CN112983789A

CN112983789A - Compressor unit

Info

Publication number: CN112983789A
Application number: CN202110296539.6A
Authority: CN
Inventors: 手塚智志; 濑山胜广
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2020-06-29
Filing date: 2021-03-19
Publication date: 2021-06-18
Also published as: JP6759482B1; GR1010122B; NO20210744A1; JP2022010692A; KR102342035B1

Abstract

The invention provides a compressor unit. The compressor includes a first reciprocating compressor including a first pressure regulating valve, a first discharge pressure detecting unit, and a first supply pressure detecting unit, a second reciprocating compressor including a second pressure regulating valve, a second discharge pressure detecting unit, and a second supply pressure detecting unit, and a controller that determines whether or not detected pressures of the first discharge pressure detecting unit and the second discharge pressure detecting unit converge within a predetermined range, and adjusts opening degrees of the first pressure regulating valve and the second pressure regulating valve so that the detected pressures of the first supply pressure detecting unit and the second supply pressure detecting unit approach a pressure value required by the other demand side when the detected pressures converge within the predetermined range. This prevents the target gas from increasing in pressure on the gas discharge path from the plurality of reciprocating compressors to the demand side.

Description

Compressor unit

Technical Field

The present invention relates to a compressor unit for supplying a target gas, which is a boil-off gas, from an LNG storage tank of a ship to a demand side.

Background

An evaporated gas compression unit has been developed which supplies the evaporated gas to an engine or the like while increasing the pressure of the evaporated gas (see japanese patent application laid-open No. 2018-534206). The boil-off gas compression section of japanese patent laid-open publication No. 2018-534206 has a main compression section and a preliminary compression section provided in parallel with the main compression section. The main compression part has 5 compressors. The preliminary compression unit is constituted by the same number of compressors as or more compressors than the main compression unit. The boil-off gas compressed by the main compression unit and the preliminary compression unit is supplied to the ME-GI engine. When the main compression unit and the preliminary compression unit are connected in series, a part of the boil-off gas passing through only a part of the plurality of compressors of the main compression unit and a part of the boil-off gas passing through only a part of the plurality of compressors of the preliminary compression unit can be branched and sent to DFGE (hereinafter, referred to as a "sub-demand side") respectively.

The gas supplied to the sub-consumer flows to the gas discharge passage at a pressure higher than the gas pressure actually required by the sub-consumer, and is depressurized before flowing into the sub-consumer. Therefore, the piping and instrumentation from the reciprocating compressor to the secondary customer side need to be of high pressure specifications, which increases the cost of the piping and instrumentation. When a plurality of reciprocating compressors are used to supply gas to the sub-consumers, the cost of piping and instrumentation is further increased.

Disclosure of Invention

The invention aims to provide a compressor unit which prevents the target gas from being increased in pressure on a gas outlet from a plurality of reciprocating compressors to a demand side.

A compressor unit according to an aspect of the present invention is provided in a ship and compresses a target gas, which is a boil-off gas, sucked from a liquefied natural gas storage tank of the ship. The compressor unit includes: a first reciprocating compressor having a plurality of compression stages, compressing a target gas and supplying the same to a demand side; a second reciprocating compressor having a plurality of compression stages and connected in parallel with the first reciprocating compressor in such a manner as to compress a target gas and supply it to the one demand side; and a control section. The first reciprocating compressor includes: a first branch flow path that branches from a segment connecting flow path connecting one compression segment and the next compression segment and is connected to a gas lead-out path that leads the target gas to another demand side; a first check valve provided in the first branch flow passage so as to prevent the target gas from flowing backward from the gas lead-out passage to the segment connecting flow passage; a first pressure regulating valve provided in the first branch flow passage so as to regulate the pressure of the target gas supplied to the gas lead-out passage on the upstream side of the first check valve; a first discharge pressure detection unit that detects a pressure of the target gas on a discharge side of the one compression stage; and a first supply pressure detecting unit that detects a pressure of the target gas on a downstream side of the first pressure regulating valve. The second reciprocating compressor includes: a second branch flow path that branches from a section connecting flow path connecting one compression section and the next compression section and is connected to the gas lead-out path; a second check valve provided on the second branch flow passage so as to prevent the target gas from flowing backward from the gas lead-out passage to the section connecting flow passage of the second reciprocating compressor; a second pressure adjustment valve provided in the second branch flow passage so as to adjust the pressure of the target gas supplied to the gas lead-out passage on the upstream side of the second check valve; a second discharge pressure detection unit that detects a pressure of the target gas on a discharge side of the one compression stage of the second reciprocating compressor; and a second supply pressure detecting unit that detects a pressure of the target gas on a downstream side of the second pressure regulating valve. The control unit determines whether or not the detection pressures of the first and second discharge pressure detection units have converged within a predetermined range, and adjusts the opening degrees of the first and second pressure adjustment valves so that the detection pressures of the first and second supply pressure detection units approach a pressure value required by the other demand side when the detection pressures have converged within the predetermined range.

