JP7009669B1 - How to operate the compressor unit, screw compressor and compressor unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a fluctuation of pressure on a discharge side of a first compressor when the second compressor is started while the first compressor is being driven. SOLUTION: A compressor unit 10 is a reciprocating second type provided on a first compressor 12 and a reciprocating equipment connection flow path 16 branching from a demand destination connection flow path 14 connected to the first compressor 12. A compressor 18 and a control unit 27 are provided. The first compressor includes a screw type compression unit 22, a bypass flow path 23a connecting the demand destination connection flow path 14 and the storage tank connection flow path 3, and a bypass valve 23b. The control unit 27 increases the processing amount of the compression unit 22 when the second compressor 18 is started, and the bypass valve 23b so that the flow rate corresponding to the increased processing amount returns to the storage tank connection flow path 3. The opening degree is increased, and then the second compressor 18 is started and the opening degree of the bypass valve 23b is reduced. [Selection diagram] Fig. 1

Description

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

Conventionally, as disclosed in Patent Document 1 below, there is known a compressor unit that recovers boil-off gas generated in a liquefied gas tank and supplies at least a part thereof to a gas demand destination. The compressor unit disclosed in Patent Document 1 includes a first compressor that compresses the boil-off gas generated in the liquefied gas tank, and the discharge-side flow paths of the first compressor are two flow paths. Branches to. One of the channels is connected to the propulsion engine of the ship, and a part of the gas compressed by the first compressor is used by the propulsion mechanism. The other flow path is connected to the liquefied gas tank so that the excess gas can be returned to the liquefied gas tank. A second compressor and a heat exchanger for liquefaction are provided in the other flow path, and the gas flowing through the flow path is compressed by the second compressor, and then the heat exchanger and the JT are provided. It is liquefied through a (Joule-Thomson) valve. The liquefied liquefied gas recirculates in the liquefied gas tank.

Japanese Unexamined Patent Publication No. 49-88904

By the way, when the boil-off gas is being supplied from the first compressor to the propulsion engine of the ship, the second compressor may be started. In this case, when the second compressor is started, the pressure on the discharge side of the first compressor is reduced by the amount of the boil-off gas to be processed in the second compressor. Even if the capacity control of the first compressor is performed by feedback control such as PID control in order to prevent this, it is difficult to cope with the sudden pressure fluctuation due to the start of the second compressor. Therefore, there is a possibility that the operation in which the pressure of the gas supplied to the propulsion engine is stable is hindered.

Therefore, the present invention has been made in view of the above-mentioned prior art, and an object of the present invention is the first compression even when the second compressor is started while the first compressor is being driven. The purpose is to suppress fluctuations in pressure on the discharge side of the machine.

In order to achieve the above object, the present invention is a compressor installed in a ship, recovers a target gas which is a boil-off gas of liquefied gas from a storage tank provided in the ship, and supplies at least a part thereof to a demand destination. The machine unit, the first compressor that sucks the target gas from the storage tank through the storage tank connection flow path, the demand destination connection flow path that connects the first compressor to the demand destination, and the demand destination connection flow. A reciprocal second compression that is provided on the reliquefaction equipment connection flow path branching from the path and connected to the reliquefaction equipment and further compresses the target gas before flowing into the reliquefaction equipment. It includes a machine and a control unit that controls the first compressor and the second compressor. The first compressor has a screw-type compression unit connected to the storage tank connection flow path to compress the target gas, and at least a part of the target gas from the demand destination connection flow path to the storage tank connection flow path. It is provided with a bypass means for returning. The bypass means includes a bypass flow path connecting the demand destination connection flow path and the storage tank connection flow path, and a bypass valve provided in the bypass flow path. The control unit corresponds to the required flow rate of the target gas to be processed by the second compressor by the operation of the second compressor when the second compressor is started while the compression unit is being driven. A start-up preparation control is executed to increase the opening degree of the bypass valve so that the processing amount of the compression unit is increased by the flow rate and the flow rate corresponding to the increased processing amount returns to the storage tank connection flow path. After the start preparation control is executed, the second compressor is started, and the start control is configured to reduce the opening degree of the bypass valve, which has been increased by the start preparation control, by a predetermined opening degree.

In the compressor unit according to the present invention, even when the second compressor is started while the compression unit of the first compressor is in operation, it is possible to suppress a pressure drop in the demand destination connection flow path. Moreover, since the processing amount of the compression unit is increased in advance before the start control for starting the second compressor, it is only necessary to reduce the opening degree of the bypass valve when starting the second compressor. Therefore, it is possible to cope with a sudden pressure fluctuation accompanying the start of the second compressor.

