CN114776556B - Compressor unit and control method of compressor unit - Google Patents
Compressor unit and control method of compressor unit Download PDFInfo
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- CN114776556B CN114776556B CN202210465819.XA CN202210465819A CN114776556B CN 114776556 B CN114776556 B CN 114776556B CN 202210465819 A CN202210465819 A CN 202210465819A CN 114776556 B CN114776556 B CN 114776556B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B37/00—Pumps having pertinent characteristics not provided for in, or of interest apart from, groups F04B25/00 - F04B35/00
- F04B37/10—Pumps having pertinent characteristics not provided for in, or of interest apart from, groups F04B25/00 - F04B35/00 for special use
- F04B37/18—Pumps having pertinent characteristics not provided for in, or of interest apart from, groups F04B25/00 - F04B35/00 for special use for specific elastic fluids
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/06—Control using electricity
- F04B49/065—Control using electricity and making use of computers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/22—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by means of valves
- F04B49/24—Bypassing
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- General Engineering & Computer Science (AREA)
- Computer Hardware Design (AREA)
- Filling Or Discharging Of Gas Storage Vessels (AREA)
Abstract
The invention provides a compressor unit and a control method thereof. The compressor unit includes: a plurality of compression stages for sequentially increasing the pressure of the target gas from the storage tank; a bypass flow path bypassing at least the first compression section; a bypass valve provided on the bypass flow path; an upstream pressure sensor and a temperature sensor provided on the storage tank connection flow path; a downstream pressure sensor provided in a flow path connecting an inlet side end portion of the bypass flow path; an opening degree adjusting unit that controls an opening degree of the bypass valve so that the gas flow rate in the bypass flow path is increased when a detected pressure of the downstream pressure sensor is higher than a predetermined set pressure, and the gas flow rate in the bypass flow path is decreased when the detected pressure of the downstream pressure sensor is lower than the set pressure; and a set pressure changing unit that increases the set pressure if the temperature detected by the temperature sensor decreases. Accordingly, when low-temperature gas flows from the reserve tank into the compressor unit, a pressure increase in the flow path on the reserve tank side can be suppressed.
Description
Technical Field
The present invention relates to a compressor unit and a method for controlling the compressor unit.
Background
It is known that boil-off Gas generated from LNG (Liquefied Natural Gas) in a storage tank is pressurized and supplied to a compressor unit on a demand side such as an engine, installed on an LNG carrier. Japanese patent laid-open publication No. 2017-129112 discloses a compressor unit including: a plurality of compressors; a bypass flow path connecting the suction side flow path and the discharge side flow path; a regulating valve arranged on the bypass flow path; a control unit for controlling the opening of the regulating valve; and a pressure gauge provided on the ejection-side flow path. In the compressor unit disclosed in japanese patent laying-open No. 2017-129112, the control unit controls the opening degree of the regulating valve of the bypass flow path by using a command value set in accordance with the pressure difference between the pressure of the discharge side flow path and the target pressure. Further, japanese patent No. 6294243 and japanese patent laid-open publication No. 2018-103954 disclose a compressor unit including: a bypass flow path provided in a manner bypassing the compression section; a bypass valve disposed on the bypass flow path; and a control device that adjusts the opening degree of the bypass valve.
In the compressor units of japanese patent laid-open publication nos. 2017-129112, 6294243, and 2018-103954, the bypass flow path is provided so as to cross the first compression stage. In this compressor unit, the opening degree of the bypass valve in the bypass flow path may be controlled so that the pressure on the discharge side of the first compression stage reaches a set pressure. The set pressure is set in consideration of a balance between the compression ratio of the first compression stage and the compression ratios of the other compression stages.
The set pressure is set in consideration of an intake temperature (for example, 40 ℃) of the boil-off gas which is generally estimated during steady operation of the compressor unit. However, the temperature of the boil-off gas may fluctuate, and the boil-off gas having a temperature lower than the above temperature may be sucked into the first compression stage.
Generally, if the temperature of the boil-off gas is lowered, the gas density becomes high, so that the gas throughput of the first compression stage is increased. At this time, if the set pressure is set based on the normally estimated suction temperature of the boil-off gas, the flow rate of the gas returned through the bypass passage tends to increase, and the gas pressure may increase in the passage on the accumulator side (the suction-side passage of the first compression stage).
Disclosure of Invention
An object of the present invention is to provide a compressor unit and a method of controlling the compressor unit, which can suppress a pressure rise in a flow path on a storage tank side when low-temperature gas flows into the compressor unit from the storage tank.
One aspect of the present invention relates to a compressor unit provided in a ship, which recovers boil-off gas, i.e., target gas, from a liquefied natural gas storage tank of the ship and supplies at least a part thereof to a demand side. This compressor unit includes: a plurality of reciprocating compression stages for sequentially pressurizing the target gas; the crankshaft mechanism drives the piston of each compression section; a bypass flow path bypassing at least the first compression section; a bypass valve disposed on the bypass flow path; an upstream pressure sensor provided on a storage tank connection flow path connecting the liquefied natural gas storage tank and the first compression stage; a temperature sensor provided on the storage tank connection flow path; a downstream pressure sensor provided in a flow path that is located downstream of the reservoir connection flow path and connects an inlet side end of the bypass flow path; an opening degree adjustment unit that controls an opening degree of the bypass valve as follows: increasing the gas flow rate of the bypass flow path when the detected pressure of the downstream pressure sensor is higher than a predetermined set pressure; reducing the gas flow rate of the bypass flow path when the detected pressure of the downstream pressure sensor is lower than the set pressure; and a set pressure changing unit that increases the set pressure if the temperature detected by the temperature sensor decreases.
