AU2016428816B2 - Natural gas liquefaction facility - Google Patents

Abstract

[Problem] To provide a natural gas liquefaction facility having high operability and high energy efficiency. [Solution] This natural gas liquefaction facility comprises a liquefaction processing device 15 which performs processing for liquefying natural gas. An internal combustion engine 31 burns fuel gas and drives a first generator 32, a steam generation unit 33 generates steam using the combustion exhaust gas of the internal combustion engine 31, and a steam turbine 41 drives a second generator 42 using the steam generated by the steam generation unit 33. A fluid heating unit 101 heats a fluid to be heated using the steam extracted from the steam turbine 41, and a refrigerant compression unit 21 is driven by a motor 22, which consumes power generated by the first and second generators 32, 42, and compresses the refrigerant gas obtained by cooling natural gas using the liquefaction processing device.

Description

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NATURAL GAS LIQUEFACTION FACILITY

Technical Field

[0001] The present invention relates to an energy supply

technology in a natural gas liquefaction facility.

Background Art

[0002] Natural gas (NG) produced in a gas well or the like is

liquefied in a natural gas liquefaction facility (NG liquefaction

facility) and then shipped as liquefied natural gas (LNG) to a

consumption area through an LNG tanker or a pipeline.

The NG liquefaction facility includes devices and equipment,

for example, various pretreatment devices configured to remove

impurities, such as moisture, a liquefaction processing device

configured to perform liquefaction processing of NG, and a storage

tank (LNG tank) configured to store liquefied LNG.

[0003] In the liquefaction processing device, refrigerant is

used for cooling NG and is gasified by heat exchange with the NG,

andthe refrigerantgasis re-used forcoolingNGthroughcompression

using a refrigerant compressor (refrigerant compression part) and

a decrease in temperature in association with adiabatic expansion.

The refrigerant compressor is a device indispensable for

producing LNG and is one of the devices in which the consumption

amount of energy is largest in the NG liquefaction facility.

Therefore, the refrigerant compressor is required to be stably

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operated and be efficiently supplied with energy. A motor is known

as a power source of the refrigerant compressor which is excellent

in operability and maintainability, and is capable of stably

operating the refrigerant compressor for a long period of time,

as compared to the case in which a gas turbine is used as a power

source of the refrigerant compressor.

[0004] For example, in Non Patent Literature 1, there are

described results obtained by investigating through simulation the

feasibility of a large-scale LNG plant (NG liquefaction facility)

having an annual production capacity of 9,000,000 tons using a

motor-driven refrigerant compressor. In this investigation, there

is described a power generation system configured to generate steam

from combustion exhaust gas of a gas turbine power generator through

use of a heat recovery steam generator and generate electric power

by a steam turbine power generator through use of the steam (Fig.

3).

However, in thepowergenerationsystemdescribedinNonPatent

Literature1, acondensingsteamturbinepowergeneratorisemployed,

andwasteheatisdiscardedontoasurfacecondenserside. Therefore,

high thermal efficiency is obtained based on the evaluation of the

steam turbine power generator as a single element, but there is

room for improvement of thermal efficiency in the entire LNG plant.

[0005] Further, in Non Patent Literature 2, there is described

an LNG plant using, as a heat source of a process, hot oil obtained

by performing waste heat recovery with a gas turbine power generator

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configured to supply electric power to a motor-driven refrigerant

compressor (pp. 11-12). However, heat recovery as hot oil is

performed with sensible heat of oil, and hence a heat recovery unit

is increased in size in a large-scale LNG plant.

Citation List

Non Patent Literature

[0006] [NPL 1] "A Large (9 mta) Electric Motor-Driven LNG plant

is Feasible" (LNG Journal January/February 2004, pp. 53-58)

[NPL 2] "THE SNOHVIT DESIGN REFLECTS A SUSTAINABLE

ENVIRONMENTAL STRATEGY" (14th International Conference &Exhibition

on Liquefied Natural Gas, Paper session PS5-4)

Summary of Invention

Technical Problem

[0007] The present invention has been made in view of the

above-mentioned circumstances and has an object toprovide anatural

gasliquefactionfacilityhavingsatisfactoryoperabilityandenergy

efficiency.

