JPH01159568A - Method of controlling operation of cryogenic liquefying refrigerator - Google Patents

Abstract

PURPOSE: To ensure smooth and efficient operation by controlling the intermediate pressure of an expander at the inlet valve thereof depending on the load of an object to be cooled and controlling the flow rate of high pressure gas being introduced to a cryogenic liquefaction chiller through a Joule-Thomson valve. CONSTITUTION: A refrigeration load signal 27 is delivered from an object 20a-20n to be cooled to a setter 28 and an intermediate pressure set signal 29 of an expander corresponding to the refrigeration load is delivered to a controller 34 for the inlet valve 12 of the expander. At the same time, a high pressure gas flow rate set signal 30 is delivered to a controller 31 for a Joule-Thomson valve(JT valve). The controller 31 controls a JT valve 13 by producing a control signal 33 from a high pressure gas flow rate signal 32 and the signal 30. The controller 34 controls the inlet valve 12 by producing a control signal 36 from an intermediate pressure signal 35 and the signal 29. Consequently, a cryogenic liquefaction chiller can be held easily in a correct operating state for various load conditions of the object 20a-20n resulting in smooth and efficient operation control.

Description

[Detailed Description of the Invention] [Field of Application] The present invention relates to a method for controlling the operation of a cryogenic liquefaction refrigeration system, and particularly relates to a method for controlling the operation of a cryogenic liquefaction refrigeration system, particularly for cooling equipment having various load conditions such as refrigeration load, liquefaction load, refrigeration load + liquefaction load, etc. The present invention relates to a method for controlling the operation of a cryogenic liquefaction refrigeration system that cools the body.

[Conventional technology]

In cryogenic liquefaction refrigeration equipment, particularly helium liquefaction refrigeration equipment, the theoretical power (minimum power) required to obtain refrigeration capacity at cryogenic temperatures is approximately 70 times the refrigeration capacity. Furthermore, considering equipment efficiency, loss due to heat intrusion from the outside, etc., in practice, a power that is 500 to 1000 times the refrigeration capacity is required. Therefore, it is of course important to improve the efficiency of the equipment, but it is also important to ensure that the equipment operates smoothly and efficiently.
This is an important issue.

Generally, cryogenic liquefaction refrigeration equipment consists of a compressor that compresses gas, a heat exchanger that cools the compressed high-pressure gas to below the reversal temperature, and an expansion of the high-pressure gas that has been cooled to below the reversal temperature. A Joule-Thomson valve that generates liquefied gas by refrigeration, an expander arranged in two stages in series that generates the refrigeration necessary to cool the high-pressure gas flowing through the Joule-Thomson valve, and an expander. It consists of an expander inlet valve that controls the amount of gas flowing.

Operational control of the cryogenic liquefaction refrigeration system, which consists of these components, is performed by operating the Joule-Thomson valve and the expander valve, but depending on the load conditions of the object to be cooled, the appropriate opening degree of the multivalve may vary. In addition, for a constant load that is less than the maximum equipment capacity, there are an infinite number of combinations of the opening degrees of the multiple valves mentioned above, and when temperature control is performed, the time constant is large, the response is slow, and the Automatic control was difficult because it showed a reverse response. For this,
Conventional cryogenic liquefaction refrigeration systems require operators to perform operations through trial and error, do not perform operations that correspond to load conditions, or directly control the capacity of the compressor. .

As a control method for this type of cryogenic liquefaction refrigeration equipment, for example, there is a method disclosed in Japanese Patent Application Laid-open No. 108557/1982. Compressor capacity is controlled based on temperature.

[Problem that the invention seeks to solve]

The above-mentioned conventional cryogenic liquefaction refrigeration equipment, that is, the former, is complicated to operate and is difficult to operate properly in response to load conditions.

In addition, in the latter, that is, the one disclosed in Japanese Patent Application Laid-Open No. 57-108557, the expander inlet valve and the Joule Φ Thomson valve are not operated, so the load condition only exists in - mode (for example, refrigeration load). However, when various load conditions exist, efficient control is difficult.