In the compressor unit, the compression unit of the first compressor may be composed of two screw type compressors arranged in parallel with each other. In this case, the bypass means is provided in the two bypass flow paths and the two bypass flow paths for returning the target gas discharged from the two screw type compressors from the demand destination connection flow path to the storage tank connection flow path. It may include two bypass valves provided one by one . In the start-up preparation control, the control unit increases the processing amount of each of the two screw compressors by half of the flow rate corresponding to the required flow rate, and half of the flow rate corresponding to the increased processing amount. The opening degree of each of the two bypass valves may be increased so that the flow rate returns from each of the two bypass flow paths to the storage tank connection flow path.

In this aspect, even when the compression unit of the first compressor is composed of two screw type compressors, appropriate start-up preparation control can be realized.

In the compressor unit, the compression unit of the first compressor may be composed of two screw type compressors arranged in parallel with each other. In this case, the bypass means is a first bypass that returns the target gas discharged from one of the two screw compressors from the demand destination connection flow path to the storage tank connection flow path. The target gas discharged from the flow path, the first bypass valve provided in the first bypass flow path, and the other screw type compressor of the two screw type compressors is sent from the demand destination connection flow path. A second bypass flow path that returns to the storage tank connection flow path and a second bypass valve provided in the second bypass flow path may be included. Assuming that the processing amount of the one screw type compressor is A1, the processing amount of the other screw type compressor is A2, and the flow rate corresponding to the required flow rate is B, the control unit performs the start-up preparation control. The processing amount of the one screw compressor is increased by the flow rate obtained by B × A2 / (A1 + A2), and the flow rate obtained by B × A2 / (A1 + A2) is the flow rate connected to the storage tank from the first bypass flow path. The opening degree of the first bypass valve is increased so as to return to the road, the processing amount of the other screw compressor is increased by the flow rate obtained by B × A1 / (A1 + A2), and B × A1 /. The opening degree of the second bypass valve may be increased so that the flow rate obtained in (A1 + A2) returns from the second bypass flow path to the storage tank connection flow path.

In this aspect, even when the compression unit of the first compressor is composed of two screw type compressors, appropriate start-up preparation control can be realized.

The first compressor may include a rotation speed adjusting means of the compression unit or a capacity adjusting means of the compression unit, which can increase the processing amount of the compression unit in the start-up preparation control.

In this aspect, the processing amount can be easily adjusted.

The screw compressor according to the present invention is a screw compressor that sucks a target gas, which is a boil-off gas of liquefied gas, from a storage tank provided in a ship through a storage tank connection flow path and discharges the target gas to a demand destination connection flow path. , A screw type compressor connected to the storage tank connection flow path to compress the target gas, a bypass flow path connecting the demand destination connection flow path and the storage tank connection flow path, and the bypass flow path are provided. It is provided with a bypass valve, a bypass means for returning at least a part of the target gas from the demand destination connection flow path to the storage tank connection flow path, and a control unit. When the control unit receives a command to start the second compressor provided in the reliquefaction facility connection flow path that branches from the demand destination connection flow path and is connected to the reliquefaction facility connection flow path while the compression unit is being driven. The processing amount of the compression unit is increased by the flow rate corresponding to the required flow rate of the target gas to be processed by the second compressor by the operation of the second compressor, and corresponds to the increased processing amount. The start preparation control for increasing the opening degree of the bypass valve is executed so that the flow rate returns to the storage tank connection flow path, and after the execution of the start preparation control, a start permission signal for starting the second compressor is output. At the same time, the start control is configured to reduce the opening degree of the bypass valve, which has been increased by the start preparation control, by a predetermined opening degree.

The method for operating the compressor unit according to the present invention is a method for operating the compressor unit that recovers a target gas, which is a boil-off gas of liquefied gas, from a storage tank provided in a ship and supplies at least a part thereof to a demand destination. The compressor unit is branched from the first compressor, which sucks the target gas from the storage tank through the storage tank connection flow path and discharges the target gas to the demand destination connection flow path, and the demand destination connection flow path. It is equipped with a reciprocal type second compressor provided in the reliquefaction equipment connection flow path connected to the reliquefaction equipment. The first compressor includes a screw-type compression unit connected to the storage tank connection flow path to compress the target gas, a bypass flow path connecting the demand destination connection flow path and the storage tank connection flow path, and the like. It has a bypass valve provided in the bypass flow path. The operation method includes a drive step for driving the compression unit of the first compressor, and the second compression by the operation of the second compressor when the second compressor is started while the compression unit is being driven. The processing amount of the compressor is increased by the flow rate corresponding to the required flow rate of the target gas to be processed by the machine, and the bypass is such that the flow rate corresponding to the increased processing amount returns to the storage tank connection flow path. After the start preparation step for increasing the valve opening and the start preparation step, the second compressor is started and the bypass valve opening increased in the start preparation step is reduced by a predetermined opening. And, including.

