KR102425480B1 - Compressor unit, screw compressor, and operating method of compressor unit - Google Patents

Abstract

The present invention relates to a compressor unit, a screw compressor, and an operating method of the compressor unit. According to the present invention, the compressor unit (10) comprises: a first compressor (12); a reciprocating second compressor (18) placed on a reliquefaction equipment access flow path (16) branched from a consumer access flow path (14) connected to the first compressor (12); and a control unit (27). The first compressor includes: a screw-type compression unit (22); a bypass flow path (23a) accessing the consumer access flow path (14) and a detention reservoir access flow path (3); and a bypass valve (23b). The control unit (27) increases the treatment volume of the compression unit (22) when starting the second compressor (18) and simultaneously increases the opening degree of the bypass valve (23b) so that the flow rate corresponding to the increased treatment volume can return to the detention reservoir access flow path (3), and starts the second compressor (18) afterwards and simultaneously reduces the opening degree of the bypass valve (23b).

Description

COMPRESSOR UNIT, SCREW COMPRESSOR, AND OPERATING METHOD OF COMPRESSOR UNIT

The present invention relates to a compressor unit, a screw compressor and a method of operating the compressor unit.

Conventionally, as disclosed in Japanese Patent Laid-Open No. 49-88904, there is known a compressor unit that recovers boil-off gas generated in a liquefied gas tank and supplies at least a part of the boil-off gas to a gas demander. A compressor unit disclosed in Japanese Patent Laid-Open No. 49-88904 has a first compressor for compressing a boil-off gas generated in a liquefied gas tank. The flow path on the discharge side of the first compressor is branched into two flow paths. One flow path is connected to the propulsion engine of the ship, and a part of the gas compressed by the 1st compressor is used by the propulsion mechanism. The other flow path is connected to the liquefied gas tank so that excess gas can be returned to the liquefied gas tank. The other flow path is provided with a second compressor and a heat exchanger for liquefaction, and the gas flowing through the flow path is compressed by the second compressor and then liquefied through the heat exchanger and a JT (Joule Thompson) valve. The liquefied liquefied gas is refluxed into the liquefied gas tank.

By the way, when the boil-off gas is being supplied to the propulsion engine of a ship from a 1st compressor, a 2nd compressor may be started. In this case, when the second compressor is started, the pressure on the discharge side of the first compressor is lowered by the amount of boil-off gas to be processed by the second compressor. In order to prevent this, even if the capacity control of the first compressor is performed by feedback control such as PID control, it is difficult to cope with sudden pressure fluctuations due to the start of the second compressor. For this reason, there exists a possibility that the operation in which the pressure of the gas supplied to a propulsion engine is stabilized may be prevented.

It is an object of the present invention to suppress fluctuations in pressure on the discharge side of the first compressor even when the second compressor is started while the first compressor is being driven.

A compressor unit according to an aspect of the present invention is a compressor unit installed in a ship, recovering a target gas, which is a boil-off gas of liquefied gas, from a storage tank provided in the ship, and supplying at least a portion of the target gas to a consumer, from the storage tank to the storage tank A first compressor for sucking the target gas through a connection flow path, a demand connection flow path connected from the first compressor to the demand side, and a reliquefaction facility connection flow path branching from the demand connection flow path and connected to the reliquefaction facility; It is provided on the reliquefaction facility connection flow path, and a reciprocal type second compressor for further compressing the target gas before flowing into the reliquefaction facility, and a control unit for controlling the first compressor and the second compressor. The first compressor includes a screw-type compression unit connected to the storage tank connection flow path to compress the target gas, and bypass means for returning at least a portion of the target gas from the customer connection flow path to the storage tank connection flow path. The bypass means includes a bypass flow path for connecting the customer connection flow path and the storage tank connection flow path, and a bypass valve provided in the bypass flow path. When the second compressor is started while the compression unit is being driven, the control unit is configured to control the compression unit by a flow rate corresponding to a required flow rate of the target gas to be processed by the second compressor by the operation of the second compressor. While increasing the throughput, start preparation control is executed to increase the opening degree of the bypass valve so that the flow rate corresponding to the increased throughput returns to the storage tank connection flow path, and after execution of the start preparation control, the second It is comprised so that the start control which makes the opening degree of the said bypass valve increased by the said start preparation control small by the predetermined opening degree may be performed while starting a compressor.

A screw compressor according to an aspect of the present invention is a screw compressor that sucks in a target gas, which is a boil-off gas of liquefied gas, from a storage tank provided on a ship through a storage tank connection flow path and discharges it to a demand destination connection flow path, and is connected to the storage tank connection flow path. a screw-type compression unit for compressing the target gas, a bypass flow path connecting the demand connection flow path and the storage tank connection flow path, and a bypass valve provided in the bypass flow path, wherein the storage tank is connected from the demand connection flow path A bypass means for returning at least a part of the target gas to the flow path and a control unit are provided. When the control unit receives a command to start a second compressor provided in the reliquefaction facility connection passage branched from the demand destination connection passage and connected to the reliquefaction facility while the compression unit is driven, the second compressor operates The second compressor increases the throughput of the compression unit by a flow rate corresponding to the required flow rate of the target gas to be processed, and the opening degree of the bypass valve so that the flow rate corresponding to the increased throughput returns to the storage tank connection flow path Executes start preparation control to increase It is configured to execute the start control to reduce the degree of acceleration.

