WO2015128903A1

WO2015128903A1 - Receiving equipment for liquefied natural gas

Info

Publication number: WO2015128903A1
Application number: PCT/JP2014/001101
Authority: WO
Inventors: 裕馬坂本; 篤志神谷; 安達　修; 浩二郎倉田
Original assignee: 日揮株式会社
Priority date: 2014-02-28
Filing date: 2014-02-28
Publication date: 2015-09-03
Also published as: JP5959782B2; PH12016501683B1; JPWO2015128903A1; PH12016501683A1; SG11201606268QA

Abstract

The purpose of the present invention is to provide receiving equipment for liquefied natural gas, that is capable of stably processing boil-off gas generated in a storage tank for liquefied natural gas. This receiving equipment for liquefied natural gas is characterized by comprising: a storage tank (2) that stores liquefied natural gas received from outside; a discharging line (102) comprising a vaporizer (42) for vaporizing liquefied natural gas, said discharging line being for vaporizing liquefied natural gas sent from the storage tank by using the vaporizer and discharging same in a gas state; a boil-off gas line (103) for discharging pressure-boosted boil-off gas and comprising a gas compression unit (3) that boosts the pressure of boil-off gas generated inside the storage tank; a gas engine (6) that uses the boil-off gas generated inside the storage tank as fuel and drives a generator (61); and a fuel gas line (104) for supplying boil-off gas inside the storage tank to the gas engine.

Description

Receiving facility for liquefied natural gas

The present invention relates to a technology for utilizing boil-off gas generated in a storage tank that stores liquefied natural gas.

The natural gas produced at the wellhead of the gas field is cooled, liquefied and stored in a storage tank (LNG tank) as liquefied natural gas (LNG), then regasified and demand through the pipeline Supplied first. Also, in general, LNG is transported using an LNG tanker to a remote consumption area.

The receiving facility for receiving the LNG from the LNG tanker is provided with an LNG tank (storage tank) for storing the LNG. In the LNG tank, boil off gas (BOG: Boil Off Gas) mainly composed of nitrogen and methane is generated due to the heat input from the outer wall, the heat input when receiving the LNG, the liquid level rise in the LNG tank, etc. Do.

BOG generated in the LNG tank is extracted to the outside in order to prevent the pressure rise in the tank, boosted by the gas compressor, and then discharged to the customer along with the vaporized LNG, or reliquefied, and then the LNG is liquefied. It is returned to the tank. However, in the former method, BOG needs to be pressurized to a relatively high pressure, and the processing cost such as the electricity cost for operating the compressor becomes high. On the other hand, the latter method has a problem that nitrogen is circulated and concentrated by reliquefying BOG containing nitrogen and returning it to the LNG tank, and the heat amount of the gas discharged from the LNG tank is reduced.

Here, in Patent Document 1, power generation is performed using vaporized gas (BOG) generated in a low temperature tank (LNG tank) as fuel for a gas turbine generator, and generated power and exhaust heat of the gas turbine are reduced to low temperature liquefied gas ( The technology to be effectively used in the storage facility of LNG) is described. However, the gas turbine requires equipment for compressing the fuel gas to a high pressure, the equipment cost is high, and the energy conversion efficiency tends to be reduced due to the influence of changes in the outside air temperature and load fluctuations.

Further, Patent Document 2 describes a technique of burning a BOG generated at an LNG base with a gas engine to perform power generation, and utilizing exhaust heat of exhaust gas as power generation by a refrigerant turbine or vaporization heat of LNG.

JP, 10-267197, A: Claim 1, paragraphs 0015 to 0021, FIGS. JP 2012-241604 A: Paragraphs 0022 to 0025, FIG.

In general, gas engines do not have to compress fuel gas to high pressure as compared with gas turbines, and can realize stable energy conversion efficiency over a wide range of outside air temperature and load range. On the other hand, in a receiving facility that receives LNG from, for example, an LNG tanker, the amount of BOG generated at the time of receiving LNG sharply increases to several times that in normal times, and the property of BOG is also large due to changes in the properties of the received LNG. A changing phenomenon is seen.
However, Patent Document 2 does not describe a technique for coping with such changes in BOG generation amount and properties.

The present invention has been made under such circumstances, and an object thereof is to provide a facility for receiving liquefied natural gas capable of stably processing boil off gas generated in a storage tank for liquefied natural gas. It is.