As described above, according to the present invention, even when the second compressor is started while the first compressor is being driven, the fluctuation of the pressure on the discharge side of the first compressor is suppressed. Can be done.

It is a figure which shows roughly the structure of the compressor unit which concerns on 1st Embodiment. It is a flow diagram for demonstrating the operation operation at the time of starting the 2nd compressor in the compressor unit. It is a flow diagram for demonstrating start-up preparation control. It is a flow diagram for demonstrating activation control. It is a figure which shows roughly the structure of the compressor unit which concerns on 2nd Embodiment. It is a figure which shows roughly the structure of the screw compressor which concerns on other embodiment.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

(First Embodiment)
The compressor unit 10 (see FIG. 1) according to the present embodiment is a compressor unit installed in a ship (not shown) and recovering a target gas which is a boil-off gas of liquefied gas from a storage tank 1 provided in the ship. be. At least a part of the target gas recovered by the compressor unit 10 is supplied to the demand destination. Examples of the demand destination include a propulsion engine (propulsion engine, etc.) of a ship, a power generation device installed in the ship, and the like. These are gas utilization devices that accept gas in a predetermined pressure range. Examples of the liquefied gas include liquefied natural gas (LNG) and liquefied hydrogen (LH2).

As shown in FIG. 1, the compressor unit 10 includes a first compressor 12 connected to a storage tank connection flow path 3 connected to a storage tank 1 in which liquefied gas is stored, a first compressor 12, and the demand destination. A second compressor provided in the demand destination connection flow path 14 connecting the two, the reliquefaction facility connection flow path 16 branching from the demand destination connection flow path 14 and connecting to the reliquefaction facility 5, and the reliquefaction facility connection flow path 16. It is equipped with 18. The reliquefaction facility 5 is a facility for reliquefying the gas in order to return the surplus portion of the gas compressed by the first compressor 12 to the storage tank 1. The second compressor 18 is a compressor that compresses the gas before it flows into the reliquefaction facility 5, and is composed of a reciprocating compressor. That is, the second compressor 18 can be driven independently of the first compressor 12. The liquefied gas reliquefied by the reliquefaction equipment 5 is returned to the storage tank 1.

An on-off valve 20 is provided in the reliquefaction equipment connection flow path 16. The on-off valve 20 is opened when the second compressor 18 is operated. Further, a spillback flow path 16a having a spillback valve 16b is connected to the reliquefaction facility connection flow path 16 so as to bypass the second compressor 18.

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

The bypass means 23 includes a bypass flow path 23a that connects the demand destination connection flow path 14 and the storage tank connection flow path 3 while bypassing the compression unit 22, and a bypass valve 23b provided in the bypass flow path 23a. When the bypass flow path 23a is opened by the bypass valve 23b, a part of the gas discharged from the compression unit 22 passes through the bypass flow path 23a from the demand destination connection flow path 14 to the storage tank connection flow path 3 (that is, the first compressor). It is returned to the suction side of 12).

The first compressor 12 has an adjusting means 12a capable of increasing the amount of gas processed by the compression unit 22. The adjusting means 12a is a capacity adjusting means configured so that the compressed capacity of the compression unit 22 can be adjusted. More specifically, the capacity adjusting means of the screw type compression unit 22 includes a slide valve (not shown) capable of adjusting the gas discharge capacity. When the first compressor 12 has an inverter, the rotation speed adjusting means (that is, the rotation speed adjusting means) configured so that the rotation speed of the compression unit 22 can be adjusted in place of the adjusting means 12a or together with the adjusting means 12a. It may have other adjusting means which is an inverter control means).