According to the present invention, it is possible to prevent the target gas from becoming high-pressure on the gas lead-out path from the plurality of reciprocating compressors to the demand side.

The objects, features and advantages of the present invention will become more apparent from the detailed description and accompanying drawings.

Drawings

Fig. 1 is a schematic view of a compressor unit.

Fig. 2 is a schematic diagram of a portion of a compressor train.

Fig. 3 is a schematic diagram of a portion of a compressor train.

Fig. 4 is a schematic flowchart showing control for supplying the target gas from the first reciprocating compressor of the compressor unit to the sub-consumer.

Fig. 5 is a schematic flowchart showing supply stop control for stopping supply of the target gas to the sub-consumer.

Detailed Description

Fig. 1 is a schematic diagram of a compressor train 100. Fig. 2 and 3 are schematic diagrams of a part of the compressor unit 100. A compressor train 100 is described with reference to fig. 1 to 3.

The compressor train 100 is installed in a ship (not shown) having an LNG storage tank 101 for storing LNG (Liquefied Natural Gas). The compressor unit 100 sucks a target gas (boil off gas) generated in the LNG storage tank 101 and compresses the sucked target gas. The compressor unit 100 supplies compressed target gas to a main demand side 501 (e.g., an engine) and a sub-demand side 502 (e.g., a generator and an engine). In the following description, terms "upstream" and "downstream" are used with reference to the flow direction of the target gas.

The compressor string 100 has a first reciprocating compressor 300, a second reciprocating compressor 400 connected in parallel with the first reciprocating compressor 300, and a control part 420 controlling the first reciprocating compressor 300 and the second reciprocating compressor 400. The first reciprocating compressor 300 and the second reciprocating compressor 400 are the same configuration.

The first reciprocating compressor 300 includes: a flow path 110 through which the target gas flows toward the main demand side 501; first to sixth compression stages 201 to 206 for sequentially increasing the pressure of the target gas; a plurality of coolers 281-285; and a driving unit (not shown). The drive unit includes a drive source (a motor, an engine, and the like) and a crank mechanism that transmits power of the drive source to the first compression stage 201 to the sixth compression stage 206.

The flow path 110 is provided with 2 first compression stages 201, and the flow path 110 is provided with 1 second compression stage 202 to sixth compression stage 206.

The flow path 110 connects the LNG storage tank 101 and the main consumer 501 so that the boil-off gas generated in the LNG storage tank 101 can be supplied to the main consumer 501. The flow path 110 includes a storage tank connection flow path 111, a plurality of stage connection flow paths 115 to 119, and a request side supply flow path 114.

The storage tank connection line 111 has an upstream end connected to the LNG storage tank 101 and a downstream end connected to the first compression stage 201 of the compressor train 100. Specifically, the storage tank connection passage 111 includes a main pipe 121 extending from an upper portion of the LNG storage tank 101, and

branch pipes

122 and 123 branching into two branches at a downstream end of the main pipe 121 and connected to the 2 first compression stages 201. That is, the 2 first compression stages 201 are connected to the storage tank connection passage 111 in parallel with each other.

