JP5959782B2 - Facility for receiving liquefied natural gas - Google Patents

Description

  The present invention relates to a technique for utilizing boil-off gas generated in a storage tank for storing liquefied natural gas.

  The natural gas produced at the well of the gas field is cooled, liquefied, stored in a storage tank (LNG tank) as liquefied natural gas (LNG), and then gasified again for demand through the pipeline. Supplied first. In general, LNG is transported to a remote consumer area using an LNG tanker.

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

  The BOG generated in the LNG tank is extracted outside in order to prevent the pressure in the tank from rising, and after the pressure is increased by the gas compressor, the LNG is discharged to the customer with the vaporized LNG, or reliquefied. Or returned to the tank. However, in the former method, it is necessary to increase the pressure of BOG to a relatively high pressure, which increases processing costs such as electricity costs for operating the compressor. On the other hand, the latter method has a problem that the BOG containing nitrogen is re-liquefied and returned to the LNG tank, whereby nitrogen is circulated and concentrated, and the amount of heat of gas discharged from the LNG tank is reduced.

  Here, in Patent Document 1, electric power is generated using vaporized gas (BOG) generated in a low temperature tank (LNG tank) as a fuel for a gas turbine generator, and the generated electric power and exhaust heat of the gas turbine are converted into low temperature liquefied gas ( LNG) describes techniques for effective use within storage facilities. However, the gas turbine requires equipment for compressing the fuel gas to high pressure, and the equipment cost is high, and the energy conversion efficiency tends to decrease due to the influence of changes in outside air temperature and load fluctuations.

  Patent Document 2 describes a technology in which BOG generated at an LNG base is burned by a gas engine to generate power, and exhaust heat of exhaust gas is used as power generation by a refrigerant turbine or as heat of LNG vaporization.

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

In general, a gas engine does not need to compress fuel gas to a higher pressure than a gas turbine, and can realize stable energy conversion efficiency in a wide range of outside air temperature and load. On the other hand, for example, in an acceptance facility that accepts LNG from an LNG tanker, the amount of BOG generated at the time of accepting LNG suddenly increases to several times that of normal time, and the properties of BOG are also large due to changes in the properties of accepted LNG. There is a changing phenomenon.
However, Patent Document 2 does not describe a technique corresponding to such a change in the amount of BOG generated or properties.

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

The liquefied natural gas receiving facility of the present invention comprises a storage tank for storing liquefied natural gas received from an external liquefied natural gas tanker ,
A vaporizer for vaporizing liquefied natural gas; vaporizing the liquefied natural gas sent from the storage tank with the vaporizer; and a discharge line for discharging in a gas state;
A gas compression unit that pressurizes the boil-off gas generated in the storage tank, and a boil-off gas line for discharging the boosted boil-off gas to the discharge line;
A gas engine for driving the the generator,
A fuel gas line provided to be branched from the boil-off gas line and provided independently of the discharge line, and for supplying boil-off gas generated in the storage tank as fuel to the gas engine;
A gas mixing section provided in the fuel gas line, for absorbing a change in the amount of boil-off gas supplied to the fuel gas line and mitigating a change in the properties of the boil-off gas supplied to the gas engine And a gas holder .

A liquefied natural gas receiving facility according to another invention includes a storage tank for storing liquefied natural gas received from an external liquefied natural gas tanker ,
A vaporizer for vaporizing liquefied natural gas; vaporizing the liquefied natural gas sent from the storage tank with the vaporizer; and a discharge line for discharging in a gas state;
A gas compression unit for boosting and liquefying the boil-off gas generated in the storage tank, and returning the liquefied boil-off gas to the storage tank or supplying the boil-off gas to the vaporizer;
A gas engine for driving the the generator,
A fuel gas line provided to be branched from the boil-off gas line and provided independently of the discharge line, and for supplying boil-off gas generated in the storage tank as fuel to the gas engine;
A gas mixing section provided in the fuel gas line, for absorbing a change in the amount of boil-off gas supplied to the fuel gas line and mitigating a change in the properties of the boil-off gas supplied to the gas engine And a gas holder .