The liquefied natural gas receiving facility of the present invention comprises a storage tank for storing liquefied natural gas received from the outside,
A vaporizer for vaporizing liquefied natural gas, and a vaporizing line for vaporizing liquefied natural gas delivered from the storage tank by the vaporizer and discharging the gas in the form of a gas;
A boil-off gas line for discharging a boil-off gas, which is provided with a gas compression unit for pressurizing the boil-off gas generated in the storage tank;
A gas engine that drives a generator using boil-off gas generated in the storage tank as fuel;
And a fuel gas line for supplying boil-off gas in the storage tank to the gas engine.

A receiving facility for liquefied natural gas according to another invention comprises a storage tank for storing liquefied natural gas received from the outside,
A vaporizer for vaporizing liquefied natural gas, and a vaporizing line for vaporizing liquefied natural gas delivered from the storage tank by the vaporizer and discharging the gas in the form of a gas;
A boil-off gas line for returning the liquefied boil-off gas to the storage tank or supplying the gas to the vaporizer; and a gas compression unit for pressurizing and liquefying the boil-off gas generated in the storage tank;
A gas engine that drives a generator using boil-off gas generated in the storage tank as fuel;
And a fuel gas line for supplying boil-off gas in the storage tank to the gas engine.

The liquefied natural gas receiving facility may have the following features.
(A) The gas compression unit includes a multistage gas compressor, and the fuel gas line is connected to the discharge side of the middle stage of the gas compressor. Alternatively, the fuel gas line is branched from the boil-off gas line on the front side of the gas compression unit, and includes a pressure raising unit that boosts the boil-off gas supplied to the gas engine to a receiving pressure of the gas engine.
(B) A supply stop unit is provided to stop the supply of the boil-off gas to the fuel gas line when the property of the boil-off gas supplied to the gas engine deviates from a preset reference value. The fuel gas line may be provided with a property detection unit for detecting the property of the boil-off gas. At this time, the property of the boil off gas is a methane number or a heat amount.
(C) The fuel gas line is provided with a gas holder. In addition, this gas holder mixes the boil-off gas used until now with the boil-off gas of liquefied natural gas newly received from the outside, and is a gas mixture for alleviating the change in fuel properties of the gas engine. Provide a department.
(D) The combustion gas line is provided with a nitrogen removal part for reducing the concentration of nitrogen contained in the boil-off gas supplied to the gas engine.
(E) An exhaust heat recovery unit for recovering exhaust heat of cooling water discharged from the gas engine or exhaust heat of exhaust gas, the exhaust heat recovery unit comprising: the vaporizer; It is for providing a heat source to at least one of the heat regulation equipment for supplying oil gas, or the heater of the said storage tank.
(F) A power supply facility is provided that supplies the power generated by the generator to a power consuming device in the facility receiving the liquefied natural gas.

According to the present invention, a boil-off gas line for boosting and discharging the boil-off gas generated in the storage tank for liquefied natural gas, or liquefying the boil-off gas and returning it to the storage tank or supplying it to the vaporizer Since the fuel gas line for supplying the boil-off gas to the gas engine is also provided, it is possible to select an appropriate processing destination according to the change in the amount of boil-off gas generated and the property, and to perform stable processing. it can.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows the structural example of the LNG receiving installation which concerns on embodiment of this invention. It is a flow figure showing the flow of judgment which performs supply cut of BOG to a fuel gas line in the above-mentioned LNG receiving equipment. It is explanatory drawing which shows the structural example of the LNG receiving installation which concerns on other embodiment. It is explanatory drawing which shows the structural example of the LNG receiving installation which concerns on another embodiment.

Hereinafter, an embodiment in which the present invention is applied to a receiving facility for receiving the LNG transported by the LNG tanker 1 will be described with reference to FIG.
The receiving facility comprises an LNG tank 2 for storing LNG,

LNG pumps

21 and 41 for delivering the LNG from the LNG tank 2 for delivering gas to the customer 7, and gasification of LNG by gasifying the LNG. And a heat quantity adjustment unit 43 for adding liquefied petroleum gas (LPG: Liquefied Petroleum Gas) for heat quantity adjustment to the vaporized gas.