The stage connecting channels 115-119 are arranged so that the target gas flows from 1 compression stage to the next compression stage. The stage connection flow path 115 flows the target gas from the 2 first compression stages 201 to the second compression stage 202. That is, the stage connecting passage 115 includes a main pipe 124 extending from the second compression stage 202 toward the first compression stage 201, and

branch pipes

125 and 126 branching into two at an upstream end of the main pipe 124 and connected to 2 first compression stages 201. The stage connecting flow path 116 connects the second compression stage 202 and the third compression stage 203. The stage connecting passage 117 connects the third compression stage 203 and the fourth compression stage 204. The stage connection flow path 118 connects the fourth compression stage 204 and the fifth compression stage 205. The stage connecting flow path 119 connects the fifth compression stage 205 and the sixth compression stage 206.

The consumer supply flow path 114 is a flow path connecting the sixth compression stage 206 to the main consumer 501.

The coolers 281 to 285 exchange heat between the target gas and cooling water having a lower temperature than the target gas. The cooler 281 is provided in the stage connecting flow path 116 so as to cool the target gas discharged from the second compression stage 202. The cooler 282 is provided in the stage connecting passage 117 so as to cool the target gas discharged from the third compression stage 203. The cooler 283 is provided in the stage connecting passage 118 so as to cool the target gas discharged from the fourth compression stage 204. The cooler 284 is provided in the stage connecting flow path 119 so as to cool the target gas discharged from the fifth compression stage 205. The cooler 285 is provided in the demand side supply passage 114 so as to cool the target gas discharged from the sixth compression stage 206.

The compressor unit 100 has bypass flow paths 411 to 414 for adjusting the pressure of the target gas in the flow path 110. The bypass channels 411 to 413 return the target gas to the upstream side from the branching sections 311 to 313 in the

segment connecting channels

116, 117, and 119. The branching portions 311 to 313 are located downstream of the

coolers

281, 282, 284.

The bypass passage 411 bypasses the first compression stage 201 and the second compression stage 202 and is connected to the main pipe 121 of the reserve tank connection passage 111. The bypass flow path 412 bypasses the third compression stage 203, and is connected to the stage connection flow path 116 at a connection portion 315 on the downstream side of the branch portion 311 and on the upstream side of the third compression stage 203. The bypass passage 413 bypasses the fourth compression stage 204 and the fifth compression stage 205, and is connected to the stage connection passage 117 on the downstream side of the branch portion 312 and on the upstream side of the fourth compression stage 204. The bypass passage 414 returns the target gas to the upstream side from the branching portion 314 provided in the demand-side supply passage 114 on the downstream side of the cooler 285. The bypass passage 414 bypasses the sixth compression stage 206 and is connected to the stage connection passage 119 on the downstream side of the branch portion 313 and on the upstream side of the sixth compression stage 206.

Bypass valves 421 to 424 are respectively installed in the bypass flow paths 411 to 414.

Pressure sensors 431 to 434 are disposed in the flow path 110 corresponding to the bypass flow paths 411 to 414. The pressure sensor 431 is attached to the stage connection flow path 116 on the downstream side of the cooler 281 and on the upstream side of the branching portion 311 so as to detect the discharge pressure of the second compression stage 202. The pressure sensor 432 is attached to the stage connection flow path 117 on the downstream side of the cooler 282 and on the upstream side of the branch portion 312 so as to detect the discharge pressure of the third compression stage 203. The pressure sensor 433 is attached to the stage connection flow path 119 on the downstream side of the cooler 284 and on the upstream side of the branch portion 313 so as to detect the discharge pressure of the fifth compression stage 205. The pressure sensor 434 is attached to the demand side supply passage 114 on the downstream side of the cooler 285 and on the upstream side of the branch portion 314 so as to detect the discharge pressure of the sixth compression stage 206.

