JP2023525386A - Vessel liquefied gas re-vaporization method and system - Google Patents

Abstract

[Problem] To re-vaporize liquefied gas, the present invention enables stable operation of the cycle by maintaining constant operating conditions at major points of a cycle in which a heat medium that exchanges heat with liquefied gas circulates. The present invention relates to a liquefied gas re-vaporization method and system for ships. A liquefied gas re-vaporization method for a ship according to the present invention vaporizes a first heat medium in a liquid state condensed by heat exchange in a vaporizer, and converts the vaporized first heat medium into It is supplied to an expander generator and expanded to produce electric power, the expanded first heat medium is supplied to the evaporator, and the pressure before or after the expander generator is controlled to the evaporator to control the post-pressure of the

Description

The present invention relates to a liquefied gas re-vaporization method and system for a ship. It relates to the thing which can operate the cycle stably.

In general, natural gas is produced in the state of liquefied natural gas (LNG), which is liquefied at cryogenic temperatures at a production site, and then transported to a destination over a long distance using an LNG carrier. LNG is obtained by cooling natural gas to an extremely low temperature of about −163° C. under atmospheric pressure, and its volume is reduced to about 1/600 of that of gaseous natural gas. Therefore, it is very suitable for long-distance transportation by sea.

LNG regasification vessels or floating offshore structures such as LNG-RVs (LNG Regasification Vessel) and LNG-FSRUs (Floating Storage and Regasification Units) It is a vessel whose purpose is to supply natural gas that has been re-vaporized to onshore gas consumers.

These LNG regasification vessels are equipped with LNG storage tanks that store LNG and regasification equipment that regasifies the LNG stored in the LNG storage tanks and supplies it to onshore users. The natural gas produced is transported to onshore users via pipelines.

The regasification equipment on the LNG regasification vessel consists of a high-pressure pump that compresses the LNG stored in the LNG storage tank to the pressure required by the customer, and a vaporizer that vaporizes the high-pressure LNG compressed by the high-pressure pump into natural gas. Prepare.

Seawater, which is easily supplied, is mainly used as a heat source for vaporizing LNG in a vaporizer. At this time, low-temperature seawater, which is directly or indirectly heat-exchanged with LNG and recovers the cold heat of LNG, is discharged to the sea. In other words, the cold energy of LNG recovered by seawater during the process of re-vaporizing LNG is discharged to the sea as it is.

Although LNG has 200 kcal of cold energy per 1 kg, in LNG re-vaporization ships, the cold energy recovered in the process of re-vaporizing LNG is wasted without being used.

The present invention improves energy efficiency by recovering the cold heat that is discarded in the process of re-vaporization of liquefied gas to produce electricity, and controls the pressure to stably operate the system. A liquefied gas re-vaporization method and system are provided.

In order to achieve the above object, in one embodiment of the present invention, heat is exchanged between a liquefied gas and a first heat medium in a vaporizer to vaporize the liquefied gas, and cold heat of the first heat medium is discharged from the vaporizer. is recycled to the vaporizer after recovering the first heat medium to recover the cold heat of the first heat medium, the first heat medium in a liquid state condensed by heat exchange in the vaporizer is vaporized in the first heat exchanger and supplies the vaporized first heat medium to an expander generator to expand it to produce electric power, supplies the expanded first heat medium to the vaporizer, and supplies the expanded first heat medium to the expander generator in the front stage of the expander generator. Alternatively, there is provided a liquefied gas re-vaporization method for a ship, comprising controlling the pressure in the rear stage to control the pressure in the rear stage of the vaporizer.

In order to achieve the above object, in another embodiment of the present invention, a vaporizer for vaporizing a liquefied gas by heat exchange with a first heat medium; the first heat medium in a liquid state condensed by heat exchange in the vaporizer. an expander generator that expands the first heat medium vaporized in the first heat exchanger to produce electric power; and control the pressure before or after the expander generator pressure control means for controlling the pressure before or after the expander generator to control the pressure after the vaporizer.

In order to achieve the above object, in still another embodiment of the present invention, heat is exchanged between a liquefied gas and a first heat medium in a vaporizer to vaporize the liquefied gas, and the first heat is discharged from the vaporizer. After recovering the cold heat of the medium, recirculating it to the vaporizer, and recovering the cold heat of the first heat medium, the first heat medium in a liquid state condensed by heat exchange in the vaporizer is subjected to the first heat exchange. and supplying the vaporized first heat medium to an expander generator for expansion to produce electric power, supplying the expanded first heat medium to the vaporizer, and generating power from the expander. for controlling the post-pressure of the machine, a receiver receives the first heat medium discharged from the evaporator, the first heat medium is discharged from the receiver and vaporized, and the pressure measurement value of the receiver reaches a set value; When the pressure measurement value of the receiver is larger than the set value, the high-temperature first heat medium expanded by the expander generator is operated in a detour mode to bypass the evaporator and be supplied to the receiver, and when the pressure measurement value of the receiver is greater than the set value, the A method for re-vaporizing a liquefied gas in a marine vessel is provided, comprising operating in a quench mode in which a low-temperature first heat medium discharged from a vaporizer is injected into an upper portion of said receiver.

Preferably, the first heat medium is selected from refrigerants that change phase by heat exchange in the vaporizer and the first heat exchanger.

Preferably, the temperature of the low-temperature first heat medium discharged from the vaporizer after heat exchange and the temperature of the re-vaporized gas discharged from the vaporizer after heat exchange are maintained at set values. Adjust the flow rate of liquefied gas supplied to

Preferably, an output value for maintaining the temperature of the low-temperature first heat medium discharged from the vaporizer after heat exchange at a set value and the temperature of the re-vaporized gas discharged from the vaporizer after heat exchange are set. The flow rate of the liquefied gas supplied to the vaporizer is controlled based on the smaller value of the output values to be maintained.

Preferably, the temperature setting value of the first heat medium is the saturation temperature of the first heat medium, and the expander power generation is performed by changing the temperature setting value of the first heat medium based on the saturation pressure of the first heat medium. Controls the post pressure of the machine.

Preferably, the re-vaporized gas vaporized by the vaporizer is heat-exchanged with the second heat medium by the trim heater to be heated to a temperature required by the gas consumer.

Preferably, when the downstream pressure of the expander generator is lower than a set value or the power generation load is low, the gaseous first heat medium bypasses the expander generator and is transferred to the downstream stage. Control.

In still another embodiment of the present invention, in order to achieve the above object, a vaporizer for vaporizing a liquefied gas by exchanging heat with a first heat medium; low-temperature first heat discharged from the vaporizer after heat exchange. A receiver containing a medium; a first heat exchanger for vaporizing a first heat medium in a liquid state supplied from the receiver; an extract for producing electric power by expanding the first heat medium vaporized in the first heat exchanger an expander power generator; a first heat medium line through which the first heat medium expanded from the expander power generator is transferred to the vaporizer, and the first heat medium recovered from the cold heat of the liquefied gas in the vaporizer is transferred to the receiver; a second valve downstream of the expander generator for controlling the transfer of the first heat medium to the receiver bypassing the evaporator; and opening said second valve when said receiver pressure measurement is below a set value and opening said third valve when above a set value. A second control for opening a valve is provided.