Another aspect of the present invention relates to a method for controlling a compressor unit that is provided in a ship, and that recovers a target gas, which is a boil-off gas, from a liquefied natural gas storage tank of the ship and supplies at least a part thereof to a demand side. The compressor unit includes: a plurality of reciprocating compression stages for sequentially increasing the pressure of the target gas; a bypass flow path bypassing at least the first compression stage; a bypass valve provided on the bypass flow path; and a storage tank connection passage connecting the liquefied natural gas storage tank and the first compression stage. The control method of the compressor unit comprises the following steps: detecting the pressure of the target gas flowing through the storage tank connection passage by an upstream pressure sensor; detecting the temperature of the target gas flowing through the storage tank connection passage by a temperature sensor; detecting, by a downstream pressure sensor, a pressure of the target gas flowing through a flow path located on a downstream side of the storage tank connection flow path and connected to an inlet side end portion of the bypass flow path; controlling the opening of the bypass valve in the following manner: increasing the gas flow rate of the bypass flow path when the detected pressure of the downstream pressure sensor is higher than a predetermined set pressure; reducing the gas flow rate of the bypass flow path when the detected pressure of the downstream pressure sensor is lower than the predetermined set pressure; and increasing the set pressure if the detected temperature of the temperature sensor decreases.
According to the present invention, when low-temperature gas flows from the reserve tank into the compressor unit, a pressure increase in the flow path on the reserve tank side can be suppressed.
Drawings
Fig. 1 is a schematic configuration diagram of a configuration of a compressor unit according to a first embodiment.
Fig. 2 is a diagram schematically showing the relationship between the detected pressure of the upstream pressure sensor and the set pressure in the compressor unit according to the first embodiment.
Fig. 3 is a flowchart schematically showing a control method of the controller according to the first embodiment.
Fig. 4 is a configuration diagram showing a part of a compressor unit according to a second embodiment.
Fig. 5 is a diagram schematically showing the relationship between the detected pressure of the upstream pressure sensor and the set pressure in the compressor unit according to the second embodiment.
Fig. 6 is a schematic configuration diagram of the configuration of a compressor unit according to the third embodiment.
Detailed Description
(first embodiment)
Fig. 1 is a schematic configuration diagram of a compressor train 100 according to a first embodiment. A compressor package 100 is described with reference to fig. 1.
The compressor train 100 is installed in a ship (not shown) having a storage tank 101 for storing LNG (Liquefied Natural Gas). The compressor unit 100 recovers the target gas, which is the boil-off gas generated in the storage tank 101, and boosts the pressure to, for example, about 300barG, and then supplies the boosted target gas to the specified demand side 600. In the following description, terms "upstream" and "downstream" are used with reference to the flow direction of the target gas.
The compressor unit 100 includes: a gas flow path 110 through which the target gas flows from the storage tank 101 to the demand side 600; a plurality of compression stages (first compression stage 201 to sixth compression stage 206) for sequentially increasing the pressure of the target gas; and a drive unit (not shown) for driving the compression stages 201 to 206. The gas flow path 110 is provided with 2 first compression stages 201, and the downstream side of the 2 first compression stages 201 is provided with second compression stages 202 to sixth compression stages 206 in this order.
The drive unit includes a drive source (such as a motor or an engine) and a crank mechanism that transmits power of the drive source to the first compression stage 201 to the sixth compression stage 206. The crankshaft mechanism has a plurality of crosshead connected to the piston rods of the first compression stage 201 to the sixth compression stage 206, respectively. 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 first compression stage 201 to the sixth compression stage 206 each have a reciprocating compression mechanism.
The first compression stage 201 to the sixth compression stage 206 each include: a cylinder portion; a piston accommodated in the cylinder portion; a piston ring mounted on the piston; a piston rod (not shown) extends from the piston and is connected to the crank mechanism. The cylinder part is provided with a rod sealing ring. The first to fifth compression stages 201 to 205 are oil-starved compression stages that do not supply lubricating oil to the piston rings and the rod seal rings, and the sixth compression stage 206 is an oil-starved compression stage that supplies lubricating oil to the piston rings and the rod seal rings.
The gas flow path 110 includes: a storage tank connection passage 111 through which the target gas flows from the storage tank 101; a plurality of connection flow paths 112 to 116 between the plurality of compression sections 201 to 206; and a demand side supply passage 117 for supplying the target gas to the demand side 600.
The reserve tank connection passage 111 is connected to the upper portion of the reserve tank 101, and is connected to the 2 first compression stages 201 in two branches. That is, the 2 first compression stages 201 are configured to be parallel to each other.
The stage connection channel 112 is configured to allow the target gas to flow from the 2 first compression stages 201 to the second compression stage 202. That is, the stage connection channels 112 extend from the 2 first compression stages 201, converge to 1 channel, and are connected to the second compression stage 202.