The LNG tank 2 is a storage tank for storing the LNG received from the LNG tanker 1 in the state of liquid cooled to about -162 ° C., and its type (ground tank, underground tank, underground tank, etc.) and capacity There is no particular limitation on The LNG tank is provided with a heater to prevent freezing of the ground. For example, in underground tanks, heaters are provided on the side and bottom, and in ground tanks, heaters are provided on the bottom. FIG. 1 shows an example of a ground-type tank in which the upper surface of a cylindrical side wall is covered with a dome-shaped roof. The bottom of the LNG tank 2 is provided with a heater 22 for passing a heat medium for preventing freezing of the ground.

In the LNG tank 2, an LNG receiving line 101 for receiving the LNG unloaded from the LNG tanker 1 via the unloading arm 11 into the LNG tank 2, and an LNG via the LNG pump 21 disposed in the LNG tank 2. The LNG delivery line 102a to be delivered is connected. A delivery pump 41 for boosting is interposed in the LNG delivery line 102 a, and its end is connected to the LNG vaporizer 42.

The LNG vaporizer 42 is a device for vaporizing the LNG delivered from the LNG tank 2 in a liquid state and discharging the gas as a gas adjusted to the pressure required by the customer 7. The LNG vaporizer 42 is conventionally an open rack system that vaporizes LNG using seawater or bubbling combustion gas obtained by burning gas with a gas burner that opens downward into a water tank into water in the water tank. The thing of the submerged conversion system etc. which vaporize LNG with the warm water heated by this is used. In the receiving facility of this embodiment, since the exhaust heat of the cooling water of the gas engine 6 described later or the exhaust heat of the exhaust gas can be used, direct heat exchange with the exhaust gas, or a heat medium heated by the exhaust gas The system may be configured as an LNG vaporizer 42 that heats and vaporizes the LNG by indirect heat exchange via the

The LNG vaporizer 42 is connected to a vaporized gas discharge line 102 b that discharges the vaporized gas, and the end of the vaporized gas discharge line 102 b is connected to the heat amount adjustment unit 43. The heat amount adjustment unit 43 is a facility for mixing LPG for heat amount adjustment with the vaporized gas and discharging the product gas having the heat amount required by the customer 7. The LPG (butane or propane) stored in the LPG tank 8 is delivered to the heat amount adjustment unit 43 in a liquid state via the LPG pump 81. The LPG is vaporized by the heat quantity adjustment unit 43 using the heat medium, and mixed with the vaporized gas delivered from the LNG vaporizer 42 side to become a product gas. The product gas whose heat quantity has been adjusted by the LNG vaporizer 42 is discharged to the customer 7 through the shipping line 105.
The above-described LNG delivery line 102a, the vaporized gas delivery line 102b, and the shipping line 105 in the site of the receiving facility correspond to the delivery line of this example.

The equipment for receiving LNG having the basic configuration described above is provided with equipment for processing BOG generated in the LNG tank 2. Hereinafter, the structural example of the installation which processes the said BOG is demonstrated.
As shown in FIG. 1, the LNG tank 2 is connected to a BOG extraction line 103a for extracting BOG generated therein. The BOG extraction line 103a is connected to the BOG compressor 3 which is a compressor for boosting the BOG pressure.

The BOG compressor 3 of this example is configured as, for example, a multi-stage gas compressor having three compression stages 31 to 33. For example, the BOG compressor 3 pressurizes BOG having a pressure on the suction side of the compression stage 31 of about 12 to 22 kPa-G to about 2 to 7.5 MPa-G. The BOG pressurized by the BOG compressor 3 flows through the high pressure BOG line 103b and then merges with the vaporized gas delivery line 102b through which the vaporized gas flows, and after adjusting the amount of heat, it is delivered to the customer 7 as a product gas.
The BOG extraction line 103a and the high pressure BOG line 103b constitute a boil-off gas line of this example.

Furthermore, in the LNG receiving facility according to the present embodiment, BOG is used as a fuel gas for gas engine 6, and power generated by driving generator 61, exhaust heat from cooling water of gas engine or combustion of fuel gas Exhaust heat of exhaust gas is used in each device in the receiving facility.
Here, as described in the background art, the gas engine 6 can use a fuel gas with a lower pressure than a gas turbine. On the other hand, the pressure is not sufficient to use the BOG extracted from the LNG tank 2 as it is, and the BOG after being pressurized by the BOG compressor 3 is too high in pressure, so a pressure reduction operation is required. Energy loss occurs.