Preferably, a first valve for adjusting the flow rate of the liquefied gas supplied to the vaporizer; the temperature of the low-temperature first heat medium discharged from the vaporizer after heat exchange; and the heat exchange from the vaporizer. a first controller for controlling the first valve so that the temperature of the re-vaporized gas discharged later maintains a set value;

Preferably, the temperature setpoint of the first heat medium is the saturation temperature of the first heat medium, and a third control unit that adjusts the temperature setpoint of the first heat medium based on the pressure measurement of the receiver; Prepare more.

Preferably, there is provided a trim heater for additionally heating the re-vaporized gas vaporized in the vaporizer to a temperature required by the gas demand destination.

Preferably, it further comprises a second cycle in which a second heat medium is circulated to exchange heat with the re-vaporized gas in the trim heater to recover cold heat from the re-vaporized gas.

Preferably, a third flow control valve for adjusting the first heat medium vaporized in the first heat exchanger to bypass the expander generator and be transferred downstream of the expander generator; and the expander A governor for controlling the third flow control valve in accordance with the downstream pressure of the generator and the power generation load of the expander generator.

Preferably, the vaporizer is a one-pass type shell and tube heat exchanger.

Preferably, the trim heater is a two-pass type shell and tube heat exchanger.

In order to achieve the above object, in still another embodiment of the present invention, heat is exchanged between a liquefied gas and a first heat medium in a vaporizer to vaporize the liquefied gas, and the first heat is discharged from the vaporizer. After recovering the cold heat of the medium, recirculating it to the vaporizer, and recovering the cold heat of the first heat medium, the first heat medium in a liquid state condensed by heat exchange in the vaporizer is subjected to the first heat exchange. supply the vaporized first heat medium to an expander generator for expansion to produce electric power; supply the expanded first heat medium to the vaporizer; The first heat medium vaporized in the vessel is contained in a knockout drum before being supplied to the expander generator, and the output of the expander generator is increased when the pressure measurement value of the knockout drum is higher than a set value. A method for re-vaporizing a liquefied gas in a marine vessel is provided, comprising controlling the pre-pressure of said expander generator with a liquefied gas.

Preferably, increasing the output of the expander generator increases the opening rate of a second flow control valve that allows the first heat medium to flow from the knockout drum to the expander generator, and the expander generator generates increasing the output of the machine corresponding to the rate of opening of the second flow control valve.

Preferably, the rotation speed of the expander generator is controlled by a sixth control section, and the opening of the second flow control valve is controlled by a control signal transmitted from a fifth control section based on the pressure measurement value. 6 control unit.

Preferably, when the opening rate of the second flow rate control valve is maximized or the output of the expander generator is maximized, the fifth control unit controls that the first heat medium is released from the knockout drum into the expander. Open the third flow control valve that regulates the flow bypassing the generator and downstream of the expander generator.

Preferably, increasing the output of the expander generator adjusts the first heat transfer medium from the knockout drum to bypass the expander generator and downstream of the expander generator. After opening the third flow control valve first, the output of the expander generator is increased within the allowable range while decreasing the opening rate of the third flow control valve, and the expander generator is released from the knockout drum. and increasing the opening rate of the second flow control valve that allows the first heat medium to flow in.

Preferably, the rotation speed of the expander generator is controlled by a sixth control unit, and the seventh control unit for controlling the displacement of the third flow control valve controls the opening rate of the third flow control valve to 0%. A signal is transmitted to the sixth control section so as to increase the rotation speed of the expander generator until .

Preferably, the circulation flow rate of the first heat medium is determined by the heating duty of the vaporizer.

In still another embodiment of the present invention, in order to achieve the above object, a vaporizer for vaporizing a liquefied gas by exchanging heat with a first heat medium; first heat in a liquid state condensed by heat exchange in the vaporizer a first heat exchanger that vaporizes a medium; an expander generator that expands the first heat medium vaporized in the first heat exchanger to produce electric power; a knockout that accommodates the first heat medium vaporized in the vaporizer drum; a second flow control valve whose opening is adjusted so that the gaseous first heat medium discharged from the knockout drum is supplied to the expander generator; gas discharged from the knockout drum a third flow control valve whose opening is adjusted so that the first heat transfer medium in state bypasses the expander generator; and controlling the output of said expander generator based on said knockout drum pressure measurement. and a sixth control unit that adjusts the opening degree of the second flow control valve according to the output of the expander generator, and controls the pre-stage pressure of the expander generator. A system is provided.

Preferably, a signal for increasing the output of the expander generator is sent to the sixth control unit based on the pressure measurement of the knockout drum, and the third flow rate adjustment is performed when the output of the expander generator reaches a maximum. A fifth controller for opening the valve is further provided.

preferably a pressure regulator that opens said third flow control valve when said knockout drum pressure measurement is higher than a set value; and until the rate of opening of said third flow control valve reaches a minimum. A seventh control section for transmitting a rotational speed increase signal to the sixth control section.

In the liquefied gas re-vaporization method and system for ships according to the present invention, the energy efficiency of the entire system is improved by recovering the cold heat of the discarded liquefied gas to produce electric power, and the fuel consumption for producing electric power can be reduced, resulting in reduced greenhouse gas emissions.

Also, by controlling the post-pressure of the vaporizer via the pressure control of the receiver, it responds in controlling the temperature of the first heat transfer medium for controlling the post-pressure of the vaporizer and the flow rate of the liquefied gas to be vaporized. improve sexuality.

In addition, by controlling the pressure on the inlet side (high pressure side) of the expander generator, the temperature of the first heat medium for controlling the post pressure of the vaporizer and the flow rate of the liquefied gas to be vaporized are controlled. Improves responsiveness in

In addition, since electric power is produced using the first heat medium, even if the heat capacity of the first heat medium is insufficient in the vaporizer, the trim heater can be used to heat the re-vaporized gas to a minimum delivery temperature or higher. It can be stably sent to the demand destination.

In addition, by using the trim heater, the heat balance between the liquefied gas supply amount and the first heat medium supply amount in the loop cycle of the first heat medium at the beginning of the start of the re-vaporization system is not maintained, so that the liquefaction Since it is possible to prevent the problem that the gas is not sufficiently vaporized, the system can be stably operated.

1 is a configuration diagram simply illustrating a liquefied gas system of a ship according to an embodiment of the present invention; FIG. FIG. 4 is a diagram for explaining the configuration for controlling the post-stage pressure of the vaporizer according to the first embodiment of the present invention; FIG. 7 is a diagram for explaining a configuration for controlling post-stage pressure of a vaporizer according to a second embodiment of the present invention; FIG. 11 is a diagram for explaining a configuration for controlling inlet pressure of an expander generator according to a third embodiment of the present invention; FIG. 11 is a diagram for explaining a configuration for controlling inlet pressure of an expander generator according to a fourth embodiment of the present invention;

For a full understanding of the operational advantages of the invention and the objectives achieved by embodiments of the invention, reference should be made to the accompanying drawings, which illustrate embodiments of the invention and the description therein.

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, in adding reference numerals to constituent elements in each drawing, it should be noted that the same constituent elements are indicated with the same reference numerals as much as possible even if they are displayed on other drawings. Also, the following embodiments can be modified into various other embodiments, and the scope of the present invention is not limited by the following embodiments.

