KR102355150B1 - Compressor unit and program for controlling compressor unit - Google Patents

Abstract

Provided is a compressor unit comprising a first reciprocating compressor, a second reciprocating compressor connected in parallel with the first reciprocating compressor, and a control part. The first reciprocating compressor includes a first check valve, a first pressure sensor, a first bypass flow passage, and a first bypass valve. The second reciprocating compressor includes a second check valve, a second pressure sensor, a second bypass flow passage, and a second bypass valve. The control part controls the opening degree of the first bypass valve so that the pressure detected by the first pressure sensor becomes a first set value, and, at the same time, controls the opening degree of the second bypass valve so that the pressure detected by the second pressure sensor becomes a second set value lower than the first set value.

Description

COMPRESSOR UNIT AND PROGRAM FOR CONTROLLING COMPRESSOR UNIT

The present invention relates to a compressor unit and a program for controlling the compressor unit.

DESCRIPTION OF RELATED ART Conventionally, in the carrier of liquefied natural gas, etc., the compressor unit used in order to compress the boil-off gas which generate|occur|produces by evaporation of the liquefied gas in a storage tank is known. In this type of compressor unit, there are some in which a plurality of multi-stage compressors are provided in parallel. In this compressor unit, the gas discharged from each compressor is supplied to a demand destination, such as an engine, respectively.

This kind of technology is disclosed in Japanese Patent Publication No. 2018-518415, Japanese Patent Publication No. 2018-534206, and Japanese Patent Publication No. 2019-11735. Japanese Patent Application Laid-Open No. 2018-518415 discloses a boil-off gas compressor mounted on an LNG ship or the like. In this boil-off gas compressor, a reciprocating compressor and a centrifugal compressor are provided in parallel. Japanese Patent Publication No. 2018-534206 discloses that, in a boil-off gas treatment system for an LNG carrier, a main compression section and a preliminary compression section for use in general when the main compression section is unavailable are provided. It is disclosed by Unexamined-Japanese-Patent No. 2019-11735 that two gas compressors are installed in parallel in an LNG carrier similarly to Unexamined-Japanese-Patent No. 2018-534206, and one of them is operated as a spare.

When gas is supplied from the boil-off gas compressor disclosed in Japanese Patent Publication No. 2018-518415 to a consumer, the sum of the gas throughput (gas supply amount) of each compressor installed in parallel needs to satisfy the gas demand of the consumer. Here, if the gas demand amount of the consumer fluctuates, the total gas supply amount from the compressors does not match the gas demand amount, and as a result, the discharge pressure of each compressor fluctuates. Specifically, when the gas demand increases, the discharge pressure decreases, and when the gas demand decreases, the discharge pressure rises.

On the other hand, by controlling each compressor so that the discharge pressure is maintained at a predetermined set pressure, it is considered to match the gas supply amount from the compressor to the gas demand amount after fluctuation. However, when the discharge pressure set value (target value) of each compressor is made the same, the control becomes complicated because it is necessary to adjust the gas throughput of both compressors based on the pressure information on the discharge side (demand side). That is, when the precision of the pressure control is deteriorated, it may become difficult to match the gas supply amount from the compressor to the gas demand amount of the consumer.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a compressor unit and a program for controlling the compressor unit capable of easily matching the gas supply amount from the compressor to the gas demand amount of the consumer.

A compressor unit according to an aspect of the present invention is a compressor unit that is installed in a ship and compresses a target gas that is boil-off gas sucked from an LNG storage tank of the ship. This compressor unit has a plurality of compression stages, a first reciprocating compressor for compressing the target gas and supplying it to a consumer, and a plurality of compression stages, the first reciprocating compressor having a plurality of compression stages to compress the target gas and supply it to the consumer A second reciprocating compressor connected in parallel with the compressor, and a control unit for controlling driving of the first reciprocating compressor and the second reciprocating compressor are provided. The first reciprocating compressor includes a first check valve provided downstream of a final compression stage, a first pressure sensor provided between the final compression stage and the first check valve, and at least the final compression stage. It includes a first bypass passage passing through, and a first bypass valve provided in the first bypass passage. The second reciprocating compressor is configured to bypass at least a second check valve provided downstream of a final compression stage, a second pressure sensor provided between the final compression stage and the second check valve, and at least the final compression stage. It includes a second bypass flow passage passing through, and a second bypass valve provided in the second bypass flow passage. The compressor unit is configured such that the target gas discharged from the second reciprocating compressor and the target gas discharged from the first reciprocating compressor join in a flow path downstream of the first and second check valves, have. The control unit controls the opening degree of the first bypass valve so that the pressure detected by the first pressure sensor becomes a first set value, and the pressure detected by the second pressure sensor is lower than the first set value. and an opening degree control unit for controlling an opening degree of the second bypass valve to be a second set value.