Therefore, in the receiving facility of this embodiment, an intermediate pressure of the BOG compressor 3 is used to boost the pressure of the BOG by dividing the pressure into a plurality of stages, and by extracting BOG from the discharge side of the intermediate pressure, an appropriate pressure (for example, 0. The BOG pressurized to 5 to 1 MpaG) is supplied to the gas engine 6 as fuel gas. In the example shown in FIG. 1, the base end of the fuel gas line 104 a for supplying the fuel gas to the gas engine 6 is connected to the discharge side of the first compression stage 31 of the BOG compressor 3.

Furthermore, the fuel gas lines 104a to 104c that supply BOG as fuel gas to the gas engine 6 are provided with various devices for stably operating the gas engine 6 in response to fluctuations in BOG generation amount and properties. There is.
The supply shutoff valve 51 is an on-off valve that executes supply and stop of BOG to the downstream side of the fuel gas line 104a. The supply shutoff valve 51 is a supply stop unit that stops the supply of BOG to the downstream side of the fuel gas line 104a when the property of the BOG supplied from the LNG tank 2 side deviates from a preset reference value. Function.

As a property of BOG used as the reference | standard which performs BOG supply and stop by the supply cut-off valve 51, a methane value and calorie | heat amount can be mentioned.
The methane number is an index showing the difficulty of occurrence of knocking (anti-knock performance) in a gas engine, and corresponds to the octane number of gasoline in a gasoline engine. Fuel gases having a low methane number are prone to knocking, and fuel gases having a high methane number are less likely to cause knocking. As a calculation method of the methane number, the one standardized by AVL, and the standard of CARB (California Air Resources Board) ("Petroleum and Natural Gas Review" (National Administrative Agency for Petroleum Natural Gas and Metals and Mineral Resources) vol. 39 No. .5 see p20) and so on. As a standard of the supply cut judgment of the fuel gas in the supply cut valve 51, the methane number calculated according to the calculation method adopted to the specification of gas engine 6 provided in the receiving facility concerned is adopted.

Further, as the heat quantity, a calorific value generated when BOG is burned, or an index such as a Wobbe index obtained by dividing the calorific value by 1/2 root of BOG specific gravity is adopted.
The methane value and heat quantity required for BOG supplied to the gas engine 6 as a fuel gas have a reference value range set in advance as the specification of the gas engine 6.

Further, an analyzer 55 (property detection unit) including a methane value analyzer and a gas calorimeter online is interposed in the BOG extraction line 103a. The methane value and heat value of BOG detected by the analyzer 55 are output to the control unit 511 including a DCS (Distributed Control System) that controls the receiving facility, and the opening / closing operation of the supply shutoff valve 51 is performed. It is used for judgment.

The position where the analyzer 55 is provided is not limited to the fuel gas line 104 a on the outlet side of the BOG compressor 3. For example, the analyzer 55 may be provided on the fuel gas line 104b after nitrogen is removed by the PSA unit 52 described later.
Further, the present invention is not limited to the case of providing the on-line analyzer 55 in the fuel gas line 104a, but the BOG supplied to the fuel gas line 104a is periodically sampled and analyzed off-line. It is good also as composition which judges.

On the downstream side of the supply shutoff valve 51, a PSA (pressure swing absorption) unit 52, which is a nitrogen removing unit for reducing the concentration of nitrogen (N ₂ ) contained in BOG serving as fuel gas for the gas engine 6, is disposed. It is done. The PSA unit 52 is composed of two adsorption towers packed with an adsorbent that adsorbs nitrogen, and BOG is allowed to flow on one side to adsorb and remove nitrogen in BOG. Further, in the other side of the adsorption column where BOG is not conducted, the pressure in the column is lowered to desorb nitrogen from the adsorbent, and the regeneration operation of discharging the nitrogen together with the air supplied into the column is performed.

Then, the process of removing nitrogen from BOG can be continuously performed by alternately switching the adsorption towers in which the adsorption operation of nitrogen and the regeneration operation of adsorbent are performed.
Here, the nitrogen removal method adopted in the nitrogen removal part is not limited to the case of the PSA method. For example, a cryogenic separation method may be employed in which BOG is cooled, liquefied, and separated into nitrogen and fuel gas components such as methane by distillation.

The BOG from which nitrogen has been removed in the PSA unit 52 is introduced into the gas holder 53 via the fuel gas line 104b. The gas holder 53 temporarily stores BOG supplied to the gas engine 6 as fuel gas. The configuration of the gas holder 53 is not limited to a special type, but in this example, the gas holder 53 is provided with a piston 532 that moves up and down according to the amount of BOG stored in the gas holder 53.