A method of operating a compressor unit according to an aspect of the present invention is a method of operating a compressor unit for recovering a target gas, which is a boil-off gas of liquefied gas, from a storage tank provided on a ship and supplying at least a portion of the target gas to a consumer, the compressor unit comprising: , a first compressor that sucks the target gas from the storage tank through the storage tank connection flow path and discharges the target gas to the demand connection flow path, and a recipe provided in the reliquefaction facility connection flow path branched from the demand connection flow path and connected to the reliquefaction facility A second compressor is provided. The first compressor includes a screw-type compression unit connected to the storage tank connection flow path to compress the target gas, a bypass flow path connecting the demand destination connection flow path and the storage tank connection flow path, and a bypass valve provided in the bypass flow path. has The operation method includes a driving step of driving the compression unit of the first compressor, and when the second compressor is started while the compression unit is being driven, the second compressor is operated by the operation of the second compressor to process the processing. A start preparation step of increasing the throughput of the compression unit by a flow rate corresponding to the required flow rate of the target gas to be used and increasing the opening degree of the bypass valve so that the flow rate corresponding to the increased throughput returns to the storage tank connection flow path and a starting step of starting the second compressor after the start preparation step and reducing the opening degree of the bypass valve increased in the start preparation step by a predetermined opening degree.

1 is a diagram schematically showing the configuration of a compressor unit according to a first embodiment.
2 is a flowchart for explaining an operation operation when a second compressor is started in the compressor unit.
3 is a flowchart for explaining the start preparation control.
4 is a flowchart for explaining start control.
5 is a diagram schematically showing the configuration of a compressor unit according to the second embodiment.
6 is a diagram schematically showing the configuration of a screw compressor according to another embodiment.

EMBODIMENT OF THE INVENTION Hereinafter, it demonstrates in detail, referring drawings for the form for implementing this invention.

(First embodiment)

The compressor unit 10 (refer to FIG. 1 ) according to the present embodiment is a compressor unit that is installed in a ship (not shown) and recovers target gas that is a boil-off gas of liquefied gas from a storage tank 1 provided in the ship. At least a part of the target gas recovered by the compressor unit 10 is supplied to a consumer. As a demand destination, the propulsion engine (propulsion engine etc.) of a ship, the power generation apparatus installed in a ship, etc. are mentioned, for example. These are gas utilization devices that receive a gas in a predetermined pressure range. Examples of the liquefied gas include liquefied natural gas (LNG) and liquefied hydrogen (LH2).

As shown in FIG. 1 , the compressor unit 10 includes a first compressor 12 connected to a storage tank connection passage 3 connected to a storage tank 1 in which liquefied gas is stored, a first compressor 12 and the A customer connection flow path 14 for connecting the demand side, a reliquefaction facility connection flow path 16 connected to the reliquefaction facility 5 while branching from the demand side connection flow path 14, and a reliquefaction facility connection flow path 16 A second compressor (18) provided in the . The reliquefaction facility 5 is a facility for reliquefying gas in order to return the surplus part among the gas compressed by the 1st compressor 12 to the storage tank 1 . The second compressor 18 is a compressor that compresses the gas before flowing into the reliquefaction facility 5, and is constituted by a reciprocating compressor. That is, the second compressor 18 can be driven independently of the first compressor 12 . The liquefied gas reliquefied by the reliquefaction facility 5 is returned to the storage tank 1 .

The on-off valve 20 is provided in the reliquefaction facility connection flow path 16 . The on/off valve 20 opens when the second compressor 18 operates. Moreover, the spillback flow path 16a which has the spillback valve 16b is connected to the reliquefaction facility connection flow path 16 so that the 2nd compressor 18 may be bypassed.

The first compressor 12 is a compressor for compressing a target gas that is a boil-off gas generated in the storage tank 1 to a predetermined pressure, and includes a compression unit 22 connected to the storage tank connection passage 3 , and a compression unit ( 22) and a separate bypass means 23 is provided. The compression unit 22 is constituted by a screw compressor, and includes a pair of male and female screw rotors (not shown) and a housing (not shown) for accommodating the screw rotors.

The bypass means 23 is provided in the bypass flow path 23a which connects the customer connection flow path 14 and the storage tank connection flow path 3 to each other while bypassing the compression part 22, and the bypass flow path 23a. and a pass valve 23b. When the bypass flow path 23a is opened by the bypass valve 23b, a part of the gas discharged from the compression unit 22 is transferred from the customer connection flow path 14 through the bypass flow path 23a to the storage tank connection flow path 3 ) (that is, the suction side of the first compressor 12).

The first compressor 12 has an adjustment means 12a capable of increasing the amount of gas processed by the compression unit 22 . The adjusting means 12a is a capacity adjusting means configured to be able to adjust the compression capacity of the compression unit 22 . More specifically, the capacity adjusting means of the screw-type compression unit 22 includes a slide valve (not shown) capable of adjusting the gas discharge capacity. Moreover, when the 1st compressor 12 has an inverter, the rotation speed adjustment means comprised so that the rotation speed of the compression part 22 can be adjusted instead of the adjustment means 12a or together with the adjustment means 12a. (that is, inverter control means), you may have other adjustment means.