A program for controlling a compressor unit according to another aspect of the present invention is a program for controlling the operation of the compressor unit, and configures a computer constituting the control unit so that the pressure detected by the first pressure sensor becomes the first set value. Controlling the opening degree of the first bypass valve and making it function as an opening degree control unit that controls the opening degree of the second bypass valve so that the pressure detected by the second pressure sensor becomes the second set value, stored in the computer's storage medium.

1 is a schematic diagram of a compressor unit according to an embodiment.
Fig. 2 is a functional block diagram of the control unit in the first embodiment.
3 : is a flowchart for demonstrating opening degree control of a 1st bypass valve.
4 : is a flowchart for demonstrating the opening degree control of a 2nd bypass valve.
5 is a functional block diagram of a control unit in the second embodiment.

(First embodiment)

Hereinafter, a compressor unit and a program for controlling the compressor unit according to an embodiment will be described in detail based on the drawings. 1 is a schematic diagram of a compressor unit 100 .

The compressor unit 100 is installed in the ship (not shown) which has the LNG storage tank 101 in which LNG (Liquefied Natural Gas: liquefied natural gas) was stored. The compressor unit 100 is configured to suck a target gas that is a boil-off gas generated in the LNG storage tank 101 and compress the sucked target gas. Moreover, the compressor unit 100 is comprised so that the compressed target gas may be supplied to the consumer 501 (for example, an engine). In the following description, the terms "upstream" and "downstream" are used based on the flow direction of the target gas.

The compressor unit 100 includes a first reciprocating compressor 300 that compresses the target gas and supplies it to the demand 501 , and the first reciprocating compressor 300 in parallel with the first reciprocating compressor 300 to compress the target gas and supply it to the demand 501 . It has the connected 2nd reciprocating compressor 400, and the control part 420 which controls the driving of the 1st reciprocating compressor 300 and the 2nd reciprocating compressor 400. FIG. The first reciprocating compressor 300 and the second reciprocating compressor 400 have basically the same structure.

The compressor unit 100 is provided with the flow path 102 which flows the target gas which is boil-off gas generated in the LNG storage tank 101 toward the consumer 501. The flow path 102 connects the LNG storage tank 101 and the demand 501 to each other so that the target gas can be supplied to the demand 501 . The flow path 102 includes a first flow path 110 through which the target gas flows to the first reciprocating compressor 300 , and a first flow path 110 connected to the first flow path 110 and configured to flow the target gas through the second reciprocating compressor 400 . It has two flow paths 210 . The second flow path 210 branches off from the first flow path 110 at a location between the LNG storage tank 101 in the first flow path 110 and a first compression stage 201 to be described later. It is connected to the first flow path 110 on the downstream side of the sixth compression stage 206 (final compression stage).

The first reciprocating compressor 300 includes a first compression stage 201 to a sixth compression stage 206 for sequentially boosting the target gas, a plurality of coolers 281 to 285 , and a driving unit (not shown), have. The drive unit includes a drive source (a motor, an engine, etc.) and a crank mechanism that transmits the motive power of the drive source to the first compression stages 201 to 206 .

Two first compression stages 201 are provided on the first flow passage 110 , and the second compression stages 202 to sixth compression stages 206 are provided on the first flow passage 110 , respectively. One is provided. In addition, it is not limited to the configuration in which the two first compression stages 201 are provided in parallel with each other. The structure in which one 1st compression stage 201 is provided may be sufficient.

The first flow path 110 includes a storage tank connection flow path 111 , a plurality of stage connection flow paths 115 to 119 , and a customer supply flow path 114 .

The storage tank connection flow path 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 unit 100 . Specifically, the storage tank connection flow path 111 is divided into a main pipe 121 extended from the upper part of the LNG storage tank 101 and a downstream end of the main pipe 121, and is divided into two first compression stages ( It has branch pipes 122 and 123 connected to 201 . That is, the two first compression stages 201 are connected to the storage tank connection passage 111 so as to be parallel to each other.

The stage connection flow paths 115 to 119 are respectively piped so as to flow the target gas from one compression stage to the next compression stage. The stage connection flow path 115 is configured to flow the target gas from the two first compression stages 201 to the second compression stage 202 . That is, the stage connection flow path 115 is divided into a main pipe 124 installed extending from the second compression stage 202 toward the first compression stage 201, and an upstream end of the main pipe 124, It includes branch pipes 125 , 126 connected to two first compression stages 201 . The stage connection flow path 116 connects the second compression stage 202 and the third compression stage 203 to each other. The stage connection flow path 117 connects the third compression stage 203 and the fourth compression stage 204 to each other. The stage connection flow path 118 connects the fourth compression stage 204 and the fifth compression stage 205 to each other. The stage connection flow path 119 connects the fifth compression stage 205 and the sixth compression stage 206 to each other.

The demand source supply flow path 114 is a flow passage connecting the sixth compression stage 206 to the demand destination 501 .