Further, inside the gas holder 53, a baffle plate 531 for mixing the BOG in the gas holder 53 and the BOG received from the fuel gas line 104b is disposed. The baffle plate 531 changes the property of BOG greatly due to the property change of the LNG received from the LNG tanker 1, the BOG in the gas holder 53 used until now and the BOG generated from the new LNG are used The gas mixing section serves as a gas mixing unit for sufficiently mixing and reducing property changes of the fuel gas supplied to the gas engine 6.

The BOG in the gas holder 53 described above is supplied to the gas engine 6 via the fuel gas line 104c. The gas engine 6 is an internal combustion engine capable of generating electric power by driving a generator 61 with BOG mainly containing methane as fuel gas. The gas engine 6 can be operated in a wide load range of, for example, 30% to 100%, and is characterized by being less susceptible to changes in the outside air temperature than gas turbines.

The electric power generated by driving the generator 61 by the gas engine 6 is received by the BOG compressor 3, the LNG pumps 21 and 41, the LPG pump 81, etc. Power consumption equipment such as lighting.
Further, the exhaust gas after burning BOG by the gas engine 6 and driving the internal cylinder is used for the vaporization of LNG and LPG in the LNG vaporizer 42 and the heat quantity adjustment unit 43, and heating of the bottom surface of the LNG tank 2 and the like. . When cooling water is used as a heat source, the cooling water is a heat medium, and heat is supplied to the LNG vaporizer 42, the heat quantity adjustment unit 43, and the heater 22. When the cooling water and the exhaust gas itself are used as a heat source, the cooling water and the exhaust gas discharged from the gas engine 6 are supplied as they are to the LNG vaporizer 42, the heat amount adjustment unit 43, and the heater 22. In this case, these

devices

42, 43, 22 constitute an exhaust heat recovery unit. When steam or hot water is generated by a boiler (not shown) using the heat of the exhaust gas and this is used as a heat medium (heat source), the boiler becomes an exhaust heat recovery unit.

A specific example of the operation of processing BOG generated in the LNG tank 2 in the LNG receiving facility having the configuration described above will be described. Here, FIG. 2 is a flow chart showing the flow of the open / close judgment of the supply shutoff valve 51.
When the LNG from the LNG tanker 1 is not received in the LNG tank 2 shown in FIG. 1, it is assumed that, for example, a BOG of 5 t / h (tons per hour) is generated. The gas engine 6 has an output capable of supplying the electric power in the receiving facility, and consumes, for example, 1 t / h of BOG in the power consumption balance.

Accordingly, 4 t / h of the BOG supplied to the BOG compressor 3 via the BOG discharge line 103 a is mixed with the vaporized gas, and is dispensed to the customer 7 as a product gas. And the amount of delivery of LNG delivered from the LNG tank 2 will be increased / decreased in consideration of the mixture of said BOG.

On the other hand, BOG supplied to the gas engine 6 as fuel gas is extracted from the intermediate stage of the BOG compressor 3 to the fuel gas line 104a, and the methane number and heat quantity are measured by the analyzer 55 (start of FIG. 2) ). Then, when the methane number and heat amount of BOG both satisfy the reference value (step S101; YES and S102; YES in the same figure), BOG is supplied downstream via the fuel gas line 104a. (Step S103 in the figure).

The BOG supplied from the fuel gas line 104a is nitrogen-removed in the PSA unit 52, and then flows into the gas holder 53 to be temporarily stored, and then supplied to the gas engine 6 and burned as a fuel gas. . The power generated by burning the BOG is consumed by the BOG compressor 3, the LNG pumps 21, 41 and the like. Further, the exhaust heat of the cooling water discharged from the gas engine 6 or the exhaust heat of the combustion exhaust gas is used by the LNG vaporizer 42, the heat amount adjustment unit 43, and the heater 22.

Here, the reception of the LNG from the LNG tanker 1 is performed once to several times a month, but at this time, the amount of BOG generated in the LNG tank 2 is several times, for example, about four times as normal. Increase. In this case, the amount of BOG mixed with the vaporized gas via the BOG compressor 3 is increased, while the amount of LNG delivered from the LNG tank 2 is reduced to absorb the increased amount of BOG. At this time, the gas engine 6 consumes BOG in balance with the amount of power consumption in the receiving facility.
When BOG exceeding the amount that can be mixed with the vaporized gas is generated, the supply amount to the fuel gas line 104a may be increased, and the storage amount of BOG in the gas holder 53 may be temporarily increased.

