JPH0648124B2 - Operation control method for gas liquefaction refrigeration system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling the operation of a gas liquefaction refrigeration system equipped with an expansion turbine and a compressor.

[0002]

2. Description of the Related Art In a gas liquefaction refrigeration system in which an expansion turbine and a compressor are provided in different gas circulation paths, the thrust force generated on the rotary shaft of the expansion turbine is generated by a thrust bearing provided on the rotary shaft. Supported. However, since this thrust bearing is composed of a gas bearing or the like, its load capacity is limited. Therefore, conventionally, as shown in FIG. 5, the impeller of the expansion turbine 2 and the impeller of the compressor 3 are respectively connected to both ends of the rotating shaft 1 to form an impeller arrangement, and in the normal pressure operation, the expansion turbine 2 side is provided. The shape, size, gas pressure and the like of each impeller are designed so that the thrust force of the above and the thrust force of the compressor 3 side are substantially the same, and the thrust forces of the both impellers are substantially canceled each other. Then, the thrust bearing 4 having an appropriate load capacity with respect to the residual thrust force
Are provided to deal with the thrust forces created by normal pressure operation.

The range of the load capacity of the thrust bearing 4 is also against the thrust force generated at the time of starting and stopping the expansion turbine and the variable pressure operation in the pressure adjustment in the gas circulation path 7 by the pressure maintaining devices 5 and 6. It is configured to be handled within.

On the other hand, for example, when the thrust bearing 4 is composed of a gas bearing as described above, the bearing gas pressure is lost due to some abnormality in the bearing gas supply system, or
When the expansion turbine operating gas pressure rises due to an abnormality on the side of the supply device, which causes overspeed of the expansion turbine, and when abnormalities such as compressor cooling water cutoff occur, some of these abnormalities occur There is a risk of causing a serious malfunction as a whole. Therefore, the gas liquefaction refrigeration system with the above-mentioned configuration is provided with an abnormality detector such as a gas pressure detection switch, a turbine rotation speed detector, a water cutoff detector, etc. at an appropriate place. In the event of an emergency such as when the emergency stop button is operated by the operator, the compressor 3 is stopped, and the emergency shutoff valve 8 provided in the gas inlet side pipe to the expansion turbine 2 in FIG. The valve is closed, so that the expansion turbine 2 is quickly stopped.

[0005]

However, conventionally, when the above-mentioned emergency operation stop is performed,
There is a problem that each thrust bearing 4 is easily damaged. That is, when the emergency shutoff valve 8 is closed as described above, the exhaust pressure as well as the supply pressure of the expansion turbine 2 fluctuates significantly within a very short period of time, and therefore the thrust force acting on the rotary shaft 1 also changes. Although a large change occurs, during this time, a large unbalanced state is likely to occur with the changing thrust force on the compressor 3 side as well. As a result, there is a risk that a thrust force exceeding the load capacity of the thrust bearing 4 is generated and the thrust bearings 4 supporting the rotary shaft 1 are seriously damaged until the apparatus is completely stopped. Of.

The present invention has been made in consideration of the above-mentioned conventional problems, and an object thereof is to suppress fluctuations in thrust force generated in a rotating shaft when an operation is stopped in an emergency in a thrust bearing. Another object of the present invention is to provide an operation control method for a gas liquefaction refrigeration system capable of maintaining the load capacity within the range.

[0007]

In order to achieve the above object, an operation control method for a gas liquefaction refrigerating apparatus of the present invention has an expansion turbine impeller at one end of a rotary shaft and a compressor impeller at the other end. Are coupled to each other, and the operation control method of the gas liquefaction refrigeration system in which the expansion turbine and the compressor are provided in different gas circulation paths, respectively, in an emergency requiring an emergency stop of operation, the gas to the expansion turbine It is characterized in that the supply is stopped and the operation is stopped by opening an emergency pressure relief valve provided in the middle of the bypass path connecting the both gas circulation paths.

[0008]

According to the above method, in the event of an emergency, gas is supplied to the expansion turbine and the circulation path on the expansion turbine side and the circulation path on the compressor side are communicated with each other through the bypass path. The pressure changes of 1 and 2 have the same tendency. Therefore, changes in gas thrust on the expansion turbine side and the compressor side occur in the same cycle,
As a result, fluctuations in the thrust force on the compressor, which occur on the rotary shaft, also occur at the same cycle as fluctuations in the thrust force on the expansion turbine. As a result, the thrust forces of both of them are maintained until they cancel each other, and therefore, it is possible to prevent the thrust bearing from being applied with an excessive thrust force exceeding its load capacity limit. .

[0009]

EXAMPLE A specific example of the present invention will be described below with reference to FIG.