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

The signal output from the pressure detector 25 is input to the control unit 27. The control unit 27 is configured by a computer including a CPU, a memory device, and the like, and exerts a predetermined function by executing a stored program. The first compressor 12, the second compressor 18, the bypass valve 23b, and the on-off valve 20 are electrically connected to the control unit 27, and the control unit 27 is configured to control these. That is, the functions of the control unit 27 include the first drive control unit 27a, the second drive control unit 27b, and the bypass control unit 27c. The first drive control unit 27a is configured to control the adjusting means 12a of the first compressor 12. The second drive control unit 27b is configured to control the second compressor 18 and open / close the on-off valve 20. The bypass control unit 27c is configured to control the opening degree of the bypass valve 23b.

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

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

The start control is executed after the start preparation control is completed. That is, in the start control, the driving of the second compressor 18 is started, but the start of the start control is not permitted until the start preparation control is completed. Therefore, the second compressor 18 is not started only by inputting a command for starting the second compressor 18 from the ship side to the control unit 27, and the control unit 27 permits the start of the second compressor 18. The second compressor 18 is started only after the control for the operation is executed.

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

As shown in FIG. 2, while the first compressor 12 is being driven, that is, while the compression unit 22 is being driven (step ST11 (drive step)), the opening degree of the bypass valve 23b and the position of the slide valve (or the compressor). The number of revolutions) has been adjusted. That is, the bypass control unit 27c controls the bypass valve 23b and the first drive control unit 27a controls the slide valve (or the compressor rotation speed control) so that the gas of a predetermined pressure is supplied to the demand destination at a predetermined flow rate. ) Is being performed. Therefore, the pressure and flow rate of the gas supplied from the compressor unit 10 to the demand destination are controlled. Then, when the control unit 27 receives a command for starting the second compressor 18 while the first compressor 12 is being driven (step ST12), the control unit 27 executes the start preparation control (step ST13 (start preparation). Step)). In the start-up preparation control, as will be described later, control is performed to increase the processing amount of the compression unit 22 in the first compressor 12 and increase the opening degree of the bypass valve 23b. Therefore, the gas pressure in the demand destination connection flow path 14 may temporarily fluctuate. Therefore, the system waits until the opening degree of the bypass valve 23b falls within a predetermined range (step ST14). After that, the start control can be executed (step ST15 (start step)).

The start preparation control is executed when a command for starting the second compressor 18 is received, but the second compressor 18 is not started only by receiving this command. When the control unit 27 receives this command, as shown in FIG. 3, the control unit 27 (first drive control unit 27a) starts control for increasing the gas processing amount by the compression unit 22 of the first compressor 12 (1st drive control unit 27a). Step ST131). That is, since the second compressor 18 is started in the later start control, the second compressor 18 is processed so that the gas pressure of the demand destination connection flow path 14 does not decrease with this start. The gas processing amount by the compression unit 22 of the first compressor 12 is increased by the flow rate corresponding to the gas processing amount.

In order to increase the gas processing amount, the first drive control unit 27a controls the adjusting means 12a of the first compressor 12. For example, the first drive control unit 27a controls to move the slide valve to the load side. Instead of / in addition to this, the first drive control unit 27a may perform control to increase the rotation speed of the screw type compression unit 22.

When moving the slide valve, the first drive control unit 27a moves the slide valve to the load side until the opening degree set value of the bypass valve 23b stored in advance in the control unit 27 is reached. Alternatively, when increasing the rotation speed of the compression unit 22, the first drive control unit 27a rotates the compression unit 22 until the opening degree setting value of the bypass valve 23b stored in advance in the control unit 27 is reached. Increase the number.

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

When the slide valve starts moving to the load side (or the rotation speed starts to increase), the discharge pressure of the demand destination connection flow path 14 acquired by the pressure detector 25 tends to increase. The control unit 27 (bypass control unit 27c) starts to increase the opening degree of the bypass valve 23b in order to maintain the discharge pressure constant (step ST132). Therefore, even if the amount of gas processed by the compression unit 22 increases, the discharge pressure (or flow rate) of the gas supplied to the demand destination does not increase.

Then, when the opening degree of the bypass valve 23b reaches the above-mentioned opening degree setting value, the movement of the slide valve is stopped (or the increase in the rotation speed is stopped).

In the present embodiment, with respect to the required flow rate of the target gas newly required by starting the second compressor 18, the opening degree of the bypass valve 23b corresponding to the corresponding flow rate is stored in advance in the control unit 27. .. However, the present invention is not limited to this, and after receiving the command for starting the second compressor 18, the newly required flow rate is calculated, and the bypass valve 23b is used so that the calculated flow rate is output. The opening degree may be controlled.