The stage connecting passage 113 connects the second compression stage 202 and the third compression stage 203. The stage connection flow path 114 connects the third compression stage 203 and the fourth compression stage 204. The stage connection flow path 115 connects the fourth compression stage 204 and the fifth compression stage 205. The stage connecting flow path 116 connects the fifth compression stage 205 and the sixth compression stage 206.
The segment connecting passage 116 is provided with: an on-off valve 352 for opening and closing the flow of the target gas from the fifth compression stage 205 to the sixth compression stage 206; and an intermediate check valve 353 for preventing the reverse flow of the target gas from the sixth compression stage 206 to the fifth compression stage 205. The intermediate check valve 353 is disposed between the opening-closing valve 352 and the sixth compression stage 206.
The customer supply flow path 117 connects the sixth compression stage 206 and the customer 600. The demand side supply flow path 117 is connected to: a check valve 354 for preventing the reverse flow of the object gas from the demand direction 600 to the sixth compression stage 206; and a discharge passage 118 for discharging the remaining target gas to the combustion device 500. The exhaust passage 118 is provided with an exhaust valve 355 for opening and closing the flow of the target gas to the combustion apparatus 500.
The plurality of segment connecting channels 112 to 116 and the customer supply channel 117 are provided with a plurality of coolers 212 to 216. The plurality of coolers 212 to 216 are configured to exchange heat between the target gas and cooling water that is lower in temperature than the target gas.
The cooler 212 is provided in the stage connecting passage 113 so as to cool the target gas discharged from the second compression stage 202. The cooler 213 is provided in the stage connecting passage 114 so as to cool the target gas discharged from the third compression stage 203. The cooler 214 is provided in the stage connection flow path 115 so as to cool the target gas discharged from the fourth compression stage 204. The cooler 215 is provided upstream of the on-off valve 352 in the stage connection passage 116 so as to cool the target gas discharged from the fifth compression stage 205. The cooler 216 is provided on the upstream side of the check valve 354 in the demand side supply flow path 117 so as to cool the target gas discharged from the sixth compression stage 206.
The compressor unit 100 further includes: bypass flow paths 301 to 304 for returning the target gas from the downstream side to the upstream side; and a reliquefaction line 119 for reliquefying the target gas and returning the reliquefied gas to the storage tank 101.
The bypass passage 301 extends from an inlet end 322 connected to the stage connection passage 113 to an outlet end 321 connected to the reserve tank connection passage 111. That is, the bypass passage 301 connects the stage connection passage 113 and the reserve tank connection passage 111 so as to bypass the first compression stage (i.e., the first compression stage located at the most upstream) 201 and the second compression stage 202. The inlet end 322 is disposed downstream of the cooler 212 of the stage connecting flow path 113.
Similarly, the bypass passage 302 is formed to extend from the inlet side end connected to the stage connection passage 114 to the outlet side end connected to the stage connection passage 113, and bypasses the third compression stage 203. The bypass passage 303 is formed to extend from an inlet side end connected to the stage connection passage 116 to an outlet side end connected to the stage connection passage 114, and bypasses the fourth compression stage 204 and the fifth compression stage 205. The bypass flow path 304 is formed to extend from an inlet side end connected to the demand side supply flow path 117 to an outlet side end connected to the stage connection flow path 116, and bypasses the sixth compression stage 206.
Bypass valves 311 to 314 are provided in the bypass flow paths 301 to 304, respectively. The bypass valves 311 to 314 receive signals from a controller 420 described later and adjust the opening so that the detected pressures of the target gases at the inlet-side ends of the bypass flow paths 301 to 304 reach set pressures that are predetermined target pressures.
The reliquefaction line 119 extends from an inlet-side end portion connected to the upstream side of the intermediate check valve 353 in the stage connection flow path 116 toward an unillustrated liquefaction device (e.g., a heat exchanger or the like).
The compressor unit 100 includes: an upstream pressure sensor 401; a temperature sensor 403; a second pressure sensor 412, a third pressure sensor 413 to a sixth pressure sensor 416 functioning as the downstream pressure sensor 402; and a controller 420.
The upstream pressure sensor 401 and the temperature sensor 403 are disposed between the outlet-side end 321 of the bypass passage 301 and the first compression stage 201 in the reserve tank connection passage 111 in order to detect the pressure or temperature of the target gas in the suction-side passage of the first compression stage 201.
The second pressure sensor 412 (downstream pressure sensor 402) is provided on the downstream side of the cooler 212 in the stage connecting passage 113 so as to detect the gas pressure in the discharge-side passage of the second compression stage 202, that is, the gas pressure at the inlet-side end 322 of the bypass passage 301.
The third pressure sensor 413 is provided on the downstream side of the cooler 213 in the stage connecting passage 114 to detect the gas pressure in the discharge-side passage of the third compression stage 203, that is, the gas pressure in the inlet-side end portion of the bypass passage 302. The fourth pressure sensor 414 is provided between the cooler 215 and the on-off valve 352 in the stage connecting passage 116, in order to detect the gas pressure in the discharge-side passage of the fifth compression stage 205, that is, the gas pressure at the inlet-side end of the bypass passage 303. The fifth pressure sensor 415 is disposed between the intermediate check valve 353 and the sixth compression stage 206 in the stage connection flow path 116. The sixth pressure sensor 416 is disposed between the cooler 216 and the check valve 354 in the demand side supply passage 117 in order to detect the gas pressure in the discharge side passage of the sixth compression stage 206, that is, the gas pressure at the inlet side end of the bypass passage 304.