The coolers 281 to 285 are configured to heat exchange the target gas with cooling water that is lower in temperature than the target gas. The cooler 281 is provided in the stage connection 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 connection flow path 117 so that the target gas discharged from the 3rd compression stage 203 may be cooled. The cooler 283 is provided in the stage connection passage 118 so as to cool the target gas discharged from the fourth compression stage 204 . The cooler 284 is provided in the stage connection flow path 119 so that the target gas discharged from the 5th compression stage 205 may be cooled. The cooler 285 is provided in the customer supply flow path 114 so as to cool the target gas discharged from the sixth compression stage 206 .

The compressor unit 100 (the first reciprocating compressor 300 ) has bypass flow passages 411 to 413 and 414A in order to adjust the pressure of the target gas in the first flow passage 110 . The bypass flow passages 411 to 413 are configured to return at least a part of the target gas from the branch portions 311 to 313 on the stage connection flow passages 116 , 117 , and 119 to the upstream side. The branch portions 311 to 313 are located downstream of the coolers 281 , 282 , 284 .

The bypass flow path 411 is connected to the main pipe 121 of the storage tank connection flow path 111 while bypassing the first compression stage 201 and the second compression stage 202 . The bypass flow path 412 bypasses the third compression stage 203 , and is a stage connection flow path in the connection part 315 on the downstream side of the branching part 311 and upstream of the third compression stage 203 . It is connected to (116). The bypass flow path 413 bypasses the fourth compression stage 204 and the fifth compression stage 205 , while being on the downstream side of the branch 312 and on the upstream side of the fourth compression stage 204 . It is connected to the stage connection flow path 117 . The bypass flow path 414A (first bypass flow path) is configured to return at least a portion of the target gas from the branch 314 of the demand supply flow path 114 located on the downstream side of the cooler 285 to the upstream side, have. That is, the bypass flow path 414A is a first bypass flow path that bypasses at least the final compression stage. The bypass flow passage 414A bypasses the sixth compression stage 206 (the final compression stage), and is stage-connected on the downstream side of the branching part 313 and on the upstream side of the sixth compression stage 206 . It is connected to the flow path 119 .

Bypass valves 421A, 422A, 423A, and 424A are provided in the bypass flow passages 411 to 413 and 414A, respectively. The bypass valve 424A provided in the bypass flow path 414A corresponds to the 1st bypass valve provided in the 1st bypass flow path which bypasses at least the last compression stage.

Corresponding to the bypass flow passages 411 to 413 and 414A, pressure sensors 431 to 433 and 434A are disposed in the first flow passage 110 . The pressure sensor 431 detects a discharge pressure, which is the pressure of the gas discharged from the second compression stage 202, in a stage connection flow path ( 116) is installed. The pressure sensor 432 is a stage connection flow path ( 117) is installed. The pressure sensor 433 is a stage connection flow path ( 119) is installed. The pressure sensor 434A (first pressure sensor) detects a discharge pressure, which is the pressure of the gas discharged from the sixth compression stage 206 , and is used to control the demand-end supply pressure, the cooler 285 . It is provided in the demand-supply flow path 114 on the downstream side of the branching part 314 and on the downstream side of the branching part 314 .

A first check valve 451 is provided in the first flow path 110 downstream of the sixth compression stage 206 . Specifically, the first check valve 451 is provided downstream of the branch 314 in the demand source supply flow path 114 , and counter-flows the target gas from the consumer 501 side to the sixth compression stage 206 side. and counterflow from the second reciprocating compressor 400 .

In the following description, in the demand-supply flow path 114 , a site upstream from the first check valve 451 (a site on the first reciprocating compressor 300 side) is referred to as “the first compressor-side flow path unit 114A”. do. In addition, a site|part of the demand-supply flow path 114 on the downstream side rather than the 1st check valve 451 is called "the 1st demand side flow path part 114D". Among the demand supply flow passages 114 in the second flow passage 210 , a portion upstream of a second check valve 452 described later (a portion on the second reciprocating compressor 400 side) is defined as a “second compressor-side flow passage”. part 114B". In the second flow path 210 , in the supply flow path 114 of the demand side, a site downstream of the second check valve 452 is referred to as a "second demand side flow path part 114C". The second demand-side flow passage 114C is connected to the first demand-side flow passage 114D. The pressure sensor 434A is provided between the branching part 314 and the first check valve 451 in the first compressor-side flow path part 114A.

As shown in FIG. 1 , the upstream end of the second flow path 210 is connected to the main pipe 121 of the storage tank connection flow path 111 in the first flow path 110 . In addition, the downstream end of the second flow path 210 is connected to the demand destination supply flow path 114 in the first flow path 110 . That is, the target gas discharged from the second reciprocating compressor 400 through the second demand-side flow passage 114C and the target gas discharged from the first reciprocating compressor 300 through the first demand-side flow passage 114D. joins at the confluence point (13).

