CN111287934B

CN111287934B - Compressor unit and control method of compressor unit

Info

Publication number: CN111287934B
Application number: CN202010094917.8A
Authority: CN
Inventors: 手塚智志; 濑山胜广; 名仓见治
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2019-07-03
Filing date: 2020-02-14
Publication date: 2021-07-02
Anticipated expiration: 2040-02-14
Also published as: GR1009938B; CH716405A2; NO20200261A1; GR20200100156A; CN111287934A; JP2021008947A; DK202070068A1; JP6595143B1

Abstract

The invention discloses a compressor unit which is arranged in a ship and compresses object gas which is evaporated gas sucked from an LNG storage tank of the ship and a control method of the compressor unit. The compressor unit includes: a plurality of compression stages for sequentially pressurizing the target gas; a crankshaft mechanism driving the pistons of the plurality of compression stages; a cooler that cools the target gas ejected from one of the plurality of compression stages; a discharge passage through which the target gas cooled by the cooler flows toward a generator or an internal combustion engine that is a demand side; and a heat insulating member provided in the lead-out passage. Accordingly, the target gas having a temperature within a temperature range preferred by the demand side can be supplied to the demand side.

Description

Compressor unit and control method of compressor unit

Technical Field

The present invention relates to a compressor unit that compresses target gas that is boil-off gas from an LNG storage tank of a ship, and a method for controlling the compressor unit.

Background

Conventionally, a compressor has been developed which boosts a pressure of a boil-off Gas (hereinafter referred to as "target Gas") generated from LNG (liquefied Natural Gas) and supplies the boosted pressure to a demand side such as an engine or a generator (japanese patent publication No. 6371930, japanese patent laid-open publication No. 2011 and 517749, and japanese patent laid-open publication No. 2018 and 128039).

In order to operate a demand side such as an engine or a generator under a preferable operating condition, the temperature of the target gas supplied to the demand side is sometimes required to be within a predetermined temperature range. However, if the atmospheric heat dissipation of the target gas excessively occurs in the process of reaching the demand side, the target gas may be supplied to the demand side in a state of being lower than the temperature range required by the demand side.

Disclosure of Invention

The purpose of the present invention is to provide a compressor unit that supplies a target gas having a temperature within a temperature range preferred by a demand side to the demand side, and a method for controlling the compressor unit.

One aspect of the present invention relates to a compressor unit provided in a ship and configured to compress a target gas, which is boil-off gas sucked from an LNG storage tank of the ship. The compressor unit includes: a plurality of compression stages for sequentially pressurizing the target gas; a crankshaft mechanism driving the pistons of the plurality of compression stages; a cooler that cools the target gas ejected from one of the plurality of compression stages; an outlet passage through which the target gas cooled by the cooler flows toward a generator or an internal combustion engine that is a demand source; and a heat insulator provided in the lead-out passage. The cooler is provided in a stage connection flow path that circulates the target gas from the one compression stage to the next compression stage. The lead-out passage is a flow passage branched from the segment connection flow passage downstream of the cooler. The compressor string further includes other thermal insulation disposed in a portion of the segment connecting flow path from the cooler to the outlet path.

Another aspect of the present invention relates to another compressor unit, which is provided in a ship, and compresses boil-off gas, i.e., target gas, sucked from an LNG storage tank of the ship. The compressor unit includes: a plurality of compression stages for sequentially pressurizing the target gas; a crankshaft mechanism driving the pistons of the plurality of compression stages; a cooler that cools the target gas ejected from a last compression stage of the plurality of compression stages; an outlet passage through which the target gas cooled by the cooler flows toward a generator or an internal combustion engine that is a demand source; and a heat insulating member provided in the lead-out passage.

A further aspect of the invention relates to a method for controlling a compressor group, for controlling said compressor group. The cooler includes: a cooling water flow path through which cooling water for cooling the target gas flows; and a control valve provided in the cooling water flow path and capable of adjusting the flow rate of the cooling water. The control method includes a step of adjusting the opening degree of the adjustment valve so that the temperature of the target gas flowing out of the cooler is maintained within a predetermined range.

According to the present invention, it is possible to supply the target gas having a temperature within a temperature range preferred by the demand side to the demand side.

The objects, features and advantages of the present invention will be further apparent from the following detailed description and the accompanying drawings.

