JP6922113B1 - Compressor unit, compressor unit control program and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately meet a demand of a demand destination. A compressor unit 2 has a screw compressor 21 to which a slide valve 22 is attached, and a control unit 28. The control unit 28 has a control unit and a data storage unit. The data storage unit is set according to the load of the demand destination, and shows the first characteristic data indicating the relationship between the engine load and the pressure, the total required flow rate of the demand destination, and the screw with respect to the total required flow rate. Second characteristic data showing the relationship with the pressure of the target gas required in the discharge side flow path of the compressor is stored. The control unit derives the first comparison target pressure from the first characteristic data and the second comparison target pressure from the second characteristic data based on the requested flow rate from the demand destination, and derives the second comparison target pressure from the first comparison target pressure. The larger one of the target pressures is set as the set pressure, and the screw compressor is controlled so as to have the set pressure. [Selection diagram] Fig. 1

Description

The present invention relates to a compressor unit, a control program for the compressor unit, and a control method.

In a liquefied natural gas (LNG) carrier or the like, boil-off gas (BOG) generated in an LNG storage tank that stores the LNG is supplied to the engine of the ship as fuel (Patent Document 1). In the technique disclosed in Patent Document 1, the BOG is compressed by a screw compressor and then supplied to the engine.

Patent Document 2 is provided so as to bypass the slide valve of the screw compressor and the screw compressor so that the pressure of the gas supplied to the demand destination becomes constant in the compression of the gas using the screw compressor. A technique for controlling a bypass valve of a bypass pipe is disclosed.

Japanese Unexamined Patent Publication No. 2006-348752 Japanese Unexamined Patent Publication No. 2-294592

By the way, in an LNG carrier, a demand destination such as a generator may require gas (BOG) in addition to the engine. Therefore, in the screw compressor, it is necessary to control the discharge pressure in consideration of the total amount of gas consumed by all the demand destinations. Further, the load of the engine may fluctuate, and the pressure of the gas required by the engine also fluctuates according to the fluctuation of the load. Therefore, the screw compressor also needs to control the discharge pressure according to the engine load.

In the technique disclosed in Patent Document 2, the slide valve and the bypass valve are only controlled so that the discharge pressure becomes constant, so that the discharge pressure change request according to the load fluctuation of the demand destination can be dealt with. Can not.

The present invention has been made in view of the above circumstances, and an object of the present invention is to realize discharge pressure control of a screw compressor that appropriately meets the demands of demand destinations.

The compressor unit according to one aspect of the present invention is installed in a ship, compresses a target gas which is a boil-off gas sucked from an LNG storage tank of the ship, and supplies the target gas to a demand destination including an engine and a generator. The compressor unit according to this embodiment includes a screw compressor, a flow rate sensor, a data storage unit, and a control unit. The screw compressor compresses the target gas and supplies it to a demand destination. The flow rate sensor is provided in the discharge side flow path of the screw compressor to acquire the flow rate of the gas supplied to the demand destination. The data storage unit stores characteristic data. The control unit controls the pressure of the target gas discharged from the screw compressor.

Here, in the compressor unit according to this aspect, the characteristic data includes the first characteristic data and the second characteristic data. The first characteristic data is characteristic data showing the relationship between the load and pressure of the engine. The second characteristic data is characteristic data showing the relationship between the total required flow rate of the demand destination and the pressure of the target gas required in the discharge side flow path of the screw compressor with respect to the total required flow rate. be.

The control unit derives the first comparison target pressure from the first characteristic data based on the load information obtained from the engine, and the second from the second characteristic data based on the total required flow rate obtained from the flow sensor. Derivation of the pressure to be compared. Further, the control unit sets the larger of the first comparison target pressure and the second comparison target pressure as the set pressure, and controls the screw compressor so as to be the set pressure.

In the compressor unit according to the above aspect, the first comparison target pressure derived from the first characteristic data corresponding to the required flow rate of the engine and the second comparison target pressure derived from the second characteristic data with respect to the total required flow rate. Whichever is larger is set as the set pressure, and the discharge pressure of the screw compressor is controlled. As a result, the flow rate of gas required by the entire demand destination can be secured, and the flow rate of gas required by the engine can be satisfied even if the load of the engine fluctuates. In addition, the effect of reducing power can be obtained as compared with the case of controlling so as to always maintain a high constant discharge pressure.