A signal indicating the detected pressure P1 output from the upstream pressure sensor 401, a signal indicating the detected temperature T1 output from the temperature sensor 403, and a signal indicating the detected pressure P2 output from the second pressure sensor 412 (the downstream pressure sensor 402) are transmitted to the controller 420.
The controller 420 is formed of a microcomputer including a ROM, a RAM, a CPU, and the like. The ROM of the controller or the like stores a control program and a predetermined relational expression for causing the controller 420 to function as the set pressure changing section 431 and the opening degree adjusting section 441.
The predetermined relational expression indicates the relationship between the detected pressure P1 (i.e., the pressure on the suction side of the first compression stage 201) and the detected temperature T1 (i.e., the temperature on the suction side of the first compression stage 201) and the set pressure PS1 of the stage connection passage 113 on the discharge side of the second compression stage 202. The set pressure changing unit 431 derives the set pressure PS1 from the detected pressure P1 and the detected temperature T1 with reference to the relational expression. The opening degree adjusting unit 441 changes the opening degree set value of the bypass valve 311 so that the detected pressure P2 reaches the set pressure PS1.
Fig. 2 is a diagram showing a relationship between the set pressure PS1, the detected pressure P1, and the detected temperature T1. In fig. 2, the horizontal axis represents the detected pressure P1, and the vertical axis represents the set pressure PS1. In the area a indicated by a hatched parallelogram in fig. 2, the set pressure PS1 is set based on the detected pressure P1 and the detected temperature T1.
A lower side CE11 of the region a in fig. 2 represents a change in the set pressure PS1 with respect to the detection pressure P1 when the detection temperature T1 is a constant temperature (first temperature) T11. The first temperature T11 corresponds to the upper limit temperature of the estimated temperature of the target gas, and is 40 ℃. If the target gas having a temperature exceeding the first temperature T11 temporarily flows in, the set pressure PS1 is calculated based on the relationship between the detected pressure P1 and the set pressure PS1 at the first temperature T11 (the relationship indicated by the side CE 11).
The upper side CE13 of the area a in fig. 2 represents a change in the set pressure PS1 with respect to the detection pressure P1 when the detection temperature T1 is a constant temperature (second temperature) T13. The second temperature T13 is lower than the first temperature T11, and is 20 ℃. Actually, a gas having a temperature lower than the second temperature T13 may flow in. When the temperature of the target gas is equal to or lower than the second temperature T13, the set pressure PS1 is calculated based on the relationship between the detected pressure P1 and the set pressure PS1 (the relationship indicated by the side CE 13) at the second temperature T13.
The straight line portion CE12 located between the sides CE11, CE13 and inclined the same as them represents a change in the set pressure PS1 with respect to the detection pressure P1 in the case of the temperature (third temperature) T12 at which the detection temperature T1 is constant. The third temperature T12 is a temperature between the first temperature T11 and the second temperature T13. As described above, in the area a, the straight line portions inclined at the same angles as the sides CE11 and CE13 indicate changes in the set pressure PS1 with respect to the detection pressure P1 when the detection temperature T1 is a constant temperature.
When the detected temperature T1 is constant, the set pressure changing unit 431 changes the set pressure PS1 so that the increase in the set pressure PS1 with respect to the detected pressure P1 of the upstream pressure sensor 401 becomes linearly large. The relationship between the detected pressure P1 and the set pressure PS1 is represented by a straight line such as the sides CE11 and CE13 in fig. 2. That is, when the pressure of the target gas on the suction side of the first compression stage 201 increases while the detected temperature T1 is constant, the compressor unit 100 increases the target pressure of the target gas on the discharge side of the second compression stage 202 according to the magnitude of the increase in the pressure.
In the region a of fig. 2, as the detected temperature T1 of the temperature sensor 403 becomes lower, a straight line indicating the relationship between the detected pressure P1 and the set pressure PS1 is shown as moving upward in parallel in the vertical axis direction. That is, the set pressure changing unit 431 increases the set pressure PS1 as the detected temperature T1 becomes lower. That is, in the compressor unit 100, when the temperature of the target gas on the suction side of the first compression stage 201 decreases, the target pressure of the target gas on the discharge side of the second compression stage 202 is increased according to the extent of the decrease in the temperature.
Here, a specific example when the set pressure PS1 is changed will be described with reference to fig. 2. For example, if a state (state B) is assumed in which the detected temperature T1 of the target gas on the suction side of the first compression stage 201 is the temperature T11 and the detected pressure P1 of the target gas on the suction side is the pressure P11, the pressure P21 is set to the set pressure PS1.
Further, if a state (state C) is assumed in which the detected temperature T1 is the temperature T11 and the detected pressure P1 is the pressure P12 that is greater than the pressure P11, the pressure P22 is set to the set pressure PS1. If a state (state D) is assumed in which the detected temperature T1 is the temperature T12 and the detected pressure P1 is the pressure P11, the pressure P23 is set to the set pressure PS1. If a state (state E) is assumed in which the detected temperature T1 is the temperature T12 and the detected pressure P1 is the pressure P12, the pressure P24 is set to the set pressure PS1.