Until the opening degree of the bypass valve 23b is within a predetermined range, the system waits without shifting to the start control (step ST14 in FIG. 2). Then, when the opening degree of the bypass valve 23b falls within this predetermined range, a start permission signal is sent to the second drive control unit 27b, and the start control is started (step ST15 in FIG. 2). In the present embodiment, instead of the bypass valve opening setting value, it is determined whether to shift to start control based on whether the gas flow rate converted from the opening setting value is within a predetermined range. You may. In step ST14, it may also be confirmed whether or not the detection pressure of the pressure detector 25 is within a predetermined range.

In the start control, as shown in FIG. 4, the control unit 27 (second drive control unit 27b) receives the start permission signal and starts the second compressor 18 (step ST151). Then, when the second compressor 18 is started and it is confirmed that the second compressor 18 is being driven at a predetermined rotation speed, the control unit 27 (bypass control unit 27c) opens the bypass valve 23b. Is reduced by a predetermined opening (step ST152). That is, since the gas pressure in the demand destination connection flow path 14 decreases as the second compressor 18 starts, the gas pressure in the demand destination connection flow path 14 is reduced by reducing the opening degree of the bypass valve 23b. Suppresses the decrease in gas. At this time, the bypass control unit 27c may reduce the opening degree of the bypass valve 23b by the amount increased in step ST132. That is, the opening degree of the bypass valve 23b that has increased in step ST132 may be returned to the original opening degree. As a result, the gas pressure in the demand destination connection flow path 14 after the second compressor 18 is started becomes substantially the same as the gas pressure in the demand destination connection flow path 14 before the start preparation control is started. At this time, the bypass control unit 27c resets the opening degree setting of the bypass valve 23b in step ST132.

As described above, according to the present embodiment, even when the second compressor 18 is started while the compression unit 22 of the first compressor 12 is in operation, the pressure drop in the demand destination connection flow path 14 is reduced. It can be suppressed. Moreover, since the processing amount of the compression unit 22 is increased in advance before the start control for starting the second compressor 18, it is only necessary to reduce the opening degree of the bypass valve 23b when starting the second compressor 18. I'm done. Therefore, it is possible to cope with a sudden pressure fluctuation accompanying the start of the second compressor 18.

In the present embodiment, the opening degree of the bypass valve 23b is reduced after the rotation speed of the second compressor 18 reaches a predetermined rotation speed, but the present invention is not limited to this. For example, the operation of lowering the opening degree of the bypass valve 23b may be started at the same time as starting the second compressor 18 by the start permission signal, or the bypass valve 23b may be started in a state where the rotation speed of the second compressor 18 is increasing. You may start the operation of lowering the opening degree of.

(Second Embodiment)
FIG. 5 shows a second embodiment of the present invention. Here, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

In the first embodiment, the compression unit 22 of the first compressor 12 is composed of one screw type compressor, whereas in the second embodiment, the compression unit 22 of the first compressor 12 has two screws. It is composed of a type compressor. That is, the compression unit 22 includes a first compression unit 22a and a second compression unit 22b.

Specifically, the storage tank connecting flow path 3 includes a main flow path 3a connected to the storage tank 1 and two branch flow paths 3b and 3c that branch from the downstream end of the main flow path 3a. One branch flow path 3b is provided with a first compression unit 22a made of a screw type compressor, and the other branch flow path 3c is provided with a second compression part 22b made of a screw type compressor. That is, the first compression unit 22a and the second compression unit 22b are connected in parallel to each other with respect to the storage tank connection flow path 3. In the present embodiment, the screw type compressor constituting the first compression unit 22a and the screw type compressor constituting the second compression unit 22b are compressors having the same compression capacity. However, the first compression unit 22a and the second compression unit 22b do not necessarily have to be compressors having the same compression capacity.

The demand destination connection flow path 14 includes two branch paths 14b and 14c and a combined flow path 14a where both branch paths 14b and 14c merge and connect to the demand destination. One branch path 14b is connected to the discharge section of the first compression section 22a, and the other branch path 14c is connected to the discharge section of the second compression section 22b. The gas discharged from the first compression unit 22a and the second compression unit 22b flows into the junction flow path 14a through the corresponding branch paths 14b and 14c.

The bypass means 23 includes two bypass flow paths 23a (first bypass flow path 23a1 and second bypass flow path 23a2) and two bypass valves 23b (first bypass valve 23b1 and) provided in the two bypass flow paths 23a. Second bypass valve 23b2) and the like.