As shown in fig. 2, the first reciprocating compressor 300 has a first branch flow path 320 for supplying the target gas to a sub-consumer 502 (e.g., a generator, an engine, a gas combustion facility). The first branch flow path 320 branches from the section connecting flow path 116 connecting the second compression section 202 and the third compression section 203. More specifically, the first branch flow path 320 branches from the stage connection flow path 116 between the branch portion 311 of the bypass flow path 411 of the stage connection flow path 116 and the connection portion 315 of the bypass flow path 412 of the counter stage connection flow path 116.

The downstream end of the first branch flow path 320 is connected to the gas outlet passage 102 extending from the sub-consumer 502. In the first reciprocating compressor 300, the discharge gas of the second compression stage 202 that is closest to the pressure required by the sub-consumer 502 and has a discharge pressure higher than the required pressure is supplied to the sub-consumer 502.

The first branch flow path 320 is provided with a first opening/closing valve 321, a first pressure regulating valve 322, a pressure sensor 324, and a first check valve 323 in this order toward the gas lead-out path 102. The first check valve 323 prevents the reverse flow of the target gas from the gas outlet passage 102. The first pressure regulating valve 322 regulates the pressure of the target gas supplied to the gas lead-out passage 102 on the upstream side of the first check valve 323. The pressure sensor 324 detects the pressure of the target gas on the downstream side of the first pressure regulating valve 322 (more specifically, the pressure between the first pressure regulating valve 322 and the first check valve 323).

The upstream end of the flow path 110 of the second reciprocating compressor 400 is connected to the main pipe 121 of the reserve tank connection flow path 111 of the first reciprocating compressor 300. The downstream end of the flow path 110 of the second reciprocating compressor 400 is connected to the demand side supply flow path 114 of the first reciprocating compressor 300.

As shown in fig. 3, the second reciprocating compressor 400 supplies the object gas to the sub-consumer 502 together with the first reciprocating compressor 300. The second reciprocating compressor 400 is provided with a second branch flow passage 330, a second on-off valve 331, a second pressure regulating valve 332, a pressure sensor 334, and a second check valve 333, which are similar to the first branch flow passage 320, the first on-off valve 321, the first pressure regulating valve 322, the pressure sensor 324, and the first check valve 323 of the first reciprocating compressor 300. The second branch flow passage 330 is provided with a second opening/closing valve 331, a second pressure regulating valve 332, a pressure sensor 334, and a second check valve 333 in this order toward the gas lead-out passage 102. In addition, other configurations of the second reciprocating compressor 400 are also the same as the first reciprocating compressor 300. In the compressor unit 100, since the first reciprocating compressor 300 and the second reciprocating compressor 400 have the same structure, the components used in each can be used in a common manner.

The control unit 420 shown in fig. 1 acquires information indicating the pressures detected by the pressure sensors 431 to 434, 324, 334 of the first reciprocating compressor 300 and the second reciprocating compressor 400. Although not shown in fig. 1, the control unit 420 is electrically connected to the pressure sensors 431 to 434, 324, and 334. The control unit 420 is electrically connected to the bypass valves 421 to 424, the first on/off valve 321, the second on/off valve 331, the first pressure regulating valve 322, and the second pressure regulating valve 332.

The control unit 420 adjusts the opening degrees of the bypass valves 421 to 424 based on the pressures detected by the pressure sensors 431 to 434 in order to maintain the pressure balance among the storage tank connection flow path 111, the plurality of stage connection flow paths 115 to 119, and the demand side supply flow path 114 in the first reciprocating compressor 300 constant. The controller 420 controls the first on-off valve 321 and the first pressure regulating valve 322 based on the pressures detected by the pressure sensor 431 and the pressure sensor 324 so as to supply the gas having the constant pressure from the first reciprocating compressor 300 to the sub-demand side 502. In the following description, the pressure sensor 431 of the first reciprocating compressor 300 is referred to as a "first discharge pressure detecting portion 431A". The pressure sensor 324 of the first reciprocating compressor 300 is referred to as a "first supply pressure detecting portion 324".