Solution to Problem

[0008] According to one embodiment of the present invention,

there is provided a natural gas liquefaction facility, which is

configured to liquefy natural gas, including: a liquefaction

processing device configured to perform liquefaction processing

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of natural gas; an internal combustion engine configured to drive

a first power generator by burning fuel gas; a steam generation

part configured to generate steam by heat exchange with combustion

exhaustgasobtainedbyburningthefuelgasintheinternalcombustion

engine; a steam turbine configured to drive a second power generator

through use of the steam generated in the steam generation part;

a fluid heating part, which is provided in a natural gas processing

device forming the natural gas liquefaction facility, and is

configured to heat a fluid to be heated flowing through the natural

gas processing device through use of the steam extracted from the

steam turbine; and a refrigerant compression part, which is driven

by a motor consuming electric power generated by the first power

generator and the second power generator, and is configured to

compress refrigerant gas that has cooled the natural gas in the

liquefaction processing device.

[0009] The natural gas liquefaction facility may have the

following features:

(a) the natural gas processing device includes an acid gas

removing unit including a gas absorbing part configured to bring

the naturalgas before being supplied to the liquefaction processing

device into contact with a gas absorbing liquid to remove acid gas

contained in the natural gas, and

the fluid heating part includes a reboiler of a gas absorbent

regeneration part, which is provided to the acid gas removing unit,

and is configured to heat the gas absorbing liquid fed from the

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gas absorbing part to release acid gas, to thereby regenerate the

gas absorbing liquid;

(b) the natural gas processing device includes a gas-liquid

separation unit including a gas-liquid separation part configured

to separate thenaturalgasbeforebeingsuppliedto the liquefaction

processing device and a liquid containing an antifreeze liquid

contained in the natural gas from each other, and the fluid heating

part includes a reboiler of an antifreeze liquid regeneration part,

whichisprovidedtothegas-liquidseparationunit, andisconfigured

to heat an antifreeze liquid fed from the gas-liquid separation

part to release moisture, to thereby regenerate the antifreeze

liquid;

(c) the natural gas processing facility includes a

fractionation unit configured to fractionate a heavy liquid

component separated from the natural gas cooled in the liquefaction

processing device into a condensate that is a liquid at normal

temperature and ethane, propane, and butane that are components

lighter than the condensate, and the fluid heating part includes

a reboiler of the fractionation unit;

(d) the natural gas liquefaction facility further includes

a dehydration unit including a moisture removing unit configured

to bring the natural gas before being supplied to the liquefaction

processing device and an adsorbent into contact with each other

to cause the adsorbent to adsorb moisture contained in the natural

gas, to thereby remove the moisture, and a regeneration gas heating

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unit configured to heat dry natural gas extracted from the natural

gas from which the moisture has been removed and supply the heated

dry natural gas to the moisture removing unit as regeneration gas

for regenerating the adsorbent after adsorbing the moisture, the

regenerationgasheatingunitbeingconfiguredtoheatthedrynatural

gas through use of the steam generated in the steam generation part

before being supplied to the steam turbine or the combustion exhaust

gas of the internal combustion engine;

(e) the steam turbine includes a multi-stage steam turbine

having a surface condenser provided on an exhaust side of a

low-pressure stage, and the fluid heating part is supplied with

steam extracted from a stage on a high-pressure side with respect

to the low-pressure stage; and

(f) the internal combustion engine includes a gas turbine.

Advantageous Effects of Invention

[0010] In the present invention, electric power is supplied

to the motor configured to drive the refrigerant compression part

through use of the internal combustion engine configured to drive

the first power generator and the steam turbine configured to drive

the secondpower generator throughuse ofthe steamgenerated through

use of the combustion exhaust gas of the internal combustion engine.

In addition, the fluid to be heated flowing through the natural

gas processing device in the natural gas liquefaction facility is

heated through use of the steam extracted from the steam turbine.

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As a result, the natural gas liquefaction facility, in which the

refrigerant compression part can be stably operated with the motor

having satisfactory operability and energy efficiency is high, can

be achieved.

Brief Description of Drawings

[0011] FIG. 1is a schematic view for illustrating an overview

of an entire configuration of a natural gas liquefaction facility

according to an embodiment of the present invention.

FIG. 2 is an explanatoryview for illustrating a configuration

ofapowergenerationsystemofthenaturalgasliquefactionfacility.

Description of Embodiments

[0012] First, a configuration example of a natural gas (NG)

liquefaction facility according to an embodiment of the present

invention is described with reference to FIG. 1.