The demand connection flow path 14 is provided with a pressure detector 25 that detects the pressure of the gas flowing through the demand connection flow path 14 . The pressure detector 25 is disposed on the downstream side of the connection part of the bypass flow path 23a in the demand connection flow path 14 . The pressure detector 25 outputs a signal indicating the detected pressure.

The signal output from the pressure detector 25 is input to the control unit 27 . The control unit 27 is constituted by a computer including a CPU and a memory device and the like, and by executing a stored program, it exerts a predetermined function. The control part 27 is electrically connected to the 1st compressor 12, the 2nd compressor 18, the bypass valve 23b, and the on-off valve 20, and the control part 27 is comprised so that these may be controlled. . That is, the functions of the control unit 27 include the first driving control unit 27a , the second driving control unit 27b , and the bypass control unit 27c . The first drive control unit 27a is configured to control the adjustment means 12a of the first compressor 12 . The second drive control unit 27b is configured to open and close the on-off valve 20 while controlling the second compressor 18 . The bypass control part 27c is comprised so that the opening degree control of the bypass valve 23b may be performed.

When the control unit 27 executes the above program, the start preparation control and the start control are executed.

The start preparation control and the start control are controls performed when the second compressor 18 is started while the first compressor 12 is being driven, and the start preparation control is executed before the start control is executed. That is, the start preparation control is a control performed before driving the second compressor 18 , and is executed when the control unit 27 receives a command for starting the second compressor 18 . This command may be output from the ship side by predetermined operation by the operator of a ship, for example, or when the gas pressure in the storage tank 1 exceeds a predetermined value, it may be output from the ship side.

The start control is executed after the start preparation control ends. That is, although the drive of the 2nd compressor 18 is started in the start control, the start of this start control is not permitted until the start preparation control is complete|finished. For this reason, only when the command for starting the 2nd compressor 18 from the ship side is input into the control part 27, the 2nd compressor 18 does not start, and the control part 27 does not turn on the 2nd compressor 18. The second compressor 18 starts up only after the control for permitting the start of .

Here, the operation method of the compressor unit 10 will be described with reference to FIGS. 2 to 4 . Note that this operation method is an operation method when the second compressor 18 is started while the first compressor 12 is being driven.

As shown in FIG. 2 , during the driving of the first compressor 12 , that is, during the driving of the compression unit 22 (step ST11 (drive step)), the opening degree of the bypass valve 23b and the The position (or compressor operator) is being adjusted. That is, the bypass control unit 27c controls the bypass valve 23b and the first drive control unit 27a controls the slide valve (or rotates the compressor) so that the gas of a predetermined pressure is supplied to the consumer at a predetermined flow rate. number control) is being performed. Accordingly, the pressure and flow rate of the gas supplied from the compressor unit 10 to the consumer are controlled. Then, when the control unit 27 receives a command for starting the second compressor 18 while the first compressor 12 is being driven (step ST12), the control unit 27 executes start preparation control (step ST13 (step ST13)). start preparation step)). In the start preparation control, control to increase the opening degree of the bypass valve 23b while increasing the throughput of the compression part 22 in the 1st compressor 12 is performed so that it may mention later. For this reason, the gas pressure in the demand-destination connection flow path 14 may fluctuate temporarily. Therefore, it waits until the opening degree of the bypass valve 23b converges within a predetermined range (step ST14). After that, execution of start control becomes possible (step ST15 (start step)).

The start preparation control is executed when a command for starting the second compressor 18 is received, but only by receiving this command, the second compressor 18 does not start. When the control unit 27 receives this command, as shown in FIG. 3 , the control unit 27 (the first drive control unit 27a ) controls the amount of gas processed by the compression unit 22 of the first compressor 12 . Increase control is started (step ST131). That is, in order to start the second compressor 18 in the subsequent start control, the gas to be processed by the second compressor 18 in order to prevent the gas pressure in the demand connection flow path 14 from being lowered with this start-up. The gas processing amount by the compression unit 22 of the first compressor 12 is increased by the flow rate corresponding to the processing amount.

In order to increase the gas throughput, the first drive control unit 27a controls the adjusting means 12a of the first compressor 12 . For example, the 1st drive control part 27a performs control which moves a slide valve to the rod side. Moreover, instead of/in addition to this, the 1st drive control part 27a may perform control which increases the rotation speed of the screw type compression part 22. As shown in FIG.

When moving a slide valve, the 1st drive control part 27a moves a slide valve to the rod side until it becomes the opening degree set value of the bypass valve 23b memorize|stored previously in the control part 27. make it That is, the first drive control unit 27a moves the slide valve to the rod side to increase the amount of gas discharged from the compression unit 22 , while gradually opening the bypass valve 23b to the pressure supplied to the consumer. I try not to overdo it. Alternatively, in the case of increasing the rotation speed of the compression unit 22 , the first drive control unit 27a operates until the opening degree of the bypass valve 23b stored in advance in the control unit 27 becomes the set value. , the number of rotations of the compression unit 22 is increased.