Drawings

Fig. 1 is a schematic flow chart of a compressor unit according to a first embodiment.

Fig. 2 is a schematic flow diagram of a cooler of the compressor unit.

Fig. 3 is an enlarged flow path diagram around the discharge passage of the compressor unit.

Fig. 4 shows a schematic cross section of the lead-out passage.

Fig. 5 is a flowchart schematically showing temperature control of the target gas.

Fig. 6 is an enlarged flow path diagram around the discharge passage of the compressor unit according to the second embodiment.

Fig. 7 is an enlarged flow path diagram around the discharge passage of the compressor unit according to the third embodiment.

Detailed Description

Fig. 1 is a schematic flow chart of a compressor unit 100 according to a first embodiment. A compressor package 100 is described with reference to fig. 1.

The compressor unit 100 is installed in a ship (not shown) having an LNG storage tank 101 for storing LNG (liquefied Natural Gas). The compressor unit 100 sucks the target gas, which is the boil-off gas generated in the LNG storage tank 101, and compresses the sucked target gas. In detail, the compressor train 100 boosts the target gas to about 300bar, and supplies the boosted target gas to the specified

consumers

102, 103. In the present embodiment, the demand side 102 is an internal combustion engine. The demand side 103 is a generator or an internal combustion engine. In the following description, terms "upstream" and "downstream" are used with reference to the flow direction of the target gas.

The compressor train 100 includes: a flow path 110 through which the target gas flows toward the

customers

102, 103; a plurality of compression stages (first compression stage 201 to fifth compression stage 205) for sequentially increasing the pressure of the target gas; and a plurality of coolers 281 to 284. The compressor train 100 further includes a crank mechanism (not shown) used as a common drive source for the first to fifth compression stages 201 to 205. In fig. 1, a compressor unit 100 is shown as a device including components shown in a two-dot chain line of fig. 1.

The upstream end of the flow path 110 is connected to the upper portion of the LNG storage tank 101 so that the boil-off gas generated in the LNG storage tank 101 flows in. The downstream end of the flow path 110 is connected to a pipe 104 extending from the demand side 102.

The flow path 110 includes a storage tank connection flow path 111, a block connection flow path 113, a lead-out path 114, and a lead-out path 115.

The storage tank connection line 111 is connected to the LNG storage tank 101 and guides the boil-off gas to the first compression stage 201 of the compressor train 100. Since the compressor unit 100 includes two first compression stages 201, the storage tank connection passage 111 includes a main pipe 111C extending from the LNG storage tank 101 and

branch portions

111A and 111B branching from the main pipe 111C. These

branch portions

111A and 111B are connected to the first compression stage 201, respectively. That is, the two first compression stages 201 are connected to the two

branch portions

111A and 111B in parallel with each other. In addition, the compressor train 100 may also have a first compression stage 201.

The stage connection channel 113 connects the first to fifth compression stages 201 to 205 so that the target gas flows from one compression stage to the next compression stage. The upstream portion of the stage connecting passage 113 is a

branch portion

113A, 113B that branches into two at a connection portion with the first compression stage 201. The second to fifth compression stages 202 to 205 are provided in other portions of the stage connecting passage 113. The second to fifth compression stages 202 to 205 are arranged in series so as to sequentially increase the pressure of the target gas compressed in the first compression stage 201.

The outlet passage 114 is a flow path for guiding the target gas compressed in the final fifth compression stage 205 to the consumer 102. The outlet passage 114 extends from the fifth compression stage 205 toward the consumer 102. The discharge passage 115 is a flow path for guiding the target gas compressed in the second compression stage 202 to the consumer 103. The lead-out passage 115 branches from a passage section 119a connecting the second compression stage 202 and the third compression stage 203 in the stage connection passage 113, and is connected to a pipe line 105 extending from the demand side 103. Further, a heat insulator is preferably provided over the entire length of the pipe 105.

The diameters of the pistons and the inner diameters of the cylinder portions of the first to fourth compression stages 201 to 204 are smaller as the compression stage is located downstream. The piston diameter of the fifth compression stage 205 and the inner diameter of the cylinder part are smaller than those of the first compression stage 201 to the fourth compression stage 204.