The NGliquefaction facilityincludes a gas-liquid separation

unit 11, a mercury removing device 12, an acid gas removing unit

13, a dehydration unit 14, a liquefaction processing device 15,

and a storage tank 16. The gas-liquid separation unit 11 is

configured to separate aliquid fromNG. Themercuryremovingdevice

12is configured toremovemercury fromthe NG. The acidgas removing

unit 13 is configured to remove acid gas, such as carbon dioxide

and hydrogen sulfide, from the NG. The dehydration unit 14 is

configured to remove a trace amount of moisture contained in the

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NG. The liquefaction processing device 15 is configured to perform

liquefaction processing of the NG having those impurities removed

therefrom. The storage tank 16 is configured to store the liquefied

LNG.

[0013] The gas-liquid separation unit 11 is configured to

separate a condensate, which is a liquid at normal temperature,

contained in the NG transported through a pipeline or the like.

The gas-liquid separation unit 11 includes a gas-liquid separation

part (illustrated as the gas-liquid separation unit 11 in FIG. 1),

which includes an elongated pipe and a drum arranged so as to be

inclined, and is configured to separate a liquid from the NG through

useofadifferenceinspecificgravity. Further, inorder toprevent

the NG and free water from forming a solid gas hydrate under

predetermined temperature andpressure conditions to cause clogging

of the pipeline, an antifreeze liquid may be added to the NG

transported through the pipeline. As the antifreeze liquid, for

example, a moisture absorbing liquid that absorbs moisture, such

as monoethylene glycol (MEG) and triethylene glycol (TEG), is

employed.

[0014] As justdescribed, whentheNGreceivedfromthepipeline

contains the antifreeze liquid, an antifreeze liquid regeneration

part 111 configured to release moisture contained in the antifreeze

liquid may be further juxtaposed to the gas-liquid separation unit

11.

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In the gas-liquid separation part, the antifreeze liquid

containing moisture and the condensate are further phase-separated

from the liquid after being subjected to gas-liquid separation,

andtheantifreezeliquidis fedtotheantifreezeliquidregeneration

partlll. Theantifreezeliquidregenerationpartllisconstructed

as a stripping column configured to heat the antifreeze liquid with

a reboiler 112 to release moisture.

[0015] The mercury removing device 12 is configured to remove

a trace amount of mercury contained in the NG having the liquid

separated therefrom. For example, the mercury removing device 12

has a configuration in which a mercury removal adsorbent is filled

in an adsorption column, and is configured to adsorb and remove

mercury by causing the NG to flow through a layer filled with the

mercury removaladsorbent. As the mercury removaladsorbent, there

may be given an example using an activated charcoal-based mercury

removal adsorbent in which sulfur is carried on activated charcoal

or using a metal-based mercury removal adsorbent in which a sulfide

of copper or zinc is carried on a carrier.

[0016] The acid gas removing unit 13 includes, for example,

an absorption column (gas absorbing part) configured to bring a

gas absorbing liquid containing an amine compound and the natural

gas having mercury removed therefrom into countercurrent contact

witheachotherandcause acidgas, suchascarbondioxideandhydrogen

sulfide, which are liable to be solidified in LNG at a time of

liquefaction, to be absorbed and removed by the gas absorbing liquid

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(illustrated as the acid gas removing unit 13 in FIG. 1). As the

gas absorbingliquid containingan amine compound, there are various

liquids, and there may be given, for example, methyldiethanolamine

(MDEA) and di-isopropanolamine (DIPA). Besides, as the gas

absorbing liquid that does not contain an amine compound, sulforane

or the like may be used.

[0017] Further, a regeneration column (gas absorbent

regeneration part) 131 configured to regenerate the gas absorbing

liquid by releasing acid gas from the gas absorbing liquid having

absorbed the acid gas is juxtaposed to the acid gas removing unit

13. The gas absorbing liquid having absorbed the acid gas in the

absorption column is transferred to the regeneration column 131

and dispersedly supplied from a column top side of the regeneration

column 131. Meanwhile, the gas absorbing liquid in the column is

heated by a reboiler 132 provided on a column bottom side, and the

acid gas is stripped off from the gas absorbing liquid.

[0018] Gas containing the acid gas (e.g., carbon dioxide and

hydrogen sulfide) stripped off from the gas absorbing liquid is

burnt and then discharged to the atmosphere throughrequiredexhaust

gas processing. Meanwhile, the gas absorbing liquid regenerated

in the regeneration column 131 is returned to the absorption column

of the acid gas removing unit 13 and re-used for removing the acid

gas from NG.

