JP4240589B2 - Method of starting operation of low-temperature gas turbocompressor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an operation start method for a low temperature gas turbo compressor, and more particularly to an operation start method for early pumping of a low temperature gas turbo compressor such as an LNG boil-off gas.
[0002]
[Prior art]
For example, BOG (boil-off gas) generated in a low-temperature liquefied gas tank of LNG is compressed by a compressor, sucked into a pump from the low-temperature liquefied gas tank, and is combined with the gas generated by heating, and is then used in boilers and gas turbines. It is sent to consumers for fuel, city gas, or general industry.
[0003]
The amount of BOG generated in the low-temperature liquefied gas tank varies with changes in atmospheric temperature and pressure, and a large amount of BOG is generated when transferring low-temperature liquefied gas from the ship to the on-shore low-temperature liquefied gas tank. A plurality of compressors are installed in parallel, and unit control is performed in which the number of operating units to be processed is determined according to the amount of BOG generated. For this reason, the compressor is frequently started and stopped repeatedly, but the compressor in which the low-temperature gas does not flow and the piping before and after the compressor are at the atmospheric temperature while the compressor is stopped. Normally, at least one compressor is always operated, and the discharge line has a predetermined discharge pressure.
[0004]
As shown in FIG. 4, the low-temperature gas turbo compressor has a characteristic that when the discharge flow rate Q is the same, the discharge pressure decreases when the suction temperature Ti is high. In the example of FIG. 4, when the planned suction temperature Ti is −140 ° C., the planned discharge pressure, that is, the pressure of the discharge line cannot be obtained at a temperature higher than −130 ° C.
[0005]
When a compressor that is at an atmospheric temperature is started while it is stopped, the compressor starts to suck low-temperature BOG, but the suction pipe and the compressor that are at an atmospheric temperature are cooled down to a predetermined temperature, In the example shown in FIG. 4, which is higher than the discharge pressure of the discharge line, that is, the pressure of the discharge line, air cannot be blown to the discharge line unless it is cooled down to −130 ° C. For this reason, the following starting method is conventionally performed, and this conventional method will be described with reference to FIG.
[0006]
In FIG. 3, 1 is a low-temperature liquefied gas tank, 2 is a pipe connected to the ceiling of the low-temperature liquefied gas tank 1 in order to take out the BOG 3 generated in the low-temperature liquefied gas tank 1, and the pipe 2 is a suction line. The pipe 2 is connected to a suction drum 41 for controlling the temperature of the pipe 2 at a constant level by flushing.
[0007]
Further, a suction pipe 5 having a suction valve 4 is connected to the pipe 2 in the middle, and the tip of the suction pipe 5 is connected to the inlet side of a low-temperature gas turbo compressor 7 that can be driven by a driving device 6. It is connected.
[0008]
A discharge pipe 9 provided with a discharge valve 8 is connected to the outlet side of the compressor 7, and the tip of the discharge pipe 9 is connected to a pipe line 10. Thus, the conduit 10 is a discharge line.
[0009]
A bypass pipe 12 including a bypass valve 11 is connected to the compressor 7 side of the discharge pipe 9 with respect to the discharge valve 8, and the tip of the bypass pipe 12 is connected to the pipe line 13. Thus, the pipe line 13 is a bypass line, and the tip thereof is connected to the ceiling portion of the low-temperature liquefied gas tank 1.
[0010]
When the compressor 7 is started by the driving device 6 with the above-described equipment, the suction valve 4 and the bypass valve 11 are opened, and the discharge valve 8 is closed.
[0011]
Therefore, for example, BOG 3 having a temperature of −140 ° C. generated in the low temperature liquefied gas tank 1 is introduced into the compressor 7 driven through the pipe line 2 and the suction pipe 5 and compressed, but does not reach a desired pressure. It is discharged to the discharge pipe 9 at a low pressure, is fed to the pipe line 13 through the bypass pipe 12, and the BOG 3 introduced into the pipe line 13 is returned to the low-temperature liquefied gas tank 1. Therefore, in this case, the BOG 3 is not introduced into the conduit 10 that is a discharge line.