The liquefied gas described later in the embodiment of the present invention is a liquefied gas that can be transported by liquefying the gas at a low temperature. Liquefied petrochemical gases such as ethylene gas (Liquefied Ethylene Gas) and liquefied propylene gas (Liquefied Propylene Gas). It also includes liquid gases such as liquefied carbon dioxide, liquefied hydrogen, and liquefied ammonia. However, in the embodiments described later, LNG, which is a representative liquefied gas, will be described as an example.

Moreover, although the LNG regasification system according to an embodiment of the present invention described below is applied on a ship, it may be applied on land.

In addition, the LNG regasification vessel in one embodiment of the present invention includes all types of vessels equipped with LNG regasification equipment that regasifies LNG and supplies it to gas demand destinations, such as LNG-RVs (Regasification Vessel). including self-propelled vessels, as well as offshore structures such as LNG-FSRUs (Floating Storage Regasification Units). However, in the embodiments described later, the LNG-FSRU will be explained as an example.

Further, the LNG regasification vessel according to one embodiment of the present invention can regasify LNG on the sea and supply the regasification gas (Regas) to gas demand destinations on land via a piping network.

Hereinafter, a liquefied gas re-vaporization method and system for a ship according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG.

The liquefied gas re-vaporization system for ships according to the present embodiment supplies LNG discharged from a LNG storage tank (not shown) that stores LNG to a pressure required by a gas demand destination (not shown) or higher. A high-pressure pump (not shown) for compression, a vaporizer (120) for vaporizing the high-pressure LNG compressed by the high-pressure pump by heat exchange with the first heat medium, and a re-vaporized gas vaporized by the vaporizer (120), That is, the trim heater (130) adjusts the natural gas to the temperature required by the gas consumer, or completely vaporizes the LNG that has not been vaporized in the vaporizer (120) and heats it to the temperature required by the gas consumer. ).

The LNG storage tank may be provided with a feed pump (not shown) that discharges the stored LNG to feed the high pressure pump. The feed pump is, for example, an in-tank pump that is installed inside the LNG storage tank, or a semi-submersible pump that can operate submerged in the LNG stored in the LNG storage tank.

The high-pressure pump of this embodiment compresses the LNG to be re-vaporized to the re-vaporized gas pressure required by the gas demand destination and supplies it to the vaporizer (120). The pressure required at the gas consumer varies from jetty to jetty, but generally ranges from about 50 bar to 100 bar. That is, the high-pressure pump of the present embodiment can compress LNG to a pressure in the range of about 50 bar to 100 bar, or to a certain level higher than that in consideration of pressure loss and the like.

In the vaporizer (120) of the present embodiment, the high-pressure LNG compressed by the high-pressure pump at the pressure of the re-vaporized gas required at the gas demand destination heat-exchanges with the first heat medium that circulates in the first cycle. It becomes a gaseous state, or partially vaporizes and becomes a gas-liquid mixture. The temperature of the compressed LNG vaporized in the vaporizer (120) varies depending on the state of the heat source, such as the temperature and flow rate of the first heat medium and/or seawater.

The vaporizer (120) of this embodiment is, for example, a shell-and-tube heat exchanger, particularly a one-pass type shell-and-tube heat exchanger in which the tubes pass through the shell only once. be.

The trim heater (130) of the present embodiment heats the re-vaporized gas vaporized by the vaporizer (120) to a temperature required by the gas consumer and supplies the gas to the gas consumer. In addition, if there is LNG that has not been vaporized in the vaporizer (120) due to insufficient heat capacity of the first heat medium, the trim heater (130) vaporizes the entire amount and heats it to the temperature required by the gas demand destination. be done.

The trim heater (130) of this embodiment is, for example, a shell-and-tube heat exchanger, particularly a two-pass type shell-and-tube heat exchanger in which the tubes pass through the shell twice. be.

Onshore gas demand typically requires re-vaporized gas in the range of about 0°C to 10°C, or 8°C to 10°C, in the range of 50 bar to 100 bar, so the trim heater (130) is a vaporizer ( 120), the re-vaporized gas supplied to the gas demand destination on land is heated to a temperature in the range of about 0° C. to 10° C. and supplied to the gas demand destination.

According to this embodiment, LNG stored in the LNG storage tank flows along a liquefied gas line (LL), is compressed by a high pressure pump, is vaporized by a vaporizer (120), and is heated by a trim heater (130). transported to the gas demand destination.

On the other hand, the liquefied gas line (LL) has a first valve (LV) provided upstream of the vaporizer (120) for controlling the flow rate of LNG supplied to the vaporizer (120).

The first valve (LV) is the output value using the temperature measurement value of the second temperature control unit (TIC02) that measures the temperature of the first heat medium discharged after heat exchange with LNG in the vaporizer (120). , is controlled by the output value using the temperature measurement value of the first temperature control unit (TIC01) that measures the temperature of the re-vaporized gas that is vaporized and discharged from the vaporizer (120).

The first temperature control unit (TIC01) in the present embodiment includes a temperature measuring device (TT01) for measuring temperature and a temperature measurement value of the temperature measuring device (TT01) to control various means necessary for temperature control. is a name that includes all temperature controllers that calculate the output values of and send control signals to various means.

In addition, the second temperature control unit (TIC02) also includes a temperature measuring device (TT02) for measuring temperature, and an output for controlling various means necessary for temperature control, which is transmitted with the temperature measurement value of the temperature measuring device (TT02). The name includes all temperature controllers that calculate values and send control signals to various means.

A first controller (LS1) that controls the first valve (LV) is, for example, a low selector. That is, the first control unit (LS1) selects the output value based on the temperature measurement value of the second temperature control unit (TIC02) and the output value based on the temperature measurement value of the first temperature control unit (TIC01), A small value controls the first valve (LV).

In addition, the liquefied gas re-vaporization system for ships according to the present embodiment performs heat exchange with LNG in the vaporizer (120) to circulate the first heat medium, which is a heat source for vaporizing the LNG, in the first cycle of the Rankine cycle. Prepare.

The first heat medium of the present embodiment is, for example, a refrigerant that undergoes a phase change while circulating through the first cycle.

Conventionally, glycol water is mainly used as a heat medium for vaporizing LNG in the vaporizer (120). When glycol water is selected, there is no phase change in the process of heat exchange with LNG in the vaporizer (120) and the process of heating while exchanging heat with seawater in the heat exchanger, so heat is generated only by using sensible heat. transmission takes place.

On the other hand, when a refrigerant that undergoes a phase change during the process of heat exchange with LNG in the vaporizer (120) and the process of being heated while exchanging heat with seawater in the heat exchanger, as in the present embodiment, is adopted as the heat medium. Since heat transfer is also performed by latent heat, when the duty for vaporizing LNG is the same as the standard, the flow rate of the heat medium that circulates in the first cycle is decrease significantly. Therefore, the power of the pump for circulating the heat medium can be reduced, and the efficiency of the entire system is improved.

The first cycle of the present embodiment includes a first pump (210) that circulates the first heat medium, a first heat exchanger (220) that vaporizes the first heat medium pressurized by the first pump (210), an expander-generator (230) that expands the vaporized first heat medium in the first heat exchanger (220) and converts the expansion work of the first heat medium into power to produce electric power; A receiver (240) is provided for storing the first heat medium condensed by heat exchange with LNG in the vessel (120).

While flowing along the first heat medium line (RL), the first heat medium is pressurized by the first pump (210), vaporized in the first heat exchanger (220), and expanded by the expander generator (230). ), condensed in the vaporizer (120) and circulated through the first cycle of the loop cycle formed to be circulated to the first pump (210) via the receiver (240).