Further, at the timing of receiving the LNG from the LNG tanker 1, the property of the LNG may greatly change depending on the difference of the production area or the well. In such a case, the properties of BOG generated in the LNG tank 2 also largely change, and the combustion state of BOG in the gas engine 6 also changes. However, since the gas holder 53 is provided on the inlet side of the gas engine 6 and the BOG used so far and the BOG generated from the new LNG are mixed by the baffle plate 531, the gas engine 6 burns. Changes in BOG progress slowly. As a result, the gas engine 6 can follow the change of the BOG property with a margin, and can continue the operation while changing the operating conditions such as the air supply amount.
Furthermore, since the PSA unit 52 is interposed in the fuel gas lines 104a to 104b of this example, even if there is a change in the property that the nitrogen concentration in BOG increases, the nitrogen content is reduced and a stable amount of heat is obtained. The fuel gas which it has can also be supplied to the gas engine 6.

On the other hand, if the change range of the BOG property is large and the methane value and heat value deviate from the standard values that can be used by the gas engine 6 (step S101 in FIG. 2; NO or S102; NO), supply The shutoff valve 51 is closed to stop the supply of BOG from the fuel gas line 104a to the downstream side (step S104 in the figure). Even if the supply of BOG from the fuel gas line 104a is stopped, the BOG is stored in the gas holder 53, so the gas engine 6 can continue operation.

In addition, when the property change of the BOG is likely to last for a long time, the operation of the gas engine 6 may be reduced and the operation of the gas engine 6 may be continued with the BOG stored in the gas holder 53. As a result, when the amount of power generation of the generator 61 is reduced and the power supply to the power consuming device in the receiving facility can not be supplied, the power may be purchased from the outside.

In the above-described example in which the supply of BOG to the downstream side of the fuel gas line 104a is stopped, the BOG not sent to the gas engine 6 is mixed with the vaporized gas through the high pressure BOG line 103b. At this time, when an amount of BOG exceeding the amount that can be mixed into the vaporized gas is generated, the excess BOG may be extracted to a flare stack (not shown) and burned.

Here, for example, in the fuel gas line 104a on the upstream side of the supply shutoff valve 51, a recycle line (not shown) for returning the BOG extracted from the intermediate stage of the BOG compressor 3 to the suction side of the BOG compressor 3 is provided Even if the supply of BOG to the downstream side is stopped, analysis of the fuel gas by the analyzer 55 can be performed. Then, when the property of BOG detected by the analyzer 55 becomes a value within the reference value, the supply shutoff valve 51 is opened to supply BOG downstream of the fuel gas line 104a (step S101 in FIG. 3; YES) And S102; YES, S103). At this time, in order to supplement BOG in the gas holder 53 consumed during the period when the supply shutoff valve 51 is closed, the amount of BOG supplied toward the gas holder 53 is greater than the consumption of BOG in the gas engine 6 You may also increase it temporarily.

The LNG receiving facility according to the embodiment of the present invention has the following effects. An LNG delivery line 102a for boosting and discharging BOG generated in the LNG tank 2, a vaporized gas delivery line 102b, a shipping line 105, and fuel gas lines 104a to 104c for supplying BOG to the gas engine 6 are provided. Because of this, it is possible to select an appropriate processing destination according to changes in the amount of BOG generated and properties, and perform stable processing.

Next, FIG. 3 shows an example in which a gas engine 6 is added to an LNG receiving facility of a type that reliquefies BOG. In the receiving facility of this example, the number of compression stages 31, 32 of the BOG compressor 3a is smaller than that of the BOG compressor 3 of FIG. 1, and the discharge pressure is lower, and The condenser 44 is provided for cooling and liquefying BOG by heat exchange of the BOG, and the BOG liquefied in the condenser 44 is recovered to the LNG tank 2 via the liquefaction BOG line 103c, or the liquefaction BOG delivery line This embodiment is different from the example shown in FIG. 1 in that after being joined to the LNG delivered from the LNG tank 2 via 107, it is delivered to the customer 7.