The opening degree adjusting section 441 compares the set pressure PS1 set by the set pressure changing section 431 with the detected pressure P2 of the second pressure sensor 412 (downstream pressure sensor 402), and controls the opening degree of the bypass valve 311 so that the detected pressure P2 of the second pressure sensor 412 reaches the set pressure PS1.
For example, when the detected pressure P2 of the second pressure sensor 412 is higher than the set pressure PS1, the opening degree adjuster 441 increases the opening degree of the bypass valve 311 in order to increase the flow rate of the gas flowing through the bypass flow path 301. When the detected pressure P2 of the second pressure sensor 412 is lower than the set pressure PS1, the opening degree of the bypass valve 311 is decreased to decrease the flow rate of the gas in the bypass passage 301.
(operation explanation and control method)
Here, the operation when the compressor unit 100 is driven will be described. When the compressor unit 100 is driven, the opening/closing valve 352 is opened and the discharge valve 355 is closed, and the storage tank 101 and the demand side 600 are communicated with each other through the gas passage 110. In this state, the compression stages 201 to 206 are driven.
The target gas supplied from the storage tank 101 to the storage tank connection passage 111 is led out to the customer supply passage 117 through the compression steps of the first to sixth compression stages 201 to 206 and the cooling steps of the coolers 212 to 216. Further, a part of the target gas flowing through the stage connection channel 116 is returned from the reliquefaction line 119 to a reliquefaction apparatus not shown. The target gas of the demand side supply flow path 117 is led out to the demand side 600. If the target gas remains, the discharge valve 355 is opened, and the remaining target gas is discharged to the combustion device 500 through the discharge passage 118.
The compressor unit 100 can return a part of the target gas flowing through the stage connection passages 113 to 116 and the demand side supply passage 117 from the downstream passage to the upstream passage through the bypass passages 301 to 304. Accordingly, it is possible to flexibly cope with a change in the required amount of the target gas of the customer 600.
In the first compression stage 201 and the second compression stage 202, a part of the target gas in the stage connection passage 113 can be returned to the reserve tank connection passage 111 through the bypass passage 301 provided with the bypass valve 311 whose opening degree can be adjusted by the controller 420. In the third compression stage 203, a part of the target gas in the stage connection passage 114 can be returned to the stage connection passage 113 through the bypass passage 302 provided with the bypass valve 312. In the fourth compression stage 204 and the fifth compression stage 205, a part of the target gas in the stage connection passage 116 can be returned to the stage connection passage 114 through the bypass passage 303 provided with the bypass valve 313. In the sixth compression stage 206, a part of the target gas in the demand side supply passage 117 can be returned to the stage connection passage 116 through the bypass passage 304 provided with the bypass valve 314.
Here, a control method when the controller 420 adjusts the opening degree of the bypass valve 311 will be described with attention paid to the bypass valve 311 of the bypass passage 301 spanning the first compression stage 201 and the second compression stage 202.
Fig. 3 shows a flowchart of a control method when the controller 420 adjusts the opening degree of the bypass valve 311.
First, the compressor unit 100 starts operation upon receiving an instruction to start operation, and the target gas in the storage tank connection passage 111 is sucked into the first compression stage 201 and the target gas compressed in the second compression stage 202 is discharged to the stage connection passage 113. At this time, the controller 420 receives signals of the detected pressure P1 and the detected temperature T1 from the upstream pressure sensor 401 and the temperature sensor 403 (step S100). Note that the controller 420 also receives a signal of the detected pressure P2 from the second pressure sensor 412.
The controller 420 derives the set pressure PS1 based on a relational expression for deriving the set pressure PS1 with the detected pressure P1 and the detected temperature T1 as parameters, and values acquired from the upstream pressure sensor 401 and the temperature sensor 403 (step S200). This relational expression is set so that the set pressure PS1 converges within the region a of fig. 2. The opening degree adjuster 441 adjusts the opening degree of the bypass valve 311 so that the received detected pressure P2 approaches the set pressure PS1 derived from the relational expression (step S300).
As described above, in the compressor unit 100, when the detected temperature T1 is lower than the first temperature T11 (upper limit temperature), the set pressure PS1 is changed to a higher value, and the opening degree of the bypass valve 311 is adjusted. Therefore, the target gas in the stage connecting passage 113 is less likely to be returned from the bypass passage 301 to the reserve tank connecting passage 111. Therefore, even when the processing amount of the target gas in the first compression stage 201 and the second compression stage 202 increases due to the intake of the low-temperature target gas, the increase in the flow rate of the target gas to be returned to the storage tank connection passage 111 is suppressed. As a result, the pressure of the reserve tank connection passage 111 can be suppressed from becoming excessively high.
In the compressor unit 100, when the set pressure changing unit 431 changes the set pressure PS1, if the temperature T1 detected by the temperature sensor 403 is equal to or lower than the preset lower limit temperature T13, the set pressure PS1 is maintained at a value corresponding to the temperature T13. Accordingly, the set pressure PS1 is prevented from rising excessively, and deterioration in the pressure balance between the compression stages 201 to 206 due to increase in the discharge pressure of the first compression stage 201 and the second compression stage 202 is prevented. As a result, the increase in power of the compressor unit can be suppressed.