Similarly, the control unit 420 adjusts the opening degrees of the bypass valves 421 to 424 based on the pressure sensors 431 to 434 in order to maintain the pressure balance of the

flow paths

111, 115 to 119, and 114 in the second reciprocating compressor 400 constant. The controller 420 controls the second on-off valve 331 and the second pressure regulating valve 332 based on the pressures detected by the

pressure sensors

431 and 324 to supply the gas having the constant pressure to the sub-demand side 502. In the following description, the pressure sensor 431 of the second reciprocating compressor 400 is referred to as a "second discharge pressure detecting portion 431B". The pressure sensor 334 of the second reciprocating compressor 400 is referred to as a "second supply pressure detecting portion 334".

Next, the operation of the first reciprocating compressor 300 will be described. If the first reciprocating compressor 300 is driven, the object gas is sequentially compressed through the first to sixth compression stages 201 to 206. The target gas discharged from the second to sixth compression stages 202 to 206 is cooled by passing through coolers 281 to 285. The high-pressure target gas discharged from the sixth compression stage 206 is supplied to the main demand side 501 through the demand side supply passage 114.

During driving of the first reciprocating compressor 300, the pressure of the target gas in each part of the flow path 110 is acquired by the first discharge pressure detecting unit 431A and the other pressure sensors 432 to 434. When the pressure detection values of the first discharge pressure detection section 431A and the other pressure sensors 432 to 434 are within a predetermined normal range, the bypass valves 421 to 424 are closed. When the pressure detection values of the first discharge pressure detection unit 431A and the other pressure sensors 432 to 434 deviate from the normal range, the opening degree of the bypass valves 421 to 424 is controlled by the control unit 420 so that the pressure detection values of the first discharge pressure detection unit 431A and the other pressure sensors 432 to 434 return to the normal range. The above operation is also the same for the second reciprocating compressor 400.

In the first reciprocating compressor 300, while the target gas is supplied to the main demand side 501, the target gas is also supplied to the sub demand side 502. Fig. 4 is a diagram illustrating a flow of supplying the target gas from the first reciprocating compressor 300 to the sub-consumer 502. However, while the target gas is being supplied to the main demand side 501, the target gas does not always need to be supplied to the sub-demand side 502.

When the first reciprocating compressor 300 is started, the control part 420 closes the first opening and closing valve 321 (step S110). The controller 420 refers to the detection pressure of the first discharge pressure detector 431A (hereinafter, sometimes referred to as the primary-side detection pressure) in order to check the pressure of the target gas on the upstream side (hereinafter, sometimes referred to as the primary side) of the first pressure regulating valve 322. The control unit 420 determines whether the primary side detected pressure has converged within a predetermined range set in advance (step S120), and if the primary side detected pressure has not converged within the predetermined range, maintains the state in which the first on-off valve 321 is closed (step S120: no). If the primary side detected pressure converges within the specified range, the control portion 420 opens the first opening/closing valve 321 (step S130).

After the first on-off valve 321 is opened, the controller 420 acquires the detected pressure (hereinafter, sometimes referred to as the detected pressure on the secondary side) of the first supply pressure detector 324 located on the downstream side (hereinafter, sometimes referred to as the secondary side) of the first pressure regulating valve 322. Then, the controller 420 adjusts the opening degree of the first pressure regulating valve 322 based on the detected pressure on the secondary side so that the pressure of the target gas becomes the required pressure of the sub demand side 502 (step S140).

When the primary-side detected pressure deviates from the specified range, the control section 420 performs control to close the first opening/closing valve 321 (step S110). By interrupting the supply of the target gas to the sub-consumer 502, the pressure balance of the

flow paths

111, 115 to 119, 114 of the first reciprocating compressor 300 can be stabilized. In addition, during this time, the supply of the target gas from the second reciprocating compressor 400 to the sub-consumer 502 may be continued. Then, the detection pressure of the primary side is continuously acquired (step S120), and if the detection pressure is reconverged within the specified range, the supply of the target gas from the first reciprocating compressor 300 to the sub demand side 502 is restarted (steps S130, S140).