[0019] The dehydration unit 14 is constructed as an adsorption

column filled with an adsorbent for adsorbing and removing moisture

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in the NG, such as a molecular sieve or silica gel. The dehydration

unit14inthisembodimentincludesapluralityofadsorptioncolumns,

and the NG having the acid gas removed therefrom is supplied to

anyoneoftheadsorptioncolumnsbyswitching. Theadsorptioncolumn

supplied with the NG serves as amoisture removingunit (illustrated

as the dehydration unit 14 in FIG. 1) configured to adsorb and remove

moisture contained in the NG by causing the NG to flow through a

layer filled with the adsorbent.

[0020] The adsorption column that has not been supplied with

the NGis subjected to regeneration processing ofreleasingmoisture

adsorbed to the adsorbent to regenerate the adsorbent, and then

stands by until the supply destination of the NG is switched

(illustrated as an adsorbent regeneration column 141 in FIG. 1).

In the regeneration of the adsorbent, the dehydration unit

14 in this embodiment uses the NG (dry NG) having moisture removed

therefrom. The dry NG is heated to a temperature of, for example,

from about 280°C to about 300°C by a regeneration gas heating unit

142 and then supplied to the adsorbent regeneration column 141 as

regeneration gas for the adsorbent. The supply destination of the

regeneration gas can also be switched among the plurality of

adsorption columns.

[0021] When the regeneration gas having high temperature is

supplied to the adsorbent regeneration column 141, the moisture

adsorbed to the adsorbent is released to a regeneration gas side,

thereby being capable of regenerating the adsorbent. The

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regeneration gas (NG), which has been used for regenerating the

adsorbent and contains moisture, is discharged from the adsorbent

regeneration column 141, and is cooled and subjected to gas-liquid

separation. Thereafter, the regeneration gas (NG) is used as fuel

gas to be consumed in the NG liquefaction facility.

[0022] TheNGhavingtheimpuritiesremovedtherefrombyvarious

pretreatment devices describedabove is suppliedtothe liquefaction

processing device 15 to be liquefied. The liquefaction processing

device 15 includes devices such as a precooling heat exchanger,

ascrubcolumn, amaincryogenicheatexchanger (MCHE), arefrigerant

compressor (refrigerant compression part) 21, and an aftercooler.

The precooling heat exchanger is configured to precool the NG with

precooling refrigerant containing propane as amain component. The

scrub column is configured to remove a heavy component from the

precooledNG. Themaincryogenicheatexchanger (MCHE) isconfigured

tocool, liquefy, andsubcooltheNGwithmixedrefrigerantcontaining

a plurality of kinds of refrigerant raw materials, such as nitrogen,

methane, ethane, and propane. The refrigerant compressor

(refrigerant compression part) 21 is configured to compress gas

of the precooling refrigerant and the mixed refrigerant that are

gasified by heat exchange. The aftercooler is configured to cool

the compressed refrigerant. In FIG. 1, each of the above-mentioned

devices is not shown except that individual refrigerant compressors

(low-pressure MR compressor 21a and high-pressure MR compressor

21b for mixed refrigerant, and C3 compressor 21c for precooling

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refrigerant) ofthe precoolingrefrigerantand themixedrefrigerant

are collectively described as one component.

[0023] Further, a fractionation unit 151 is juxtaposed to the

liquefaction processing device 15. The fractionation unit 151

includes a deethanizer configured to separate ethane from a liquid

(heavyliquidcomponent) separatedfromthe cooledNG, adepropanizer

configured to separate propane from the liquid having ethane

separated therefrom, andadebutanizerconfigured toseparatebutane

from the liquid having propane separated therefrom to obtain a

condensate thatis aliquidatnormaltemperature. Thedeethanizer,

the depropanizer, and the debutanizer are each constructed as a

fractionator configured to heat the liquid with a reboiler 152 (a

plurality of reboilers 152 are illustrated as one reboiler in FIG.

1) to fractionate each component.

[0024] Liquefied natural gas (LNG), which has been liquefied

and subcooled in the liquefaction processing device 15, is fed to

and stored in the storage tank 16. The LNG stored in the storage

tank 16 is fed with an LNG pump (not shown) and shipped to an LNG

tanker or a pipeline.