In the compressor unit according to the above aspect, the first characteristic data may include a proportional portion in which the pressure linearly increases with respect to the load. Further, in the compressor unit according to the above aspect, the second characteristic data may include a proportional portion in which the pressure of the target gas linearly increases with respect to the total required flow rate of the demand destination.

In the compressor unit according to the above aspect, since the first characteristic data and the second characteristic data have a linear relationship (relationship of a linear function), the first comparison target pressure and the second comparison target pressure are set respectively. It can be easily derived.

In the compressor unit according to the above aspect, the number of the engines may be two or more. Further, in the compressor unit according to the above aspect, the control unit may derive the first comparison target pressure from the first characteristic data based on the largest load among the load information obtained from the engine.

In the compressor unit according to the above aspect, the pressure required for the engine is required even when a plurality of engines are provided by deriving the first comparison target pressure from the first characteristic data according to the engine having the largest load. Gas can be supplied.

In the compressor unit according to the above aspect, a bypass flow path connecting the suction side flow path and the discharge side flow path so as to bypass the screw compressor, and an opening degree adjustable spill provided on the bypass flow path. A spill back portion having a back valve may be further provided. Further, in the compressor unit according to the above aspect, the screw compressor may include a slide valve for adjusting the processing amount of the target gas. Further, the control unit is configured to control the opening degree of the slide valve and the spillback valve based on the first characteristic data and the second characteristic data stored in the data storage unit. May control the flow rate of the target gas discharged from the screw compressor.

In the compressor unit according to the above aspect, the pressure and the flow rate can be appropriately controlled by using the spillback valve together with the slide valve.

The compressor unit according to the above aspect may further include a spillback unit, an electric motor, and an inverter. The spillback portion includes a bypass flow path that connects a suction side flow path and a discharge side flow path so as to bypass the screw compressor, and a spill back valve that is provided on the bypass flow path and has an adjustable opening degree. May have. The electric motor may drive the screw compressor. The inverter may adjust the rotation speed of the motor.

Further, the control unit is configured to control the rotation speed of the motor and the opening degree of the spillback valve based on the first characteristic data and the second characteristic data stored in the data storage unit. Thereby, the flow rate of the target gas discharged from the screw compressor may be controlled.

In the compressor unit according to the above aspect, the pressure and the flow rate can be appropriately controlled by using the rotation speed control of the motor using the inverter and the spillback valve in combination.

The control program according to one aspect of the present invention is a screw compressor installed in a ship, compresses a target gas which is a boil-off gas sucked from an LNG storage tank of the ship, and supplies it to a demand destination including an engine and a generator. It is a program that causes a computer to control the compressor unit including it. The control program according to this aspect includes a reception step and a control step. The reception step is a step of receiving the load information of the engine and the total requested flow rate of the demand destination. The control step is a step of controlling the discharge pressure of the target gas discharged from the screw compressor based on the characteristic data.

Here, in the control program according to this aspect, the characteristic data used in the control step includes a first characteristic data and a second characteristic data. The first characteristic data is characteristic data showing the relationship between the load and pressure of the engine. The second characteristic data is characteristic data showing the relationship between the total required flow rate of the demand destination and the pressure of the target gas required in the discharge side flow path of the screw compressor with respect to the total required flow rate. be.

In the control step, the first comparison target pressure is derived from the first characteristic data based on the load information obtained from the engine, and the second characteristic data is derived from the second characteristic data based on the total required flow rate obtained from the flow sensor. Derivation of the pressure to be compared. Further, in the control step, the larger of the first comparison target pressure and the second comparison target pressure is set as the set pressure, and the screw compressor is controlled so as to be the set pressure.

In the control program according to the above aspect, either the first comparison target pressure derived from the first characteristic data corresponding to the required flow rate of the engine or the second comparison target pressure derived from the second characteristic data with respect to the total required flow rate. The larger one is set as the set pressure, and the discharge pressure of the screw compressor is controlled. As a result, the flow rate of gas required by the entire demand destination can be secured, and the appropriate gas pressure according to the load of the engine can be satisfied, and the effect of reducing the power in the compressor unit can be obtained.