The liquefied natural gas receiving facility may have the following characteristics.
(A) The gas compressor includes a multi-stage gas compressor, and the fuel gas line is connected to a discharge side of a stage before the final stage of the gas compressor and branches from the boil-off gas line and by that, Rukoto BOG boosted until receiving the pressure of the gas engine is supplied to the gas engine. Alternatively, the fuel gas line includes a boosting unit that branches from the boil-off gas line on the front side of the gas compression unit and boosts the boil-off gas supplied to the gas engine to an acceptance pressure of the gas engine.
(B) A supply stop unit that stops 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 is provided with a property detection unit for detecting the property of the boil-off gas. At this time, the boil-off gas has a methane number or a calorific value.
(C) The prior Ki燃material gas lines, comprise a nitrogen removal unit for reducing the concentration of nitrogen contained in the boil-off gas supplied to the gas engine.
( D ) An exhaust heat recovery unit that recovers exhaust heat of the cooling water exhausted from the gas engine or exhaust heat of the exhaust gas is provided, and the exhaust heat recovery unit liquefies the vaporized gas to adjust the amount of heat. It is for supplying a heat source to at least one of a calorie adjusting facility for supplying petroleum gas or a heater of the storage tank.
( E ) Provided with a power supply facility for supplying power generated by the generator to a power consuming device in the liquefied natural gas receiving facility.

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

It is explanatory drawing which shows the structural example of the LNG receiving equipment which concerns on embodiment of this invention. It is a flowchart which shows the flow of judgment which performs the supply interruption | blocking of BOG to a fuel gas line in the said LNG receiving equipment. It is explanatory drawing which shows the structural example of the LNG receiving equipment which concerns on other embodiment. It is explanatory drawing which shows the structural example of the LNG receiving equipment which concerns on another embodiment.

Hereinafter, an embodiment in which the present invention is applied to a receiving facility that receives LNG transported by an LNG tanker 1 will be described with reference to FIG.
The receiving facility includes an LNG tank 2 for storing LNG, LNG pumps 21 and 41 for delivering LNG from the LNG tank 2 to discharge gas to the demand destination 7, and vaporizing LNG into a gas state. The LNG vaporizer 42 and the calorific value adjusting unit 43 for adding liquefied petroleum gas (LPG) to the vaporized gas.

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

The LNG tank 2 has 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 an LNG pump 21 disposed in the LNG tank 2. and LNG payout lined 102a are sent are connected. The LNG dispensing line-102a, feed pump 41 for boosting is interposed, its distal 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 it as a gas adjusted to the pressure required by the customer 7. The LNG vaporizer 42 has conventionally bubbled the combustion gas obtained by burning gas with an open rack system that vaporizes LNG using seawater or a gas burner that opens downward in the water tank into the water in the water tank. A submerged conversion system that vaporizes LNG with hot water heated by the above-described method is used. In the receiving facility of this example, the exhaust heat of the cooling water of the gas engine 6 or the exhaust heat of the exhaust gas, which will be described later, can be used. Therefore, direct heat exchange with the exhaust gas or a heat medium heated by the exhaust gas Alternatively, the LNG vaporizer 42 may be configured to heat and vaporize the LNG by indirect heat exchange via the.