[0012]
Note that since the temperature of the BOG 3 returned to the low temperature liquefied gas tank 1 has risen, the low temperature liquefied gas is flushed and cooled at the inlet in the low temperature liquefied gas tank 1, thereby generating new BOG 3.
[0013]
When the suction pipe 5 and the compressor 7 are cooled down to a predetermined temperature by the BOG 3 fed through the pipe line 2 and the suction pipe 5, the discharge valve 8 is opened and the bypass valve 11 is closed. The BOG 3 is compressed to a predetermined pressure by the compressor 7 and fed from the discharge pipe 9 through the pipe line 10 to the downstream side.
[0014]
After the compressor 7 is started, during the bypass operation in which the BOG 3 is returned to the low-temperature liquefied gas tank 1 from the pipeline 13 serving as a bypass line in order to cool down the compressor 7, the BOG 3 is connected to the pipeline 10 serving as a discharge line. Therefore, the power for driving the compressor 7 is wasted during this time. Further, the power for boosting the new BOG 3 generated by the flushing in the low temperature liquefied gas tank 1 is wasted.
[0015]
In order to shorten the time for this bypass operation, in Japanese Utility Model Publication No. 6-43519, the start-up bypass valve 42 shown in FIG. When the temperature reaches a predetermined discharge pressure (−130 ° C. in the example of FIG. 4) before reaching (−140 ° C. in the example of 4), the bypass valve 42 starts to close and the pumping to the discharge line is started. It has been proposed. In this method, the relationship between the discharge flow rate and the discharge pressure of the low-temperature gas turbo compressor moves on the arrow line in FIG.
[0016]
In FIG. 5, 43 is a low-temperature gas turbo compressor, 44 is a suction line, 45 is a discharge line, 46 is a bypass line, 47 is a temperature detector, 48 is a pressure detector, 49 is a temperature detector, and 50 is a flow rate. A detector 51 is a controller.
[0017]
[Problems to be solved by the invention]
However, even in this method, the bypass operation time required for the cool-down from −130 ° C. to −140 ° C. can be shortened in the example of FIG. Bypass operation must be performed, and therefore, the bypass operation time for cool-down is not significantly reduced.
[0018]
In view of the above-described circumstances, the present invention can shorten the bypass operation time for cool-down performed at the start-up of the low-temperature gas turbo-type compressor that compresses BOG, and can reduce the wasteful power consumption of the compressor. It was made for the purpose of doing.
[0019]
[Means for Solving the Problems]
The operation start method of the low-temperature gas turbocompressor according to the present invention is a low-temperature liquefied gas storage facility in which BOG generated in a low-temperature liquefied gas tank and fed through a suction line can be compressed by a low-temperature gas turbo-type compressor. , When pre-cooling the compressor and a predetermined portion of the suction pipe for introducing BOG into the compressor before starting ,
At least a part of the BOG is branched and cooled from a discharge line through which the BOG discharged from the compressor flows, and the compressor that is stopped by the cooled BOG and a predetermined suction pipe that introduces BOG into the compressor The part is precooled .
[0020]
Also, the operation start method of the low-temperature gas turbo compressor according to the present invention is a low-temperature liquefied gas in which BOG generated in a low-temperature liquefied gas tank and fed through a suction line can be compressed by a low-temperature gas turbo-type compressor. In the storage facility, when the compressor and a predetermined portion of the suction pipe for introducing BOG into the compressor are pre-cooled before starting, and then starting,
The BOG is introduced into the compressor from the low-temperature liquefied gas tank through the suction line, flows out of the compressor, and is then fed to a predetermined low-pressure line having a pressure lower than that of the suction line. A predetermined portion of a suction pipe for introducing BOG into the compressor is precooled.
[0022]
ADVANTAGE OF THE INVENTION According to this invention, the time of the bypass operation for the cool down performed at the time of starting of the compressor which compresses BOG can be shortened, Therefore The useless consumption of the power at the time of compressor cool down can be reduced. Furthermore, useless power consumption for boosting new BOG generated by flushing in the low temperature liquefied gas tank can be reduced.