The configuration of the second reciprocating compressor 400 is the same as that of the first reciprocating compressor 300 (the same number of compression stages). In FIG. 1 , the components corresponding to each other between the second reciprocating compressor 400 and the first reciprocating compressor 300 are basically assigned the same reference numerals. That is, the second reciprocating compressor 400 includes first to sixth compression stages 201 to 206 . A bypass flow passage 411 bypassing the first compression stage 201 and the second compression stage 202 , a bypass flow passage 412 bypassing the third compression stage 203 , and a fourth compression stage A bypass flow path 413 bypassing the 204 and the fifth compression stage 205 is provided. Bypass valves 421B, 422B, and 423B are provided in these bypass flow passages 411 to 413, respectively. In addition, a second bypass flow passage 414B that bypasses the sixth compression stage 206 is provided. A second bypass valve 424B is provided in the second bypass flow passage 414B. The second bypass flow path 414B is a bypass flow path that bypasses at least the final compression stage.

Moreover, the 2nd reciprocating compressor 400 further includes the 2nd check valve 452 provided downstream of the 6th compression stage 206, and the 2nd pressure sensor 434B. The second check valve 452 is provided downstream of the branch 314 among the demand-supply flow passages 114 in the second flow passage 210 , and counter-flows the target gas from the first reciprocating compressor 300 side. to block The second pressure sensor 434B is provided between the sixth compression stage 206 and the second check valve 452 , that is, in the second compressor-side flow path part 114B in the second flow path 210 .

In the compressor unit 100, since the 1st reciprocating compressor 300 and the 2nd reciprocating compressor 400 have a fundamentally same structure, commonization of the components used for each can be aimed at.

As shown in FIG. 2 , the control unit 420 includes a detection pressure receiving unit 461 , a determination unit 463 , an opening degree control unit 464 , and a storage unit 466 .

The detection pressure receiving unit 461 receives data indicating the pressure detected by the first pressure sensor 434A and the pressure detected by the second pressure sensor 434B, respectively.

The set value of the discharge pressure in the sixth compression stage 206 of the second reciprocating compressor 400 (hereinafter referred to as “the second set value”) is the sixth compression stage ( 206), which is lower than the set value of the discharge pressure (hereinafter referred to as a “first set value”). The first set value is set to the same value as the required pressure of the demand destination 501 . In the present embodiment, the second set value is a value of 99% or more and less than 100% of the first set value. In the description below, the first set value is 30 MPa, and the second set value is 29.9 MPa. In addition, the 2nd set value may be set as other values of 29.7 MPa or more and less than 30 MP.

The determination part 463 compares the pressure detected by the 1st pressure sensor 434A with a 1st set value, and determines their magnitude relationship, while determining the pressure detected by the 2nd pressure sensor 434B as a 2nd They are compared with the set values to determine their magnitude relationship. The determination part 463 outputs the information of each determination result to the opening degree control part 464.

The opening degree control part 464 controls the opening degree of the 1st bypass valve 424A so that the detection pressure of the 1st pressure sensor 434A may become a 1st set value, and while controlling the opening degree of the 2nd pressure sensor 434B. The opening degree of the second bypass valve 424B is controlled so that the detection pressure becomes the second set value. The opening degree control part 464 is an opening degree change signal (opening degree increase) to the 1st bypass valve 424A and the 2nd bypass valve 424B based on the information of the determination result output from the determination part 463. signal or openness reduction signal). This control content will be described in detail later.

In the storage unit 466 , a program for controlling the operation of the compressor unit 100 is stored. This compressor unit control program causes the computer constituting the control unit 420 to function as the detection pressure receiving unit 461 , the determining unit 463 , and the opening degree control unit 464 . That is, the computer (CPU: Central Processing Unit) constituting the control unit 420 reads and executes the program stored in the storage unit 466 , thereby detecting the pressure receiving unit 461 , the determining unit 463 , and the opening degree control unit 464 . ) of each function is obtained. The storage unit 466 is constituted by a storage medium such as various memory devices, and a program for controlling the compressor unit is stored in the storage medium.

The control part 420 can also control the opening degree of the bypass valve 421A based on the detection pressure of the pressure sensor 431 of the 1st reciprocating compressor 300 by the functional structure similar to the above. Similarly, the control unit 420 may control the opening degrees of the bypass valves 422A and 423A, respectively, based on the pressure detected by the pressure sensors 432 and 433 . The same applies to the control of the bypass valves 421B to 423B of the second reciprocating compressor 400 .

In addition, the control part 420 may be comprised by the some controller provided corresponding to each bypass valve 421A-424A, 421B-424B, respectively. In this case, each controller has a function corresponding to the detection pressure receiving unit 461 , the determining unit 463 , the opening degree control unit 464 , and the storage unit 466 .

Hereinafter, the opening degree control of the 1st bypass valve 424A and the 2nd bypass valve 424B by the opening degree control part 464 is demonstrated based on the flowchart of FIG.3 and FIG.4. 3 : is a flowchart for demonstrating the opening degree control of the 1st bypass valve 424A, and FIG. 4 is a flowchart for demonstrating the opening degree control of the 2nd bypass valve 424B.