In the gas liquefaction refrigeration system constructed by applying the present invention, an impeller (not shown) of the expansion turbine 12 is coupled to one end side of the rotating shaft 11, and an impeller (not shown) of the compressor 13 is connected to the other end side. Are combined. Rotating shaft 1
The bearing 1 is supported by the thrust bearing 14 and the journal bearings 15 and 15 between the expansion turbine 12 and the compressor 13. In the gas circulation path 16 in which the expansion turbine 12 is provided, an emergency cutoff valve 17 is provided on the air supply side of the expansion turbine 12. And the gas circuit 1
The discharge port of the compressor 13 provided in 8 and the exhaust port of the expansion turbine 12 in the gas circulation path 16 are connected by a bypass path 19, and an emergency pressure relief valve 20 is provided in the middle of the bypass path 19. Has been. The emergency pressure relief valve 20 is configured to be controlled by a signal wiring 21 of the same system as the emergency shutoff valve 17. The emergency pressure relief valve 20 is closed during normal operation, and the emergency shutoff valve 17 is connected through the signal wiring 21.
When the signal for closing is released, the emergency pressure relief valve 20 is opened at the same time when the emergency shutoff valve 17 is closed.

In the above structure, in case of an emergency that requires closing of the emergency shutoff valve 17, an emergency signal is transmitted through the signal wiring 21 and the emergency pressure relief valve 20 is opened.
As a result, fluctuations in the thrust force on the compressor 13 side that occur on the rotary shaft 11 in an emergency occur at least in the same cycle as fluctuations in the thrust force on the expansion turbine 12 side. The forces will cancel each other out. As a result, thrust bearing 1
The magnitude and direction of the residual thrust force acting on No. 4 is maintained within the load capacity of the thrust bearing 14 from the time when the emergency shutoff valve 17 is closed until the operation of the gas liquefaction refrigeration system is completely stopped. To be done.

It should be noted that the bypass passage 19 is only required to connect the gas circulation passages 16 and 18, and the connecting portion is not limited to the above position. For example, as shown in FIG. 2, the suction port of the compressor 13 and the exhaust port of the expansion turbine 12 may be connected. Moreover, as shown in FIG. 3, the expansion turbine 12 side of the bypass passage 19 may be connected to the intermediate pressure take-out portion 12 a of the expansion turbine 12.

Further, as shown in FIG. 4, the bypass 1
When the throttle 22 is formed on the upstream side of the emergency pressure relief valve 20 in No. 9, the emergency stop can be performed within the load capacity range of the thrust bearing in the gas liquefaction refrigeration system as in the above embodiment. At the same time, the throttle 22 gradually changes the pressure when the emergency pressure relief valve 20 is opened. That is, the pressure in the gas circulation passage 18 in which the compressor 13 is installed is
The internal pressure of the gas circulation passage 18 decreases as the pressure of the expansion turbine 12 decreases while maintaining a differential pressure higher than the pressure inside 2 by the flow resistance of the gas passing through the throttle 22. As a result, the gas flow in the bypass passage 19 at the time of opening the emergency pressure relief valve 20 will be performed more gradually than in the above embodiment.

[0014]

As described above, the operation control method of the gas liquefaction refrigeration system of the present invention stops the supply of gas to the expansion turbine in an emergency requiring an emergency stop of the operation, and at the same time, both of the gas circulation paths described above. The operation is stopped by opening an emergency pressure relief valve provided in the middle of the bypass path connecting the.

As a result, when the operation is stopped in an emergency, the expansion turbine side and the compressor side reach the complete stop state while exhibiting the same tendency as each other.
The rotating shaft maintains a state in which the thrust forces on the compressor side and the expansion turbine side cancel each other out. Therefore,
It is possible to prevent an excessive thrust force exceeding the limit of the load capacity from being generated in the thrust bearing.

[Brief description of drawings]

FIG. 1 is a configuration explanatory diagram of a main part of a gas liquefaction refrigeration apparatus to which the present invention is applied.

FIG. 2 is a configuration explanatory diagram of a main part of another gas liquefaction refrigeration apparatus to which the present invention is applied.

FIG. 3 is a configuration explanatory view of a main part of still another gas liquefaction refrigeration apparatus to which the present invention is applied.

FIG. 4 is a configuration explanatory diagram of a main part of still another gas liquefaction refrigeration apparatus to which the present invention is applied.

FIG. 5 is an explanatory diagram of a configuration showing a conventional example.

[Explanation of symbols]

 11 rotary shaft 12 expansion turbine 13 compressor 16/18 gas circulation path 19 bypass path 20 emergency pressure relief valve

Claims (1)

[Claims] 1. A gas liquefaction refrigeration system in which an impeller of an expansion turbine is connected to one end of a rotary shaft and an impeller of a compressor is connected to the other end, and the expansion turbine and the compressor are provided in different gas circulation paths, respectively. A method for controlling the operation of an apparatus, wherein in the event of an emergency requiring an emergency stop of operation, the supply of gas to the expansion turbine is stopped, and an emergency pressure relief provided in the middle of a bypass path connecting both gas circulation paths A method for controlling the operation of a gas liquefaction refrigeration system, characterized by opening the valve to stop the operation.