The control method according to one aspect of the present invention is a screw compressor installed in a ship, compressing a target gas which is a boil-off gas sucked from an LNG storage tank of the ship, and supplying it to a demand destination including an engine and a generator. It is a method of controlling the compressor unit including. The control method according to this aspect includes a reception step and a control step. The reception step is a step of receiving the load information of the engine and the required flow rate of the demand destination. The control step is a step of controlling the discharge pressure of the target gas discharged from the screw compressor based on the characteristic data.

Here, in the control method according to this aspect, the characteristic data used in the control step includes a first characteristic data and a second characteristic data. The first characteristic data is characteristic data showing the relationship between the load and pressure of the engine. The second characteristic data is characteristic data showing the relationship between the total required flow rate of the demand destination and the pressure of the target gas required in the discharge side flow path of the screw compressor with respect to the total required flow rate. be.

In the control step, the first comparison target pressure is derived from the first characteristic data based on the load information obtained from the engine, and the second characteristic data is derived from the second characteristic data based on the total required flow rate obtained from the flow sensor. Derivation of the pressure to be compared. Further, in the control step, the larger of the first comparison target pressure and the second comparison target pressure is set as the set pressure, and the screw compressor is controlled so as to be the set pressure.

In the control method according to the above aspect, either the first comparison target pressure derived from the first characteristic data corresponding to the required flow rate of the engine or the second comparison target pressure derived from the second characteristic data with respect to the total required flow rate. The larger one is set as the set pressure, and the discharge pressure of the screw compressor is controlled. As a result, the flow rate of gas required by the entire demand destination can be secured, and the appropriate gas pressure according to the load of the engine can be satisfied, and the effect of reducing the power in the compressor unit can be obtained.

In each of the above aspects, it is possible to realize the discharge pressure control of the screw compressor that appropriately meets the demands of the demand destination.

It is a figure which shows the structure of the compressor unit which concerns on 1st Embodiment. It is a block diagram which shows the partial structure of the control device in a compressor unit. It is a figure which illustrates the 1st characteristic data which shows the relationship between the load and pressure of an engine. It is a figure which illustrates the 2nd characteristic data which shows the relationship between the discharge pressure and the total required flow rate. It is a flowchart of discharge pressure control. It is a figure which shows the relationship between the 1st characteristic data and the 2nd characteristic data. It is a figure which shows the partial structure of the compressor unit which concerns on 2nd Embodiment. It is a figure which shows another example of a compressor unit.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The forms described below exemplify the configuration and actions / effects of the present invention, and the present invention is not limited to any of the following forms except for its essential configuration.

[First Embodiment]
1. 1. Configuration of Compressor Unit 2 The configuration of the compressor unit 2 according to the first embodiment will be described with reference to FIG.

As shown in FIG. 1, the compressor unit 2 according to the present embodiment is installed in the ship 1. In addition to the compressor unit 2, the ship 1 includes a demand destination 3 and an LNG storage tank 4. The compressor unit 2 includes a screw compressor 21, gas flow paths 23 and 24, a flow rate sensor 29, and a control unit 28. The screw compressor 21 includes a slide valve 22 and a spill back portion 25. The slide valve 22 is attached to the screw compressor 21, and adjusts the flow rate of the BOG (boil-off gas, hereinafter simply referred to as “gas”) discharged from the screw compressor 21 to the gas flow path 24. It is a valve for. The spillback portion 25 has a bypass flow path 26 and a spillback valve 27. The bypass flow path 26 connects the gas flow path 23 on the suction side and the gas flow path 2424 on the discharge side so as to bypass the screw compressor 21. The spillback valve 27 is provided in the bypass flow path 26, and is a valve that adjusts the flow rate of the gas returned from the gas flow path 24 to the gas flow path 23 through the bypass flow path 26. The flow rate sensor 29 is provided in the discharge-side flow path 24 of the screw compressor 21 (hereinafter, referred to as “discharge-side flow path 24”), and acquires the flow rate of the gas before it is supplied to the demand destination 3. In FIG. 1, the flow rate sensor 29 is located on the upstream side of the bypass flow path 26.

The demand destination 3 is composed of an engine 31 and a generator 35 for propelling the ship 1. Vessel 1 is provided with a demand destination control device 36. A plurality of engines 31 and a plurality of generators 35 may be provided.