First, the opening degree control of the 1st bypass valve 424A is demonstrated based on FIG. First, the first pressure sensor 434A detects the gas pressure in the first compressor-side flow path portion 114A, and transmits data indicating the detected pressure to the detection pressure receiving unit 461 (step S10). Next, the determination unit 463 compares the detected pressure of the first pressure sensor 434A (hereinafter also referred to as “first detected pressure”) with a first set value, and the first detected pressure is the first set value. It is determined whether or not it is greater than (step S20).

When the first detection pressure is larger than the first set value (Yes in step S20), the opening degree control unit 464 receives the information of the determination result from the determination unit 463, and the first bypass valve The opening degree of 424A is increased (step S30). As a result, the flow rate of the target gas flowing into the first pipeline 414A from the branch 314 increases, so that the pressure detected by the first compressor-side flow passage 114A gradually decreases. On the other hand, when the first detection pressure is equal to or less than the first set value (No in step S20), the opening degree control unit 464 does not increase the opening degree of the first bypass valve 424A, and proceeds to step S40. do.

In step S40, the determination part 463 compares a 1st detection pressure and a 1st set value, and determines whether the 1st detection pressure is less than a 1st set value. When the first detection pressure is less than the first set value (YES in step S40), the opening degree control unit 464 receives the information of the determination result from the determination unit 463, and the first bypass valve ( 424A) is decreased (step S50). As a result, the flow rate of the target gas flowing into the first bypass flow passage 414A from the branching portion 314 decreases, so that the pressure detected in the first compressor-side flow passage 114A gradually increases. On the other hand, when the first detection pressure is equal to the first set value (No in step S40), the opening degree control unit 464 does not increase or decrease the opening degree of the first bypass valve 424A, but proceeds to step S10. go back By repeating the above steps S10 to S50, the first detection pressure detected in the first compressor-side flow path portion 114A approaches the first set value (for example, 30 MPa).

4 : has shown the flow of opening degree control of the 2nd bypass valve 424B. This control flow is at the point where the second pressure sensor 434B is used instead of the first pressure sensor 434A, the second setpoint is used instead of the first setpoint, and the first bypass valve 424A Instead, it is the same as the control flow of FIG. 3 except that the opening degree of the second bypass valve 424B is controlled. Accordingly, a detailed description of the control flow of the second bypass valve 424B is omitted. By repeating steps S11 to S51 in FIG. 4 , the pressure detected by the second pressure sensor 434B in the second compressor-side flow path portion 114B approaches the second set value (eg, 29.9 MPa).

As described above, the second reciprocating compressor 400 is controlled so that the pressure of the target gas in the second compressor-side flow path part 114B becomes the second set value, while the first compressor-side flow path part 114A The 1st reciprocating compressor 300 is controlled so that the pressure of the target gas in this may become a 1st set value.

In the compressor unit 100 , the first compressor-side flow passage 114A and the second compressor are compared with the pressure of the target gas in the first demand-side flow passage 114D and the second demand-side flow passage 114C. When the pressure of the target gas in the side flow path portion 114B is higher, the target gas is supplied to the demand 501 from each of the compressors 300 and 400 .

As described above, the first set value of the discharge pressure of the first reciprocating compressor 300 is larger than the second set value of the discharge pressure of the second reciprocating compressor 400 . For this reason, the opening degree of the 1st bypass valve 424A of the 1st reciprocating compressor 300 becomes smaller than the opening degree of the 2nd bypass valve 424B of the 2nd reciprocating compressor 400 . As a result, the quantity of the target gas supplied from the 1st reciprocating compressor 300 to the demand 501 becomes larger than the quantity supplied from the 2nd reciprocating compressor 400 .

On the other hand, when the demand for gas from the consumer 501 decreases, the consumption of the target gas decreases, so that the pressures in the first demand-side flow passage 114D and the second demand-side flow passage 114C increase. And when the said pressure exceeds a 2nd set value, the 2nd reciprocating compressor 400 will be in the state which does not send a target gas to the downstream rather than the 2nd check valve 452. Accordingly, the target gas is supplied to the consumer 501 only by the first reciprocating compressor 300 .

In this way, by making the second set value lower than the first set value, even if control is not performed to adjust the flow rate balance of both compressors 300 and 400 each time when a change occurs in the gas demand amount of the consumer 501, the consumer ( The target gas in an amount suitable for the required amount of 501 may be supplied to the demand 501 .

However, there are cases in which the device of the consumer 501 is cut off by a trip or the like. In this case, in order to prevent the entire amount of the target gas discharged from both compressors 300 and 400 from flowing to the second demand-side flow path portion 114C, the control unit 420 bypasses all the compression stages 201 to 206 . The opening degrees of the valves 421A to 424A and 421B to 424B are forcibly increased. At this time, since the amount of the target gas discharged from the first reciprocating compressor 300 is larger than that of the second reciprocating compressor 400 , the opening degree of the bypass valves 421A to 424A in the first reciprocating compressor 300 . The increase width of is larger than the increase width of the opening degree of the bypass valves 421B to 424B of the second reciprocating compressor 400 . Thereby, it is possible to prevent the target gas from being supplied to the demand 501 in a state in which the load is cut off from both compressors 300 and 400. In addition, the opening degree of the bypass valves 421A to 424A and 421B to 424B can be prevented. With respect to the increase width, correction may be made in consideration of the characteristics of each bypass valve.