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

A pressure detector 25 is provided in each of the branch paths 14b and 14c of the demand destination connection flow path 14, but one pressure detector 25 may be provided in the combined flow path 14a of the demand destination connection flow path 14. .. The on-off valves 31 and 32 are provided in the branch paths 14b and 14c, respectively. A check valve may be provided in place of the on-off valves 31 and 32, or together with the on-off valves 31 and 32.

In the second embodiment, the first drive control unit 27a is newly required by starting the second compressor 18 in the start preparation control (step ST13) in each of the first compression unit 22a and the second compression unit 22b. The gas processing amount is increased by half of the flow rate corresponding to the required flow rate of the target gas (step ST131). That is, the required flow rate is covered by both the first compression unit 22a and the second compression unit 22b, but when the second compressor 18 is started, the amount of gas processed by the first compression unit 22a and the second compression unit 22b increases. The minutes are the same, and the loads of the first compression unit 22a and the second compression unit 22b are the same.

In the start-up preparation control (step ST13), the bypass control unit 27c returns half of the newly required flow rate from the first bypass flow path 23a1 and the second bypass flow path 23a2 to the storage tank connection flow path 3, respectively. As described above, the opening degree of the first bypass valve 23b1 and the opening degree of the second bypass valve 23b2 are increased (step ST132). In the present embodiment, the opening degree of the first bypass valve 23b1 and the opening degree of the second bypass valve 23b2 are increased by the same opening degree.

Then, in the start control (step ST15), the bypass control unit 27c reduces the opening degree of the bypass valve 23b by the amount increased in step ST132 (step ST152). That is, the opening degree of the first bypass valve 23b1 and the opening degree of the second bypass valve 23b2 are reduced by the same opening degree.

According to the second embodiment, even when the compression unit 22 of the first compressor 12 is composed of two screw type compressors, appropriate start-up preparation control can be realized.

In the second embodiment, in the start-up preparation control, half of the newly required required flow rate is increased in the first compression unit 22a and the second compression unit 22b, but the configuration is limited to this. It is not something that can be done. For example, the first compression unit 22a may be made larger than the second compression unit 22b.

In this case, it is assumed that 80% of the flow rate of the gas supplied to the demand destination is covered by the first compression unit 22a and 20% is covered by the second compression unit 22b. That is, it is assumed that the processing amount A1 of the first compression unit 22a is 80% and the processing amount of the second compression unit 22b is 20%. In this case, assuming that the required flow rate B newly required by starting the second compressor 18 is 70% of the capacity of the first compressor 12, in the start preparation control, the capacity increase of the first compression unit 22a is performed. , B × A2 / (A1 + A2) = 0.7 × 0.2 × (0.8 + 0.2) = 0.14, and the capacity increase of the second compression unit 22b is B × A1 / (A1 + A2) = 0. It may be set to 0.7 × 0.8 × (0.8 + 0.2) = 0.56. That is, the gas processing amount may be increased 1.14 times for the first compression unit 22a, and the gas processing amount may be increased 1.56 times for the second compression unit 22b. That is, the increase in the gas processing amount is suppressed in the first compression unit 22a having a large gas processing amount, while the increase in the gas processing amount is further increased in the second compression unit 22b having a relatively small gas processing amount. At this time, the increase in the opening degree of the first bypass valve 23b1 is set to 0.7 × 0.2 × (0.8 + 0.2) = 0.14, which is 1.14 times the current opening degree. Further, the increase in the opening degree of the second bypass valve 23b2 is set to 0.7 × 0.8 × (0.8 + 0.2) = 0.56, which is 1.56 times the current opening degree. The opening degree of the first bypass valve 23b1 and the second bypass valve 23b2 is set according to the scale opening degree. As a result, when the operation is performed in a state where there is a difference in the gas processing amount between the first compression unit 22a and the second compression unit 22b, the difference in the load between the first compression unit 22a and the second compression unit 22b after the increase can be obtained. Can be reduced.

Although the description of other configurations, actions and effects will be omitted, the description of the first embodiment can be incorporated into the second embodiment.

(Other embodiments)
It should be noted that the embodiments disclosed this time are exemplary in all respects and are not considered to be restrictive. The present invention is not limited to the above-described embodiment, and various modifications and improvements can be made without departing from the spirit of the present invention. For example, as shown in FIG. 6, a screw compressor 50 including a screw-type compression unit 22, a bypass means 23, and a control unit 27 may be configured. Although the control unit 27 does not include the second drive control unit 27b for controlling the drive of the second compressor 18, the control unit 27 issues a command for starting the second compressor 18. It is possible to receive.