A branch portion 32 is provided in the discharge side flow path 24. The branch portion 32 has a branch flow path 33 connected to the generator 35 and a switching valve 34 provided in the branch flow path 33. When the switching valve 34 is in the open state, the gas discharged from the screw compressor 21 is supplied to both the engine 31 and the generator 35. On the other hand, when the switching valve 34 is closed, the gas discharged from the screw compressor 21 is supplied only to the engine 31. The demand destination control device 36 executes opening / closing control of the switching valve 34. Further, the demand destination control device 36 transmits the load information of the engine 31 to the control unit 28 of the compressor unit 2. The load information is, for example, the flow rate or load ratio of the gas consumed by the engine 31, but in the present embodiment, it will be described as the gas flow rate (hereinafter, referred to as “engine required flow rate”). Further, in the following description, the term "flow rate" means "mass flow rate" unless otherwise specified.

The LNG storage tank 4 stores LNG inside. The gas flow path 23 is connected to the upper part of the LNG storage tank 4. The gas (BOG) generated in the LNG storage tank 4 is supplied to the screw compressor 21 through the gas flow path 23.

2. Configuration of Control Unit 28 The configuration of the control unit 28 in the compressor unit 2 will be described with reference to FIG. The control unit 28 of the compressor unit 2 according to the present embodiment includes a discharge pressure control unit 281, a data storage unit 282, and a comparison unit 283. The control unit 28 may be integrated with the demand destination control device 36. The discharge pressure control unit 281 is composed of a microprocessor including an MPU / CPU, an ASIC, a ROM, a RAM, and the like. The ROM stores a control program for executing the control of the compressor unit 2. The data storage unit 282 is composed of a storage medium such as a ROM, and stores characteristic data described later. Then, the comparison unit 283 calculates the discharge pressure according to the load condition of the demand destination 3 and transmits it to the discharge pressure control unit 281. The arithmetic processing performed by the comparison unit 283 will be described later.

The discharge pressure control unit 281 controls the opening degree of the slide valve 22 and the spillback valve 27 based on the discharge pressure calculated by the comparison unit 283. The discharge pressure control unit 281 controls the slide valve 22 and the spillback valve 27 by executing the control program stored in the ROM. When the screw compressor 21 is driven, when the discharge pressure, that is, the pressure in the discharge side flow path 24 is stable, the discharge pressure control unit 281 opens the spillback valve 27 by a predetermined opening degree (for example, 5% to 15%). It is maintained at a predetermined opening) in the range of%. As a result, when it becomes necessary to reduce the discharge pressure, the opening degree of the spillback valve 27 is increased. When it becomes necessary to increase the discharge pressure, the opening degree of the spillback valve 27 is decreased. The spillback valve 27 is fully opened before the start of driving the screw compressor 21, which makes it possible to reduce the load at the start of driving the screw compressor 21.

The data storage unit 282 according to the present embodiment includes a first data storage unit 282a and a second data storage unit 282b. The characteristic data stored in the first and second data storage units 282a and 282b will be described below.

3. 3. First characteristic data stored in the first data storage unit 282a The first characteristic data stored in the first data storage unit 282a in the data storage unit 282 will be described with reference to FIG. In the first characteristic data 911, the vertical axis shows the engine required flow rate (that is, the load of the engine 31), and the horizontal axis shows the gas pressure corresponding to the engine required flow rate. In the first characteristic data 911, it is set linearly from the lower limit point PT1, that is, only in the proportional portion LN10 in which the rate of change of the engine required flow rate has a constant linear function relationship. The pressure of the gas with respect to the required flow rate of the engine is determined based on the proportional portion LN10.

4. Second characteristic data stored in the second data storage unit 282b The second characteristic data 915 stored in the second data storage unit 282b will be described with reference to FIG. In the second characteristic data 915, the vertical axis is the required flow rate of gas from the engine 31 and the generator 35, that is, all the demand destinations to which the gas is supplied from the screw compressor 21, and the gas flow path 24 passes through the bypass flow path 26. The sum of the flow rates of the gas returned from the gas flow path 23 to the gas flow path 23 (hereinafter, referred to as “total required flow rate”) is shown. The discharge pressure of the screw compressor 21 is shown on the horizontal axis of the second characteristic data 915. The total required flow rate is set linearly from the point PT10 to the point PT3 in FIG. 4, that is, only in the proportional portion LN11 in which the rate of change of the total required flow rate has a constant linear function relationship. The discharge pressure of the screw compressor 21 with respect to the total required flow rate is determined based on the proportional portion LN11.