Here, the pre-stored opening degree set value of the bypass valve 23b refers to the flow rate corresponding to the gas processing amount to be processed by the second compressor 18 in the storage tank connection flow path 3 (the first compressor 12 ). It is the set value of opening required to return to the suction side of

When the slide valve starts to move to the rod side (or increases in rotation speed), the discharge pressure of the customer connection flow path 14 acquired by the pressure detector 25 is going to increase. The control unit 27 (bypass control unit 27c) starts to increase the opening degree of the bypass valve 23b in order to keep the discharge pressure constant (step ST132). Therefore, even if the gas processing amount of the compression unit 22 increases, the discharge pressure (or flow rate) of the gas supplied to the consumer does not increase.

And when the opening degree of the bypass valve 23b becomes the opening degree set value mentioned above, the movement of a slide valve will stop (or an increase in rotation speed stops).

In the present embodiment, the opening degree of the bypass valve 23b corresponding to the flow rate corresponding to the required flow rate of the target gas newly required by the start of the second compressor 18 is determined by the control unit 27 . is memorized in advance. However, it is not limited to this, After receiving the instruction|command for starting the 2nd compressor 18, the flow volume required newly is calculated, and the opening degree of the bypass valve 23b so that the flow volume obtained by calculation may be obtained. may be controlled.

Until the opening degree of the bypass valve 23b falls within a predetermined range, it waits without shifting to start control (step ST14 in FIG. 2). And when the opening degree of the bypass valve 23b enters this predetermined range, a start permission signal is sent to the 2nd drive control part 27b, and it moves to start control (step ST15 in FIG. 2). In addition, in this embodiment, instead of the opening degree set value of a bypass valve, you may judge whether to shift to start control based on whether the gas flow rate converted from the said opening degree set value falls within a predetermined range. In step ST14, it may be collectively confirmed whether or not the pressure detected by the pressure detector 25 falls within a predetermined range.

In start control, as shown in FIG. 4, the control part 27 (2nd drive control part 27b) receives a start permission signal, and starts the 2nd compressor 18 (step ST151). Then, when the second compressor 18 is started and it is confirmed that the second compressor 18 is being driven by the predetermined number of operations, the control unit 27 (bypass control unit 27c) opens the bypass valve 23b. The degree is reduced by a predetermined opening degree (step ST152). That is, since the gas pressure in the demand connection flow path 14 decreases as the second compressor 18 starts up, by reducing the opening degree of the bypass valve 23b, the demand connection flow path 14 is suppression of a decrease in gas pressure. At this time, the bypass control part 27c may make small the opening degree of the bypass valve 23b by the amount increased in step ST132. That is, the opening degree of the bypass valve 23b increased in step ST132 may be returned to the original opening degree. Thereby, the gas pressure in the customer connection flow path 14 after the 2nd compressor 18 starts becomes substantially equal to the gas pressure in the customer connection flow path 14 before the start preparation control is started. In addition, at this time, the bypass control part 27c resets the opening degree setting of the bypass valve 23b in step ST132.

As described above, according to the present embodiment, even when the second compressor 18 is started during operation of the compression unit 22 of the first compressor 12, the pressure drop in the customer connection flow path 14 is reduced. can be suppressed In addition, since the throughput of the compression unit 22 is increased in advance before the start control for starting the second compressor 18, the opening degree of the bypass valve 23b is lowered when the second compressor 18 is started. It is solved only by making it small. Accordingly, it is possible to cope with sudden pressure fluctuations accompanying the start-up of the second compressor 18 .

In addition, in this embodiment, although the opening degree of the bypass valve 23b is made low after the rotation speed of the 2nd compressor 18 reaches a predetermined rotation speed, it is not limited to this. For example, the second compressor 18 may be started by the start permission signal and the operation of lowering the opening degree of the bypass valve 23b may be started, or the rotational speed of the second compressor 18 is increasing. The operation of lowering the opening degree of the bypass valve 23b may be started.

(Second embodiment)

5 shows a second embodiment of the present invention. In addition, here, the same code|symbol is attached|subjected to the same component as 1st Embodiment, and the detailed description is abbreviate|omitted.

In the first embodiment, the compression unit 22 of the first compressor 12 is constituted by one screw compressor, whereas in the second embodiment, the compression unit 22 of the first compressor 12 is configured. is constituted by two screw compressors. That is, the compression unit 22 includes a first compression unit 22a and a second compression unit 22b.

Specifically, the storage tank connection flow path 3 includes a main flow passage 3a connected to the storage tank 1 and two branch flow passages 3b and 3c branching from the downstream end of the main flow passage 3a. A first compression section 22a made of a screw compressor is provided in one branch flow passage 3b, and a second compression section 22b made of a screw compressor is provided in the other branch flow passage 3c. . That is, the 1st compression part 22a and the 2nd compression part 22b are mutually connected in parallel with respect to the storage tank connection flow path 3 . In this embodiment, the screw compressor which comprises the 1st compression part 22a, and the screw compressor which comprises the 2nd compression part 22b are compressors of the same compression capacity. However, the first compression unit 22a and the second compression unit 22b do not necessarily have to be compressors having the same compression capacity.