In the first reciprocating compressor 300, if a stop signal is input to the controller 420 (step S210), the controller 420 performs control to decrease the opening degree of the first pressure regulating valve 322 (step S220). As a result, the detected pressure on the secondary side of the first pressure regulating valve 322 gradually decreases. If the detected pressure on the secondary side is lower than the specified threshold value (step S230), the control portion 420 closes the first opening and closing valve 321 (step S240). In the first reciprocating compressor 300, the first opening/closing valve 321 is closed after the opening degree of the first pressure adjustment valve 322 is decreased and the flow of the gas to the secondary side is suppressed, and therefore, the pressure on the primary side is prevented from rapidly changing.

In the second reciprocating compressor 400, the target gas is also supplied to the sub-consumer 502 by the same procedure as in fig. 4. That is, when the second reciprocating compressor 400 is started, the controller 420 closes the second on-off valve 331 between the second discharge pressure detector 431B and the second pressure regulating valve 332 (step S110). The controller 420 determines whether or not the pressure on the primary side (upstream side) of the second pressure regulating valve 332 is within a predetermined range set in advance, based on the pressure detected by the second discharge pressure detector 431B (step S120). If the detected pressure on the primary side converges in the specified range, the control portion 420 opens the second opening and closing valve 331 (step S130).

After the second on-off valve 331 is opened, the controller 420 adjusts the opening degree of the second pressure regulating valve 332 based on the detected pressure of the second supply pressure detector 334 so that the pressure of the target gas on the secondary side of the second pressure regulating valve 332 reaches the required pressure of the sub demand side 502 (step S140).

In the second reciprocating compressor 400, when the detected pressure on the primary side of the second pressure regulating valve 332 deviates from the predetermined range, the controller 420 performs control for closing the second on-off valve 331, as in the first reciprocating compressor 300 (step S110). Accordingly, the supply of the target gas from the second reciprocating compressor 400 to the sub-consumer 502 is interrupted. During this time, the supply of the target gas from the first reciprocating compressor 300 to the sub-consumer 502 may be continued. Then, if the detected pressure of the primary side converges again within the specified range, the supply of the target gas from the second reciprocating compressor 400 to the sub-consumer 502 is restarted (steps S120, S130, S140).

In the second reciprocating compressor 400, if a stop signal is input to the controller 420 (step S210), the controller 420 performs control to decrease the opening degree of the second pressure regulating valve 332 (step S220). If the detected pressure on the secondary side is lower than the specified threshold value (step S230), the second opening and closing valve 331 is closed (step S240). In the second reciprocating compressor 400, the second opening/closing valve 331 is closed after the opening degree of the second pressure adjusting valve 332 is decreased, and therefore, the pressure on the primary side is prevented from rapidly changing.

As described above, according to the embodiment of the present invention, since the pressure of the target gas is reduced in the flow path on the downstream side of the first pressure regulating valve 322 and the second pressure regulating valve 332, the piping constituting the gas lead-out passage 102 and the instrumentation attached to the gas lead-out passage 102 do not need to use high-pressure standard products. As a result, the cost of the piping and the instrument can be reduced. Further, the piping between the first pressure regulating valve 322 and the first check valve 323 and between the second pressure regulating valve 332 and the second check valve 333 may be set to a high pressure specification.

In the first reciprocating compressor 300, by providing the first check valve 323, even if the pressure on the downstream side of the first check valve 323 abnormally rises, the influence on the upstream side can be prevented. When the detected pressure on the primary side of the first pressure regulating valve 322 deviates from the predetermined range, the first on-off valve 321 is closed, and therefore the target gas is prevented from flowing out to the sub demand direction 502 in a state where the pressure of the gas on the upstream side of the first pressure regulating valve 322 is not stabilized. This is the same for the second reciprocating compressor 400.

In the first reciprocating compressor 300, the first branch flow passage 320 is provided downstream of the second compression stage 202 having the smallest discharge pressure among the second to sixth compression stages 202 to 206 having a discharge pressure larger than the required pressure of the sub-consumer 502. This prevents the pressure on the primary side of the first pressure regulating valve 322 from becoming unnecessarily high, and thus the pressure on the secondary side can be easily regulated. This is the same for the second reciprocating compressor 400.