As described in the background art, there is a problem that nitrogen is circulated and concentrated in the receiving facility that recovers the reliquefied BOG, but nitrogen is concentrated by constantly extracting the BOG toward the gas engine 6 The degree can be reduced. Further, since BOG from which nitrogen has been removed by the PSA unit 52 is supplied to the gas engine 6 as fuel gas, even if nitrogen is concentrated by reliquefaction of BOG, the influence of the increase in nitrogen concentration on the gas engine 6 is suppressed. be able to.

Here, the BOG flowing through the high pressure BOG line 103b shown in FIG. 1 is not limited to the case where the BOG is mixed with the vaporized gas of the vaporized gas delivery line 102b and dispensed. For example, the heat quantity may be adjusted without being mixed with the vaporized gas, and may be discharged as a product gas.

Moreover, the method of adjusting the pressure of BOG supplied to the gas engine 6 is not limited to the method of extracting BOG from the middle stage of the

multistage BOG compressors

3 and 3a. For example, as shown in FIG. 4, the fuel gas line 104a is branched on the front side of the BOG compressor 3, and a fuel gas compressor 54 (boosting portion) for boosting is provided on the fuel gas line 104a. The pressure may be increased to a receiving pressure (eg, 0.5 to 1 MpaG).

As described above, FIGS. 1, 3 and 4 show an example of a receiving facility of a type that receives LNG from the LNG tanker 1, vaporizes the LNG with the LNG vaporizer 42, and ships the LNG to the customer 7. The applicable equipment is not limited to the receiving equipment of the type that receives LNG from the LNG tanker 1. For example, the present invention can be applied to a delivery facility for an LNG liquefaction base that receives LNG obtained by cooling and liquefying natural gas produced from the wellhead of a gas field. In this case, the connection source of the LNG receiving line 101 shown in each of the above-mentioned drawings is replaced by the LNG tanker 1 and becomes the dispensing facility of the LNG liquefaction base provided in the gas field.

Furthermore, in the case of a delivery facility for an LNG liquefaction base that receives LNG obtained by cooling and liquefying natural gas produced from the wellhead of the gas field, in the case of delivering the LNG in the LNG tank 2, the LNG is vaporized. It is not essential to For example, the present invention can be applied to a delivery facility of an LNG liquefaction base configured to deliver LNG in the LNG tank 2 to the LNG tanker 1 in a liquid state.

Furthermore, in the LNG receiving facility according to the present invention, all of the supply shutoff valve 51 (supply stop unit), the PSA unit 52 (nitrogen removal unit), and the gas holder 53 are provided for the fuel gas lines 104a to 104c. Is not a required requirement. Depending on the property change of LNG or BOG stored in the LNG tank 2 or the change of the BOG generation amount, any one of these

facilities

51, 52, 53 may be selected and provided.

Furthermore, for example, in a receiving facility provided with a plurality of LNG tanks 2 in a common site, it is not essential to provide the fuel gas lines 104a to 104b and the gas engine 6 in all the LNG tanks 2. Only one of the plurality of LNG tanks 2 is provided with the fuel gas lines 104a to 104b (where the fuel gas compressor 54 shown in FIG. 4 is installed), and all the BOG generated in the LNG tank 2 is a gas. The fuel gas of the engine 6 may be used. On the other hand, the other LNG tanks 2 are BOG withdrawal line 103a-BOG compressor 3-high pressure BOG line 103b (FIG. 1), BOG withdrawal line 103a-BOG compressor 3a-liquefied BOG line 103c, and liquefied BOG delivery as usual. A line 107 (FIG. 3) is provided, and BOG is not supplied to the gas engine 6. Then, the fuel gas line 104 a of the LNG tank 2 connected to the gas engine 6 is branched, and this branch line is connected to the BOG extraction line 103 a of the other LNG tank 2.

As a result, when viewed across the receiving facility provided with a plurality of LNG tanks 2, the receiving facility boosts BOG and discharges it (BOG extraction line 103a-BOG compressor 3-high pressure BOG line 103b), or A system for reliquefying and recovering and discharging (BOG discharge line 103a-BOG compressor 3a-liquefied BOG line 103c, liquefied BOG delivery line 107), and fuel gas line 104a for supplying BOG to the gas engine 6 The configuration is such that ~ 104c is provided side by side.