As mentioned above, although the 1st Embodiment of this invention was described, as a comparative example with respect to 1st Embodiment in the case where two reciprocating compressors 300 and 400 are to be operated together, each final compression stage is The discharge pressure control which makes the set value of the discharge pressure in this equal is conceivable. However, in such a discharge pressure control, it is necessary to control so that the opening degrees of the first and second bypass valves 424A and 424B are always equal. It is necessary to change the opening degree of both bypass valves by the same amount to follow. For this reason, the discharge pressure control of the compressor unit 100 becomes complicated.

On the other hand, in the compressor unit 100 according to the present embodiment, a difference is provided in the set value of the discharge pressure of the sixth compression stage 206 , that is, the final compression stage. As a result, when a change occurs in the gas demand amount of the consumer 501 , the target gas is supplied from both compressors 300 and 400 to a state in which the target gas is supplied by only the first reciprocating compressor 300 . is converted That is, even if the discharge pressure control according to the comparative example is not performed, it is possible to easily supply the target gas in an amount suitable for the demand of the consumer 501 to the consumer 501 .

(Second embodiment)

Next, the compressor unit and the compressor unit control program according to the second embodiment will be described with reference to FIG. 5 . In addition, since 2nd Embodiment is basically the same as that of said 1st Embodiment, only the point which differs from said 1st Embodiment is demonstrated here.

As shown in FIG. 5 , the control unit 420 according to the second embodiment further includes a set value determination unit 462 and a required pressure receiving unit 465 . The requested pressure receiving unit 465 receives data indicating the required pressure of the target gas from the demand 501 . The set value determination unit 462 determines a first set value and a second set value, respectively, based on the required pressure of the target gas received by the requested pressure accepting unit 465 . For example, when the demand pressure of the customer 501 is 30 MPa, the set value determination unit 462 sets the first set value to 30 MPa, which is the same as the required pressure, and sets the second set value to 29.7 MPa. Set to a value not less than 30 MPa.

The set value determination unit 462 sets the first set value and the second set value, respectively, while maintaining the difference between the first set value and the second set value, based on the change in the pressure requested from the consumer 501 . change For example, when the required pressure is changed from 30 MPa to 25 MPa, data indicating the required pressure after the change is input from the demand 501 to the requested pressure receiving unit 465 . Based on this input data, while changing a 1st set value from 30 MPa to 25 MPa, the set value determination part 462 changes a 2nd set value to the value of 24,75 MPa or more and less than 25 MPa.

The program for controlling the compressor unit according to the second embodiment, the program for controlling the compressor unit according to the second embodiment, also functions as a computer constituting the control unit 420 as a set value determining unit 462 and a required pressure receiving unit 465 . will make it That is, when the CPU reads and executes the program stored in the storage unit 466 , the respective functions of the set value determining unit 462 and the requested pressure receiving unit 465 are also obtained.

As mentioned above, in 2nd Embodiment, when changing a 1st set value and a 2nd set value according to the change of the requested|required pressure of the demand destination 501, the difference of both set values is maintained. Even in this case, it becomes possible to realize the operation of the compressor capable of easily responding to the gas demand of the consumer 501 .

(Third embodiment)

Next, the compressor unit 100 according to the third embodiment will be described. The second set value of the second reciprocating compressor 400 can be set to a value of 93% (28 MPa) or more and less than 99% (29.7 MPa) of the first set value of the first reciprocating compressor 300 . In this case, during the operation of the compressor unit 100 , the target gas is not normally supplied from the second reciprocating compressor 400 to the demand 501 , but only from the first reciprocating compressor 300 to the demand 501 . gas is supplied.

On the other hand, when the demand for gas from the customer 501 increases and the gas demand after the increase exceeds the maximum gas throughput (maximum gas supply amount) of the first reciprocating compressor 300 , the first bypass valve 424A is completely closed. Even if it is set to, the gas supply amount to the consumer 501 is insufficient. As a result, the amount of the target gas decreases in the first demand-side flow passage portion 114D and the second demand-side flow passage portion 114C, and the pressure gradually decreases.

Then, when the pressures of the first demand-side flow path part 114D and the second demand-side flow path part 114C are reduced to a second set value, the target gas compressed by the second reciprocating compressor 400 enters the junction 13 . It flows into the first demand-side flow path portion 114D from the supply source and is supplied to the consumer 501 . In this way, it is possible to make up for the shortfall in the gas throughput by the first reciprocating compressor 300 with the gas throughput of the second reciprocating compressor 400, and the gas demand from the demander 501 after the increase can be satisfied. have.