The first compression stage 201 through the fifth compression stage 205 are driven by a common crankshaft mechanism. The crank mechanism has a crosshead connected to a piston rod of each of the first compression stage 201 to the fifth compression stage 205. The crank mechanism converts rotation of the crankshaft into reciprocating motion of the crosshead, thereby reciprocating the piston rod and the piston connected to the distal end of the piston rod.

The coolers 281 to 284 are provided in the stage connecting flow path 113 and the lead-out path 114 in order to cool the target gas compressed in the second to fifth compression stages 202 to 205, respectively. The coolers 281 to 284 can exchange heat between the target gas and cooling water (for example, seawater) having a lower temperature than the target gas. The cooling water is used to cool the target gas. A schematic flow path diagram of cooler 281 is shown in fig. 2.

The cooler 281 is disposed in the stage connection flow path 113 between the second compression stage 202 and the third compression stage 203. Specifically, the cooler 281 is attached to the stage connection flow path 113 in the flow path section 119a between the second compression stage 202 and the connection portion 119 of the lead-out passage 115 of the stage connection flow path 113. The length of the pipe line extending between the cooler 281 and the connection portion 119 of the lead-out passage 115 of the opposite-stage connection flow passage 113 is shorter than the length of the pipe line extending between the connection portion 119 and the third compression stage 203.

The cooler 281 exchanges heat between the target gas and cooling water having a lower temperature than the target gas. For example, the cooler 281 may include a gas flow path 291 connected to the stage connection flow path 113 so as to flow the target gas, a casing 292 housing the gas flow path 291, and a cooling water flow path 293 through which cooling water flowing in and out of the casing 292 flows. The cooler 281 further includes an adjustment valve 416 provided in the cooling water flow path 293 in order to adjust the flow rate of the cooling water to the housing 292.

The cooler 282 is disposed in the stage connecting passage 113 between the third compression stage 203 and the fourth compression stage 204. The cooler 283 is disposed in the stage connecting flow path 113 between the fourth compression stage 204 and the fifth compression stage 205. The cooler 284 is disposed in the lead-out passage 114.

These coolers 282-284 differ from cooler 281 only in the point where there is no trim valve 416. Therefore, the flow rate of the cooling water flowing through the cooler 281 is adjusted by the adjustment valve 416, and the flow rate of the cooling water flowing through the coolers 282 to 284 is substantially constant. In addition, the coolers 282 to 284 can also adjust the flow rate of the cooling water, as in the case of the cooler 281.

The compressor unit 100 performs control for adjusting the pressure, flow rate, and temperature of the target gas supplied to the

consumers

102 and 103. The control-related parts used in these controls are described below.

In order to perform the above-described adjustment control of the target gas, the compressor unit 100 includes a bypass line 411, a control valve 412, a pressure sensor 413, a control unit 414, and a temperature detection unit 415 (temperature sensor).

The bypass line 411 branches from the stage connection passage 113 at a passage section 119b between the connection portion 119 of the lead-out passage 115 of the stage connection passage 113 and the third compression stage 203, and is connected to the storage tank connection passage 111. That is, the bypass line 411 returns the target gas cooled in the cooler 281 to the suction side of the first compression stage 201 across the first compression stage 201 and the second compression stage 202.

The control valve 412 is provided in the bypass line 411. The pressure sensor 413 and the temperature detection unit 415 are attached to the stage connection flow path 113 in a flow path section 119a between the connection portion 119 of the lead-out path 115 of the stage connection flow path 113 and the cooler 281. The pressure sensor 413 detects the pressure of the target gas on the suction side of the third compression stage 203. Temperature detecting unit 415 detects the temperature of the target gas flowing out of cooler 281.

The pressure sensor 413, the control valve 412, the adjustment valve 416, the temperature detection unit 415, and the cooler 281 are electrically connected to the control unit 414. The controller 414 controls the opening degrees of the control valve 412 and the regulating valve 416 based on the pressure and the temperature detected by the pressure sensor 413 and the temperature detector 415, respectively. Specifically, the opening degree of the control valve 412 is adjusted by the control unit 414 so as to obtain a pressure preferred by the demand side 103. The opening degree of the adjustment valve 416 is adjusted by the controller 414 so that the temperature of the target gas flowing out of the cooler 281 is within a temperature range (for example, 30 to 60 ℃) preferable for the demand side 103. The control unit 414 may be constructed as a program or may be constructed using a dedicated circuit.