The customer connection flow path 14 includes two branch paths 14b and 14c, and a merging path 14a through which both branch paths 14b and 14c join and connect to the customer. One branch path 14b is connected to the discharge part of the first compression part 22a, and the other branch path 14c is connected to the discharge part of the second compression part 22b. The gas discharged from the first compression unit 22a and the second compression unit 22b flows into the merging path 14a through the corresponding branch paths 14b and 14c.

The bypass means 23 includes two bypass flow passages 23a (first bypass flow passage 23a1 and second bypass flow passage 23a2) and two bypass passages provided in the two bypass flow passages 23a. and a pass valve 23b (first bypass valve 23b1 and second bypass valve 23b2).

The first bypass flow path 23a1 connects one branch flow path 3b in the storage tank connection flow path 3 and one branch path 14b in the demand destination connection flow path 14 to each other. That is, the first bypass flow path 23a1 returns a part of the gas discharged from the first compression part 22a to the storage tank connection flow path 3 . The second bypass flow path 23a2 connects the other branch flow path 3c in the storage tank connection flow path 3 and the other branch path 14c in the demand destination connection flow path 14 to each other. have. That is, the second bypass flow path 23a2 returns a part of the gas discharged from the second compression unit 22b to the storage tank connection flow path 3 .

Although the pressure detector 25 is provided in each branch path 14b, 14c of the customer connection flow path 14, respectively, one pressure detector 25 may be provided in the merging path 14a of the customer connection flow path 14. . Moreover, the on-off valves 31 and 32 are provided in each branch path 14b, 14c, respectively. In addition, a check valve may be provided instead of the on-off valves 31 and 32 or together with the on-off valves 31 and 32 .

In the second embodiment, the first drive control unit 27a controls the second compressor 18 in the start preparation control (step ST13) in each of the first compression unit 22a and the second compression unit 22b. The gas processing amount is increased by half of the flow rate corresponding to the required flow rate of the target gas newly required by startup (step ST131). That is, although the required flow rate is supplied by both the 1st compression part 22a and the 2nd compression part 22b, at the time of the 2nd compressor 18 starting WHEREIN: The 1st compression part 22a and the 2nd compression part 22b WHEREIN: The increase in the amount of gas processing in the portion 22b is made equal, so that the loads of the first compression portion 22a and the second compression portion 22b are equal.

In the interlocking preparation control (step ST13), the bypass control unit 27c is connected to the storage tank from the first bypass flow path 23a1 and the second bypass flow path 23a2 so that the flow rate of half of the required flow rate newly required is respectively The opening degree of the 1st bypass valve 23b1 and the opening degree of the 2nd bypass valve 23b2 are respectively enlarged so that it may return to the flow path 3 (step ST132). In this embodiment, the opening degree of the 1st bypass valve 23b1 and the opening degree of the 2nd bypass valve 23b2 are respectively enlarged by the same opening degree.

And in the start control (step ST15), the bypass control part 27c makes the opening degree of the bypass valve 23b small by the amount increased in step ST132 (step ST152). That is, the opening degree of the 1st bypass valve 23b1 and the opening degree of the 2nd bypass valve 23b2 are made small by the same opening degree, respectively.

According to the second embodiment, even when the compression section 22 of the first compressor 12 is constituted by two screw compressors, appropriate start preparation control can be realized.

Further, in the second embodiment, in the start preparation control, the flow rate of half of the required flow rate newly required is increased in the first compression section 22a and the second compression section 22b, respectively, but this It is not limited to the configuration. For example, you may make it increase the 1st compression part 22a further than the 2nd compression part 22b.

In this case, it is assumed that 80% of the flow rate of the gas supplied to the consumer is procured by the first compression unit 22a and 20% is procured by the second compression unit 22b. That is, it is assumed that the throughput A1 of the first compression unit 22a is 80% and the throughput A2 of the second compression unit 22b is 20%. In this case, assuming that the required flow rate B newly required by the start of the second compressor 18 is 70% of the capacity of the first compressor 12, in the start preparation control, the first compression unit 22a The capacity increase is B×A2/(A1+A2)=0.7×0.2×(0.8+0.2)=0.14, and the capacity increase of the second compression unit 22b is B×A1/(A1+A2). ) = 0.7 x 0.8 x (0.8 + 0.2) = 0.56. That is, for the first compression unit 22a, the gas processing amount may be increased by 1.14 times, and for the second compression unit 22b, the gas processing amount may be increased by 1.56 times. That is, while the increase in the gas processing amount is suppressed in the first compression unit 22a having a large gas processing amount, the increase in the gas processing amount is made larger in the second compression unit 22b having a relatively small gas processing amount. In addition, at this time, the increment of the opening degree of the 1st bypass valve 23b1 is made into 0.7x0.2x(0.8+0.2)=0.14, and let it be 1.14 times the current opening degree. Moreover, the increment of the opening degree of the 2nd bypass valve 23b2 is made into 0.7x0.8x(0.8+0.2)=0.56, and let it be 1.56 times of the current opening degree. In other words, the opening degrees of the first bypass valve 23b1 and the second bypass valve 23b2 are set according to the scale opening degrees. As a result, when the operation is performed in a state where there is a difference in the gas throughput of the first compression section 22a and the second compression section 22b, the first compression section 22a and the second compression section 22b after the increase can reduce the load difference of

In addition, although the description is abbreviate|omitted for other structures, an effect|action, and an effect, the description of the said 1st Embodiment can be invoked for 2nd Embodiment.