An object of the present invention is to provide a method for controlling the operation of a cryogenic liquefaction refrigeration system, which allows the system to operate smoothly and efficiently even if the load conditions of the object to be cooled vary.

[Means for solving problems]

The above objects include a compressor that compresses gas, a heat exchanger that cools the compressed high-pressure gas below the inversion temperature, and a Joule-Thomson that expands the high-pressure gas cooled to the inversion temperature to generate liquefied gas. A pole comprising a valve, an expander arranged in two stages in series to generate refrigeration for cooling the high pressure gas flowing through the valve, and an expander inlet valve to control the amount of gas flowing to the expander. In the low temperature liquefaction refrigeration system, the intermediate pressure of the expander is controlled by the expander inlet valve in response to the load of the object to be cooled, and the high pressure gas introduced into the cryogenic liquefaction refrigeration system is controlled by the Joule-Thompson valve. This is achieved by controlling the flow rate.

[For production]

In response to the load of the object to be cooled, the intermediate pressure of the expanders arranged in two stages in series is controlled by the expander inlet valve, and the flow rate of high-pressure gas introduced into the cryogenic liquefaction refrigeration equipment is controlled by the Joule-Thomson valve. By doing so, the apparatus can be operated smoothly and efficiently even if the load conditions of the object to be cooled are diverse.

〔Example〕

In a cryogenic liquefaction refrigeration system, appropriate distribution and control of high-pressure gas compressed by a compressor is performed using a Joule-Thomson valve and an expander inlet valve, thereby making it possible to demonstrate appropriate equipment capacity in response to load conditions. The load conditions include liquefaction load only, refrigeration load only, and liquefaction load + refrigeration load, but each requires a Joule-Thompson valve and an expander inlet valve to achieve the maximum capacity of the device. The relationships among six or more different appropriate opening degrees will be explained with reference to FIG.

FIG. 2 is an example of a characteristic diagram of a cryogenic liquefaction refrigeration system. In Figure 2, Ao is the characteristic curve when the Joule-Thompson valve and the expander inlet valve are properly adjusted, and A1 is the Joule-Thompson valve opening at which the maximum refrigerating capacity can be achieved when there is no liquefaction load. is the characteristic curve when the expander artificial valve is fixed, and A2 is the characteristic curve when the Joule-Thomson valve and the expander inlet valve are fixed at the valve opening that can generate the maximum liquefaction capacity when there is no refrigeration load. be. Characteristic curve A
, indicates the maximum capacity when the maximum capacity of the compressor is used, and there is only one combination of opening degrees of the Joule-Thompson valve and the expander inlet valve corresponding to each point. Furthermore, characteristic curve A. Each point corresponds to the intermediate pressure of the two-stage expander (the inlet pressure of the second-stage expander) in a 1:1 ratio in a cryogenic refrigeration system that uses two stages of expanders in series. On the other hand, inside the characteristic curve A0, there are infinite combinations of opening degrees of the Joule-Thompson valve and the expander inlet valve to realize each point.

Based on the characteristics of cryogenic liquefaction refrigeration equipment as described above, in order to operate the equipment smoothly and efficiently in response to the load conditions of the object to be cooled (refrigeration load or liquefaction load), it is necessary to control the equipment on the characteristic curve Ao. do it. To control on the characteristic curve Ao, it is sufficient to control two of the following: Joule-Thomson valve opening, expander inlet valve opening, high pressure gas flow rate, and two-stage expander intermediate pressure, but from the viewpoint of reliability and safety. The best method is to control the inlet pressure of the two-stage expander with an expander inlet valve and control the flow rate of high pressure gas with a Joule-Thompson valve.

