JPH067024B2 - Helium refrigeration equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a helium refrigerating apparatus for obtaining a cryogenic temperature.

(Prior Art) In recent years, development of a helium refrigerating device for obtaining a cryogenic temperature has been underway, and for example, a cryogenic refrigerating device described in Japanese Patent Publication No. 58-21186 is proposed. That is, in a Joule-Thomson circuit (hereinafter referred to as a JT circuit), after cooling high-pressure helium gas discharged from one compressor with low-pressure helium gas returning to the compressor and a precooler provided separately, Thomson valve (hereinafter referred to as JT valve)
By decompressing, a cryogenic helium gas-liquid mixed state) is obtained, and the latent heat of vaporization of helium in this gas-liquid mixed state is used for cryogenic cooling.

(Problems to be Solved by the Invention) Generally, in a helium refrigeration system, a JT to a compressor is used.
The return pressure of the circuit is about 1 atm, but the discharge pressure of about 20 atm is required. Therefore, when the helium gas is compressed by one gas compressor as in the above-mentioned known example, the load of the compressor is reduced. There is a drawback that is too large.

Therefore, an attempt has been made to reduce the load on each compressor by connecting two gas compressors having different capacities in series to compress the helium gas.

However, in the helium refrigerator before startup, each pressure is equalized, and the capacities of both compressors connected in series are significantly different (for example, the capacity of the low-stage compressor is different from that of the high-stage compressor). Since it is several times larger than the capacity), when both compressors are started at the same time, the discharge gas amount of the low-stage compressor immediately after start-up is considerably larger than that during steady operation. Therefore, the intake volume of the small capacity high-stage compressor cannot catch up, and finally,
An abnormal state occurs in which the suction pressure of the high-stage compressor becomes higher than the discharge pressure, making normal operation impossible. In particular, when a rotary compressor is used as the compressor, the back pressure of the blades decreases, making normal compression operation impossible, and continuing operation under abnormal pressure conditions.

The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to smoothly start up two compressors on the JT circuit side in a helium refrigeration system.

(Means for Solving Problems) In the present invention, as means for solving the above problems,
As shown in FIG. 1, a J-T having a pre-cooling refrigeration circuit 1 having a pre-cooling compressor 3 and an expander 6, a large-capacity low-stage compressor 8 and a small-capacity high-stage compressor 10 connected in series. In the helium refrigeration system including the circuit 2 and cooling the high-pressure refrigerant gas flowing in the JT circuit 2 by the pre-cooling refrigeration circuit 1, the low-stage compressor 8 is delayed by a predetermined time after the high-stage compressor 10 is started. Control means 4 for controlling operation to start
3 is attached.

(Operation) According to the present invention, the small-capacity high-stage compressor 10 is first operated at the time of start-up by the above means, and the pressure equalizing level of the low-stage compressor 8 is lowered (that is, the suction pressure of the high-stage compressor 10 is substantially reduced. Therefore, it is possible to obtain the effect that the low-stage compressor 8 is started after waiting for the discharge amount of the low-stage compressor 8 to be suppressed immediately after the start.

(Examples) Hereinafter, preferred examples of the present invention will be described with reference to the accompanying drawings.

This helium refrigeration system is composed of a pre-cooling refrigeration circuit 1, a JT circuit 2 and a control means 43.

The pre-cooling refrigeration circuit 1 includes a pre-cooling compressor 3 for compressing pre-cooling helium gas, an oil separator 4, an adsorber 5, an expander 6 and a surge bolt 7, which will be described in detail later, in sequence as a refrigerant gas line (that is, The high pressure refrigerant gas line 23 and the low pressure refrigerant gas line 24) are connected to each other. Here, the pre-cooling compressor 3, the oil separator 4, the adsorber 5, and the surge bolt 7 constitute a pre-cooling compressor unit A.

On the other hand, the JT circuit 2 includes a large capacity low-stage compressor 8, an oil separator 9, a small capacity high-stage compressor 10, an oil separator 11, an adsorber 12, and a first Joule-Thomson heat exchanger ( Below, J-
(T heat exchanger) 13, adsorber 14, first precooler 1
5, second J-T heat exchanger 16, adsorber 17, second precooler 18, third J-T heat exchanger 19, adsorber 20, J-T valve 21, cooler 22, the third, second And the first J-T heat exchangers 19, 16 and 13 are sequentially connected to the refrigerant gas pipe (that is,
The high pressure refrigerant gas pipe 25 and the low pressure refrigerant gas pipe 26) are connected to each other. Here, the low-stage and high-stage compressors 8 and 10, the oil separators 9 and 11, the adsorber 12, and the gas ballast tank 37 described below are the JT side compressor unit B.
Are configured.