The compressor unit 100 has a heat insulator 116 covering the outer surface of the outlet passage 115 so that the target gas can be supplied to the demand side 103 while maintaining the temperature substantially adjusted by the control unit 414. Fig. 3 is an enlarged flow path diagram around the lead-out passage 115. Fig. 4 shows a schematic cross section of the lead-out passage 115 covered with the heat insulator 116. In fig. 1, the heat insulator 116 is shown by hatching on the lead-out passage 115. The heat insulator 116 covers the entire outer surface of the outlet passage 115. However, the heat insulator 116 may partially cover the outlet passage 115 as long as the temperature of the target gas is maintained within the above-described temperature range. When fluid devices (valves and measuring instruments) are attached to the outlet passage 115, these fluid devices may be exposed from the heat insulator 116 or may be covered with the heat insulator 116. The heat insulator 116 is formed using a heat insulator such as glass wool or polyurethane.

In the present embodiment, the stage connecting passage 113 connecting the second compression stage 202 and the third compression stage 203 is a non-heat insulating portion where no heat insulator is provided. In the stage connection flow path 113 connecting the second compression stage 202 and the third compression stage 203, the distance of the flow path section 119b, which is a portion from the connection portion 119 of the lead-out passage 115 to the third compression stage 203, in the stage connection flow path 113 is longer than the length of the flow path section 119a, which is a portion from the cooler 281 to the connection portion 119 of the lead-out passage 115. That is, by making the distance from cooler 281 to connecting portion 119 short, the target gas is guided to lead-out passage 115 while heat radiation thereof is suppressed as much as possible.

Next, the operation of the compressor unit 100 and the flow of the target gas will be described with reference to fig. 1, 2, and 5. Fig. 5 is a schematic flowchart showing the temperature control of the target gas by the controller 414.

When the compressor unit 100 is driven, the suction and discharge of the target gas into the two compression chambers are alternately repeated in the first compression stage 201 to the fourth compression stage 204. In the fifth compression stage 205, the intake and discharge of the target gas in one compression chamber are performed. The target gases discharged from the second to fifth compression stages 202 to 205 are cooled by the coolers 281 to 284. Part of the target gas cooled in the cooler 281 is sequentially boosted in pressure by the third to fifth compression stages 203 to 205, and is supplied to the customer 102 or returned to the upstream side through the bypass line 411. The remaining target gas is supplied to the customer 103 through the lead-out passage 115.

In order to supply the target gas at a pressure preferred by the demand side 103, the pressure sensor 413 detects the pressure of the target gas flowing into the lead-out passage 115 (i.e., the suction pressure of the third compression stage 203). The detected pressure data is output to the control unit 414. The controller 414 controls the opening of the control valve 412 based on the acquired pressure data so that the pressure of the target gas flowing into the outlet passage 115 becomes substantially constant.

The temperature detector 415 detects the temperature of the target gas flowing into the lead-out passage 115 in order to supply the target gas at a temperature preferred by the customer 103. The detected temperature data is output to the control unit 414. The controller 414 determines whether the temperature of the target gas flowing out of the cooler 281 is within a predetermined range based on the temperature data (step S110). The predetermined range used in the determination process is set such that the target gas having a temperature in the temperature range preferred by the consumer 103 flows into the consumer 103. For example, the predetermined range is set to a range of 30 ℃ to 60 ℃.

If the temperature of the target gas is within the predetermined range, the controller 414 maintains the opening degree of the adjustment valve 416 (step S120). If the temperature of the target gas exceeds the upper threshold of the predetermined range (step S110: up), the opening degree of the regulating valve 416 is increased (step S130). As a result, the flow rate of the cooling water increases, and the temperature of the target gas flowing out of the cooler 281 decreases. The processing loop of steps S110 and S130 continues until the temperature of the target gas converges to the predetermined range. If the temperature of the target gas is lower than the lower threshold of the predetermined range (step S110: lower), the opening degree of the regulating valve 416 is decreased (step S140). As a result, the flow rate of the cooling water decreases, and the temperature of the target gas flowing out of the cooler 281 increases. The processing loop of steps S110 and S140 continues until the temperature of the target gas converges to the predetermined range.