[0023]
The compressor and the compressor are introduced by a BOG that is introduced from the low-temperature liquefied gas tank to the compressor through the suction line and flows out of the compressor, and then is supplied to a predetermined low-pressure line lower than the suction line. When a predetermined portion of the suction pipe for introducing BOG into the compressor is precooled, the existing low-pressure line can be used effectively, and the equipment cost can be reduced. In this case, pre-cooling is possible even with a single compressor.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0025]
FIG. 1 shows an example of an embodiment of the present invention. Among the plurality of compressors 7 shown in FIG. 3, the state in the vicinity of the second or third compressor 7 from the left is a suction line, a discharge line, Shown with bypass line. 1, the same components as those shown in FIG. 3 are denoted by the same reference numerals.
[0026]
A pipe line 14 is connected to the pipe line 10 serving as a discharge line, and the tip of the pipe line 14 is connected to the compressor 7 side of the suction valve 4 connecting portion of the suction pipe 5.
[0027]
A pressure reducing valve 15, a cooler 16, an orifice 17, a check valve 18, a flow control valve 19, and a shut-off valve 20 are connected to the pipeline 14 sequentially from the upstream side to the downstream side in the flow direction of the BOG 3. .
[0028]
A flow rate detector 22 is connected to the flow rate detection tube 21 connected to the pipeline 14 so as to sandwich the front and rear of the orifice 17, and the flow rate 23 per unit time of the BOG 3 flowing through the pipeline 14 detected by the flow rate detector 22 is , And can be given to the flow rate indicating controller 24 as a signal.
[0029]
A temperature detector 25 is connected to the compressor 7, and the temperature 26 of the compressor 7 detected by the temperature detector 25 can be given to the temperature indicating controller 27 as a signal.
[0030]
In the flow rate indicating controller 24, a deviation between the flow rate 23 of the BOG 3 detected by the flow rate detector 22 and a preset flow rate of the BOG 3 is obtained, and the obtained deviation is a proportional integral controller built in the flow rate indicating controller 24. So that it can be given to the low signal selector 30 as a command signal 28.
[0031]
In the temperature indicating controller 27, a deviation between the temperature 26 of the compressor 7 detected by the temperature detector 25 and a preset temperature of the compressor 7 is obtained, and the obtained deviation is incorporated in the temperature indicating controller 27. The signal is adjusted by a proportional integration controller and can be supplied to the low signal selector 30 as a command signal 29.
[0032]
The low signal selector 30 selects a low signal from the command signal 28 from the flow rate indicating controller 24 and the command signal 29 from the temperature indicating controller 27, and uses the selected low signal as a valve opening / closing command signal 31. 19 can be given.
[0033]
A pipe 33 having a shut-off valve 32 is connected to the compressor 7 side of the discharge pipe 9 with respect to the bypass pipe 12 and the tip of the pipe 33 is connected to the pipe 2 which is a suction line. Has been.
[0034]
In FIG. 1, reference numeral 34 denotes a check valve provided between the discharge valve 8 of the discharge pipe 9 and the connection portion of the bypass pipe 12.
[0035]
Next, the operation of the embodiment of the present invention will be described.
[0036]
In the present embodiment, the compressor 7 is precooled in a stopped state. Thus, when the compressor 7 is pre-cooled, the shut-off valve 32 is open, the bypass valve 11 is closed as well as the intake valve 4 and the discharge valve 8, and the opening degree of the flow control valve 19 is adjusted.
[0037]
For example, the BOG 3 introduced at a temperature of about 10 ° C. and a pressure of about 9 kg / cm ² G from the pipeline 10 serving as a discharge line is depressurized by the pressure reducing valve 15 and fed to the cooler 16. For example, the cooled BOG 3 is cooled to −140 ° C. by a low-temperature liquefied gas having a temperature of −160 ° C., the cooled BOG 3 passes through the pipe line 14, the flow rate is controlled by the flow control valve 19, and the low-temperature BOG 3 whose flow rate is controlled is 5 is sent. The pressure in the suction pipe 5 is slightly higher than the pressure in the pipe line 2 as a suction line, for example, about 1000 mmAq.