Embodiment disclosed this time is an illustration in all points, and it should be interpreted that it is not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and it is intended that all changes within the meaning and scope equivalent to the claims are included. Accordingly, the following aspects are also included in the scope of the present invention.

Although the above-mentioned embodiment demonstrated the case where only the bypass mechanism (bypass flow path and bypass valve) was used to control the pressure of target gas, it is not limited to this. As control of the processing amount and pressure of target gas, in addition to the control using a bypass mechanism, you may further combine well-known controls, such as unloader control, for example.

In the above embodiment, although the case where both the first reciprocating compressor 300 and the second reciprocating compressor 400 have six compression stages has been described, the number of compression stages may be 5 or less, or 7 or more. . In addition, the number of stages of the compression stages of the first reciprocating compressor 300 and the second reciprocating compressor 400 may be different from each other.

The customer 501 is not limited to an engine, and other marine equipment such as a generator may be used.

In the above embodiment, the bypass flow path 414A (the first bypass flow path) bypasses only the final compression stage, but instead of this, the bypass flow path 414A includes the final compression stage and one of the preceding stages. Alternatively, a plurality of compression stages may be bypassed. In addition, although the second bypass flow path 414B bypasses only the final compression stage, instead of this, the second bypass flow path 414B bypasses the final compression stage and one or a plurality of compression stages preceding it. You can bypass it.

Here, the embodiment will be schematically described.

(1) The compressor unit according to the above embodiment is a compressor unit that is installed in a ship and compresses target gas that is boil-off gas sucked in from an LNG storage tank of the ship. This compressor unit has a plurality of compression stages, a first reciprocating compressor for compressing the target gas and supplying it to a consumer, and a plurality of compression stages, the first reciprocating compressor having a plurality of compression stages to compress the target gas and supply it to the consumer A second reciprocating compressor connected in parallel with the compressor, and a control unit for controlling driving of the first reciprocating compressor and the second reciprocating compressor are provided. The first reciprocating compressor includes a first check valve provided downstream of a final compression stage, a first pressure sensor provided between the final compression stage and the first check valve, and at least the final compression stage. It includes a first bypass passage passing through, and a first bypass valve provided in the first bypass passage. The second reciprocating compressor is configured to bypass at least a second check valve provided downstream of a final compression stage, a second pressure sensor provided between the final compression stage and the second check valve, and at least the final compression stage. It includes a second bypass flow passage passing through, and a second bypass valve provided in the second bypass flow passage. The compressor unit is configured such that the target gas discharged from the second reciprocating compressor and the target gas discharged from the first reciprocating compressor join in a flow path downstream of the first and second check valves, have. The control unit controls the opening degree of the first bypass valve so that the pressure detected by the first pressure sensor becomes a first set value, and the pressure detected by the second pressure sensor is lower than the first set value. and an opening degree control unit for controlling an opening degree of the second bypass valve to be a second set value.

In this compressor unit, while the discharge pressure of a 1st reciprocating compressor is controlled to a 1st set value, the discharge pressure of a 2nd reciprocating compressor is controlled to a 2nd set value lower than a 1st set value. When two reciprocating compressors are to be operated together, as a comparative example of the present invention, a discharge pressure control in which the set value of the discharge pressure in each final compression stage is the same can be considered. However, in such a discharge pressure control, since it is necessary to always make the opening degrees of the first and second bypass valves the same, when pressure fluctuations at the customer occur, the opening degrees of both bypass valves follow the fluctuations. needs to be changed by the same amount. For this reason, the discharge pressure control of the compressor unit becomes complicated. On the other hand, in the said embodiment, the difference is set in the discharge pressure setting value of the last compression stage. For this reason, when a fluctuation|variation generate|occur|produces in the gas demand amount of a demand, it switches from the state in which the target gas is supplied from both reciprocating compressors to the state in which the target gas is supplied only by the 1st reciprocating compressor. That is, even if the discharge pressure control according to the comparative example is not performed, it is possible to easily supply the target gas in an amount suitable for the demand of the demanding party.

(2) In the compressor unit, the second set value may be a value of 99% or more and less than 100% of the first set value.

According to this configuration, since the second set value is slightly smaller than the first set value, when the gas supply amount from the first reciprocating compressor becomes insufficient, the discharge pressure of the first reciprocating compressor immediately reaches the second set value. reach For this reason, when the gas supply amount from a 1st reciprocating compressor is insufficient, gas supply from a 2nd reciprocating compressor to a demand can be started quickly.

(3) in the compressor unit, wherein the control unit includes: a request pressure receiving unit for receiving the required pressure of the target gas from the demand; and the first set value and You may further include the setting value determination part which determines the said 2nd setting value. The said set value determination part may change the said 1st set value and the said 2nd set value based on the change of the said required pressure, maintaining the difference of the said 1st set value and the said 2nd set value.

According to this configuration, when the first set value and the second set value are changed in accordance with the change in the required pressure of the customer, the difference between the two set values is maintained, so as before the change of the set value, the gas from the first reciprocating compressor is It becomes possible to quickly start the gas supply from the second reciprocating compressor when the supply amount is insufficient.