In the first heat exchanger (220) of the present embodiment, the first heat medium is sucked by a seawater pump (not shown) and supplied to the first heat exchanger (220) along the first seawater line (SL1). Vaporized by heat exchange with sea water.

In the first heat exchanger (220), the seawater is cooled while vaporizing the first heat medium, and the cooled seawater is discharged from the first heat exchanger (220) along the first seawater line (SL1). .

In this embodiment, seawater is used as a heat source for vaporizing the first heat medium in the first heat exchanger (220). Steam can also be used, and seawater and steam can be used complementary to each other.

Complementary use of seawater and steam includes, for example, that the first heat exchanger (220) comprises a three-stream heat exchanger for exchanging heat between seawater, steam, and the first heat medium. Alternatively, the first heat medium is heated in stages by installing a first stage heat exchanger for exchanging heat between seawater and the first heat medium and a second stage heat exchanger for exchanging heat between steam and the first heat medium in series. Alternatively, a first heat exchanger (220) is installed in parallel with a first stage heat exchanger that exchanges heat between seawater and the first heat medium and a two-stage heat exchanger that exchanges heat between steam and the first heat medium. The heating temperature of the first heat medium in can also be adjusted. Alternatively, a seawater heater for heating seawater by heat exchange with steam may be additionally installed, and the seawater heated by the seawater heater may be supplied to the first heat exchanger (220).

The first heat exchanger (220) of this embodiment is, for example, a shell and tube heat exchanger or a plate heat exchanger.

The first heat medium vaporized or heated by the seawater in the first heat exchanger (220) is supplied to the expander generator (230) and expanded, and the work of expansion of the first heat medium is converted into electric power. The power produced by the expander generator (230) can be used by power demanders on board.

Downstream of the first pump (210) in the first heat medium line (RL), for adjusting the flow rate of the first heat medium supplied from the first pump (210) to the first heat exchanger (220) A first flow control valve (FV1) may be provided.

The first flow control valve (FV1) is controlled by the fourth controller (LS2) to control the rotational speed or load of the first pump (210) and the amount of the first heat medium discharged after heat exchange from the first heat exchanger (210). It is controlled based on the output value using the temperature and flow rate of the natural gas discharged from the vaporizer (120) after heat exchange.

The fourth controller (LS2) is, for example, a row selector. That is, the fourth control unit (LS2) controls the output value based on the rotation speed or the load measurement value of the first pump (210), the amount of the first heat medium discharged after heat exchange from the first heat exchanger (210), The first flow control valve (FV1) is controlled by the minimum value of the output value based on the temperature measurement value and the output value based on the flow measurement value of the natural gas discharged from the vaporizer (120) after heat exchange.

On the other hand, according to the present embodiment, the first heat medium line (RL) of the present embodiment branches upstream of the expander generator (230) and the first heat medium vaporized in the first heat exchanger (220) bypasses the expander generator (230), i.e., is supplied directly from the first heat exchanger (220) to the vaporizer (120) without going through said expander generator (230). and a first branch line (RL1).

For example, if the expander generator (230) fails and is unusable, the first branch line (RL1) is utilized to vaporize from the first heat exchanger (220) through the first branch line (RL1). By supplying the first heat medium to the vessel (120), it is possible not to adversely affect the supply of natural gas to the onshore demand destination.

The first branch line (RL1) of the present embodiment has the purpose of bypassing the first heat medium during maintenance of the expander generator (230) and the rapid re-vaporization capacity in the vaporizer (120). The purpose is to adjust the pre-stage pressure by delaying the reaction speed of the second flow control valve (FV2), which is the valve on the inlet side of the expander generator (230), when the circulation flow rate of the first heat medium increases due to the increase in Prepared by

Further, the first cycle of the present embodiment is provided between the first heat exchanger (220) and the expander generator (230), and the first heat medium vaporized in the first heat exchanger (220) is It may further comprise a knockout drum (250) for temporarily storing before supplying to the expander generator (230) and separating the liquid contained in the first heat medium to be supplied to the expander generator (230). can.

In a first heat medium line (RL) between the knockout drum (250) and the expander generator (230), gaseous state gas transferred from the knockout drum (250) to the expander generator (230) A second flow control valve (FV2) is provided to control the flow rate of the first heat medium.

The second flow control valve (FV2) controls the power generation load or speed of the expander generator (230), the pressure of the first heat medium discharged after being expanded by the expander generator (230) and the pressure of the knockout drum (250). control accordingly.

Also, a power load or speed measurement of the expander generator (230), a pressure measurement of the first heat transfer medium discharged after being expanded by the expander generator (230) and a pressure measurement of the knockout drum (250). is used to control the second flow control valve (FV2) and the third flow control valve (FV3) provided in the first branch line (RL1) to remove the first gaseous state from the knockout drum (250). The heat medium is controlled to be transferred along the first heat medium line (RL) or the first branch line (RL1).

The second flow control valve (FV2) and the third flow control valve (FV3) are controlled by the governor to control the downstream pressure of the expander generator (230), the measured output load of the expander generator (230), It is controlled based on the output value of one or more of the rotation speed of the expander generator (230) and the pressure of the knockout drum (250).

In the expander power generator (230), the first heat medium vaporized or heated by heat exchange with seawater in the first heat exchanger (220) expands and the pressure and temperature decrease.

The first heat medium expanded by the expander generator (230) is supplied to the vaporizer (120) along the first heat medium line (RL) and is cooled or condensed while exchanging heat with LNG. The first heat medium cooled or condensed in the vaporizer (120) is transferred to the receiver (240) along the first heat medium line (RL).

The receiver (240) of the present embodiment is a pressure vessel that collects the first heat medium condensed in the vaporizer (120) and controls the flow rate and pressure of the first heat medium circulating through the first cycle. It also serves as a buffer tank.

According to this embodiment, a means for regulating the pressure of the receiver (240) may be further provided, and the pressure regulating means of the receiver (240) may be a second valve (RV) and a third valve (QV) which will be described later. Prepare.

Further, according to the present embodiment, a fourth branch line (RL4) branched from the first heat medium line (RL) downstream of the first pump (210) and connected to the receiver (240) and a knockout drum (250 ) to the fourth branch line (RL4).

When the flow rate of the first heat medium required in the first heat exchanger (220) is less than the minimum flow rate in order to maintain the minimum flow rate of the first pump (210) in the fourth branch line (RL4) When there is an amount exceeding the required flow rate of the first heat medium in the discharge flow rate of the first pump (210) as in, the first water level valve (LV1) for returning the corresponding flow rate to the receiver (240) be provided. The first water level valve (LV1) is controlled based on the output value according to the rotational speed of the first pump (210).

In addition, in the fifth branch line (RL5), a second water level valve ( LV2) is provided. The second water level valve (LV2) is controlled based on the output value from the water level measurement of the knockout drum (250).

The first heat transfer medium of this embodiment is selected from substances or mixtures that undergo a phase change while circulating through the first cycle. That is, the first heat medium exchanges heat with seawater in the first heat exchanger (220), is vaporized, expands in the expander generator (230), and then condenses in the vaporizer (120).

In the present embodiment, the first heat medium can be a natural refrigerant, HFC (Hydrofluorocarbons) and HFO (Hydrofluoroolefin) refrigerants, which are basically free from fire and explosion hazards, either singly or in combination, For example, R-23, R-32, R-134a, R-407c, R-410A, etc. can be applied singly or in admixture.