The LNG vaporizer 42 is connected to a vaporized gas discharge line 102 b for discharging the vaporized vaporized gas, and the end portion of the vaporized gas discharge line 102 b is connected to the calorific value adjusting unit 43. The calorific value adjustment unit 43 is a facility for mixing the LPG for adjusting the calorific value with the vaporized gas and discharging the product gas having the calorific value required at the customer 7. LPG (butane or propane) stored in the LPG tank 8 is sent to the heat quantity adjustment unit 43 in a liquid state via the LPG pump 81. The LPG is vaporized using a heat medium in the heat quantity adjusting unit 43 and mixed with the vaporized gas sent from the LNG vaporizer 42 side to become a product gas. The product gas whose heat amount has been adjusted by the heat amount adjusting unit 43 is delivered to the customer 7 via the shipping line 105.
Above LNG dispensing line-102a, vaporized gas dispensing line 102b and the receiving equipment shipment line 105 in premises corresponds to the payout line of the present embodiment.

The LNG receiving equipment having the basic configuration described above is provided with equipment for processing BOG generated in the LNG tank 2. Hereinafter, a configuration example of equipment for processing the BOG will be described.
As shown in FIG. 1, the LNG tank 2 is connected to a BOG extraction line 103a for extracting the BOG generated inside. The BOG extraction line 103a is connected to a BOG compressor 3 that is a compression unit that boosts the BOG.

The BOG compressor 3 of this example is configured as a multistage gas compressor having, for example, three compression stages 31 to 33. For example, the BOG compressor 3 boosts the BOG whose pressure on the suction side of the compression stage 31 is about 12 to 22 kPa-G to about 2 to 7.5 MPa-G. The BOG boosted by the BOG compressor 3 flows through the high-pressure BOG line 103b, and then merges with the vaporized gas discharge line 102b through which the vaporized gas flows. After the heat amount is adjusted, the BOG is discharged to the customer 7 as product gas.
The BOG extraction line 103a and the high-pressure BOG line 103b constitute the boil-off gas line of this example.

Further, in the LNG receiving facility according to the present embodiment, the BOG is used as the fuel gas of the gas engine 6 to drive the generator 61 to generate electric power or exhaust heat of the gas engine cooling water or combustion of the fuel gas. Exhaust heat from exhaust gas is used by each device in the receiving facility.
Here, as explained in the background art, the gas engine 6 can use a fuel gas having a lower pressure than that of the 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 pressure of the BOG after being boosted by the BOG compressor 3 is too high. Energy loss.

Therefore, in the receiving facility of this example, an appropriate pressure (for example, 0. 0) is obtained by using the intermediate stage of the BOG compressor 3 that boosts the BOG in a plurality of stages and extracting BOG from the discharge side of the intermediate stage. supplied to the gas engine 6 BOG boosted to 5~1M P aG) as fuel gas. In the example shown in FIG. 1, the base end portion of the fuel gas line 104 a for supplying 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 for supplying 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 the amount of BOG generated and properties. Yes.
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 shut-off 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.

Examples of the properties of the BOG used as a reference for executing supply and stop of the BOG by the supply shutoff valve 51 include a methane number and a calorific value.
The methane number is an index indicating the difficulty of knocking in the gas engine (anti-knock performance), and corresponds to the octane number of gasoline in the gasoline engine. A fuel gas with a low methane number is likely to cause knocking, and a fuel gas with a high methane number is less likely to cause knocking. The calculation method of methane number includes those standardized by AVL and the standards of CARB (California Air Resources Board) ("Oil / Natural Gas Review" (Independent Administrative Institution Petroleum Natural Gas / Metal Mineral Resources Organization) vol.39 No .5 p20). As a reference for determining the supply cutoff of the fuel gas in the supply cutoff valve 51, a methane number calculated according to the calculation method adopted in the specification of the gas engine 6 provided in the receiving facility is adopted.

Further, as the amount of heat, an index such as a calorific value generated when BOG is burned or a Wobbe index obtained by dividing the calorific value by the 1/2 root of the BOG specific gravity is employed.
As for the methane number and heat amount required for the BOG supplied as fuel gas to the gas engine 6, a range of reference values is preset as a specification of the gas engine 6.