The pre-cooling compressor 3, low-stage and low-stage compressors 8 and 1
0 is provided with cooling water coils 27, 28 and 29, respectively.
According to the respective discharge gas coils 30, 31, 32
And the oil coils 33, 34, 35 for injection can be cooled.

The oil separated by the oil separators 4, 9 and 11 is injected into the suction sides of the compressors 3, 8 and 10, respectively.

Each of the adsorbers 5, 12, 14, 17, 20 has a function of removing impurities in the helium gas in each state.

The surge bottle 7 has the function of reducing the pulsation of the low-pressure helium gas returned to the pre-cooling compressor 3.

In the JT circuit 2, a high pressure control valve 36, a gas ballast tank 37 and an intermediate pressure control valve are provided between the high pressure refrigerant gas pipe 25 on the outlet side of the adsorber 12 and the suction side of the high pressure compressor 10. A bypass circuit 39 provided with 38 is interposed. The gas ballast tank 37 includes a high pressure control valve 36.
Alternatively, it has an action of adjusting the amount of helium gas circulating in the JT circuit 2 by controlling the opening and closing of the intermediate pressure control valve 38.

The expander 6, the JT heat exchangers 13, 16, 19, the precoolers 15, 18, the JT valve 21, and the cooler 22 are housed in a vacuum container 40 maintained at a high degree of vacuum, and The second and third J-T heat exchangers 16 and 19, the second precooler 18,
The J-T valve 21 and the cooler 22 are surrounded by the radiation shield 41 to form a cryostat C. Reference numeral 42 is a thermometer that detects the temperature of the cooler 22. The expander 6 has a high-pressure side inlet 61 connected to the discharge side of the pre-cooling compressor 3 and a low-pressure side outlet 62 connected to the suction side of the pre-cooling compressor 3, and is cooled in the expansion stroke of the high-pressure helium gas inside the expander 6. And preheating the helium gas flowing through the JT circuit 2 in the first and second precoolers 15 and 18 provided on the outer circumferences of the first and second heat stations 70 and 71. .

Therefore, as a feature of the present invention, in this helium refrigeration system, the low-stage compressor 8 in the JT circuit 2 is connected to the high-stage pressure machine 1.
A control means 43 (for example, a timer or the like) for controlling the operation so as to be started with a delay of a predetermined time (for example, about 10 seconds) after the start of 0 is attached. The control means 43
The operation control of the compressor 3 of the pre-cooling refrigeration circuit 1 is also performed, and the compressor 3 is started simultaneously with the high-stage compressor 10 of the JT circuit 2.

Next, the operation of the helium refrigeration system of the illustrated embodiment will be described.

At the start of operation, first, the compressor 3 of the pre-cooling refrigeration circuit 1 and the high-stage compressor 10 of the JT circuit 2 are simultaneously activated by a command from the control means 43, and the low-stage compressor 8 is stopped. To be done. Therefore, the temperature of each heat station 70, 71 of the expander 6 in the pre-cooling refrigeration circuit 1 drops.

On the other hand, in the JT circuit 2, only the high-stage compressor 10 is operated, so that the pressure equalizing level of the low-stage compressor 8 is lowered, and about 10 seconds after the high-stage compressor 10 is started, it is almost the same. The suction pressure of the high-stage compressor 10 is reached. Therefore, when the low-stage compressor 8 is activated by a command from the control means 43,
The discharge amount of the low-stage compressor 8 immediately after the start-up is suppressed, which is almost the same as the suction amount of the high-stage compressor 10. Therefore, the pressure inversion that occurs when the both compressors 8 and 10 are simultaneously started does not occur, and the compressors can be started without any problem. Moreover,
By starting both compressors 8 and 10 in a staggered manner, the discharge amount of the low-stage compressor 8 immediately after starting is suppressed, and both compressors 8 and 10 are
The start-up of 10 can be performed smoothly, and the start-up current of the refrigerating apparatus can be greatly reduced.