By the control shown in fig. 5, the temperature of the target gas flowing out of the cooler 281 is a value within a temperature range (30 to 60 ℃) preferable for the demand side 103. A part of the object gas flowing out of the cooler 281 is sucked into the third compression stage 203 or is returned upstream through the bypass line 411. On the other hand, the remaining target gas is supplied to the customer 103 through the lead-out passage 115. Since the lead-out passage 115 is covered with the heat insulator 116, the release of heat of the target gas flowing through the lead-out passage 115 into the atmosphere is suppressed. Therefore, the target gas is supplied to the customer 103 while maintaining the temperature of the temperature range preferred by the customer 103. Since the influence of the variation in the outside air temperature on the temperature of the target gas supplied to the customer 103 is reduced by the heat insulator 116, the variation in the outside air temperature may not be considered in the flow rate control of the cooling water described with reference to fig. 5.

The length of the pipe line extending between the cooler 281 and the connection portion 119 of the lead-out passage 115 of the opposite-stage connection flow passage 113 is shorter than the length of the pipe line extending between the connection portion 119 and the third compression stage 203. Therefore, the amount of heat released from the target gas in the flow path section 119a between the cooler 281 and the connection portion 119 of the lead-out passage 115 of the counter stage connection flow path 113 is reduced. In the flow path section 119a, the temperature of the target gas decreases a little even when atmospheric heat is radiated from the target gas. That is, the possibility that the target gas is supplied to the demand side 103 at a temperature lower than the lower limit value (30 ℃) of the preferable temperature range is low.

On the other hand, since the flow path section 119b from the connection portion 119 of the lead-out passage 115 of the pair-stage connection flow path 113 to the third compression stage 203 is relatively long, the amount of heat released from the target gas in the flow path section 119b is relatively large. That is, the temperature of the target gas decreases in the flow path section 119 b. Therefore, the temperature of the target gas sucked into the third compression stage 203 is prevented from becoming excessively high.

Fig. 6 is a diagram illustrating a part of a compressor unit 100 according to a second embodiment. In the stage connection flow path 113, another heat insulator 117 for further suppressing heat radiation is added to the flow path section 119a between the cooler 281 and the connection portion 119 of the lead-out passage 115. The heat insulator 117 covers the entire length of the flow path section 119 a. However, if the temperature of the target gas is maintained within a predetermined temperature range, the heat insulator 117 may partially cover the flow path section 119 a. When fluid devices (valves and measuring instruments) are attached to the flow path section 119a, the fluid devices may be exposed from the heat insulator 117 or may be covered with the heat insulator 117. The heat insulator 117 may be made of the same material as the heat insulator 116, or may be made of a different material. The flow path section 119b from the connection portion 119 of the lead-out passage 115 to the third compression stage 203 in the stage connection flow path 113 is left as a non-heat insulating portion where no heat insulator is provided. The distance of the flow path section 119b is longer than the length of the flow path section 119a between the cooler 281 and the connection portion 119.

Since the heat insulator 117 is provided, heat radiation from the target gas is also suppressed in the flow path section 119a between the cooler 281 and the connection portion 119 of the lead-out passage 115 of the counter stage connection flow path 113. Heat dissipation from the target gas flowing into the outlet passage 115 is suppressed by the heat insulator 116. As a result, the target gas is supplied to the demand side 103 while maintaining the temperature adjusted to the temperature range preferred by the demand side 103 by the cooler 281. Since the influence of the fluctuation of the outside air temperature on the temperature of the target gas supplied to the customer 103 is reduced by the

heat insulators

116 and 117, the fluctuation of the outside air temperature can be eliminated in the flow rate control of the cooling water described with reference to fig. 5.

On the other hand, the flow path section 119b between the connection portion 119 of the lead-out passage 115 of the stage-to-stage connection flow path 113 and the third compression stage 203 is a non-heat-insulating portion where no heat insulator is provided, and therefore, heat radiation from the target gas in this flow path section 119b is positively permitted. Since the length of the non-heat insulating portion is relatively long, the amount of heat released from the target gas increases. Therefore, the temperature of the target gas sucked into the third compression stage 203 is prevented from becoming excessively high.