On the other hand, the first heat medium expands in an isentropic process in the expander generator (230), and the temperature of the first heat medium drops in this process.

For example, if the first heat medium that is vaporized or heated by the first heat exchanger (220) and discharged is 11° C. and 5 barG, and expanded to 2 barG by the expander generator (230), the temperature of the first heat medium is drops to about -10.5°C. When the −10.5° C. first heat medium discharged from the expander generator (230) is supplied from the vaporizer (120) as a heat source for vaporizing LNG, it is discharged from the vaporizer (120) The minimum temperature requirement for natural gas, eg 8° C., is no longer met.

Therefore, in this embodiment, a trim heater (130) is further provided in order to satisfy the minimum temperature condition or higher required by the gas demanding party for the temperature of the natural gas supplied from the vaporizer (120) to the gas demanding party.

Thus, according to one embodiment of the present invention, the first heat medium vaporized in the first heat exchanger (220) decreases in temperature while producing power in the expander generator (230), thereby Even if the temperature of the first heat medium supplied to the vaporizer (120) is lower than the temperature required to heat the re-vaporized gas to the temperature required by the gas demand, the vaporizer (120) The problem can be solved by a trim heater (130) provided downstream of the .

The re-vaporization system according to one embodiment of the present invention further comprises a second cycle for circulating a second heat medium, which is a heat source for heating the natural gas, for example, in the trim heater (130).

In the trim heater (130), heat is exchanged between the second heat medium circulating in the second cycle and the natural gas, and the natural gas is heated to the minimum temperature condition, that is, the temperature required by the gas consumer or above, and the second The heat carrier recovers the cold energy of the natural gas to cool or condense it.

The second cycle of the present embodiment includes a second pump (not shown) that circulates the second heat medium, a second heat exchanger (not shown) that heats or vaporizes the second heat medium, and a trim heater ( 130) includes an expansion tank (not shown) for stabilizing the second heat medium discharged after heat exchange.

While flowing along a second heat medium line (not shown), the second heat medium is pressurized by a second pump, vaporized or heated by a second heat exchanger, and cooled or heated by a trim heater (130). It condenses and circulates through a second cycle of a loop cycle formed to be circulated through an expansion tank to a second pump.

The heat source for heating the second heat medium in the second heat exchanger of the present embodiment is seawater sucked by the seawater pump and supplied to the second heat exchanger along the second seawater line.

The seawater cooled while vaporizing or heating the second heat medium in the second heat exchanger is discharged outside along the second seawater line.

Also, in the present embodiment, seawater is used as an example of the heat source for vaporizing or heating the second heat medium in the second heat exchanger, but steam produced by an onboard steam generator can also be used as the heat source. Yes, as in the case of the first heat exchanger (220) described above, seawater and steam can be used in a mutually complementary manner.

Also, the second heat exchanger of the present embodiment is, for example, a plate heat exchanger.

The expansion tank of the present embodiment functions as a shock absorber in order to cope with volume expansion due to temperature change of the second heat medium through heat exchange in the second heat exchanger.

In addition, in the expansion tank, foreign matter such as air mixed in the second heat medium is separated from the second heat medium, and natural gas leaks from the trim heater (130) to the second heat medium. flows into the second heat medium, the gas that has flowed into the second heat medium is also separated from the second heat medium.

The second heat medium of the present embodiment is, for example, glycol water.

In the expander generator (230), the pressure and temperature decrease while the first heat medium that is vaporized or heated by heat exchange with seawater in the first heat exchanger (220) expands. Pressure changes in the first heat medium expander generator (230), except when the temperature of the seawater used as a heat source in the first heat exchanger (220) is sufficiently higher than the minimum temperature requirement of the gas demand It is difficult to heat the natural gas above the minimum temperature condition because the temperature drop during the process of is very large and the heat capacity of the first heat medium is small.

Therefore, in the present embodiment, the second heat medium, namely glycol water, is used as an intermediate heat medium for trim heating the natural gas above the minimum temperature condition.

In general, in order to heat natural gas above the minimum temperature condition, the LNG must be compressed to above the minimum pressure condition using a high-pressure pump, and vaporized and heated above the minimum temperature condition in the vaporizer (120). must. For example, if the minimum temperature condition of the natural gas discharged from the vaporizer (120) is 8° C., the temperature of the first heat medium supplied to the vaporizer (120) must meet the minimum temperature condition. It should be above 8°C. Considering that the minimum temperature difference between the heating fluid and the heated fluid in a general heat exchanger is 2-3°C, the temperature of the first heat medium supplied to the vaporizer (120) is about 11°C. °C or higher.

In addition, since the first heat medium of the present embodiment is heated by heat exchange with seawater in the first heat exchanger (220), similarly, the heat transfer between the heating fluid and the heated fluid in a general heat exchanger Considering the minimum temperature difference, the temperature of the seawater supplied to the first heat exchanger (220) should be about 14°C or higher.

However, even if the first heat medium is heated to 11° C. in the first heat exchanger (220), the temperature of the first heat medium increases while the expander generator (230) produces electric power as described above. is as low as -10.5°C.

Therefore, according to the present embodiment, the trim heater (130) must be used to heat the natural gas vaporized in the vaporizer (120) to the minimum temperature condition of the gas demand destination, that is, the final delivery temperature of the natural gas. not.

If a part of the first heat medium supplied from the first heat exchanger (220) to the expander generator (230) is branched and used as a heat medium for heating the natural gas in the trim heater (130) Then, except when the temperature of the seawater is sufficiently high and the temperature difference between the first heat medium heat-exchanging in the first heat exchanger (220) and the seawater is higher than the minimum level, the trim heater (130) Problems can arise that the natural gas cannot be heated to the final delivery temperature due to insufficient heat exchange performance.

The design of the trim heater (130) is not easy because the pinch point is determined inside the trim heater (130) due to the low heat capacity and phase change of the first heat medium. Therefore, such design difficulties can be solved by using the second heat medium, and the re-vaporized gas can be heated stably.

According to this embodiment, the first heat medium, that is, the refrigerant is used only as a heat source for the vaporizer (120) by exchanging heat with sea water in the first heat exchanger (220), and is used only as a heat source for the vaporizer (120). By supplying the second heat medium heated by heat exchange, that is, glycol water as a heat source of the trim heater (130) to prevent pinch points from occurring inside the trim heater (130), sufficient heat exchange performance is achieved. ensure that the natural gas can be stably heated to the final delivery temperature.

In addition, when the re-vaporization system is initially started, if LNG is not supplied to the vaporizer (120), the first heat medium will not be condensed in the vaporizer (120), making it impossible to circulate the first heat medium. , the load on the vaporizer (120) must be increased while maintaining a good balance between the supply of LNG and the first heat transfer medium. This causes many difficulties in driving.

According to this embodiment, by using glycol water as the second heat medium for heating the natural gas from the trim heater (130), when the re-vaporization system is initially started, the LNG supply and the first heat medium It is possible to prevent LNG from flowing into the vaporizer (120) due to the imbalance of heat, and stable operation becomes possible.

On the other hand, in this embodiment, since the expander generator (230) utilizes the cold heat of the first heat medium to produce electric power, the load on the power generation engine installed in the re-vaporization ship is reduced, and the fuel consumption is reduced. can be reduced.