[0025] In the NG liquefaction facility having the

above-mentioned configuration, the refrigerant compressor 21

(low-pressure MR compressor 21a, high-pressure MR compressor 21b,

and C3 compressor 21c) is a device indispensable for producing LNG

and is one of the devices in which the consumption amount of energy

is largest in the NG liquefaction facility. The NG liquefaction

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facility in this embodiment employs, as a power source for driving

the refrigerant compressor 21, a motor 22 which is excellent in

operability and maintainability, and is capable of stably operating

the refrigerant compressor 21 for a long period of time.

Further, the NG liquefaction facility in this embodiment

includes a power generation system configured to supply electric

power to power consumption equipment such as the motor 22 of the

refrigerant compressor 21. Now, the configuration of the power

generation system is described with reference also to FIG. 2.

[0026] As illustrated in FIG. 2, the power generation system

of this embodiment includes a plurality of, for example, five gas

turbines 31 that are internal combustion engines each configured

to drive a power generator (first power generator) 32 to generate

electricpower. The gas turbine 31is configured to drive the power

generator 32 with motive power obtained by burning the fuel gas

containing boil off gas (BOG) generated in the storage tank 16.

Because of the presence of the plurality of gas turbines 31,

even when any one of the gas turbines 31is stopped due to periodical

maintenance or trouble, the power generation system of this

embodiment can compensate for a decrease in output of the stopped

gas turbine 31 by increasing output of the remaining gas turbines

31.

[0027] A steam generation part 33 is juxtaposed to each of the

gas turbines 31. The steam generation part 33 is configured to

generate steam by heat exchange with combustion exhaust gas

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discharged from the gas turbine 31. In the steam generation part

33, steam having a relatively high temperature and high pressure,

for example, a temperature within a range of from 3850C to 5230C

and a pressure within a range of from 40 Barg to 96 Barg, is obtained.

The steam generated in each of the steam generation parts 33 is

collected to a common high-pressure steam header 47.

In FIG. 1, for convenience of illustration, the gas turbines

31, the power generators 32, and the steam generation parts 33,

which are provided as a plurality of groups as illustrated in FIG.

2, are illustrated as one group.

[0028] Further, the power generation systemofthisembodiment

is constructed as a combined cycle system including a plurality

of, for example, four steam turbines 41 each configured to drive

a power generator (second power generator) 42 to generate electric

power through use of the steam generated in the steam generation

part 33. Eachof the steamturbines 41is formed in multiple stages,

and a surface condenser 43 is provided on an outlet side of a

low-pressure stage on a lowest pressure side (condensing type).

Also in this case, the plurality of steam turbines 41 are provided,

and a decrease in output of the steam turbine 41 that is stopped

due to, for example, periodical maintenance or trouble can be

compensated for. This point is the same as that in the case of the

gas turbines 31.

Further, boiler water condensed in the surface condenser 43

iscollectedinaboilerwater treatmentpart51, andaboilercompound

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and the like are added to the boilerwater. After that, the resultant

is resupplied to the steam generation part 33.

[0029] The power generators 32 and 42 that are driven by each

of the gas turbines 31 and the steam turbines 41 generate electric

power having a voltage of, for example, 33 kV, and this electric

power is raised to, for example, 110 kV by a substation 61. The

electric power raised by the substation 61 is supplied to the motor

22 for driving the refrigerant compressor 21 through a variable

speed drive (VSD) 62. The NG liquefaction facility including the

refrigerant compressor 21 that is driven by the

electrically-operated motor 22 is referred to as "e-LNG".

Further, the electricpoweris suppliedalso toany otherpower

consumption equipment in the NG liquefaction facility.

[0030] In the power generation system having the

above-mentioned configuration, the multi-stage steam turbine 41

that obtains motive power through use of the steam obtained from

the steam generation part 33 constructs a cogeneration system for

extracting steam from an intermediate stage on a high-pressure side

with respect to the low-pressure stage connected to the surface

condenser 43 and using the steam as a heat source of a fluid heating

part 101 of a processing device 100 provided in the NG liquefaction

facility.

[0031] From each of the steam turbines 41, steam having a

temperature and a pressure lower than those of the steam generated

in the steam generation part 33, for example, having a temperature

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within a range of from 1470C to 170°C and a pressure within a range

of from 4.5 Barg to 8 Barg is extracted. The steam extracted from

each of the steam turbines 41 is collected in a common steam supply

header 46.