(Other embodiments)

In addition, it should be thought that embodiment disclosed this time is an illustration in every point and is not restrictive. This invention is not limited to the said embodiment, Various changes, improvement, etc. are possible in the range which does not deviate from the meaning. For example, as shown in FIG. 6, the screw compressor 50 provided with the screw compression part 22, the bypass means 23, and the control part 27 may be comprised. In addition, although the control part 27 does not contain the 2nd drive control part 27b for performing drive control of the 2nd compressor 18, the control part 27 gives the command for starting the 2nd compressor 18. can be received.

The compression unit 22 of the screw compressor 50 discharges gas to the customer connection flow path 14 . Although not shown, the reliquefaction facility connection flow path 16 is connected to the demand destination connection flow path 14 similarly to FIG. During the driving of the compression unit 22 of the screw compressor 50 , the control unit 27 receives an instruction for starting the second compressor 18 (not shown) provided in the reliquefaction facility connection flow path 16 , the control unit (27) executes the start preparation control. In the start preparation control, the control unit 27 (first drive control unit 27a) increases the processing amount of the compression unit 22 by a flow rate corresponding to the required flow rate of the target gas to be processed by the second compressor 18, Also, the control unit 27 (bypass control unit 27c) increases the opening degree of the bypass valve 23b so that the flow rate corresponding to the increased throughput returns to the storage tank connection flow path 3 . And when the opening degree of the bypass valve 23b enters into a predetermined range, the control part 27 executes start control. In start control, the control part 27 outputs the start permission signal which starts the 2nd compressor 18, and the bypass control part 27c makes the opening degree of the bypass valve 23b small by a predetermined opening degree.

In the above embodiment, in the start preparation control, the control method in which the opening degree of the bypass valve 23b is increased in association with the movement (or increase in rotation speed) of the slide valve to the rod side is not limited to this, but various A control method may be employed. For example, the control of the slide valve (or control of the rotation speed) and the control of the bypass valve 23b may be independently performed based on the respective control amounts set based on the throughput of the second compressor 18 . .

In the above embodiment, a temperature detector (not shown) is provided in the demand connection flow path 14, and based on the temperature detected by the temperature detector, the control of the bypass valve 23b and the capacity adjustment by the slide valve or Rotation speed adjustment may be performed. Control based on the detected temperature is performed by lubricating, pouring water, and injecting a liquid obtained by liquefying the target gas to the compression unit 22 of the first compressor 12 .

Here, the embodiment will be schematically described.

(1) The compressor unit according to the above embodiment is a compressor unit installed in a ship, recovering a target gas that is a boil-off gas of liquefied gas from a storage tank provided in the ship, and supplying at least a part of the target gas to a consumer, from the storage tank A first compressor for sucking the target gas through a storage tank connection flow path, a demand connection flow path connected from the first compressor to the demand side, and a reliquefaction facility connection flow path branching from the demand connection flow path and connected to the reliquefaction facility; , It is provided on the reliquefaction facility connection flow path, and a reciprocal type second compressor for further compressing the target gas before flowing into the reliquefaction facility, and a control unit for controlling the first compressor and the second compressor. The first compressor includes a screw-type compression unit connected to the storage tank connection flow path to compress the target gas, and bypass means for returning at least a portion of the target gas from the customer connection flow path to the storage tank connection flow path. The bypass means includes a bypass flow path for connecting the customer connection flow path and the storage tank connection flow path, and a bypass valve provided in the bypass flow path. When the second compressor is started while the compression unit is being driven, the control unit is configured to control the compression unit by a flow rate corresponding to a required flow rate of the target gas to be processed by the second compressor by the operation of the second compressor. While increasing the throughput, start preparation control is executed to increase the opening degree of the bypass valve so that the flow rate corresponding to the increased throughput returns to the storage tank connection flow path, and after execution of the start preparation control, the second It is comprised so that the start control which makes the opening degree of the said bypass valve increased by the said start preparation control small by the predetermined opening degree may be performed while starting a compressor.

In the above-mentioned compressor unit, even when the second compressor is started during operation of the compression unit of the first compressor, it is possible to suppress a decrease in the pressure in the customer connection flow path. In addition, since the throughput of the compression unit is increased in advance before the start control for starting the second compressor, it is solved only by reducing the opening degree of the bypass valve when the second compressor is started. Accordingly, it is possible to cope with sudden pressure fluctuations accompanying the start-up of the second compressor.

(2) In the above compressor unit, the compression unit of the first compressor may be constituted by two screw compressors arranged in parallel with each other. In this case, the bypass means includes two bypass flow paths for returning the target gas discharged from the two screw compressors from the customer connection flow path to the storage tank connection flow path, and 2 provided in each of the two bypass flow paths. It may include two bypass valves. In the start preparation control, the control unit increases the throughput of each of the two screw compressors by half of the flow rate corresponding to the required flow rate, and the flow rate of half the flow rate corresponding to the increased throughput is the You may be comprised so that the opening degree of each of the said two bypass valves may be enlarged so that it may return from each of the two bypass flow paths to the said storage tank connection flow path.