In the present embodiment, the inclination of the proportional portion LN 11 is smaller than the inclination of each proportional portion LN 10 shown in FIG. That is, the rate of change of the total required flow rate in the proportional part LN11 is smaller than the rate of change of the engine required flow rate in the proportional part LN10 of FIG. However, the relationship between the inclination of the proportional portion LN11 and the inclination of the LN10 is not limited to the above.

5. Setting method and pressure control method of set pressure Pset executed by comparison unit 283 (control when the compressor unit 2 is driven)
When the compressor unit 2 is driven, as shown in FIG. 5, the first characteristic data 911 and the second characteristic data 915 are read (step S10). Next, the control unit 28 acquires the load information (engine required flow rate) of the engine 31 from the demand destination control device 36. Further, the flow rate of the gas before being supplied to the demand destination 3 (engine 31 and generator 35) is acquired based on the flow rate sensor 29 of FIG. 1 (step S11). That is, the control method and the control program according to the present embodiment include a reception step for receiving the load information of the engine and the requested flow rate of the demand destination. Here, the flow rate of the gas acquired by the flow rate sensor 29 is the flow rate of the gas consumed by the demand destination 3 and the flow rate of the gas returned from the gas flow path 24 to the gas flow path 23 through the bypass flow path 26. It shows the sum and can be regarded as the total required flow rate described above. However, the total required flow rate may be the data obtained directly from the flow rate sensor 29 after the necessary calculation processing (for example, temperature correction or conversion from volume flow rate to mass flow rate) has been performed. ..

Next, the comparison unit 283 derives the first comparison target pressure P1 corresponding to the engine required flow rate based on the first characteristic data 911 (step S12). Further, the comparison unit 283 derives the second comparison target pressure P2 corresponding to the total required flow rate based on the second characteristic data 915 (step S13). Note that step S12 may be performed after or at the same time as step S13.

The comparison unit 283 compares the magnitude of the first comparison target pressure P1 and the second comparison target pressure P2 (step S14). When it is determined that the first comparison target pressure P1 is equal to or higher than the second comparison target pressure P2 (step S14: Yes), the first comparison target pressure P1 is set to the set pressure Pset (step S15).

Here, an example of steps S12 to S15 will be described with reference to FIG. FIG. 6 is a diagram showing the first characteristic data 911 of FIG. 3 and the second characteristic data 915 of FIG. 4 in an overlapping manner.

The comparison unit 283 derives the first comparison target pressure P41 at the point PT11 from the engine required flow rate F11 based on the first characteristic data 911 (proportional unit LN10) (step S12). Further, based on the second characteristic data 915 (proportional part LN11), the second comparison target pressure P42 at the point PT12 is derived from the total required flow rate F12 (step S13).

The magnitude of the first comparison target pressure P41 and the second comparison target pressure P42 are compared (step S14). It can be seen that the first comparison target pressure P41 is larger. That is, it is determined that the flow rate of the gas discharged from the screw compressor 21 at the time of step S14 does not satisfy the required flow rate of the engine 31. Therefore, the first comparison target pressure P41 is set to the set pressure Pset (step S15). Then, the information regarding the set pressure Pset is transmitted to the discharge pressure control unit 281 (step S16). The discharge pressure control unit 281 controls the opening degree of the slide valve 22 and the spillback valve 27 so as to obtain the set pressure Pset (step S17). That is, in the control method and control program according to the present embodiment, the target gas discharged from the screw compressor 21 is based on the required flow rate from the demand destination and the first characteristic data 911 and the second characteristic data 915. A control step is included to control the discharge pressure.

Here, in general, the spillback valve 27 operates faster than the slide valve 22. Therefore, for example, when trying to reduce the pressure in the gas flow path 24 on the discharge side of the screw compressor 21, the opening degree of the spillback valve 27 is increased to move the target gas to the suction side of the screw compressor 21. By returning, the pressure is quickly reduced to the set pressure Pset. During that time, the slide valve 22 can be moved to the unload side to reduce the flow rate of the target gas discharged from the screw compressor 21. As the slide valve 22 moves to the unload side, the spillback valve 27 is returned to the original opening state.

When trying to increase the pressure in the gas flow path 24 on the discharge side of the screw compressor 21, the spillback valve 27 is closed to quickly raise the pressure, and the slide valve 22 is moved to the load side during that time. The supply flow rate from the screw compressor 21 can be increased. As the slide valve 22 moves to the load side, the spillback valve 27 is returned to the original opening state.