  The BOG extraction line 103a is provided with an analyzer 55 (property detector) including an online methane number analyzer and a gas calorimeter. The methane number and heat value of the BOG detected by the analyzer 55 are output to a control unit 511 such as a DCS (Distributed Control System) for controlling the receiving facility, and the opening / closing operation of the supply shutoff valve 51 is performed. Used for judgment.

The position where the analyzer 55 is provided is not limited to the fuel gas line 104a on the outlet side of the BOG compressor 3. For example, the analyzer 55 may be provided in 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 where the online analyzer 55 is provided in the fuel gas line 104a. The BOG supplied to the fuel gas line 104a is periodically sampled and analyzed offline, and the supply shut-off valve 51 is opened and closed based on the result. It is good also as a structure which judges.

A PSA (Pressure Swing Adsorption) section 52 that is a nitrogen removal section for reducing the concentration of nitrogen (N ₂ ) contained in BOG that is the fuel gas of the gas engine 6 is disposed downstream of the supply shutoff valve 51. Has been. The PSA unit 52 is composed of two adsorption towers filled with an adsorbent that adsorbs nitrogen, and allows BOG to flow through one side to adsorb and remove nitrogen in the BOG. In the other adsorption tower where BOG is not flowing, a regeneration operation is performed in which the pressure in the tower is lowered to desorb nitrogen from the adsorbent and discharged together with the air supplied into the tower.

And the process which removes nitrogen from BOG can be performed continuously by switching the adsorption tower in which adsorption | suction of nitrogen and regeneration operation | movement of adsorption agent are performed alternately.
Here, the nitrogen removal method employed in the nitrogen removal unit is not limited to the case of the PSA method. For example, a cryogenic separation method may be employed in which BOG is cooled and liquefied and then distilled and separated into nitrogen and a fuel gas component such as methane.

  The BOG from which nitrogen has been removed by 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 includes a piston 532 that moves up and down according to the amount of BOG stored in the gas holder 53.

  Further, 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 inside the gas holder 53. The baffle plate 531 is used to store the BOG in the gas holder 53 that has been used up to now and the BOG generated from the new LNG when the properties of the BOG greatly change due to changes in the properties of the LNG received from the LNG tanker 1. It serves as a gas mixing part that is sufficiently mixed to relieve changes in the properties of the fuel gas supplied to the gas engine 6.

  The BOG in the gas holder 53 is supplied to the gas engine 6 through the fuel gas line 104c. The gas engine 6 is an internal combustion engine capable of generating electric power by driving a generator 61 using BOG mainly composed of methane as a fuel gas. The gas engine 6 can be operated over 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 a gas turbine.

The electric power generated by driving the generator 61 with the gas engine 6 is supplied to the electric motor and the receiving facility such as the BOG compressor 3, the LNG pumps 21 and 41, and the LPG pump 81 through the power supply unit 62 that is a power supply facility. Supplied to power consuming equipment like lighting.
Further, the exhaust gas after the BOG is burned by the gas engine 6 and the internal cylinder is driven is used to heat the LNG and LPG in the LNG vaporizer 42 and the calorific value adjustment unit 43, and to heat the bottom surface of the LNG tank 2 and the like. . When the cooling water is used as a heat source, the cooling water serves as a heat medium and supplies heat to the LNG vaporizer 42, the calorific value adjustment unit 43, and the heater 22. When the cooling water and the exhaust gas itself are used as the 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 adjusting unit 43, and the heater 22. In this case, these devices 42, 43, and 22 constitute an exhaust heat recovery unit. In addition, when the heat of exhaust gas is used to generate steam, hot water or the like with a boiler (not shown) and this is used as a heat medium (heat source), the boiler serves as an exhaust heat recovery unit.

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

  Accordingly, 4 t / h of the BOG supplied to the BOG compressor 3 via the BOG extraction line 103a is mixed with the vaporized gas and discharged to the customer 7 as product gas. The amount of LNG delivered from the LNG tank 2 is increased or decreased in consideration of the amount of BOG mixed.