As described above, according to the present embodiment, the cold heat of the first heat medium in the high-pressure gas state is used to drive the expander generator 230 to produce electric power, thereby driving the expander generator 230. LNG is vaporized using the first heat medium in the low-pressure gas state after the first heat transfer. The pressure control on the outlet side of the is very important.

For this purpose, the receiver (240) plays a role of controlling the outlet pressure of the expander generator (230) and stably supplies the liquid state first heat medium to the first pump (210). It plays the role of a buffer tank for

When the re-vaporization system operates normally, the temperature of the first heat medium discharged from the vaporizer (120) decreases due to heat exchange with LNG in the vaporizer (120). At this time, the temperature of the first heat medium discharged from the vaporizer (120) is adjusted by adjusting the flow rate of LNG that exchanges heat with the first heat medium, that is, the flow rate of LNG supplied to the vaporizer (120). can be adjusted.

Since the saturation pressure of the first heat medium is determined according to the temperature of the first heat medium condensed and discharged from the vaporizer (120) after heat exchange, the first heat medium discharged from the vaporizer (120) is If the temperature is not normally controlled, the pressure of the first heat medium discharged from the expander generator (230) cannot be maintained normally.

That is, the pressure of the receiver (240) should be maintained at the saturation pressure corresponding to the temperature of the first heat medium discharged from the vaporizer (120).

Under normal circumstances, the pressure of the receiver (240) is controlled and maintained stably according to the temperature of the first heat medium, but the gas flow rate of the first heat medium flowing into the receiver (240) suddenly increases. When a problem such as a transient condition occurs, the response speed becomes slow, and even if the temperature of the first heat medium discharged from the evaporator (120) is normally controlled, the pressure of the receiver (240) increases accordingly. may not follow.

Therefore, in the re-vaporization method and system according to an embodiment of the present invention, in order to improve the control responsiveness of the re-vaporization system even in such a situation where the response speed is slow, It is characterized by controlling the pressure, that is, the pressure on the low pressure side.

More specifically, the downstream pressure of the expander generator (230) is quickly controlled by controlling the downstream pressure of the vaporizer (120), ie, the pressure of the receiver (240).

Referring to FIG. 2, the re-vaporization system according to the first embodiment of the present invention is branched from the first heat medium line (RL) downstream of the expander generator (230) and connected to the receiver (240). a second branch line (RL2) and a second valve (RV) provided in the second branch line (RL2); and a third valve (QV) provided in the third branch line (RL3).

In addition, the first pressure control unit (PIC01) that measures the pressure of the receiver (240) and the output value based on the pressure measurement value of the first pressure control unit (PIC01), the second valve (RV) and the third valve ( QV) is further provided with a second control unit (BQ).

The first pressure control unit (PIC01) of the present embodiment controls a pressure measuring device (PT01) for measuring pressure and various means necessary for pressure adjustment by transmitting the pressure measurement value of the pressure measuring device (PT01). It is a name that includes all pressure controllers that calculate the output value of and send control signals to various means.

The control logic of the second control section (BQ) is split range control, if the receiver (240) pressure measurement measured by the first pressure control section (PIC01) is lower than the set value, The high-temperature first heat medium supplied from the expander generator (230) to the vaporizer (120) bypasses the vaporizer (120) via the second branch line (RL2) and is supplied to the receiver (240). As such, it includes a bypass mode that opens the second valve (RV).

Also, the control logic of the second control section (BQ) ensures that if the receiver (240) pressure measurement measured by the first pressure control section (PIC01) is higher than the set value, the carburetor (120) is discharged. A quench mode (a quenching mode ( querying mode).

The bypass mode opens the second valve (RV) to allow the high-temperature first heat transfer medium to flow into the receiver (240) when the pressure measurement value of the receiver (240) is lower than the set value. The pressure can be increased and quickly controlled in advance so that the outlet pressure of the expander generator (230) does not become low.

Bypass mode continues until the receiver (240) pressure reading reaches the set point.

On the other hand, normally, the first heat medium is supplied to the receiver (240) along the first heat medium line (RL) through a fluid inlet provided at an intermediate height of the receiver (240), while the quench mode is When operated, the third valve (QV) is opened to inject the low-temperature first heat medium through the injection nozzle provided on the upper part of the receiver (240), so that it exists in the upper part of the receiver (240). The temperature of the first heat medium in the high temperature gas state is lowered to reduce the pressure in the receiver (240). By reducing the pressure in the receiver (240), the expander generator (230) outlet pressure can be quickly controlled in advance so that it does not become too high.

The quench mode continues until the receiver (240) pressure reading reaches the set point.

On the other hand, the relationship between saturation pressure and temperature changes from the initial set value due to various factors such as the actual composition of the first heat medium. For example, when the first heat medium is a composite refrigerant in which a plurality of components are mixed, a situation occurs in which a part of the component with a low boiling point evaporates and disappears during operation, and the composition of the first heat medium changes. During operation, the relationship between pressure and temperature changes accordingly.

In this way, despite the fact that the composition of the first heat medium has changed from the initial stage of operation, if the operation is performed while maintaining the initial set values of various temperature and pressure measurements of the second control unit (BQ), A divergence occurs and the valve is operated in detour mode and quench mode more than necessary.

Therefore, in order to solve such problems, the re-vaporization system according to the second embodiment of the present invention includes a set point adjustment means for adjusting the relationship of the saturation curve between pressure and temperature. Prepare.

Referring to FIG. 3, as the means for adjusting the set value according to the second embodiment of the present invention, the pressure measurement value of the first pressure controller (PIC01) is used to adjust the set value of the second temperature controller (TIC02). It further comprises a modifying third control unit (PID).

That is, the set value of the temperature of the first heat medium discharged from the vaporizer (120), that is, the saturation temperature of the first heat medium is adjusted according to the saturation pressure of the receiver (240), and the composition of the first heat medium is adjusted. , the system can be normally controlled by adjusting the set pressure of the receiver (240) and the opening times of the second valve (BV) and the third valve (QV) accordingly.

The first heat medium of the LNG re-vaporization system according to the present embodiment is condensed by heat exchange with LNG in the vaporizer (120) during normal operation of the LNG re-vaporization system to maintain a relatively low pressure. Cycle through one cycle.

Also, in order to control the pre-pressure of the expander generator 230, that is, the pressure on the high pressure side of the first cycle, the expander generator 230 must be It is necessary to adjust the opening rate of the second flow control valve (FV2) and the third flow control valve (FV3) provided upstream of (230).

At this time, in order to maximize the power production in the expander generator (230), the first heat medium should flow into the first branch line (RL1) to bypass the expander generator (230). Rather, it is necessary to direct the flow to feed the expander generator (230).

That is, when adjusting the limited flow rate of the first heat medium to flow toward the vaporizer (120), the smaller the opening rate of the third flow rate control valve (FV3), the more the second flow rate control valve (FV2). The larger the opening rate of the expander generator (230), the more power is produced by the expander generator (230), and the entire system can be operated in an energy efficient manner.

Therefore, the re-vaporization method and system according to the third and fourth embodiments of the present invention, which will be described later, control the pre-pressure of the expander generator (230), that is, the pressure on the high pressure side, in order to improve the efficiency of the system. characterized by

Referring to FIG. 4, the method of re-vaporization according to the third embodiment of the present invention controls the pre-pressure of the expander generator (230) based on the output value of the pressure measurement of the knockout drum (250). .