By the way, in step S14 of FIG. 5, when the comparison unit 283 determines that the second comparison target pressure P2 is larger than the first comparison target pressure P1 (step S14: No), the second comparison target pressure P2 is set. The set pressure is set to Pset (step S17).

In this case, to explain using the example shown in FIG. 6, the comparison unit 283 derives the first comparison target pressure P51 at the point PT13 from the required flow rate F13 based on the first characteristic data 911 (proportional unit LN10) (step S12). ). Further, based on the second characteristic data 915 (proportional part LN11), the second comparison target pressure P52 at the point PT14 is derived from the total required flow rate F14 (step S13).

Comparing the magnitudes of the first comparison target pressure P51 and the second comparison target pressure P52 (step S14), it can be seen that the second comparison target pressure P52 is larger. That is, since it is determined that the flow rate of the gas discharged from the screw compressor 21 at the time of step S14 satisfies the required flow rate of the engine 31, the second comparison target pressure P52 is set to the set pressure Pset (that is,). , Maintaining the status quo) (step S18). Then, the information regarding the set pressure Pset is transmitted to the discharge pressure control unit 281 (step S16). The discharge pressure control unit 281 controls the opening degree of the slide valve 22 and the spillback valve 27 so as to obtain the set pressure Pset (step S17).

In the compressor unit 2, the set pressure Pset is always derived based on the flow of FIG. 5 (steps S10 to S18), and the discharge pressure control unit 281 repeatedly controls the opening degrees of the slide valve 22 and the spillback valve 27. It will be.

6. Effect In the compressor unit 2 according to the present embodiment, the first comparison target pressure P41 derived from the first characteristic data 911 corresponding to the required flow rate of the engine 31 and the second characteristic data 915 derived from the total required flow rate. The larger of the second comparison target pressure P42 to be obtained is output to the discharge pressure control unit 281 as the set pressure, and the discharge pressure of the screw compressor 21 is controlled. As a result, the gas flow rate required by the entire demand destination (that is, the engine 31 and the generator 35) can be secured, and the gas flow rate required by the engine 31 can be satisfied even if the load of the engine 31 fluctuates. Can be done. In this way, the compressor unit 2 can realize the discharge pressure control of the screw compressor that appropriately meets the demand for gas at the demand destination. In addition, the effect of reducing power can be obtained as compared with the case of controlling so as to always maintain a high constant discharge pressure.

[Modification example]
The compressor unit 2 may be used for a ship having two or more engines 31. In this case, the control unit 28 acquires the load information of each engine 31 from the demand destination control device 36. Then, the comparison unit 283 derives the first comparison target pressure P1 from the first characteristic data 911 based on the largest load information among the load information obtained from the engine 31. In this way, by deriving the first comparison target pressure P1 according to the engine 31 having the largest load, the gas having the required pressure can be supplied to all the engines 31.

[Second Embodiment]
The configuration of the compressor unit 2 according to the second embodiment of the present invention will be described with reference to FIG. 7. In the compressor unit 2 according to the present embodiment, the electric motor 51 is connected to the screw compressor 21. The screw compressor 21 is driven by transmitting the rotational force of the motor 51. An inverter 52 is connected to the motor 51. The rotation speed of the motor 51 is controlled by a signal from the inverter 52 based on a command from the control unit 28. In the compressor unit 2, the flow rate of the target gas discharged from the screw compressor 21 can be controlled by controlling the rotation speed of the screw compressor 21.

Although detailed description of the gas discharge pressure control to the demand destination 3 executed by the discharge pressure control unit 281 (see FIG. 2) in the compressor unit 2 according to the present embodiment is omitted, the control target in step S17 of FIG. 5 is omitted. Is characterized by the number of revolutions of the motor 51 and the spillback valve 27. More specifically, the rotation speed of the screw compressor 21 is controlled by the inverter 52 with the spillback valve 27 closed. Further, when the pressure control of the screw compressor 21 is required beyond the range of the rotation speed that can be adjusted by the inverter 52, the pressure control is performed by adjusting the opening degree of the spillback valve 27.

The compressor unit 2 according to the present embodiment has the same configuration as that of the first embodiment except that the screw compressor 21 is driven by the motor 51 to which the inverter 52 is connected. Further, the control program executed by the discharge pressure control unit 281 has the same basic configuration. Therefore, this embodiment can also have the same effect as that of the first embodiment.