  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). ). When both the methane number and the heat amount of the BOG satisfy the reference values (steps S101; YES and S102; YES in the figure), the BOG is supplied downstream via the fuel gas line 104a. (Step S103 in the figure).

  The BOG supplied from the fuel gas line 104a, after nitrogen is removed by the PSA unit 52, flows into the gas holder 53 and is temporarily stored, and then supplied to the gas engine 6 and burned as fuel gas. . The electric power generated by burning 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 calorific value adjustment unit 43, and the heater 22.

Here, the acceptance of LNG from the LNG tanker 1 is performed once to several times a month. In this case, the amount of BOG generated in the LNG tank 2 is several times the normal amount, for example, about four times. Increase. In this case, while increasing the amount of BOG mixed with the vaporized gas via the BOG compressor 3, the amount of LNG delivered from the LNG tank 2 is decreased to absorb the increased amount of BOG. At this time, the gas engine 6 consumes BOG in balance with the 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 side may be increased, and the storage amount of BOG in the gas holder 53 may be temporarily increased.

In addition, at the timing of receiving LNG from the LNG tanker 1, the properties of LNG may change greatly depending on the production area and the well. In such a case, the property of the BOG generated in the LNG tank 2 also changes greatly, and the combustion state of the BOG in the gas engine 6 also changes. However, a 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 change in the properties of BOG proceeds slowly. As a result, the gas engine 6 can follow the change in the BOG property with a margin, and can continue to operate while changing the operating conditions such as the air supply amount.
Further, since the fuel gas lines 104a to 104b of the present example are provided with the PSA section 52, even when there is a change in properties in which the nitrogen concentration in the BOG increases, the nitrogen content is reduced and a stable amount of heat is obtained. It is also possible to supply the fuel gas having the gas to the gas engine 6.

  On the other hand, when the change width of the BOG property is large and the methane number and the amount of heat deviate from the reference values usable in the gas engine 6 (step S101 in FIG. 2; NO or S102; NO), supply The shut-off valve 51 is closed and the supply of BOG from the fuel gas line 104a to the downstream side is stopped (step S104 in the figure). Even if the supply of the BOG from the fuel gas line 104a is stopped, the gas engine 6 can continue to operate because the BOG is stored in the gas holder 53.

  If the change in the properties of the BOG is likely to last for a long time, the operation of the gas engine 6 may be lowered 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 power generation amount of the generator 61 is reduced and it becomes impossible to supply power to the power consuming device in the receiving facility, 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, BOG that is not sent to the gas engine 6 side is mixed with vaporized gas via the high-pressure BOG line 103b. At this time, if an amount of BOG that exceeds the amount that can be mixed with the vaporized gas is generated, excess BOG may be extracted into a flare stack (not shown) and burned.

Here, for example, the fuel gas line 104 a upstream of the supply shutoff valve 51 is provided with 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. Even if the supply of BOG to the downstream side is stopped, the fuel gas can be analyzed by the analyzer 55. When the property of the 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. 2 ; YES) And S102; YES, S103). At this time, in order to replenish the 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 determined from the consumption amount of BOG in the gas engine 6. May be temporarily increased.

The LNG receiving facility according to the embodiment of the present invention has the following effects. LNG dispensing line-102a for paying out boosts the BOG generated in the LNG tank 2, the vaporized gas dispensing line 102b, the shipping line 105, and a fuel gas line 104a~104c for supplying BOG to the gas engine 6 Since it is provided side by side, an appropriate processing destination can be selected according to the amount of BOG generated and changes in properties, and stable processing can be performed.