Thus, the entire amount of BOG generated in one LNG tank 2 is burned by the gas engine 6, and if the power obtained by the power generation exceeds the power consumption in the receiving facility, the surplus power is sold. Can. When the property of BOG deviates from the standard that can be accepted by the gas engine 6, the BOG generated in the LNG tank 2 is transferred to the BOG extraction line 103a of the other LNG tank 2 via the above-described branch line. The extraction and the supply of BOG to the gas engine 6 may be stopped.

1 LNG tanker 102a LNG discharge line 102b vaporized gas discharge line 103a BOG discharge line 103b high pressure BOG line 103c liquefaction BOG line 104a to 104c
Fuel gas line 105 Shipment line 107 Liquefied BOG delivery line 2 LNG tank 22

Heater

3, 3a BOG compressors 31 to 33 Compression stage 42 LNG vaporizer 43 Heat quantity adjustment unit 51 Supply cut off valve 52 PSA unit 53 Gas holder 531 Baffle plate 54 Fuel Gas compressor 55 Analyzer 6 Gas engine 61 Generator 62 Power supply unit

Claims

A storage tank for storing liquefied natural gas received from the outside;
A vaporizer for vaporizing liquefied natural gas, and a vaporizing line for vaporizing liquefied natural gas delivered from the storage tank by the vaporizer and discharging the gas in the form of a gas;
A boil-off gas line for discharging a boil-off gas, which is provided with a gas compression unit for pressurizing the boil-off gas generated in the storage tank;
A gas engine that drives a generator using boil-off gas generated in the storage tank as fuel;
And a fuel gas line for supplying the boil-off gas in the storage tank to the gas engine.
A storage tank for storing liquefied natural gas received from the outside;
A vaporizer for vaporizing liquefied natural gas, and a vaporizing line for vaporizing liquefied natural gas delivered from the storage tank by the vaporizer and discharging the gas in the form of a gas;
A boil-off gas line for returning the liquefied boil-off gas to the storage tank or supplying the gas to the vaporizer; and a gas compression unit for pressurizing and liquefying the boil-off gas generated in the storage tank;
A gas engine that drives a generator using boil-off gas generated in the storage tank as fuel;
And a fuel gas line for supplying the boil-off gas in the storage tank to the gas engine.
The liquefaction according to claim 1 or 2, wherein the gas compression unit includes a multistage gas compressor, and the fuel gas line is connected to the discharge side of an intermediate stage of the gas compressor. Natural gas receiving facility.
The fuel gas line is branched from the boil off gas line on the front side of the gas compression unit, and includes a pressure raising unit that raises the pressure of boil off gas supplied to the gas engine to an acceptance pressure of the gas engine. The receiving facility of the liquefied natural gas according to claim 1 or 2.
The fuel cell system may further include a supply stop unit configured to stop the supply of the boil-off gas to the fuel gas line when the property of the boil-off gas supplied to the gas engine deviates from a preset reference value. Or the receiving facility for liquefied natural gas described in 2.
The facility for receiving liquefied natural gas according to claim 5, wherein the fuel gas line is provided with a property detection unit for detecting a property of a boil-off gas.
The property of the said boil off gas is a methane number, The receiving installation of the liquefied natural gas of Claim 5 characterized by the above-mentioned.
The facility for receiving liquefied natural gas according to claim 5, wherein the property of the boil-off gas is a heat quantity.
The facility for receiving liquefied natural gas according to claim 1, wherein a gas holder is provided in the fuel gas line.
The gas holder mixes the boil-off gas used so far with the boil-off gas of liquefied natural gas newly received from the outside, thereby reducing the change in the fuel property of the gas engine. The liquefied natural gas receiving facility according to claim 9, comprising:
The facility for receiving liquefied natural gas according to claim 1 or 2, wherein the combustion gas line is provided with a nitrogen removal unit for reducing the concentration of nitrogen contained in the boil-off gas supplied to the gas engine. .
The exhaust heat recovery unit recovers the exhaust heat of the cooling water discharged from the gas engine or the exhaust heat of the exhaust gas, and the exhaust heat recovery unit includes the vaporizer, and the liquefied gas for adjusting the amount of heat to the vaporized gas. The facility for receiving liquefied natural gas according to claim 1 or 2, which is for supplying a heat source to at least one of a heat quantity adjustment facility for supplying or a heater of the storage tank.
The reception facility for liquefied natural gas according to claim 1 or 2, further comprising: a power supply facility for supplying power generated by the generator to a power consumption device in the reception facility for liquefied natural gas. .