It should be understood that the embodiments disclosed this time are exemplary in all respects and are not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims. Therefore, the following embodiments are also included in the scope of the present invention.

As shown in FIG. 8, in the above embodiment, the flow rate sensor 29 is on the downstream side of the bypass flow path 26 of FIG. 1, more accurately, on the downstream side of the bypass flow path 26, and the branch flow path 33. It may be located upstream of. Even in this case, the gas returned from the gas flow path 24 to the gas flow path 23 through the bypass flow path 26 based on the opening degree of the spillback valve 27, the suction pressure and the discharge pressure of the screw compressor 21. It is possible to calculate the flow rate.

In the above embodiment, instead of the flow rate sensor 29, another flow rate sensor provided in a portion of the gas flow path 24 on the discharge side of the screw compressor 21 connected to the engine 31 and a portion connected to the generator 35 is provided. It may be used. That is, a flow rate sensor may be provided in the flow path portion connected to each demand destination. In this case, the flow rate of the gas returned from the gas flow path 24 to the gas flow path 23 through the bypass flow path 26 may be calculated as described above, or the flow rate sensor may be provided in the bypass flow path 26. It may be obtained from the flow sensor. The total required flow rate can be obtained based on the total flow rate of the gas acquired by each flow rate sensor.

Further, in the above embodiment, when the total consumption of each demand destination can be regarded as substantially equal to the flow rate of the gas discharged from the screw compressor 21, the gas passes through the bypass flow path 26 in the calculation of the total required flow rate. It is not necessary to add the flow rate of the gas returned from the flow path 24 to the gas flow path 23.

In the above embodiment, a configuration including one screw compressor 21 is adopted as an example, but the present invention is not limited thereto. For example, a form in which two or more screw compressors are connected in series or in parallel can be adopted.

In the ship 1 to which each compressor unit 2 according to the above embodiment is applied, a configuration is adopted in which the engine 31 and the generator 35 are provided in the demand destination 3 to which the BOG is supplied. It is not limited. For example, GCU (Gas Combustion Unit) and reliquefaction equipment may be added as demand destinations.

In the above embodiment, the method of comparing the first comparison target pressure P1 and the second comparison target pressure P2 and setting the larger pressure to the set pressure of the screw compressor 21 is limited to a predetermined discharge pressure range. May be carried out. Outside the above range, the discharge pressure of the screw compressor 21 may be set based only on the first characteristic data 911.

In the above embodiment, the control program for causing the computer to control the compressor unit 2 is stored in the ROM of the discharge pressure control unit 281. However, the present invention is not limited to this. No. For example, the control program may be stored in a computer-readable storage medium such as a flexible disk, a hard disk, an optical disk, or a semiconductor memory. Then, the discharge pressure control unit 281 may be configured to be accessible to these storage media.

In the above embodiment, the proportional parts of the first characteristic data 911 and the second characteristic data 915 are not necessarily limited to those that change linearly, but those that change intermittently, a multiple-order function, an exponential function, and the like. It is also possible to have a logarithmic function relationship.

In the above embodiment, a configuration in which the comparison unit 283 is omitted is adopted as the configuration of the control unit 281, and a user such as a crew member can use the first characteristic data 911 and the second characteristic data 911 and the second according to the ship 1 on which the compressor unit 2 is mounted. The set pressure Pset may be set using the characteristic data 915, and a command may be sent to the compressor unit 2.

1 Ship 2 Compressor unit 3 Demand destination 4 LNG storage tank 21 Screw compressor 22 Slide valve 25 Spillback unit 26 Bypass flow path 27 Spillback valve 28 Control unit 51 Motor 52 Inverter 281 Discharge pressure control unit 282 Data storage unit 283 Comparison unit 911 1st characteristic data 915 2nd characteristic data LN10 1st proportional part LN11 2nd proportional part

Claims (7)