In the compressor unit 100, when the pressure of the storage tank connection passage 111 increases as the amount of generation of the boil-off gas increases (irrespective of the change in the detected temperature T1), the set pressure changing unit 431 also changes the set pressure PS1 to a higher value in proportion to the detected pressure P1. Therefore, the increase in the flow rate of the target gas to be returned to the storage tank connection passage 111 is suppressed. As a result, the pressure of the reserve tank connection passage 111 can be suppressed from becoming excessively high.
(second embodiment)
A compressor unit 100 according to a second embodiment will be described with reference to fig. 4 and 5. Here, the same components as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
The second embodiment is different from the first embodiment in that: a relief valve 351 is provided in the stage connection flow path 113 of the compressor unit 100, and an upper limit pressure is provided in the set pressure PS1 changed by the set pressure changing unit 431. The other structures of the compressor unit 100 are the same as those of the first embodiment.
As shown in fig. 4, a relief valve 351 is provided between the second compression stage 202 and the cooler 212 in the stage connection flow path 113 to which the inlet side end portion 322 of the bypass flow path 301 is connected. The safety valve 351 is a safety device that opens when the pressure in the stage connection flow path 113 abnormally rises and reaches a predetermined operating pressure P30 set in the safety valve 351, and releases the gas in the stage connection flow path 113 to a predetermined location.
As shown in fig. 5, in order to prevent the set pressure PS1 from excessively approaching the operating pressure P30 of the relief valve 351, an upper limit pressure P26 that is lower than the operating pressure P30 by a predetermined value is set to the set pressure PS1, and this upper limit pressure is stored in the controller 420. Accordingly, the region a of fig. 2 is corrected not to exceed the upper limit pressure P26.
For example, let: when the detected temperature T1 is the second temperature T13, the detected pressure P1 changes from the state of pressure P15 (state L) to the state of pressure P16 higher than the pressure P15 (state M), and further changes to the state of pressure P17 higher than the pressure P16 (state N). When the state L changes to the state M, the set pressure changing unit 431 changes the set pressure PS1 from the pressure P25 to a pressure higher than the pressure P25 in accordance with a change in the detected pressure P1 from the pressure P15 to the pressure P16. The upper limit pressure at this time is an upper limit pressure P26 lower than the operating pressure P30 of the relief valve 351 by a predetermined value. Even if the state M changes to the state N, the set pressure change unit 431 maintains the set pressure PS1 at the upper limit pressure P26 because the set pressure PS1 reaches the upper limit pressure P26.
Accordingly, even when the amount of the target gas to be processed in the second compression stage 202 increases with a variation in the amount of the target gas requested from the demand side, the pressure of the stage connection passage 113 in which the safety valve 351 is provided can be suppressed from instantaneously reaching the operating pressure P30 of the safety valve 351. That is, unexpected operation of the relief valve 351 can be prevented.
Although descriptions of other structures, operations, and effects are omitted, the description of the first embodiment may be applied to the second embodiment.
(third embodiment)
A compressor unit 100 according to a third embodiment is described with reference to fig. 6. Here, the same components as those in the first and second embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.
The compressor train 100 according to the third embodiment includes first to fifth compression stages 201 to 205 of an oil-starved type. The request side supply flow path 117 is connected to the fifth compression stage 205. An upstream end of the reliquefaction line 119 is connected to a portion of the demand side supply flow path 117 downstream of the fifth compression stage 205 and upstream of the check valve 354. The stage connection passage 114 is connected to an exhaust passage 118 for discharging excess target gas to the combustion equipment 500. The fourth pressure sensor 414 is disposed on the suction side of the fourth compression stage 204 in the stage connection flow path 114, and the fifth pressure sensor 415 is disposed on the downstream side of the cooler 215 in the demand side supply flow path 117. In this case, the sixth compression stage 206, the bypass flow path 304, the bypass valve 314, the sixth pressure sensor 416, the cooler 216, the intermediate check valve 353, and the opening/closing valve 352 are omitted. The other structure is substantially the same as that of the first embodiment.
In the compressor unit 100 according to the third embodiment, as in the first embodiment, when the detected temperature T1 is lower than the first temperature T11 (upper limit temperature), the set pressure PS1 is changed to a higher value, and the opening degree of the bypass valve 311 is adjusted. Therefore, the target gas in the stage connection passage 113 is difficult to return to the storage tank connection passage 111 through the bypass passage 301. Even when the processing amount of the target gas in the first compression stage 201 and the second compression stage 202 increases due to the intake of the low-temperature target gas, the increase in the flow rate of the target gas to be returned to the storage tank connection passage 111 is suppressed.
Although descriptions of other structures, operations, and effects are omitted, the description of the first embodiment may be applied to the third embodiment.
In the first to third embodiments, when the detected temperature T1 is constant, the set pressure PS1 does not necessarily need to be changed at a constant increase rate (change indicated by a straight line in fig. 2) with respect to an increase in the detected pressure P1. For example, the set pressure PS1 may be changed in a stepwise increasing manner with respect to the increase in the detected pressure P1. Alternatively, the change may be a curve or may be a discontinuous increase.
In the first to third embodiments, the bypass passage 301 is provided so as to bypass the first compression stage 201 and the second compression stage 202, but the present invention is not limited thereto. The bypass passage 301 may bypass the first compression stage 201 to the third compression stage 203 or a compression stage on the downstream side of the third compression stage 203.