[0038]
The low-temperature BOG 3 fed to the suction pipe 5 precools a predetermined portion of the suction pipe 5 while flowing through the suction pipe 5, is introduced from the suction pipe 5 to the compressor 7, and flows through the stopped compressor 7. The compressor 7 is pre-cooled and then discharged to the discharge pipe 9 and is sent from the discharge pipe 9 to the pipe line 2 which is a suction line through the pipe line 33.
[0039]
The flow rate 23 per unit time of the BOG 3 flowing through the pipe line 14 detected by the flow rate detector 22 is given to the flow rate indicating controller 24, and the flow rate indicating controller 24 per unit time of the preset BOG 3 per unit time. The deviation between the flow rate and the detected flow rate 23 per unit time is obtained, and the obtained deviation is processed by a proportional integral controller built in the flow rate indicating controller 24 to obtain a command signal 28. Signal 28 is provided to low signal selector 30.
[0040]
The temperature 26 of the compressor 7 detected by the temperature detector 25 is given to the temperature indicating controller 27, and the temperature indicating controller 27 detects the preset temperature of the compressor 7 and the detected temperature of the compressor 7. 26 deviations are obtained, and the obtained deviations are processed by a proportional integral controller built in the temperature indicating controller 27 to obtain a command signal 29. The obtained command signal 29 is sent to the low signal selector 30. Given. In addition, the position where the temperature detector 25 is installed may be any of the inside of the compressor 7, the suction pipe 5 and the discharge pipe 9, but the temperature to be set is changed according to the installation position.
[0041]
In the low signal selector 30, the low signal is selected from the command signals 28 and 29 and is supplied to the flow control valve 19 as the valve opening / closing command signal 31, and the opening degree of the flow control valve 19 is adjusted to a predetermined state.
[0042]
Since the flow control valve 19 is controlled by a low signal of the command signals 28 and 29, the change width of the opening of the flow control valve 19 is small. For this reason, the fluctuation of the flow rate per unit time of the low-temperature BOG 3 introduced into the compressor 7 from the pipe line 14 through the suction pipe 5 is small, and the predetermined portion of the suction pipe 5 and the pre-cooling of the compressor 7 are gradually stabilized. Can be done.
[0043]
When the compressor 7 is started, the shutoff valves 20 and 32 are closed so that the precooling BOG 3 does not flow through the pipes 14 and 33, and thereafter, the valve 7 is started by a conventional valve opening / closing operation. Even in the case of adopting the above-mentioned actual fair system No. 6-43519 (system of FIG. 5), it is not necessary to change this configuration. It is also possible to add the system of this embodiment to existing equipment.
[0044]
In the embodiment of the present invention, since the suction pipe 5 and the compressor 7 are pre-cooled when stopped, the bypass operation time for cool-down after the compressor 7 is started is greatly shortened. Accordingly, it is possible to reduce power consumption for driving the compressor 7 for bypass operation, and to reduce generation of new BOG due to flushing of the low-temperature liquefied gas.
[0045]
In this embodiment, the cooler 16 is provided to cool the high-temperature BOG 3 introduced from the pipe line 10 to the pipe line 14 by the low-temperature liquefied gas, but the suction line ( If there is a gas source having a pressure higher than the pressure in the pipe line 2), it does not have to be branched from the discharge line (the pipe line 10). If there is a low-temperature precooling gas source, the cooler 16 need not be provided.
[0046]
FIG. 2 shows another example of the embodiment of the present invention.
[0047]
In recent years, when a low temperature liquefied gas tank facility is newly installed, a BOG 3 having a higher pressure than the conventional one has been introduced into the pipe line 2 serving as a suction line (conventionally, the pressure of the BOG 3 in the pipe line 2 is For example, it is about 600 mmAq, but in the case of a new installation, for example, about 1200 mmAq). Therefore, this embodiment is suitable when such a facility is newly installed and when an existing line of low pressure (for example, about 600 mmAq) is nearby as the suction line.