Fig. 7 is a diagram illustrating a part of a compressor unit 100 according to a third embodiment. The described thermal insulation technique is applicable to the target gas supplied to the demand party 103. However, the same thermal insulation technique may be applied to the target gas supplied to the demand side 102. As shown in fig. 7 (an enlarged flow path diagram around the delivery passage 114), the delivery passage 114 extending from the cooler 284 toward the demand side 102 may be entirely or partially covered with the heat insulator 118. When fluid devices (valves and measuring instruments) are attached to the outlet passage 114, these fluid devices may be exposed from the heat insulator 118 or may be covered with the heat insulator 118. The thermal insulator 118 may be made of the same material as the thermal insulator 116 or may be made of a different material. At this time, heat dissipation from the target gas is suppressed while the target gas flows through the outlet passage 114. Therefore, the target gas is supplied to the demand side 102 while substantially maintaining the temperature reduced by the cooler 284.

The cooler 284 may also not be controlled by the control section 414 if it is ensured that the temperature of the subject gas flowing out of the cooler 284 is within the temperature range preferred by the demand side 102. However, in order to prevent the temperature of the target gas flowing out of the cooler 284 from deviating from the temperature range preferred by the demand side 102, a control technique applicable to the cooler 281 may be applied to the cooler 284. In this case, another temperature detector (not shown) for detecting the temperature of the target gas flowing out of the cooler 284 may be added. The controller 414 may adjust the flow rate of the cooling water used for heat exchange in the cooler 284 based on the temperature detected by the additional temperature detector.

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

In the embodiment described above, the opening degree of the adjustment valve 416 is automatically adjusted by the control unit 414 based on the temperature detected by the temperature detection unit 415. However, the opening degree of the adjustment valve 416 may not be automatically adjusted. For example, the opening degree of the adjustment valve 416 may be determined by a preliminary experiment so as to obtain a temperature within a temperature range preferred by the demand side 103. Alternatively, if the temperature detected by the temperature detector 415 is displayed to the user, the user may adjust the opening degree of the adjustment valve 416 by looking at the displayed temperature (i.e., manual adjustment). In these cases, the opening degree control of the adjustment valve 416 described with reference to fig. 5 is not necessary.

In fig. 6, when the influence on the third compression stage 203 can be ignored, a heat insulating portion may be provided in the stage connection flow path 113 in the flow path section 119b from the connection portion 119 of the lead-out path 115 to the third compression stage 203.

In the described embodiment, a 5-stage compression stage is used. However, the arrangement of the several compression stages may be decided based on the pressure of the target gas required by the demand side. Therefore, as the compression stage, for example, a 4-stage type or 6-stage type compression stage may be used.

In the illustrated embodiment, the object gas compressed in the second compression stage 202 is supplied to the demand side 103. However, the object gas compressed in another compression stage may be supplied to the demand side 103. In this case, the heat insulator is also provided in the discharge path for circulating the target gas toward the consumer 103.

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

A compressor unit according to one aspect of the above embodiment is provided in a ship and compresses a target gas, which is a boil-off gas, sucked from an LNG storage tank of the ship. The compressor unit includes: a plurality of compression stages for sequentially pressurizing the target gas; a crankshaft mechanism driving the pistons of the plurality of compression stages; a cooler that cools the target gas ejected from one of the plurality of compression stages; an outlet passage through which the target gas cooled by the cooler flows toward a generator or an internal combustion engine that is a demand source; and a heat insulator provided in the lead-out passage. The cooler is provided in a stage connection flow path that circulates the target gas from the one compression stage to the next compression stage. The lead-out passage is a flow passage branched from the segment connection flow passage downstream of the cooler. The compressor string further includes other thermal insulation disposed in a portion of the segment connecting flow path from the cooler to the outlet path.

According to the above configuration, since the heat insulator is provided in the lead-out passage, heat radiation from the target gas flowing from the cooler to the demand side is suppressed, and the temperature of the target gas is maintained in a temperature range preferable for the generator or the internal combustion engine.

Since the lead-out passage branches from the stage connection flow passage downstream of the cooler, the target gas cooled in the cooler flows into the lead-out passage. Since the heat insulator is provided in the lead-out passage, the target gas flowing through the lead-out passage toward the demand side is suppressed from being further cooled. The heat insulator is provided in a portion of the segment connecting passage from the cooler to the lead-out passage, in addition to the lead-out passage. Therefore, heat radiation from the target gas is also suppressed in the section where the target gas flows from the cooler into the lead-out passage.

In the above configuration, a length of a portion of the segment connecting passage from the connection portion of the lead-out passage to the next compression segment may be longer than a length of a portion from the cooler to the connection portion of the lead-out passage.