The above is an attempt to control the device on the characteristic curve AO, but it is clear that the characteristic curve A is based on the load conditions. If it is possible to operate inside the 2-stage expander, it is possible to control the operation with reduced power consumption by changing the flow rate control set value or the flow rate control set value and the two-stage expander intermediate pressure control set value at the same time.

An embodiment of the present invention will be described below with reference to FIG. 1st
In the figure, 1 is a compressor, 2 is a medium pressure tank, 3 is a high pressure gas pressure regulating valve, 4 is a low pressure gas pressure regulating valve, 10 is a cold box, lla to lie are heat exchangers, 12 is an expander inlet valve, 13 1 is a Joule-Thomson valve (hereinafter abbreviated as JT valve); 14a and 14b are expanders; 15 is a gas-liquid separator; 16 is a liquefied gas transfer pipe; 17 is a low temperature gas return device;
8 is a liquid nitrogen supply pipe, 20a to 20n, which is an auxiliary cold source.
is the object to be cooled, 21 is the normal temperature gas return pipe, 27 is the refrigeration load signal, 28 is the setting device, 29 is the pressure setting signal, 30 is the flow rate setting signal, 31 is the JTTiB2 controller, 32 is the high pressure gas flow rate signal, 33 is the JTTiB2 control signal, 34 is a controller for the expander inlet valve 12, 35 is an expander intermediate pressure signal, 36 is an expander inlet valve control signal, 37 and 39 are flow meters, 38
is a pressure gauge.

Next, the operation of the cryogenic liquefaction refrigeration system configured as described above will be explained. The high-pressure gas compressed by the compressor 1 is introduced into the cold box IO, and the first heat exchanger 11
After being cooled by heat exchange with liquid nitrogen and low pressure gas at step a, it branches into a liquefaction line and an expander line. The high-pressure gas branched to the expander line passes through the expander population valve 12 and performs adiabatic expansion work to an intermediate pressure in the first expander 14a to generate refrigeration, and then is exchanged with low-pressure gas in the third heat exchanger 11c. The temperature is further lowered through heat exchange, and the second expander 14b performs adiabatic expansion work again to generate refrigeration, and the gas flows into the low pressure gas line. On the other hand, after being cooled by the first heat exchanger 11a,
The high-pressure gas branched into the liquefaction line exchanges heat with the low-pressure gas in the second to fifth heat exchangers 11b to lie, and is finally cooled to below the reversal temperature, and JTTiB2 expands to partially generate liquefied gas. The gas is then introduced into the gas-liquid separator 15.

The liquefied gas introduced into the gas-liquid separator 15 and separated into gas and liquid is
The liquefied gas is supplied to the objects to be cooled 20a to 20n through the liquefied gas transfer pipe 16, absorbs the heat load and is gasified, returns to the cold box 10 through the low-temperature gas return pipe 17, and joins the low-temperature gas separated by the gas-liquid separator 15. By exchanging heat with the heat exchangers lie to lla, the cooled air is recovered and returned to the suction side of the compressor 1.

On the other hand, a part of the low-temperature gas gasified in the objects to be cooled 20a to 20n cools the objects to be cooled 20a to 20n by sensible heat, and returns to the suction side of the compressor l through the normal temperature gas return pipe 21. .

In this embodiment, the low temperature gas returning through the low temperature gas return pipe 17 corresponds to the refrigeration load, and the normal temperature gas returning through the normal temperature gas return pipe 21 corresponds to the liquefaction load, but when the objects to be cooled 20a to 20n are in a precooled state Most of the gas returns through the normal temperature gas return pipe 21, whereas in steady state, most of the gas returns through the low temperature gas return pipe 17.
Return to 0 If there are a large number of objects to be cooled as in this embodiment, and each cooling object independently selects the operating state, there will be a large number of load conditions.