In this aspect, even when the compression part of the 1st compressor is comprised with two screw compressors, appropriate start preparation control can be implement|achieved.

(3) In the said compressor unit, the said compression part of the said 1st compressor may be comprised with the two screw compressors mutually arrange|positioned in parallel. In this case, the bypass means includes a first bypass flow path for returning the target gas discharged from one of the two screw compressors from the customer connection flow path to the storage tank connection flow path; A first bypass valve provided in one bypass flow path, a second bypass flow path for returning the target gas discharged from the other screw compressor among the two screw compressors from the customer connection flow path to the storage tank connection flow path, and You may include a 2nd bypass valve provided in the said 2nd bypass flow path. Assuming that the processing amount of the one screw compressor is A1, the processing amount of the other screw compressor is A2, and the flow rate corresponding to the required flow rate is B, then the control unit, in the start preparation control, Bx While increasing the throughput of the one screw compressor by the flow rate obtained by A2/(A1+A2), the flow rate obtained by B×A2/(A1+A2) is from the first bypass flow path to the storage tank connection flow path To return, the opening degree of the first bypass valve is increased and the throughput of the other screw compressor is increased by the flow rate obtained by B×A1/(A1+A2), and B×A1/(A1). You may be comprised so that the opening degree of the said 2nd bypass valve may be enlarged so that the flow volume obtained by +A2) may return from the said 2nd bypass flow path to the said storage tank connection flow path.

In this aspect, even when the compression part of the 1st compressor is comprised with two screw compressors, appropriate start preparation control can be implement|achieved.

(4) The first compressor may include a rotation speed adjusting means of the compression section or a capacity adjusting means of the compression section capable of increasing the throughput of the compression section in the start preparation control.

In this aspect, the throughput can be easily adjusted.

(5) The screw compressor according to the above embodiment is a screw compressor that sucks a target gas, which is a boil-off gas of liquefied gas, from a storage tank provided on a ship through a storage tank connection flow path and discharges it to a customer connection flow path, and is connected to the storage tank connection flow path and a screw-type compression unit for compressing the target gas, a bypass flow path connecting the demand connection flow path and the storage tank connection flow path, and a bypass valve provided in the bypass flow path, A bypass means for returning at least a part of the target gas to the connection flow path and a control unit are provided. When the control unit receives a command to start a second compressor provided in the reliquefaction facility connection passage branched from the demand destination connection passage and connected to the reliquefaction facility while the compression unit is driven, the second compressor operates The second compressor increases the throughput of the compression unit by a flow rate corresponding to the required flow rate of the target gas to be processed, and the opening degree of the bypass valve so that the flow rate corresponding to the increased throughput returns to the storage tank connection flow path Executes start preparation control to increase It is configured to execute the start control to reduce the degree of acceleration.

(6) The operation method of the compressor unit according to the above embodiment is a method of operating a compressor unit that recovers a target gas that is a boil-off gas of liquefied gas from a storage tank provided on a ship and supplies at least a part of the target gas to a consumer, and the compressor unit A first compressor for sucking the target gas from the storage tank through the storage tank connection flow path and discharging the target gas to the customer connection flow path, and the reliquefaction facility connection flow path branched from the demand connection flow path and connected to the reliquefaction facility. A pro-type second compressor is provided. The first compressor includes a screw-type compression unit connected to the storage tank connection flow path to compress the target gas, a bypass flow path connecting the demand destination connection flow path and the storage tank connection flow path, and a bypass valve provided in the bypass flow path. has The operation method includes a driving step of driving the compression unit of the first compressor, and when the second compressor is started while the compression unit is being driven, the second compressor is operated by the operation of the second compressor to process the processing. A start preparation step of increasing the throughput of the compression unit by a flow rate corresponding to the required flow rate of the target gas to be used and increasing the opening degree of the bypass valve so that the flow rate corresponding to the increased throughput returns to the storage tank connection flow path and a starting step of starting the second compressor after the start preparation step and reducing the opening degree of the bypass valve increased in the start preparation step by a predetermined opening degree.

As described above, even when the second compressor is started while the first compressor is being driven, it is possible to suppress fluctuations in the pressure on the discharge side of the first compressor.