  Next, FIG. 3 shows an example in which a gas engine 6 is added to an LNG receiving facility of the type for reliquefying BOG. The receiving facility of this example is that the number of compression stages 31 and 32 of the BOG compressor 3a is smaller than that of the BOG compressor 3 of FIG. 1 and its discharge pressure is low, and LNG and LNG are placed downstream of the BOG compressor 3a. The condenser 44 for cooling and liquefying the BOG by heat exchange is provided, and the BOG liquefied by the condenser 44 is collected in the LNG tank 2 via the liquefied BOG line 103c, or the liquefied BOG delivery line 1 is different from the example shown in FIG. 1 in that it joins the LNG delivered from the LNG tank 2 via 107 and then is paid out to the customer 7.

  As described in the background art, the receiving facility for collecting the reliquefied BOG has a problem that nitrogen is circulated and concentrated. However, by constantly extracting BOG toward the gas engine 6, the nitrogen concentration is performed. 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 re-liquefaction of BOG, the influence on the gas engine 6 due to the increase in nitrogen concentration 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 in the vaporized gas discharge line 102b and discharged. For example, the amount of heat may be adjusted as it is without being mixed with the vaporized gas, and discharged as product gas.

Further, the method for adjusting the pressure of the BOG supplied to the gas engine 6 is not limited to the method of extracting BOG from the intermediate stage of the multistage BOG compressors 3 and 3a. For example, as shown in FIG. 4, a fuel gas line 104 a is branched on the front side of the BOG compressor 3, and a fuel gas compressor 54 (a pressure boosting unit) for boosting is provided in the fuel gas line 104 a, and BOG is supplied to the gas engine 6. it may be increased to accept a pressure (e.g. 0.5~1M P aG).

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

  Furthermore, in the case of a LNG liquefaction base dispensing facility that accepts LNG obtained by cooling and liquefying natural gas produced from the well of the gas field, when LNG in the LNG tank 2 is dispensed, LNG is vaporized. It is not essential to let them. For example, the present invention can also be applied to a LNG liquefaction base dispensing facility configured to dispense 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 removing unit), and the gas holder 53 are provided for the fuel gas lines 104a to 104c. Is not an essential requirement. Any one of these facilities 51, 52, and 53 may be selected and provided according to changes in the properties of LNG and BOG stored in the LNG tank 2 and changes in the amount of BOG generated.

  Further, 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 engines 6 in all the LNG tanks 2. Only one of the plurality of LNG tanks 2 is provided with fuel gas lines 104a to 104b (with the fuel gas compressor 54 shown in FIG. 4 installed), and all the BOG generated in the LNG tank 2 is gas. The fuel gas of the engine 6 may be used. On the other hand, the other LNG tanks 2 are, as before, BOG extraction line 103a-BOG compressor 3-high pressure BOG line 103b (FIG. 1), BOG extraction line 103a-BOG compressor 3a-liquefied BOG line 103c, and liquefied BOG delivery. 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 in the entire receiving facility including a plurality of LNG tanks 2, a system (BOG extraction line 103a-BOG compressor 3-high pressure BOG line 103b) for boosting and discharging BOG to the receiving facility, or A system (BOG extraction line 103a-BOG compressor 3a-liquefied BOG line 103c, liquefied BOG delivery line 107) for re-liquefying and collecting and discharging, and a fuel gas line 104a for supplying BOG to the gas engine 6 To 104c.

  When the total amount of BOG generated in one LNG tank 2 is burned by the gas engine 6 and the power generated by the power generation exceeds the power consumption in the receiving facility, surplus power is sold. Can do. If the properties of the BOG deviate from the standards acceptable 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 branch line described above. Extraction and 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 extraction line 103b high pressure BOG line 103c liquefied BOG lines 104a to 104c
Fuel gas line 105 Shipping line 107 Liquefied BOG delivery line 2 LNG tank 22 Heater 3, 3a BOG compressors 31-33 Compression stage 42 LNG vaporizer 43 Heat quantity adjustment part 51 Supply shutoff valve 52 PSA part 53 Gas holder 531 Baffle plate 54 Fuel Gas compressor 55 Analyzer 6 Gas engine 61 Generator 62 Power feeding section