According to this embodiment, a second pressure controller (PIC02) measures the pressure of the knockout drum (250) and transmits the pressure measurement of the second pressure controller (PIC02) to a sixth controller (SIC). , a fifth control unit (FB) that adjusts the opening degree of the third flow control valve (FV3) based on the output value of the pressure measurement value of the second pressure control unit (PIC02); and a second pressure control unit (PIC02). A sixth control unit (SIC) that controls the output and rotation speed of the expander generator (230) and adjusts the opening of the second flow control valve (FV2) based on the output value from the pressure measurement value of Prepare.

The second pressure control unit (PIC02) of the present embodiment is a pressure measuring device (PT02) that measures the pressure of the knockout drum (250) and a pressure signal that is transmitted from the pressure measuring device (PT02). It is a name that includes all pressure controllers that calculate output values for controlling various means for adjusting the pressure and send control signals to the various means.

The fifth control unit (FB) preferentially opens the second flow control valve (FV2) using a split range control method when the pressure measurement value of the second pressure control unit (PIC02) is higher than the set value. A signal is sent to the sixth control unit (SIC), and the sixth control unit (SIC) receives the signal from the fifth control unit (FB) to increase the output of the expander generator (230), and the second The rotating speed of the expander generator (230) is maintained by opening the flow control valve (FV2) or increasing the opening rate.

At this time, if the pressure of the knockout drum (250) is continuously above the set value, or the expander When the output of the generator (230) reaches the maximum value, the split range control of the fifth control unit (FB) commands to open the third flow control valve (FV3), and the first heat medium is It also flows into the first branch line (RL1) to control the pressure of the knockout drum (250), ie the pre-pressure of the expander generator (230).

According to this embodiment, the sixth control unit (SIC) is, for example, a governor (see FIG. 1). That is, according to the present embodiment, for stable power supply, the turbine rotation speed of the expander generator (230) is monitored to determine whether it is operating properly within a set range, and the rotation speed is controlled. , etc., the governor that controls the output of the expander generator (230) serves to adjust the opening of the second flow control valve (FV2).

On the other hand, the output conversion speed of the expander generator (230) varies depending on the manufacturer of the expander generator (230), but on average it is at the level of 10% per minute. That is, when increasing the output of the expander generator (230), it must be increased within a range of 10% per minute.

As described above, in changing the output (turbine speed) of the expander generator (230) based on the output value obtained by measuring the pressure of the knockout drum (250), the amount of circulation of the first heat medium is changed. When the change occurs faster than the output regulation rate of the expander generator (230), or when a problem occurs such as a situation where the gas flow rate of the first heat medium flowing into the knockout drum (250) suddenly increases. , the inlet pressure of the expander generator (230) greatly deviates from the required pressure range, causing system overload. Therefore, the expander generator (230) cannot be stably operated.

In order to solve such a problem, the re-vaporization method according to the fourth embodiment of the present invention is based on the output value of the pressure measurement value of the second pressure control unit (PIC02), the third flow control valve (FV3) is preferentially opened to quickly control the pre-pressure of the expander generator (230).

According to this embodiment, when the pressure measurement value of the second pressure control unit (PIC02) becomes higher than the set value, by preferentially opening the third flow control valve (FV3), 1. The heat transfer medium is discharged from the knockout drum (250) to the first branch line (RL1) to rapidly control the inlet pressure of the expander generator (230) to drop to the required pressure range (set value).

Further, in this embodiment, the fifth control unit (FB) controls the third flow control valve (FV3) by transmitting the pressure measurement value from the pressure regulator of the second pressure control unit (PIC02). Unlike the mode, the pressure regulator of the second pressure control unit (PIC02) directly transmits the opening control signal to the third flow control valve (FV3) based on the output value of the pressure measurement value.

Moreover, according to this embodiment, as shown in FIG. 5, the seventh control section (ZIC) that controls the valve displacement of the third flow control valve (FV3) is further provided.

The seventh control unit (ZIC) of the present embodiment is configured such that the load required for the third flow control valve (FV3) to be in the closed state (SP: 0%) is set to the expander generator (230 ) to adjust the opening rate of the second flow control valve (FV2).

Thus, according to this embodiment, when the pressure measurement value of the knockout drum (250) is higher than the set value, the third flow control valve (FV3) is preferentially opened to ) to the set value in advance.

Next, the seventh controller (ZIC) reduces the opening rate of the third flow control valve (FV3) to the maximum possible extent, and the sixth controller (ZIC) increases the output of the expander generator (230) to the maximum. (SIC).

Accordingly, the sixth control unit (SIC) increases the opening rate of the second flow control valve (FV2) to the maximum possible extent, thereby maintaining the pre-pressure of the expander generator (230). Power generation can be maximized while varying the output of the expander generator (230) within an acceptable range.

While specific implementations of the present invention have been described above, it will be appreciated by those skilled in the art that the present invention can be embodied in other specific forms without departing from its spirit or category. self-evident for those who have Accordingly, the above-described embodiments are to be construed as illustrative rather than restrictive. Accordingly, the invention is not limited to the foregoing description, but may be modified within the scope of the appended claims and their equivalents.

120: vaporizer, 130: trim heater, 210: first pump, 220: first heat exchanger, 230: expander generator, 240: receiver, 250: knockout drum, LL: liquefied gas line, RL: third 1 heat medium line, RL1: first branch line, RL2: second branch line, RL3: third branch line, RL4: fourth branch line, RL5: fifth branch line, SL1: first seawater line, LV: third 1 valve, FV1: 1st flow control valve, FV2: 2nd flow control valve, FV3: 3rd flow control valve, LV1: 1st water level valve, LV2: 2nd water level valve, RV: 2nd valve, QV: 3rd 3 valves, TIC01: first temperature control unit, TIC02: second temperature control unit, PIC01: first pressure control unit, PIC02: second pressure control unit, LS1: first control unit, BQ: second control unit, PID : third control section, LS2: fourth control section, FB: fifth control section, SIC: sixth control section, ZIC: seventh control section.

Claims (26)