[0032] As the fluid heating part 101 of the processing device

100 configured to supply the steam from the steam supply header

46, there are given the reboiler 112 of the antifreeze liquid

regeneration part 111, the reboiler 132 of the regeneration column

131 for a gas absorbing liquid, and each of the reboilers 152 of

the fractionationunit (deethanizer, depropanizer, anddebutanizer)

151, which are described above.

[0033] As illustrated in FIG. 1, thermometers 113, 133, and

153 for a fluid to be heated each configured to measure a temperature

of a fluid to be heated (antifreeze liquid, gas absorbing liquid,

or liquid separated from NG) are provided on outlet sides of the

reboilers 112, 132, and 152, respectively. The supply amount of

steam from the steam supply header 46 to each of the reboilers 112,

132, and 152 is regulated by flow control valves 134, 144, and 154

so that the temperature of each fluid to be heated is brought close

to a target value set in advance.

The boiler water condensed by each of the reboilers 112, 132,

and 152 is collected in the boiler water treatment part 51.

[0034] Meanwhile, it is required that the regeneration gas

heating unit 142 to be used for regenerating the adsorbent in the

adsorbent regeneration column 141 heat the regeneration gas to a

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high temperature of, for example, from about 280°C to about 3000C

as described above. In this respect, it is difficult for the steam

supplied from the steam supply header 46 having a temperature of

from about 1470C to about 1700C as described above to heat the

regeneration gas to a temperature required for regenerating the

adsorbent.

[0035] In view of the foregoing, the steam having a high

temperature extracted from the high-pressure steam header 47 is

supplied to the regeneration gas heating unit 142 to be used for

heating the regeneration gas.

As illustrated in FIG. 1, a gas thermometer 143 configured

to measure a temperature of dry gas is provided on an outlet side

of the regeneration gas heating unit 142. The supply amount of the

steam to the regeneration gas heating unit 142 is regulated by the

flow control valve 144 provided on a line for extracting the steam

having high temperature from the high-pressure steam header 47 so

that the temperature of the dry gas is brought close to a target

value set in advance. The boiler water condensed by each of the

regeneration gas heating units 142 is collected in the boiler water

treatment part 51.

As a heat source for heating the dry gas in the regeneration

gasheatingunit142, awaste-heatrecoveryunitconfiguredtocollect

waste heat of the gas turbine 31 may be provided so as to heat the

dry gas by heat exchange with the combustion exhaust gas discharged

from the gas turbine 31.

[00361 In the above-mentioned power generation system, the

steam in an amount matching the heat quantity required for heating

the fluid to be heated (antifreeze liquid, gas absorbing liquid,

or liquid separated fromNG) in the fluidheatingpart101 (reboilers

112, 132, and 152) of the processing device 100 (antifreeze liquid

regenerationpart111ofgas-liquidseparationunit11, regeneration

column 131 of acid gas removing unit 13, and fractionator 151 of

liquefaction processing device 15) is supplied to the steam supply

header 46 through the steam turbine 41. However, the heat quantity

required in the fluid heating part 101 varies depending on, for

example, the processing amount of the NG and the properties of the

NG.

[0037] Inviewofthe foregoing, in thepowergenerationsystem,

the supply of the steam matching the heat quantity consumption on

the fluid heating part 101 side is guaranteed by keeping the pressure

ofthe steamsupplyheader46ata targetpressure. For thispurpose,

a pressure meter 45 is provided to the steam supply header 46, and

the opening degree of a bleed valve 44 provided on an extraction

line ofeachofthe steamturbines 41is regulatedso that the pressure

of the steam supply header 46 measured by the pressure meter 45

is set to be the target pressure set in advance.

[00381 When the pressure of the common steam supply header 46

is controlled by regulating the opening degree of the bleed valve

44 provided to each of the plurality of steam turbines 41, the bleed

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valves 44 may be opened or closed, for example, so that the opening

degrees of all the bleed valves 44 are matched with each other.

Further, the following may be possible. The priority order

forregulatingtheopeningdegreesofthebleedvalves44isdetermined

amongthepluralityofsteamturbines4l. Whentheconsumptionamount

of the steam on the processing device 100 side increases, the bleed

valve 44 of the steam turbine 41 having a high priority order is

opened. When the opening degree of the bleed valve 44 reaches an

upper limit, the opening degree of the steam turbine 41 having a

subsequent priority order is regulated to be increased. As the

setting criterion of the priority order, there may be given the

followingexample. The priorityorderofthebleedvalve 44 provided

to the steam turbine 41, in which a rate of a decrease in thermal

efficiency in association with an increase in extraction amount

is small, for example, in which the output is larger than those

of the other steam turbines 41, is set to be high.