(4) In the compressor unit, the first reciprocating compressor and the second reciprocating compressor may have the same number of the compression stages.

(5) In the compressor unit, the control unit is configured such that, when the demand destination is unloaded, the total amount of the target gas discharged from the first reciprocating compressor is on a downstream side of the final compression stage of the first reciprocating compressor. In order to return from the flow path, the opening degree of the first bypass valve is forcibly increased, and the total amount of the target gas discharged from the second reciprocating compressor is located downstream of the final compression stage of the second reciprocating compressor. In order to return from the flow path of , the opening degree of the second bypass valve may be forcibly increased, and the increase width of the opening degree of the first bypass valve may be larger than that of the second bypass valve.

According to this configuration, it is possible to prevent the target gas from being supplied to the consumer in a state in which the load is cut off from the first and second reciprocating compressors.

(6) The program for controlling the compressor unit according to the embodiment is a program for controlling the operation of the compressor unit, and configures a computer constituting the control unit so that the pressure detected by the first pressure sensor becomes the first set value. Controlling the opening degree of the first bypass valve and making it function as an opening degree control unit that controls the opening degree of the second bypass valve so that the pressure detected by the second pressure sensor becomes the second set value; It is stored in the storage medium of the computer.

By operating a computer using this program, the target gas is normally supplied to the demanding destination only from the first reciprocating compressor, so unlike the case where gas is constantly supplied to the demanding destination from two compressors, the deterioration of the precision of pressure control is prevented. can be suppressed

As is apparent from the above description, it is possible to easily match the gas supply amount from the compressor to the gas demand amount of the consumer.

This application is based on Japanese Patent Application No. 2021-851 for which it applied on January 6, 2021, The content is taken in here as a reference.

In the above, the present invention has been sufficiently described by way of example with reference to the accompanying drawings, it should be understood that various changes and modifications will be apparent to those skilled in the art. Accordingly, unless they specifically depart from the scope of the invention as defined hereinbelow, such changes and modifications should be construed as being included therein.

Claims (6)

It is a compressor unit that is installed in a ship and compresses a target gas that is a boil-off gas sucked from an LNG storage tank of the ship,
A first reciprocating compressor having a plurality of compression stages and compressing the target gas and supplying it to a consumer;
a second reciprocating compressor having a plurality of compression stages and connected in parallel with the first reciprocating compressor so as to compress the target gas and supply it to the demand;
A control unit for controlling the driving of the first reciprocating compressor and the second reciprocating compressor,
The first reciprocating compressor,
a first check valve provided downstream of the final compression stage;
a first pressure sensor provided between the final compression stage and the first check valve;
a first bypass flow path bypassing at least the final compression stage;
a first bypass valve provided in the first bypass flow path;
The second reciprocating compressor,
a second check valve provided downstream of the final compression stage;
a second pressure sensor provided between the final compression stage and the second check valve;
a second bypass flow path bypassing at least the final compression stage;
a second bypass valve provided in the second bypass flow path;
and the target gas discharged from the second reciprocating compressor and the target gas discharged from the first reciprocating compressor are configured to merge in a flow path downstream of the first and second check valves,
The control unit controls the opening degree of the first bypass valve so that the pressure detected by the first pressure sensor becomes a first set value, and the pressure detected by the second pressure sensor is lower than the first set value. and an opening degree control part controlling the opening degree of the second bypass valve to be a second set value. The method of claim 1,
The second set value is a value of 99% or more and less than 100% of the first set value. 3. The method of claim 1 or 2,
The control unit is
a demand pressure receiving unit for receiving the required pressure of the target gas from the demand;
Further comprising a set value determining unit for determining the first set value and the second set value based on the requested pressure received by the required pressure receiving unit,
The set value determining unit may change the first set value and the second set value while maintaining a difference between the first set value and the second set value based on a change in the required pressure. 3. The method of claim 1 or 2,
The first reciprocating compressor and the second reciprocating compressor have the same number of the compression stages. 3. The method of claim 1 or 2,
The control unit, when the demand destination is load cut off,
The opening degree of the first bypass valve is forcibly increased so that the entire amount of the target gas discharged from the first reciprocating compressor is returned from the flow path downstream of the final compression stage of the first reciprocating compressor, ,
The opening degree of the second bypass valve is forcibly increased so that the entire amount of the target gas discharged from the second reciprocating compressor is returned from the flow path downstream of the final compression stage of the second reciprocating compressor. ,
and an increase in the opening degree of the first bypass valve is larger than that of the second bypass valve. It is a program for controlling the operation of the compressor unit according to claim 1,
The computer constituting the control unit controls the opening degree of the first bypass valve so that the pressure detected by the first pressure sensor becomes the first set value, and the pressure detected by the second pressure sensor is adjusted to the first set value. 2 to function as an opening degree control unit that controls the opening degree of the second bypass valve to be a set value,
A program for controlling the compressor unit stored in the storage medium of the computer.

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