The embodiments disclosed herein are illustrative in all points and should not be construed as being limited thereto. 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.
Here, the embodiments are summarized.
(1) The compressor unit according to the present invention is a compressor unit installed in a ship, which recovers a target gas, which is a boil-off gas, from a liquefied natural gas storage tank of the ship and supplies at least a part of the target gas to a demand side. This compressor unit includes: a plurality of reciprocating compression stages for sequentially pressurizing the target gas; the crankshaft mechanism drives the piston of each compression section; a bypass flow path bypassing at least the first compression section; a bypass valve disposed on the bypass flow path; an upstream pressure sensor provided on a storage tank connection flow path connecting the liquefied natural gas storage tank and the first compression stage; a temperature sensor provided on the storage tank connection flow path; a downstream pressure sensor provided in a flow path that is located downstream of the reservoir connection flow path and connects an inlet side end of the bypass flow path; an opening degree adjustment unit that controls an opening degree of the bypass valve as follows: increasing the gas flow rate of the bypass flow path when the detected pressure of the downstream pressure sensor is higher than a predetermined set pressure; reducing the gas flow rate of the bypass flow path when the detected pressure of the downstream pressure sensor is lower than the set pressure; and a set pressure changing unit that increases the set pressure if the temperature detected by the temperature sensor decreases.
In the compressor unit configured as described above, when the temperature of the target gas flowing into the compressor unit from the liquefied natural gas storage tank decreases, the set pressure changing unit changes the set pressure to a higher pressure. The opening degree of the bypass valve is adjusted by the opening degree adjusting unit using the set pressure changed to a higher pressure as a target pressure of the pressure detected by the downstream pressure sensor. Therefore, the target gas is less likely to return from the discharge-side flow path to the reserve tank connection flow path through the bypass flow path, and therefore an increase in the flow rate of the target gas returning to the reserve tank connection flow path can be suppressed. As a result, when the temperature of the inflow target gas is low, the pressure of the storage tank connection passage can be suppressed from increasing.
(2) The set pressure changing unit may maintain the set pressure at a set pressure corresponding to a predetermined temperature when the temperature detected by the temperature sensor is equal to or lower than the predetermined temperature.
In this configuration, the temperature for changing the set pressure in the set pressure changing unit is set to a predetermined temperature having a lower limit. Therefore, the set pressure does not become higher than the pressure corresponding to the specified temperature, and therefore, an excessive rise in the set pressure can be suppressed. This can suppress an increase in power of the compressor unit.
(3) The set pressure changing unit may increase the set pressure as the detection pressure of the upstream pressure sensor increases.
In this configuration, when the pressure of the storage tank connection passage increases due to an increase in the amount of the generated boil-off gas, or the like, the set pressure is changed to a higher pressure. This makes it possible to suppress the flow rate of the target gas returned from the discharge-side flow path to the reserve tank connection flow path through the bypass flow path. This contributes to suppressing a pressure rise in the reserve tank connection passage.
(4) May further include: and a relief valve provided in the flow path connecting the inlet side end of the bypass flow path, the relief valve having a working pressure set at a constant value, wherein the set pressure changing unit sets an upper limit pressure lower than the working pressure of the relief valve by a predetermined value with respect to the set pressure.
In this configuration, the set pressure changing unit sets the upper limit pressure to the set pressure so that the set pressure that becomes the target pressure of the second pressure sensor does not excessively approach the operating pressure of the relief valve. Accordingly, even when the discharge amount from the compression stage varies, the pressure of the flow passage provided with the relief valve can be prevented from instantaneously reaching the operating pressure. That is, unexpected operation of the safety valve can be prevented.
(5) The temperature sensor may be provided in the reserve tank connection passage between an outlet-side end portion of the bypass passage and the first compression stage.
In this configuration, the temperature of the target gas flowing into the first compression stage can be accurately detected using the temperature sensor provided at a position closer to the suction port of the first compression stage.
(6) The method for controlling a compressor unit according to the present invention is a method for controlling a compressor unit installed in a ship, recovering a target gas, which is a boil-off gas, from a liquefied natural gas storage tank of the ship, and supplying at least a part of the target gas to a customer. The compressor unit includes: a plurality of reciprocating compression stages for sequentially pressurizing a target gas; a bypass flow path bypassing at least the first compression stage; a bypass valve provided on the bypass flow path; and a storage tank connection passage connecting the liquefied natural gas storage tank and the first compression stage. The control method of the compressor unit comprises the following steps: detecting the pressure of the target gas flowing through the storage tank connection passage by an upstream pressure sensor; detecting the temperature of the target gas flowing through the storage tank connection passage by a temperature sensor; detecting, by a downstream pressure sensor, a pressure of the target gas flowing through a flow path located on a downstream side with respect to the reserve tank connection flow path and connecting an inlet side end portion of the bypass flow path; controlling the opening degree of the bypass valve in the following manner: increasing the gas flow rate of the bypass flow path when the detected pressure of the downstream pressure sensor is higher than a predetermined set pressure; reducing the gas flow rate of the bypass flow path when the detected pressure of the downstream pressure sensor is lower than the predetermined set pressure; and increasing the set pressure if the detected temperature of the temperature sensor decreases.