The embodiments disclosed herein are illustrative in all respects and should not be construed as being limiting. The scope of the present invention is defined by the claims rather than the description above, and includes all modifications equivalent in meaning and scope to the claims.

In the illustrated embodiment, the first reciprocating compressor 300 may also have 1 first compression stage 201. The first reciprocating compressor 300 may also be composed of less than 5 compression stages. This is the same for the second reciprocating compressor 400.

The compressor unit described in connection with the above-described embodiments mainly has the following features.

A compressor unit according to one aspect of the above embodiment is provided in a ship and compresses a target gas, which is a boil-off gas sucked from a liquefied natural gas storage tank of the ship. The compressor unit includes: a first reciprocating compressor having a plurality of compression stages, compressing a target gas and supplying the same to a demand side; a second reciprocating compressor having a plurality of compression stages and connected in parallel with the first reciprocating compressor in such a manner as to compress a target gas and supply it to the one demand side; and a control section. The first reciprocating compressor includes: a first branch flow path that branches from a segment connecting flow path connecting one compression segment and the next compression segment and is connected to a gas lead-out path that leads the target gas to another demand side; a first check valve provided in the first branch flow passage so as to prevent the target gas from flowing backward from the gas lead-out passage to the segment connecting flow passage; a first pressure regulating valve provided in the first branch flow passage so as to regulate the pressure of the target gas supplied to the gas lead-out passage on the upstream side of the first check valve; a first discharge pressure detection unit that detects a pressure of the target gas on a discharge side of the one compression stage; and a first supply pressure detecting unit that detects a pressure of the target gas on a downstream side of the first pressure regulating valve. The second reciprocating compressor includes: a second branch flow path that branches from a section connecting flow path connecting one compression section and the next compression section and is connected to the gas lead-out path; a second check valve provided on the second branch flow passage so as to prevent the target gas from flowing backward from the gas lead-out passage to the section connecting flow passage of the second reciprocating compressor; a second pressure adjustment valve provided in the second branch flow passage so as to adjust the pressure of the target gas supplied to the gas lead-out passage on the upstream side of the second check valve; a second discharge pressure detection unit that detects a pressure of the target gas on a discharge side of the one compression stage of the second reciprocating compressor; and a second supply pressure detecting unit that detects a pressure of the target gas on a downstream side of the second pressure regulating valve. The control unit determines whether or not the detection pressures of the first and second discharge pressure detection units have converged within a predetermined range, and adjusts the opening degrees of the first and second pressure adjustment valves so that the detection pressures of the first and second supply pressure detection units approach a pressure value required by the other demand side when the detection pressures have converged within the predetermined range.

According to the above configuration, since the pressure of the target gas on the downstream side of the first pressure regulating valve and the second pressure regulating valve is reduced, the piping for flowing the gas to the flow path on the other demand side and the instrumentation attached to the flow path do not need to use products of high pressure specifications. As a result, the cost of the piping and the instrument can be reduced.

In the above configuration, the first reciprocating compressor may include a first on-off valve that opens and closes the first branch flow passage between the first discharge pressure detecting unit and the first pressure regulating valve. The second reciprocating compressor may further include a second on-off valve that opens and closes the second branch flow passage between the second discharge pressure detection unit and the second pressure adjustment valve. The control unit may open the first on-off valve and the second on-off valve when the detected pressure is within a predetermined pressure range.

According to the above configuration, the target gas is supplied to another demand side after confirming that the pressures on the upstream sides of the first pressure regulating valve and the second pressure regulating valve are converged within the predetermined pressure range.

In the above-described configuration, the controller may decrease the opening degrees of the first pressure regulating valve and the second pressure regulating valve in response to an instruction to stop the supply to the other demand side, and may close the first on-off valve and the second on-off valve when the detected pressures of the first supply pressure detector and the second supply pressure detector are lower than a predetermined threshold value.

According to the above configuration, since the controller decreases the opening degrees of the first pressure regulating valve and the second pressure regulating valve before the first opening/closing valve and the second opening/closing valve are closed, it is possible to prevent a rapid increase in the pressure of the stage connection flow path of the first reciprocating compressor and the second reciprocating compressor.