Claims (11)

A storage tank for storing liquefied natural gas received from an external liquefied natural gas tanker;
A vaporizer for vaporizing liquefied natural gas; vaporizing the liquefied natural gas sent from the storage tank with the vaporizer; and a discharge line for discharging in a gas state;
A gas compression unit that pressurizes the boil-off gas generated in the storage tank, and a boil-off gas line for discharging the boosted boil-off gas to the discharge line;
A gas engine that drives the generator;
A fuel gas line provided to be branched from the boil-off gas line and provided independently of the discharge line, and for supplying boil-off gas generated in the storage tank as fuel to the gas engine;
A gas mixing section provided in the fuel gas line , for absorbing a change in the amount of boil-off gas supplied to the fuel gas line and mitigating a change in the properties of the boil-off gas supplied to the gas engine A liquefied natural gas receiving facility comprising: a gas holder including: A storage tank for storing liquefied natural gas received from an external liquefied natural gas tanker;
A vaporizer for vaporizing liquefied natural gas; vaporizing the liquefied natural gas sent from the storage tank with the vaporizer; and a discharge line for discharging in a gas state;
A gas compression unit for boosting and liquefying the boil-off gas generated in the storage tank, and returning the liquefied boil-off gas to the storage tank or supplying the boil-off gas to the vaporizer;
A gas engine that drives the generator;
A fuel gas line provided to be branched from the boil-off gas line and provided independently of the discharge line, and for supplying boil-off gas generated in the storage tank as fuel to the gas engine;
A gas mixing section provided in the fuel gas line , for absorbing a change in the amount of boil-off gas supplied to the fuel gas line and mitigating a change in the properties of the boil-off gas supplied to the gas engine A liquefied natural gas receiving facility comprising: a gas holder including:   The gas compression unit includes a multi-stage gas compressor, and the fuel gas line is connected to a discharge side of a stage on the nearer side than the final stage of the gas compressor and branches from the boil-off gas line. Thus, the liquefied natural gas receiving facility according to claim 1 or 2, wherein the boil-off gas whose pressure has been increased to the receiving pressure of the gas engine is supplied to the gas engine.   The fuel gas line includes a boosting unit that branches from the boil-off gas line on the front side of the gas compression unit and boosts the boil-off gas supplied to the gas engine to an acceptance pressure of the gas engine. The facility for receiving liquefied natural gas according to claim 1 or 2.   2. A supply stop unit that stops supply of boil-off gas to the fuel gas line when a property of the boil-off gas supplied to the gas engine deviates from a preset reference value. Or the receiving facility of liquefied natural gas of 2.   6. The facility for receiving liquefied natural gas according to claim 5, wherein the fuel gas line is provided with a property detector for detecting the property of the boil-off gas.   6. The facility for receiving liquefied natural gas according to claim 5, wherein the boil-off gas has a methane value.   The liquefied natural gas receiving facility according to claim 5, wherein the boil-off gas has a calorific value. The fuel gas line, the receiving of the liquefied natural gas according to claim 1 or 2, characterized in that it comprises a nitrogen removal unit for reducing the concentration of nitrogen contained in the boil-off gas supplied to the gas engine Facility.   An exhaust heat recovery unit that recovers exhaust heat of cooling water exhausted from the gas engine or exhaust heat of exhaust gas is provided, and the exhaust heat recovery unit converts the liquefied petroleum gas for heat quantity adjustment to the vaporizer and the vaporized gas. The facility for receiving liquefied natural gas according to claim 1 or 2, wherein the facility is for supplying a heat source to at least one of a heat quantity adjusting facility for supplying or a heater for the storage tank.   3. The liquefied natural gas receiving facility according to claim 1, further comprising a power supply facility that supplies power generated by the generator to a power consuming device in the liquefied natural gas receiving facility. 4. .

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