According to the above configuration, since the portion from the cooler to the lead-out passage is relatively short, the flow section of the target gas supplied to the demand side through the lead-out passage becomes short. As a result, heat dissipation from the target gas flowing toward the demand side is suppressed.

In the above configuration, the portion of the stage connection flow path from the connection portion of the lead-out passage to the next compression stage may be a non-heat insulating portion having no heat insulator.

According to the above configuration, the target gas sucked into the next compression stage is radiated in the non-heat insulating portion. At the suction side of the next compression stage, the temperature of the subject gas drops, and therefore, the temperature of the subject gas preferred for the next compression stage is obtained.

A compressor unit according to another aspect of the above embodiment is provided in a ship and compresses a target gas, which is a boil-off gas, sucked from an LNG storage tank of the ship. The compressor unit includes: a plurality of compression stages for sequentially pressurizing the target gas; a crankshaft mechanism driving the pistons of the plurality of compression stages; a cooler that cools the target gas ejected from a last compression stage of the plurality of compression stages; an outlet passage through which the target gas cooled by the cooler flows toward a generator or an internal combustion engine that is a demand source; and a heat insulator provided in the lead-out passage.

In a method for controlling a compressor unit according to still another aspect of the embodiment, the cooler includes: a cooling water flow path through which cooling water for cooling the target gas flows; and a control valve provided in the cooling water flow path and capable of adjusting the flow rate of the cooling water. The control method includes a step of adjusting the opening degree of the adjustment valve so that the temperature of the target gas flowing out of the cooler is maintained within a predetermined range.

According to the control method, the target gas is supplied to the demand side while suppressing heat radiation from the target gas whose temperature is adjusted in the cooler by the heat insulator. Therefore, the temperature of the target gas is maintained in a temperature range preferable for the generator or the internal combustion engine.

In the method for controlling a compressor unit, the opening degree of the regulating valve may be adjusted so that the temperature of the target gas is maintained within a range of 30 to 60 ℃.

According to the control method, since the heat radiation from the target gas is suppressed by the heat insulator, the temperature of the target gas, which has been converged to the temperature range of 30 to 60 ℃ by adjusting the opening degree of the adjustment valve, is supplied to the demand side while maintaining the temperature in the temperature range.

Industrial applicability

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

Claims

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

a plurality of compression stages for sequentially pressurizing the target gas;

a crankshaft mechanism driving the pistons of the plurality of compression stages;

a cooler that cools the target gas ejected from one of the plurality of compression stages;

an outlet passage through which the target gas cooled by the cooler flows toward a generator or an internal combustion engine that is a demand source; and

a heat insulator disposed in the outlet passage, wherein,

the cooler is provided in a stage connection flow path that circulates the target gas from the one compression stage toward the next compression stage,

the lead-out passage is a flow passage branched from the segment connection flow passage downstream of the cooler,

the compressor string further includes other thermal insulation disposed in a portion of the segment connecting flow path from the cooler to the outlet path.

2. The compressor rack of claim 1,

the length of a portion of the segment connecting passage from the connection portion of the lead-out passage to the next compression segment is longer than the length of a portion from the cooler to the connection portion of the lead-out passage.

3. The compressor rack of claim 2,

the portion of the stage connection flow path from the connection portion of the lead-out path to the next compression stage is a non-heat insulating portion having no heat insulating material.

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

the cooler includes:

a cooling water flow path through which cooling water for cooling the target gas flows; and

and a regulating valve provided in the cooling water flow path and capable of regulating the flow rate of the cooling water.

5. The control method of a compressor group according to any one of claims 1 to 4,

the control method includes a step of adjusting the opening degree of the adjustment valve so that the temperature of the target gas flowing out of the cooler is maintained within a predetermined range.

6. The control method of a compressor unit according to claim 5,

the opening degree of the regulating valve is adjusted so that the temperature of the target gas is maintained within a range of 30 to 60 ℃.

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

a plurality of compression stages for sequentially pressurizing the target gas;

a cooler that cools the target gas ejected from a last compression stage of the plurality of compression stages;

a heat insulator provided in the lead-out passage,

the cooler includes:

8. The method according to claim 7, characterized by comprising a step of adjusting an opening degree of the adjustment valve so that a temperature of the target gas flowing out of the cooler is maintained within a predetermined range.

9. The control method of a compressor unit according to claim 8,