The compression unit 22 of the screw compressor 50 discharges gas to the demand destination connection flow path 14. Although not shown, the reliquefaction equipment connection flow path 16 is connected to the demand destination connection flow path 14 as in FIG. 1. While driving the compression unit 22 of the screw compressor 50, when the control unit 27 receives a command to start the second compressor 18 (not shown) provided in the reliquefaction equipment connection flow path 16, the control unit 27 receives a command. 27 executes the start preparation control. In the start-up preparation control, the control unit 27 (first drive control unit 27a) increases the processing amount of the compression unit 22 by the flow rate corresponding to the required flow rate of the target gas to be processed by the second compressor 18. Further, the control unit 27 (bypass control unit 27c) increases the opening degree of the bypass valve 23b so that the flow rate corresponding to the increased processing amount returns to the storage tank connection flow path 3. Then, when the opening degree of the bypass valve 23b falls within a predetermined range, the control unit 27 executes the start control. In the start control, the control unit 27 outputs a start permission signal for starting the second compressor 18, and the bypass control unit 27c reduces the opening degree of the bypass valve 23b by a predetermined opening degree.

In the above-described embodiment, in the start-up preparation control, the control method is such that the opening degree of the bypass valve 23b is increased in conjunction with the movement of the slide valve to the load side (or the increase in the rotation speed), but the control method is limited to this. Instead, various control methods may be adopted. For example, the control of the slide valve (or the control of the rotation speed) and the control of the bypass valve 23b may be performed independently based on the respective control amounts set based on the processing amount of the second compressor 16.

In the above embodiment, a temperature detector (not shown) is provided in the demand destination connection flow path 14, the bypass valve 23b is controlled based on the temperature detected by the temperature detector, and the capacity is adjusted or the rotation speed is adjusted by the slide valve. Adjustments may be made. The control based on the detected temperature is performed by lubricating, injecting water, injecting a liquid in which the target gas is liquefied, or the like into the compression unit 22 of the first compressor 12.

1: Storage tank 3: Storage tank connection flow path 5: Reliquefaction equipment 10: Compressor unit 12: First compressor 12a: Adjustment means 14: Demand destination connection flow path 16: Reliquefaction equipment connection flow path 18: Second compressor 22: Compression unit 22a: First compression unit 22b: Second compression unit 23: Bypass means 23a: Bypass flow path 23a1: First bypass flow path 23a2: Second bypass flow path 23b: Bypass valve 23b1: First bypass valve 23b2 : Second bypass valve 27: Control unit 50: Screw compressor ST11: Drive step ST13: Start preparation step ST15: Start step

Claims (6)