heat exchange between the liquefied gas and the first heat medium in a vaporizer to vaporize the liquefied gas, recover the cold heat of the first heat medium discharged from the vaporizer, and then recirculate it to the vaporizer;
Recovering the cold heat of the first heat medium includes:
The first heat medium in a liquid state condensed by heat exchange in the vaporizer is vaporized in the first heat exchanger, and the vaporized first heat medium is supplied to an expander generator and expanded to produce electric power. , supplying the expanded first heat medium to the vaporizer;
A method for re-vaporizing liquefied gas for a ship, comprising controlling the pressure before or after the expander generator to control the pressure after the vaporizer. In order to control the post pressure of the expander generator,
The first heat medium discharged from the vaporizer is stored in a receiver, the first heat medium is discharged from the receiver and vaporized,
When the pressure measurement value of the receiver is smaller than the set value, operate in a detour mode in which the high-temperature first heat medium expanded by the expander generator bypasses the vaporizer and is supplied to the receiver;
2. The method of claim 1, comprising operating in a quench mode for injecting a cold first heat transfer medium discharged from the evaporator into an upper portion of the receiver when the pressure measurement of the receiver is greater than a set value. liquefied gas re-vaporization method for ships. 2. The method of re-vaporizing liquefied gas for ships according to claim 1, wherein the first heat medium undergoes a phase change by heat exchange between the vaporizer and the first heat exchanger. Supplied to the vaporizer so that the temperature of the low-temperature first heat medium discharged from the vaporizer after heat exchange and the temperature of the re-vaporized gas discharged from the vaporizer after heat exchange maintain set values. 2. The liquefied gas re-vaporization method for ships according to claim 1, wherein the flow rate of the liquefied gas is adjusted. an output value for maintaining the temperature of the low-temperature first heat medium discharged from the vaporizer after heat exchange at a set value;
Among the output values for maintaining the temperature of the re-vaporized gas discharged from the vaporizer after heat exchange at a set value,
2. The liquefied gas re-vaporization method for ships according to claim 1, wherein the flow rate of the liquefied gas supplied to said vaporizer is controlled based on the small value. 2. The liquefied gas re-vaporization method for ships according to claim 1, wherein the re-vaporized gas vaporized in the vaporizer is heat-exchanged with a second heat medium to additionally heat it to a temperature required by the gas demand destination. . When the downstream pressure of the expander generator is lower than a set value or when the power generation load is low, the gaseous first heat medium bypasses the expander generator and is transferred to the downstream stage. The liquefied gas revaporization method for ships according to claim 1, characterized by: Housed in a knockout drum before supplying the first heat medium vaporized in the first heat exchanger to the expander generator,
2. The method of claim 1, wherein when the knockout drum pressure measurement is higher than a set value, the output of the expander generator is increased to control the pre-pressure of the expander generator. A method for re-vaporizing liquefied gas on ships. The increase in the output of the expander generator increases the opening rate of the second flow control valve that allows the first heat medium to flow from the knockout drum to the expander generator, and increases the output of the expander generator. 9. A method of re-vaporizing liquefied gas in a ship according to claim 8, comprising correspondingly increasing the rate of opening of the second flow control valve. The rotation speed of the expander generator is controlled by a sixth control unit,
10. The vessel according to claim 9, wherein the opening of the second flow control valve is controlled by a sixth control unit that receives a control signal based on the pressure measurement value from a fifth control unit. Liquefied gas re-vaporization method. When the opening rate of the second flow rate control valve is maximized or the output of the expander generator is maximized, the fifth control unit causes the first heat medium to move from the knockout drum to expander power generation. 10. The liquefied gas re-vaporization method for ships according to claim 9, wherein the third flow control valve is opened so that the liquefied gas bypasses the generator and is transferred to the downstream of the expander generator. The increase in output of the expander generator is
After first opening a third flow control valve for adjusting the first heat transfer medium to bypass the expander generator from the knockout drum and be transferred downstream of the expander generator,
A second flow rate for increasing the output of the expander generator within a permissible range while decreasing the opening rate of the third flow control valve to flow the first heat medium from the knockout drum to the expander generator. 9. A method for re-vaporizing a liquefied gas in a marine vessel as claimed in claim 8, comprising increasing the opening rate of the control valve. The rotation speed of the expander generator is controlled by a sixth control unit,
A seventh controller for controlling the displacement of the third flow rate control valve is configured to increase the rotation speed of the expander generator until the opening rate of the third flow rate control valve becomes 0%. 13. The ship's liquefied gas re-vaporization method according to claim 12, wherein the signal is transmitted to. The liquefied gas re-vaporization method for ships according to claim 1, wherein the circulation flow rate of the first heat medium is determined according to the heating duty of the vaporizer. a vaporizer for exchanging heat with the first heat medium to vaporize the liquefied gas;
a first heat exchanger for vaporizing a first heat medium in a liquid state condensed by heat exchange in the vaporizer;
an expander generator for expanding the first heat medium vaporized in the first heat exchanger to produce electric power;
A liquefied gas re-vaporization system for ships, wherein the pressure at the front stage or the rear stage of the expander generator is controlled to control the pressure at the rear stage of the vaporizer. a receiver that houses the low-temperature first heat medium discharged from the vaporizer after heat exchange;
a first heat medium line through which the first heat medium expanded from the expander generator is transferred to the vaporizer, and the first heat medium recovered from the cold heat of the liquefied gas in the vaporizer is transferred to the receiver;
a second valve downstream of the expander generator for regulating the transfer of the first heat transfer medium to a receiver bypassing the vaporizer;
a third valve for controlling that the first heat transfer medium discharged from the evaporator is injected through the injection nozzle on the upper part of the receiver; 16. The liquefied gas re-vaporization system for ships according to claim 15, comprising: a second controller for opening a second valve and for opening said third valve if it is higher than a set value. a first valve for adjusting the flow rate of the liquefied gas supplied to the vaporizer; and the temperature of the low-temperature first heat medium discharged from the vaporizer after heat exchange and the temperature of the first heat medium discharged from the vaporizer after heat exchange. 17. The liquefied gas re-vaporization system for ships according to claim 16, further comprising: a first controller for controlling said first valve such that the temperature of the re-vaporized gas maintains a set value. The temperature setting value of the first heat medium is the saturation temperature of the first heat medium,
18. The marine vessel liquefied gas re-vaporization system of claim 17, further comprising: a third controller that adjusts the temperature set point of the first heat transfer medium based on the pressure reading of the receiver. a third flow control valve for controlling the first heat medium vaporized in the first heat exchanger to bypass the expander generator and be transferred downstream of the expander generator;
17. The liquefied gas re-vaporization system for ships according to claim 16, further comprising: a governor for controlling said third flow control valve in accordance with the downstream pressure of said expander generator and the power generation load of said expander generator. a knockout drum containing the first heat medium vaporized in the first heat exchanger;
a second flow control valve whose opening is adjusted so that the gaseous first heat medium discharged from the knockout drum is supplied to the expander generator;
a third flow control valve whose opening is adjusted so that the gaseous first heat medium discharged from the knockout drum bypasses the expander generator; and A sixth control unit that controls the output of the expander generator and adjusts the opening degree of the second flow control valve according to the output of the expander generator;
16. The ship's liquefied gas re-vaporization system according to claim 15, characterized by controlling the pre-pressure of said expander generator. Sending a signal to increase the expander generator output to the sixth control unit based on the pressure measurement of the knockout drum, and opening the third flow control valve when the expander generator output reaches a maximum. 21. The marine vessel liquefied gas re-vaporization system of claim 20, further comprising: a fifth controller; a pressure regulator that opens said third flow control valve when said knockout drum pressure reading is higher than a setpoint; and said sixth control until the rate of opening of said third flow control valve is minimized. 21. The marine vessel liquefied gas re-vaporization system of claim 20, further comprising: a seventh control unit for sending an increase signal to the unit. 16. The vessel liquefied gas re-vaporization system according to claim 15, wherein said vaporizer is a one-pass type shell-and-tube heat exchanger. 16. The liquefied gas re-vaporization system for ships according to claim 15, further comprising: a trim heater for additionally heating the re-vaporized gas vaporized in the vaporizer to a temperature required by the gas demand destination. 25. The vessel liquefied gas re-vaporization according to claim 24, further comprising: a second cycle in which a second heat medium that exchanges heat with the re-vaporized gas in the trim heater and recovers cold heat of the re-vaporized gas is circulated. system. 25. A marine vessel liquefied gas re-vaporization system according to claim 24, characterized in that said trim heater is a two-pass type shell and tube heat exchanger.

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