[0048]
Thus, in the present embodiment, the pipe 35 is connected between the bypass pipe 12 connecting portion of the discharge pipe 9 and the compressor 7, and the pipe 35 is connected to the BOG 3 from the upstream side in the flow direction. An orifice 36, a check valve 37, a flow control valve 38, and a shut-off valve 40 are sequentially connected toward the downstream side.
[0049]
As in the case of FIG. 1, a flow rate detector 22 is connected to the flow rate detection tube 39 connected to the pipeline 35 so as to sandwich the front and back of the orifice 36, and BOG 3 flowing through the pipeline 35 detected by the flow rate detector 22. The flow rate per unit time can be given to the flow rate indicating controller 24 as a signal. The command signal 28 obtained by the flow rate indicating controller 24 in the same manner as in FIG. 1 can be supplied to the low signal selector 30.
[0050]
As in the case of FIG. 1, the temperature detector 25 is connected to the compressor 7, and the temperature 26 of the compressor 7 detected by the temperature detector 25 can be given to the temperature indicating controller 27 as a signal. ing. The command signal 29 obtained by the temperature indicating controller 27 can be given to the low signal selector 30.
[0051]
Further, the low signal selector 30 outputs a low signal as a valve opening / closing command signal 31 from among the command signal 28 given from the flow rate indicating controller 24 and the command signal 29 given from the temperature indicating controller 27. Can be given to.
[0052]
Next, the operation of the embodiment of the present invention will be described.
[0053]
Also in the present embodiment, the suction pipe 5 and the compressor 7 are precooled in a stopped state. Thus, when the suction pipe 5 and the compressor 7 are pre-cooled, the suction valve 4 is open, the discharge valve 8 and the bypass valve 11 are closed, and the flow control valve 38 is adjusted in opening.
[0054]
For example, BOG 3 having a temperature of −140 ° C. and a pressure of 1200 mmAq introduced into the suction pipe 5 from the pipe line 2 serving as a suction line is introduced into the compressor 7 by pre-cooling the suction pipe 5 and is stopped in the stopped compressor 7. Then, the compressor 7 is pre-cooled and then discharged to the discharge pipe 9 and fed from the discharge pipe 9 to the pipe 35. The reason why the BOG 3 flows from the pipeline 2 to the pipeline 35 is that the pressure in the pipeline 2 is higher than the pressure in the pipeline 35 and its downstream side.
[0055]
The flow rate of the BOG 3 fed to the pipe line 35 is controlled by a flow rate control valve 38 and fed from the pipe line 35 to, for example, a low-pressure (for example, 600 mmAq) suction line of existing equipment.
[0056]
The flow rate 23 per unit time of the BOG 3 flowing through the pipe 35 detected by the flow rate detector 22 is given to the flow rate indicating controller 24, and the command signal 28 is obtained in the same manner as in FIG. Signal 28 is provided to low signal selector 30.
[0057]
On the other hand, the temperature 26 of the compressor 7 detected by the temperature detector 25 is given to the temperature indicating controller 27 and a command signal 29 is obtained in the same manner as in FIG. 1, and the obtained command signal 29 is a low signal. It is given to the selector 30. The position where the temperature detector 25 is installed may be any of the inside of the compressor 7, the suction pipe 5, and the discharge pipe 9, but the temperature set according to the installation position is changed.
[0058]
In the low signal selector 30, the low signal is selected from the command signals 28 and 29 and is supplied to the flow control valve 38 as the valve opening / closing command signal 31, and the opening degree of the flow control valve 38 is adjusted to a predetermined state.
[0059]
Since the flow control valve 38 is controlled by a low signal of the command signals 28 and 29, the change width of the opening of the flow control valve 38 is small. For this reason, the fluctuation of the flow rate per unit time of the low-temperature BOG 3 introduced into the compressor 7 from the pipe line 2 as the suction line through the suction pipe 5 is small, and the pre-cooling of the suction pipe 5 and the compressor 7 is gradually performed. It can be performed stably.