According to the compressor unit of the present invention, when a low-temperature gas having a high gas density flows into the compressor unit from the reserve tank, an increase in pressure in the flow path on the reserve tank side can be suppressed.
Claims (6)
1. A compressor unit provided in a ship, for recovering a target gas, which is boil-off gas, from a liquefied natural gas storage tank of the ship and supplying at least a part of the target gas to a demand side, the compressor unit comprising:
a plurality of reciprocating compression stages for sequentially pressurizing the target gas;
the crankshaft mechanism drives the piston of each compression section;
a bypass flow path bypassing at least the first compression section;
a bypass valve provided on the bypass flow path;
an upstream pressure sensor provided on a storage tank connection flow path connecting the liquefied natural gas storage tank and the first compression stage;
a temperature sensor provided on the storage tank connection flow path;
a downstream pressure sensor provided in a flow path located on a downstream side of the reserve tank connection flow path and connecting an inlet side end portion of the bypass flow path;
an opening degree adjustment unit that controls an opening degree of the bypass valve as follows: increasing the gas flow rate of the bypass flow path when the detected pressure of the downstream pressure sensor is higher than a predetermined set pressure; reducing the gas flow rate of the bypass flow path when the detected pressure of the downstream pressure sensor is lower than the set pressure; and
and a set pressure changing unit that increases the set pressure if the temperature detected by the temperature sensor decreases.
2. The compressor rack of claim 1,
the set pressure changing unit maintains the set pressure at a set pressure corresponding to a predetermined temperature when a temperature detected by the temperature sensor is equal to or lower than the predetermined temperature.
3. The compressor rack of claim 2,
the set pressure changing unit increases the set pressure as the detected pressure of the upstream pressure sensor increases.
4. The set of compressors of claim 3, further comprising:
a relief valve provided on the flow path connecting the inlet side end portion of the bypass flow path, and a working pressure is set to a constant value, wherein,
the set pressure changing unit sets an upper limit pressure lower than the operating pressure of the relief valve by a predetermined value with respect to the set pressure.
5. Compressor train according to any of claims 1 to 4,
the temperature sensor is provided in the reserve tank connection passage between an outlet-side end portion of the bypass passage and the first compression stage.
6. A method for controlling a compressor unit, characterized in that the compressor unit is installed in a ship, a target gas, which is boil-off gas, is recovered from a liquefied natural gas storage tank of the ship, and at least a part of the target gas is supplied to a demand side,
the compressor unit includes: a plurality of reciprocating compression stages for sequentially pressurizing a target gas; a bypass flow path bypassing at least the first compression stage; a bypass valve provided on the bypass flow path; and a storage tank connection passage connecting the liquefied natural gas storage tank and the first compression stage,
the control method comprises the following steps:
detecting the pressure of the target gas flowing through the storage tank connection passage by an upstream pressure sensor;
detecting the temperature of the target gas flowing through the storage tank connection passage by a temperature sensor;
detecting, by a downstream pressure sensor, a pressure of the target gas flowing through a flow path located on a downstream side with respect to the reserve tank connection flow path and connecting an inlet side end portion of the bypass flow path;
controlling the opening of the bypass valve in the following manner: increasing the gas flow rate of the bypass flow path when the detected pressure of the downstream pressure sensor is higher than a predetermined set pressure; reducing the gas flow rate of the bypass flow path when the detected pressure of the downstream pressure sensor is lower than the predetermined set pressure; and
if the detected temperature of the temperature sensor decreases, the set pressure is increased.
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| JP2021129165A JP7022245B1 (en) | 2021-08-05 | 2021-08-05 | Compressor unit and control method of compressor unit |
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| CN110631295A (en) * | 2019-09-23 | 2019-12-31 | 珠海格力电器股份有限公司 | Pressure control device and pressure control method |
| CN111287934A (en) * | 2019-07-03 | 2020-06-16 | 株式会社神户制钢所 | Compressor unit and control method of compressor unit |
| CN111637358A (en) * | 2019-07-22 | 2020-09-08 | 株式会社神户制钢所 | Control method of compressor unit, compressor unit and plurality of compression sections |
| CN112983789A (en) * | 2020-06-29 | 2021-06-18 | 株式会社神户制钢所 | Compressor unit |
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| WO2012165865A2 (en) * | 2011-05-31 | 2012-12-06 | 대우조선해양 주식회사 | Cold heat recovery apparatus using an lng fuel, and liquefied gas carrier including same |
| KR101537173B1 (en) * | 2013-12-06 | 2015-07-16 | 현대중공업 주식회사 | A Treatment System Liquefied Gas |
| JP6756065B1 (en) * | 2020-06-29 | 2020-09-16 | 株式会社神戸製鋼所 | Compressor unit stop control method and compressor unit |
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| CN111287934A (en) * | 2019-07-03 | 2020-06-16 | 株式会社神户制钢所 | Compressor unit and control method of compressor unit |
| CN111637358A (en) * | 2019-07-22 | 2020-09-08 | 株式会社神户制钢所 | Control method of compressor unit, compressor unit and plurality of compression sections |
| CN110631295A (en) * | 2019-09-23 | 2019-12-31 | 珠海格力电器股份有限公司 | Pressure control device and pressure control method |
| CN112983789A (en) * | 2020-06-29 | 2021-06-18 | 株式会社神户制钢所 | Compressor unit |
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