Next, a method of controlling the cryogenic liquefaction refrigeration system having the above configuration and operation will be explained. Cooled objects 20a to 20
As a method for measuring the refrigeration load of n, for example, the object to be cooled 20
This is possible by multiplying the low temperature gas flow rate returned from a to 20n by the latent heat of the liquefied gas, which is input into the setting device 28 as the refrigeration load signal 27, and the expander intermediate pressure setting signal 29 corresponding to the refrigeration load is used to control the expander inlet valve. At the same time, a high pressure gas flow rate setting signal 30 is output to the JT valve controller 31. The JT valve controller 31 outputs a JT valve control signal 33 based on the high pressure gas flow rate signal 32 and the flow rate setting signal 30 to control JTTiB2. The expander artificial valve controller 34 controls the expander artificial valve 12 with the expander inlet valve control signal 36 in accordance with the expander intermediate pressure signal 35 and the pressure setting signal 29.

To further explain the above operation control method with reference to Fig. 2, for example, when receiving a refrigeration load corresponding to a, the expander intermediate pressure and high pressure gas introduction amount are adjusted so that the liquefaction capacity corresponding to b is also exhibited. will be controlled. However, if it is not necessary to demonstrate the maximum capacity due to the relationship between the load condition of the object to be cooled and the capacity of the cryogenic liquefaction refrigeration system (for example, if the heater is turned on in a cryogenic liquefaction refrigeration system that uses a heater to adjust the load), In this case, for example, by adding a function to modify the setting signal to the condition b' instead of b in FIG. 1, efficient operation control with reduced power consumption becomes possible.

In the above explanation, the case where control is performed using the refrigeration load has been explained, but it is clear that control can be directly performed using the flow rate of the low-temperature return gas. It is also possible to perform control based on the liquefaction load.

As described in detail above, according to this embodiment, the cryogenic liquefaction refrigeration equipment can be easily maintained in an appropriate operating state in response to various load conditions of the object to be cooled, and the operation can be controlled smoothly and efficiently. Can be done. Furthermore, since high pressure gas flow rate control is performed, pressure rise in the low pressure line due to excessive flow of high pressure gas can be prevented.
The freezing temperature can be maintained stably, and the expander overcooling that occurs when the flow rate of low-temperature return gas from the object to be cooled increases in a pulsed manner can be prevented. Furthermore, direct control has the effect of improving reliability because it relies on pressure and flow rate control using valves, which have a quick response and high stability.

〔Effect of the invention〕

As explained above, the present invention corresponds to the load of the object to be cooled, controls the intermediate pressure of the expanders arranged in two stages in series with the expander inlet valve, and controls the cryogenic liquefaction refrigeration system with the JT valve. By controlling the flow rate of the high-pressure gas introduced, the device can be operated smoothly and efficiently even if the load conditions of the object to be cooled are diverse.

4. Brief Description of the Drawings The temperature diagram is a system diagram showing an example of a cryogenic liquefaction refrigeration system embodying the present invention, and the second figure is a characteristic diagram showing an example of the characteristics of the cryogenic liquefaction refrigeration system.

1--1=-compressor, lla to 1ie--1 heat exchanger, 12-'--expander inlet valve, 13--
--- JT valve, 14a, 14b ---- Expander,
20a, 20n----1 object to be cooled, 28----general regulator, 31, 34-----1 controller 4/Fig. jl, j4-11 ψ1j mark each

Claims (1)

[Claims] 1. A compressor that compresses gas, a heat exchanger that cools the compressed high-pressure gas to below the reversal temperature, and a Joule-Thomson valve that expands the high-pressure gas cooled to the reversal temperature to generate liquefied gas. , a cryogenic liquefaction system comprising: an expander arranged in two stages in series to generate refrigeration for cooling the high-pressure gas flowing through the valve; and an expander inlet valve that controls the amount of gas flowing to the expander. In the refrigeration system, the intermediate pressure of the expander is controlled by the expander inlet valve in accordance with the load of the object to be cooled, and the flow rate of the high-pressure gas introduced into the cryogenic liquefaction refrigeration system is controlled by the Joule-Thompson valve. A method for controlling the operation of a cryogenic liquefaction refrigeration system.