A compressor unit installed in a ship that recovers a target gas, which is a boil-off gas of liquefied gas, from a storage tank provided in the ship and supplies at least a part of the target gas to a demand destination.
The first compressor that sucks the target gas from the storage tank through the storage tank connection flow path, and
A demand destination connection flow path that connects the first compressor to the demand destination,
The reliquefaction equipment connection flow path that branches from the demand destination connection flow path and connects to the reliquefaction equipment.
A reciprocating second compressor provided on the reliquefaction equipment connection flow path and further compressing the target gas before flowing into the reliquefaction equipment.
A control unit that controls the first compressor and the second compressor,
Equipped with
The first compressor is connected to the storage tank connection flow path to compress the target gas, and at least a part of the target gas is transferred from the demand destination connection flow path to the storage tank connection flow path. Equipped with a bypass means to return,
The bypass means includes a bypass flow path connecting the demand destination connection flow path and the storage tank connection flow path, and a bypass valve provided in the bypass flow path.
The control unit
When the second compressor is started while the compression unit is being driven,
The processing amount of the compression unit is increased by the flow rate corresponding to the required flow rate of the target gas to be processed by the second compressor by the operation of the second compressor, and the processing amount corresponding to the increased processing amount is increased. Executes start-up preparation control to increase the opening degree of the bypass valve so that the gas returns to the storage tank connection flow path.
After the execution of the start preparation control, the second compressor is started, and the start control is configured to reduce the opening degree of the bypass valve increased by the start preparation control by a predetermined opening degree. , Compressor unit. The compression unit of the first compressor is composed of two screw type compressors arranged in parallel with each other.
The bypass means has one bypass flow path for returning the target gas discharged from the two screw compressors from the demand destination connection flow path to the storage tank connection flow path and one for each of the two bypass flow paths. Including two bypass valves provided
The control unit
In the start preparation control,
The processing amount of each of the two screw compressors is increased by half of the flow rate corresponding to the required flow rate, and half of the flow rate corresponding to the increased processing amount is generated from each of the two bypass flow paths. The compressor unit according to claim 1, wherein the opening degree of each of the two bypass valves is increased so as to return to the storage tank connection flow path. The compression unit of the first compressor is composed of two screw type compressors arranged in parallel with each other.
The first bypass flow path in which the bypass means returns the target gas discharged from one of the two screw type compressors from the demand destination connection flow path to the storage tank connection flow path, and The target gas discharged from the first bypass valve provided in the first bypass flow path and the other screw type compressor of the two screw type compressors is sent from the demand destination connection flow path to the storage tank connection flow path. Includes a second bypass flow path back to and a second bypass valve provided in the second bypass flow path.
Assuming that the processing amount of the one screw type compressor is A1, the processing amount of the other screw type compressor is A2, and the flow rate corresponding to the required flow rate is B.
The control unit
In the start preparation control,
The processing amount of the one screw compressor is increased by the flow rate obtained by B × A2 / (A1 + A2), and the flow rate obtained by B × A2 / (A1 + A2) is the flow rate obtained from the first bypass flow path to the storage tank connection flow. Increase the opening of the first bypass valve so that it returns to the road.
The processing amount of the other screw compressor is increased by the flow rate obtained by B × A1 / (A1 + A2), and the flow rate obtained by B × A1 / (A1 + A2) is the flow rate connected to the storage tank from the second bypass flow path. The compressor unit according to claim 1, wherein the opening degree of the second bypass valve is increased so as to return to the road. The first compressor
The invention according to any one of claims 1 to 3, further comprising a means for adjusting the rotation speed of the compression unit or a means for adjusting the capacity of the compression unit, which can increase the processing amount of the compression unit in the start-up preparation control. Compressor unit. A screw compressor that sucks in the target gas, which is a boil-off gas of liquefied gas, from a storage tank provided on a ship through the storage tank connection flow path and discharges it to the demand destination connection flow path.
A screw-type compression unit that is connected to the storage tank connection flow path and compresses the target gas,
A bypass flow path connecting the demand destination connection flow path and the storage tank connection flow path, and a bypass valve provided in the bypass flow path are included, and the target is from the demand destination connection flow path to the storage tank connection flow path. Bypass means to return at least part of the gas,
With a control unit,
The control unit
While driving the compression unit, when a command is received to start the second compressor provided in the reliquefaction facility connection flow path that branches from the demand destination connection flow path and is connected to the reliquefaction facility, the second compression is performed. The processing amount of the compression unit is increased by the flow rate corresponding to the required flow rate of the target gas to be processed by the second compressor due to the operation of the machine, and the flow rate corresponding to the increased processing amount is connected to the storage tank. The start preparation control for increasing the opening degree of the bypass valve so as to return to the flow path is executed, and the start preparation control is executed.
After the execution of the start preparation control, a start permission signal for starting the second compressor is output, and a start control for reducing the opening degree of the bypass valve increased by the start preparation control by a predetermined opening degree is executed. A screw compressor that is configured to. It is a method of operating a compressor unit that recovers the target gas, which is a boil-off gas of liquefied gas, from a storage tank provided in a ship and supplies at least a part of it to a demand destination.
The compressor unit is branched from the first compressor that sucks the target gas from the storage tank through the storage tank connection flow path and discharges the target gas to the demand destination connection flow path, and branches from the demand destination connection flow path. It is equipped with a reciprocating type second compressor installed in the reliquefaction equipment connection flow path connected to the liquefaction equipment.
A screw-type compression unit in which the first compressor is connected to the storage tank connection flow path to compress the target gas, a bypass flow path connecting the demand destination connection flow path and the storage tank connection flow path, and the like. It has a bypass valve provided in the bypass flow path, and has
The above-mentioned operation method includes
A drive step for driving the compression unit of the first compressor,
When the second compressor is started while the compression unit is being driven, the compression unit has a flow rate corresponding to the required flow rate of the target gas to be processed by the second compressor due to the operation of the second compressor. A start-up preparation step in which the opening degree of the bypass valve is increased so that the processing amount is increased and the flow rate corresponding to the increased processing amount returns to the storage tank connection flow path.
The operation of the compressor unit includes, after the start-up preparation step, a start-up step of starting the second compressor and reducing the opening degree of the bypass valve increased in the start-up preparation step by a predetermined opening degree. Method.

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