A compressor unit installed inside a ship that compresses the target gas, which is the boil-off gas sucked from the LNG storage tank of the ship, and supplies it to customers including the engine and generator.
A screw compressor that compresses the target gas and supplies it to the demand destination,
A flow rate sensor provided in the discharge side flow path of the screw compressor to acquire the flow rate of the gas supplied to the demand destination, and
A data storage unit that stores characteristic data and
A control unit that controls the pressure of the target gas discharged from the screw compressor, and
With
The characteristic data is
First characteristic data showing the relationship between the engine load and pressure,
Second characteristic data showing the relationship between the total required flow rate of the demand destination and the pressure of the target gas required in the discharge side flow path of the screw compressor with respect to the total required flow rate.
Including
The control unit derives the first comparison target pressure from the first characteristic data based on the load information obtained from the engine, and the second from the second characteristic data based on the total required flow rate obtained from the flow sensor. Derived the pressure to be compared,
A compressor unit that sets the larger of the first comparison target pressure and the second comparison target pressure as a set pressure, and controls the screw compressor so as to have the set pressure. The first characteristic data includes a proportional part in which the pressure increases linearly with respect to the load.
The compressor unit according to claim 1, wherein the second characteristic data includes a proportional portion in which the pressure of the target gas increases linearly with respect to the total required flow rate of the demand destination. The number of the engines is 2 or more,
The compressor unit according to claim 1 or 2, wherein the control unit derives a first comparison target pressure from the first characteristic data based on the largest load among the load information obtained from the engine. A spillback portion having a bypass flow path connecting the suction side flow path and the discharge side flow path so as to bypass the screw compressor, and a spillback valve having an adjustable opening degree provided on the bypass flow path. Further prepare
The screw compressor includes a slide valve for adjusting the processing amount of the target gas.
The control unit is configured to control the opening degree of the slide valve and the spillback valve based on the first characteristic data and the second characteristic data stored in the data storage unit, whereby the control unit is configured to control the opening degree of the slide valve and the spillback valve. The flow rate of the target gas discharged from the screw compressor is controlled.
The compressor unit according to any one of claims 1 to 3. A spillback portion having a bypass flow path connecting a suction side flow path and a discharge side flow path so as to bypass the screw compressor, and a spillback valve having an adjustable opening degree provided on the bypass flow path. ,
An electric motor that drives the screw compressor and
An inverter that adjusts the rotation speed of the motor and
With more
The control unit is configured to control the rotation speed of the motor and the opening degree of the spillback valve based on the first characteristic data and the second characteristic data stored in the data storage unit. Controls the flow rate of the target gas discharged from the screw compressor.
The compressor unit according to any one of claims 1 to 3. A computer is made to control a compressor unit including a screw compressor which is installed in a ship and compresses a target gas which is a boil-off gas sucked from the LNG storage tank of the ship and supplies it to a demand destination including an engine and a generator. It ’s a control program,
A reception step that receives the load information of the engine and the total requested flow rate of the demand destination, and
A control step for controlling the discharge pressure of the target gas discharged from the screw compressor based on the characteristic data, and
With
The characteristic data used in the control step is
First characteristic data showing the relationship between the engine load and pressure,
Second characteristic data showing the relationship between the total required flow rate of the demand destination and the pressure of the target gas required in the discharge side flow path of the screw compressor with respect to the total required flow rate.
Including
The control step derives the first comparison target pressure from the first characteristic data based on the load information obtained from the engine, and the second from the second characteristic data based on the total required flow rate obtained from the flow sensor. Derived the pressure to be compared,
A control program in which the larger of the first comparison target pressure and the second comparison target pressure is set as a set pressure, and the screw compressor is controlled so as to be the set pressure. It is a control method that controls a compressor unit including a screw compressor that is installed in a ship and compresses a target gas that is a boil-off gas sucked from the LNG storage tank of the ship and supplies it to a demand destination including an engine and a generator. hand,
A reception step that receives the load information of the engine and the requested flow rate of the demand destination, and
A control step for controlling the discharge pressure of the target gas discharged from the screw compressor based on the characteristic data, and
With
The characteristic data used in the control step is
First characteristic data showing the relationship between the engine load and pressure,
Second characteristic data showing the relationship between the total required flow rate of the demand destination and the pressure of the target gas required in the discharge side flow path of the screw compressor with respect to the total required flow rate.
Including
The control step derives the first comparison target pressure from the first characteristic data based on the load information obtained from the engine, and the second from the second characteristic data based on the total required flow rate obtained from the flow sensor. Derived the pressure to be compared,
A control method in which the larger of the first comparison target pressure and the second comparison target pressure is set as a set pressure, and the screw compressor is controlled so as to be the set pressure.

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