed to a predetermined value. Basic operation and control are performed as described above, but it is desirable to perform minute control in order to control the optimum conditions in each operation mode, and in this case, the second expansion turbine 1
It is desirable that the outlet temperature of the valve 3B and the inlet temperature of the J-T valve 14 be controlled, and that the inlet valve 12 and the J-T valve 14 perform minute control. In this way, by loading the control device, appropriate operating conditions corresponding to each operating mode can be easily achieved.

In addition, as a method of lowering the high pressure gas pressure of the cryogenic liquefaction refrigerator 10 during refrigeration operation, it is also possible to use the inlet valve 7 of the cryogenic liquefaction refrigerator 10, and the fifth
Cryogenic liquefaction refrigerator 10 based on the characteristics of heat exchanger 11E
refrigeration capacity can be increased. However, in this case, the power consumption of the compressor 1 does not decrease.

According to the present invention, in a cryogenic liquefaction refrigeration system that requires each operation mode of liquefaction operation, refrigeration operation, and liquefaction + refrigeration operation, compression is achieved by selecting and using high-pressure side pressure conditions corresponding to each operation mode. The power consumption of the machine can be reduced, the capacity of the cryogenic liquefaction refrigeration system can be increased, and energy efficiency can be increased.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a helium liquefaction refrigerator system flow for cooling a superconducting magnet, and FIG. 2 is a T-S diagram of the cryogenic liquefaction refrigerator. 1... Compressor, 2... Medium pressure tank, 10... Cryogenic liquefaction refrigerator, 13A... First expansion turbine,
13B...Second expansion turbine, 14...J-T
Valve, 15... Gas-liquid separator, 30... Cryostat, 32... Superconducting magnet, 40... Load condition setting device, 42... Controller, 50A... Low pressure side isobar line, 50B... High pressure side isobar line, 51...Vapour-liquid equilibrium curve.

Claims (1)

[Claims] 1. Pressurizing refrigerant gas with a compressor, circulating the refrigerant gas sequentially through a group of heat exchangers of a cryogenic liquefaction refrigerator, and branching a part of the pressurized refrigerant gas. The refrigerant gas is cooled by being adiabatically expanded by an expansion turbine and merged with the return of the circulating refrigerant gas, and the remainder of the pressurized refrigerant gas is cooled to below the reversal temperature by a group of heat exchangers. The cooled refrigerant gas is adiabatically expanded by an expansion valve to generate a cryogenic refrigerant, and the vaporized gas of the cryogenic refrigerant is returned to room temperature to be liquefied directly to the compressor without going through the cryogenic liquefaction refrigerator. A refrigeration operation in which the vaporized gas of the cryogenic refrigerant is used as a return refrigerant gas of the cryogenic liquefaction refrigerator; A part of the vaporized gas of the cryogenic refrigerant is returned to room temperature to return the vaporized gas of the cryogenic refrigerant to the cryogenic liquefaction refrigerator. A method for operating a cryogenic liquefaction refrigeration system capable of performing a liquefaction + freezing operation in which the vaporized gas of the cryogenic refrigerant is returned directly to the compressor without going through a In the cryogenic liquefaction refrigeration, the discharge pressure of the refrigerant gas from the compressor is changed to a high pressure during liquefaction operation, a low pressure during refrigeration operation, and a pressure between the above two operations during liquefaction + refrigeration operation. How to operate the equipment.