[0060]
When the compressor 7 is started, the shutoff valve 40 is closed so that the precooling BOG 3 does not flow in the pipe line 35, and thereafter, the valve 7 is started by a conventional valve opening / closing operation. Even in the case of adopting the above-mentioned actual fair system No. 6-43519 (system of FIG. 5), it is not necessary to change this configuration. It is also possible to add the system of this embodiment to existing equipment.
[0061]
In the embodiment of the present invention, since the suction pipe 5 and the compressor 7 are pre-cooled when stopped, the bypass operation time for cool-down after the compressor 7 is started is greatly shortened. Accordingly, it is possible to reduce power consumption for driving the compressor 7 for the bypass operation, and to reduce generation of new BOG 3 due to flushing of the low-temperature liquefied gas.
[0062]
Further, in the embodiment of the present invention, since the means for cooling the BOG 3 for precooling the suction pipe 5 and the compressor 7 is not provided, it is particularly advantageous when there is an existing facility having a low pressure line. is there. If there is no low-pressure line, the pre-cooling BOG 3 fed to the pipeline 35 may be discharged to the atmosphere through a flare or the like, but in this case, the BOG 3 is wasted.
[0063]
In addition, this invention is not limited to the above-mentioned example, Of course, various changes can be added within the range which does not deviate from the summary of this invention.
[0064]
【The invention's effect】
According to the operation start method of the low-temperature gas turbocompressor of the present invention, in any of claims 1 and 2 , useless power consumption for cooling down the suction pipe and the compressor is reduced when the compressor is started. In addition, the generation of new BOG due to the flushing of the low-temperature liquefied gas in the low-temperature liquefied gas tank can be reduced. Further, in the case of claim 2 , the existing equipment can be used effectively, so the equipment cost is low. Various excellent effects can be obtained.
[Brief description of the drawings]
FIG. 1 is a flow sheet showing an example of an embodiment of a method for starting operation of a low-temperature gas turbocompressor according to the present invention.
FIG. 2 is a flow sheet showing another example of the embodiment of the operation start method for the low-temperature gas turbocompressor according to the present invention.
FIG. 3 is a flowchart for explaining a case where a conventional pipeline or compressor is cooled down.
4 is a graph showing the relationship between the discharge flow rate and the discharge pressure in the system shown in FIG.
FIG. 5 is a configuration diagram showing an example of a system for explaining a method of cooling a conventional low-temperature gas turbo compressor.
[Explanation of symbols]
1 Low temperature liquefied gas tank 2 Pipe line (suction line)
3 BOG
7 Compressor 10 Pipe line (discharge line)

Claims (2)

In a low temperature liquefied gas storage facility that can compress a BOG generated in a low temperature liquefied gas tank and fed through a suction line by a low temperature gas turbo type compressor, the BOG is introduced into the compressor and the compressor. When pre-cooling a predetermined part of the suction pipe to be started and then starting ,
At least a part of the BOG is branched and cooled from a discharge line through which the BOG discharged from the compressor flows, and the compressor that is stopped by the cooled BOG and a predetermined suction pipe that introduces BOG into the compressor A method for starting operation of a low-temperature gas turbocompressor, characterized by pre-cooling a portion . In a low temperature liquefied gas storage facility that can compress a BOG generated in a low temperature liquefied gas tank and fed through a suction line by a low temperature gas turbo type compressor, the BOG is introduced into the compressor and the compressor. When pre-cooling a predetermined part of the suction pipe to be started and then starting,
The BOG is introduced into the compressor from the low-temperature liquefied gas tank through the suction line, flows out of the compressor, and is then fed to a predetermined low-pressure line having a pressure lower than that of the suction line. A method for starting operation of a low-temperature gas turbocompressor, wherein a predetermined portion of a suction pipe for introducing BOG into the compressor is precooled .

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