Next, when the steady operation state is reached, the low-stage compressor 8 sucks and compresses the JT circuit return helium gas from the cryostat C, and the cooling water coil 28 cools it to room temperature 3
After cooling to 00K and oil separation in the oil separator 9, the high-stage compressor 10 sucks and compresses this helium gas. Then, the cooling water coil 29 is used to cool the cooling water to a room temperature of 300 K, the oil separator 11 separates the oil, and the adsorber 12 adsorbs impurities to supply clean high-pressure helium gas to the cryostat C.

The high-pressure helium gas supplied to the cryostat C side enters the primary side of the first J-T heat exchanger 13 and exchanges heat with the low-pressure helium gas on the secondary side returning to the J-T side compressor unit B, from room temperature 300K. Expander 6 cooled to about 70K
Enters the first precooler 15 provided on the outer periphery of the first heat station 70 (50-60K), is cooled to about 55K by the first heat station 70, and enters the primary side of the second JT heat exchanger 16. , JT side compressor unit B
Return to about 20K by exchanging heat with the low pressure helium gas on the secondary side.
The second heat station 71 of the expander 6 is cooled down to
It enters the second precooler 18 provided on the outer periphery of (15 to 20K), is cooled to about 15K by the second heat station 71, and further enters the primary side of the third JT heat exchanger 19, and then the JT Returning to the side compressor unit B, the heat is exchanged with the low pressure helium gas on the secondary side, and the heat is cooled to about 5K.
To 1. In addition, during the above process, the adsorbers 14, 17 and 17 are connected to the outlets of the JT heat exchangers 13, 16 and 19, respectively.
Impurity gases such as nitrogen, oxygen and hydrogen are adsorbed at a low temperature by 20 to make cleaner helium gas to prevent the J-T valve 21 and the precoolers 15 and 18 from being clogged.

Then, the high-pressure helium gas is throttled by the J-T valve 21, expanded by Joule-Thomson, and becomes helium in a gas-liquid mixed state of 1 atm and 4.2 K and is supplied to the cooler 22. In the cooler 22, the latent heat of vaporization of the liquid portion of helium is used for liquefying or recondensing another helium gas or for cooling the cooled object.

As a result, the low-pressure helium gas returning from the cooler 22 to the secondary side of the third JT heat exchanger 19 becomes a saturated gas of about 4.2K. And this low pressure helium gas is
In the JT heat exchangers 16 and 13, the high-pressure helium gas on the primary side is cooled, the temperature rises to about 300K, and the JT side compressor unit B is returned to. After that, the same cycle is repeated and the refrigerating operation is performed.

(Effects of the Invention) As described above, according to the present invention, in the JT circuit 2,
Since the low-stage compressor 8 is started with a delay of a predetermined time after the high-stage compressor 10 is started, the discharge amount of the low-stage compressor 8 immediately after the start is suppressed and the high-stage compressor 10 is discharged. The amount is commensurate with the suction amount, and there is an excellent effect that troubles at startup that occur when two compressors are connected in series are eliminated.

Further, there is also an effect that the start-up current of the refrigeration system can be greatly reduced by staggering the two compressors 8 and 10.

[Brief description of drawings]

FIG. 1 is a system diagram of a helium refrigeration system according to an embodiment of the present invention. 1 ... Pre-cooling refrigeration circuit 2 ... Joule Thomson circuit 3 ... Pre-cooling compressor 8 ... Low-stage compressor 10 ... High-stage compressor 43 ... Control means

Front page continuation (72) Inventor Satoshi Noguchi 1304 Kanaoka-machi, Sakai City, Osaka Prefecture Daikin Industries, Ltd. Sakai Plant Kanaoka Factory

Claims (1)

[Claims] 1. A pre-cooling refrigeration circuit (1) having a pre-cooling compressor (3) and an expander (6), a large capacity low stage compressor (8) and a small capacity high stage compressor connected in series. A Joule-Thomson circuit (2) having (10), wherein the high-pressure refrigerant gas flowing through the Joule-Thomson circuit (2) is cooled by the pre-cooling refrigeration circuit (1), the low-stage compressor (8) A helium refrigerating apparatus, further comprising a control means (43) for controlling the operation of the high-stage compressor (10) so that the high-stage compressor (10) is started after a predetermined time delay.