Claims (6)

A compressor unit installed in a ship to recover a target gas, which is a boil-off gas of liquefied gas, from a storage tank provided in the ship, and supply at least a part of the target gas to a customer,
a first compressor for sucking the target gas from the storage tank through a storage tank connection passage;
a consumer connection flow path connected from the first compressor to the consumer;
a reliquefaction facility connection flow path branched from the demand destination connection flow path and connected to the reliquefaction facility;
a second compressor provided on the reliquefaction facility connection passage to further compress the target gas before flowing into the reliquefaction facility;
A control unit for controlling the first compressor and the second compressor
to provide
The first compressor includes a screw-type compression unit connected to the storage tank connection flow path to compress the target gas, and bypass means for returning at least a portion of the target gas from the customer connection flow path to the storage tank connection flow path,
The bypass means includes a bypass flow path connecting the customer connection flow path and the storage tank connection flow path, and a bypass valve provided in the bypass flow path,
The control unit is
When the second compressor is started while the compression unit is being driven,
By the operation of the second compressor, the processing amount of the compression unit is increased by the flow rate corresponding to the required flow rate of the target gas to be processed by the second compressor, and the flow rate corresponding to the increased processing amount is transferred to the storage tank connection passage. Execute start preparation control to increase the opening degree of the bypass valve so as to return;
The compressor unit is configured to start the second compressor after execution of the start preparation control and execute start control for reducing the opening degree of the bypass valve increased by the start preparation control to a predetermined opening degree. According to claim 1,
The compression unit of the first compressor is composed of two screw compressors arranged in parallel with each other,
Two bypass passages in which the bypass means returns the target gas discharged from the two screw compressors from the demand connection flow path to the storage tank connection flow path, and two bypasses provided one by one in the two bypass flow paths. including a valve;
The control unit is
In the start preparation control,
While increasing the throughput of each of the two screw compressors by half of the flow rate corresponding to the required flow rate, a flow rate of half the flow rate corresponding to the increased throughput is connected to the storage tank from each of the two bypass flow paths A compressor unit which increases the opening degree of each of the two bypass valves so as to return to the flow path. According to claim 1,
The compression unit of the first compressor is composed of two screw compressors arranged in parallel with each other,
a first bypass flow path through which the bypass means returns the target gas discharged from one of the two screw compressors from the customer connection flow path to the storage tank connection flow path, and to the first bypass flow path A provided first bypass valve, a second bypass flow path for returning the target gas discharged from the other screw type compressor among the two screw compressors from the customer connection flow path to the storage tank connection flow path, and the second bypass Including a second bypass valve provided in the flow path,
Assuming that the throughput of the one screw compressor is A1, the throughput of the other screw compressor is A2, and the flow rate corresponding to the required flow rate is B,
The control unit is
In the start preparation control,
While increasing the throughput of the one screw compressor by the flow rate obtained by B×A2/(A1+A2), the flow rate obtained by B×A2/(A1+A2) is connected to the storage tank from the first bypass flow path To return to the flow path, the opening degree of the first bypass valve is increased,
While increasing the throughput of the other screw compressor by the flow rate obtained by BxA1/(A1+A2), the flow rate obtained by BxA1/(A1+A2) is increased from the second bypass flow path to the storage tank The compressor unit which enlarges the opening degree of the said 2nd bypass valve so that it may return to a connection flow path. 4. The method according to any one of claims 1 to 3,
the first compressor,
and a rotation speed adjusting means of the compression section or a capacity adjusting means of the compression section capable of increasing the throughput of the compression section in the start preparation control. It is a screw compressor that sucks a target gas that is a boil-off gas of liquefied gas from a storage tank provided on a ship through a storage tank connection flow path and discharges it to a customer connection flow path,
a screw-type compression unit connected to the storage tank connection flow path to compress the target gas;
A bypass for returning at least a portion of the target gas from the demand connection flow path to the storage tank connection flow path, comprising: a bypass flow path connecting the demand connection flow path and the storage tank connection flow path; and a bypass valve provided in the bypass flow path means and
having a control unit,
The control unit is
When receiving a command to start the second compressor provided in the reliquefaction facility connection passage branched from the customer connection passage and connected to the reliquefaction facility while the compression unit is being driven, the second compressor is operated by the operation of the second compressor Start to increase the opening degree of the bypass valve so that the processing amount of the compression unit is increased by the flow rate corresponding to the required flow rate of the target gas to be processed, and the flow rate corresponding to the increased processing amount returns to the storage tank connection flow path run ready control,
and outputting a start permission signal for starting the second compressor after execution of the start preparation control and executing start control for reducing the opening degree of the bypass valve increased by the start preparation control to a predetermined opening degree; There, screw compressor. A method of operating a compressor unit for recovering a target gas, which is a boil-off gas of liquefied gas, from a storage tank provided on a ship and supplying at least a portion of the target gas to a consumer,
The compressor unit includes: a first compressor that sucks the target gas from the storage tank through the storage tank connection flow path and discharges the target gas to the demand connection flow path; and a reciprocal second compressor provided in
The first compressor includes a screw-type compression unit connected to the storage tank connection flow path to compress the target gas, a bypass flow path connecting the demand destination connection flow path and the storage tank connection flow path, and a bypass provided in the bypass flow path have a valve,
In the driving method,
a driving step of driving the compression unit of the first compressor;
When the second compressor is started while the compression unit is being driven, the processing amount of the compression unit is increased by a flow rate corresponding to the required flow rate of the target gas to be processed by the second compressor by the operation of the second compressor and a start preparation step of increasing the opening degree of the bypass valve so that a flow rate corresponding to the increased throughput returns to the storage tank connection flow path;
and a starting step of starting the second compressor after the starting preparation step and reducing the opening degree of the bypass valve increased in the starting preparation step by a predetermined opening degree.

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