In the above configuration, the segment connecting passage may be provided on a discharge side of a compression segment that discharges the target gas having a pressure that is closest to the pressure value required by the other demand side and is greater than the pressure value, among the plurality of compression segments.

According to the above configuration, the pressure on the primary side of the first pressure regulating valve and the second pressure regulating valve can be kept low, and the pressure control can be easily performed.

In the configuration, the first reciprocating compressor and the second reciprocating compressor may have the same number of compression stages.

Industrial applicability

The technique according to the above-described embodiment is suitably used for a compressor unit mounted on a ship.

Claims

1. A compressor unit provided in a ship and configured to compress a target gas, which is a boil-off gas sucked from a liquefied natural gas storage tank of the ship, the compressor unit comprising:

a first reciprocating compressor having a plurality of compression stages, compressing a target gas and supplying the same to a demand side;

a second reciprocating compressor having a plurality of compression stages and connected in parallel with the first reciprocating compressor in such a manner as to compress a target gas and supply it to the one demand side; and

a control section, wherein,

the first reciprocating compressor includes:

a first branch flow path that branches from a segment connecting flow path connecting one compression segment and the next compression segment and is connected to a gas lead-out path that leads the target gas to another demand side;

a first check valve provided in the first branch flow passage so as to prevent the target gas from flowing backward from the gas lead-out passage to the segment connecting flow passage;

a first pressure regulating valve provided in the first branch flow passage so as to regulate the pressure of the target gas supplied to the gas lead-out passage on the upstream side of the first check valve;

a first discharge pressure detection unit that detects a pressure of the target gas on a discharge side of the one compression stage; and

a first supply pressure detecting unit that detects a pressure of the target gas on a downstream side of the first pressure regulating valve,

the second reciprocating compressor includes:

a second branch flow path that branches from a section connecting flow path connecting one compression section and the next compression section and is connected to the gas lead-out path;

a second check valve provided on the second branch flow passage so as to prevent the target gas from flowing backward from the gas lead-out passage to the section connecting flow passage of the second reciprocating compressor;

a second pressure adjustment valve provided in the second branch flow passage so as to adjust the pressure of the target gas supplied to the gas lead-out passage on the upstream side of the second check valve;

a second discharge pressure detection unit that detects a pressure of the target gas on a discharge side of the one compression stage of the second reciprocating compressor; and

a second supply pressure detecting unit that detects a pressure of the target gas on a downstream side of the second pressure regulating valve,

the control unit determines whether or not the detection pressures of the first and second discharge pressure detection units have converged within a predetermined range, and adjusts the opening degrees of the first and second pressure adjustment valves so that the detection pressures of the first and second supply pressure detection units approach a pressure value required by the other demand side when the detection pressures have converged within the predetermined range.

2. The compressor rack of claim 1,

the first reciprocating compressor includes a first on-off valve that opens and closes the first branch flow passage between the first discharge pressure detection unit and the first pressure adjustment valve,

the second reciprocating compressor includes a second on-off valve that opens and closes the second branch flow passage between the second discharge pressure detection unit and the second pressure adjustment valve,

the control unit opens the first on-off valve and the second on-off valve when the detected pressure is within a predetermined pressure range.

3. The compressor rack of claim 2,

the control unit reduces the opening degrees of the first pressure regulating valve and the second pressure regulating valve in response to an instruction to stop the supply to the other demand side, and closes the first on-off valve and the second on-off valve when the detected pressures of the first supply pressure detecting unit and the second supply pressure detecting unit are lower than a predetermined threshold value.

4. Compressor train according to any of claims 1 to 3,

the stage connection flow path is provided on an ejection side of a compression stage that ejects the target gas having a pressure that is closest to the pressure value required by the other demand side and that is greater than the pressure value, among the plurality of compression stages.

5. The compressor rack of claim 4,

the first reciprocating compressor and the second reciprocating compressor have the same number of compression sections.