[0039] The pressure regulation of the steam supply header 46

based on the rule set in advance using the bleed valves 44 provided

to the plurality of steam turbines 41 is performed through use of,

for example, a controlunit 7 including a computer systemconfigured

toperformintegratedcontroloftheentireNGliquefactionfacility.

[0040] Further, in the power generation system of this

embodiment, in order to keep balance of a difference between the

supply amount of the steam supplied from the steam generation part

33 and the consumption amount of the steam on the steam turbine

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41 side, for example, a fuel gas-fired steam boiler 52 is provided.

The steam boiler 52 is configured to increase or decrease the supply

amount of the steam from each of the steam boilers 52 so that the

pressure of high-temperature and high-pressure steam measured by

a pressure meter (not shown) provided to the high-pressure steam

header 47 is set to a target pressure in advance.

[0041] The action of the power generation system of the NG

liquefaction facility having the configuration described above is

described.

First, in the power generation system, it is assumed that the

power generators 32 and 42 are driven by each of the gas turbines

31and eachofthe steam turbines 41, and electricpower in a required

amount is supplied to each of the power consumption equipment in

the NG liquefaction facility including each of the refrigerant

compressors 21. Further, in the fluid heating part 101 of the

processing device 100, it is assumed that such balance is kept that

the steam having heat quantity required for heating the fluid to

beheatedis suppliedto the steamsupplyheader46throughextraction

from the steam turbine 41. Further, it is assumed that

high-temperature steam in a certain amount is supplied to the

regeneration gas heating unit 142, and a variation in supply amount

thereof does not restrict the consumption and supply balance of

the steam in the entire power generation system.

[0042] Herein, consideration is made of a case in which, due

to an increase in processing amount of the NG on the processing

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device 100 side, a change in properties of the NG, and the like,

the consumption amount of the steam in the fluid heating part 101

is increased, and the supply and consumption balance of the steam

is changed in a direction in which the pressure of the steam supply

header 46 is decreased.

In this case, adjustment is performed based on the rule set

in advance so that the pressure of the steam supply header 46 is

kept at the target pressure by increasing the opening degree of

thebleedvalve44providedontheextractionlineofthepredetermined

steam turbine 41 to increase the extraction amount of the steam

to the steam supply header 46 side.

[0043] When the extraction is performed from an intermediate

stage on a high-pressure side with respect to a low-pressure stage

connected to the surface condenser 43 in the steam turbine 41, the

amount of the steam discharged to the surface condenser 43 side

is reduced. As a result, the power generation efficiency of each

of the steam turbines 41 as a single element is reduced, and the

power generation amount of the power generator 42 is decreased.

[0044] When there is no change in power consumption amount in

theNGliquefactionfacilityinthiscase,itisrequiredtocompensate

for a decrease in power generation amount in the power generator

42.

In view of the foregoing, for example, when there is a margin

in output of the gas turbine 31, the decrement in power generation

amount in the power generator 42 can be compensated for on the power

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generator 32 side by increasing the output of the gas turbine 31.

In this adjustment method, the generation amount of the steam in

the steam generation part 33 is increased, and hence the supply

amount of the steam from the steam boiler 52 is decreased to keep

balance.

[0045] Further, when there is a margin in cooling ability on

the surface condenser 43 side, the power generation amount of the

power generator 42 can also be returned to an original amount by

increasing the supply amount of the steam from the high-pressure

steam header 47 to the steam turbine 41 while increasing the supply

amount of the cooling water to the surface condenser 43, to thereby

increase the output of the steam turbine 41. In this adjustment

method, the increment in consumption amount of the steam in the

steam turbine 41 is balanced by increasing the supply amount of

the steam from the steam boiler 52.

[0046] In the above-mentioned two adjustment methods, when the

output of each of the gas turbines 31 is increased, the fuel

consumption amount in the gas turbines 31 is increased, and when

the output of each of the steam turbines 41 is increased, the fuel

consumption amount in the steam boilers 52 is increased. As long

as the constraint on the facility side is not infringed, it is only

necessary that the adjustment method in which the fuel consumption

amount per unit power generation amount is small be employed.

[0047] Next, consideration is made of a case in which, due to

a decrease in processing amount of the NG on the processing device

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100 side, a change in properties of the NG, and the like, the

consumption amount of the steam in the fluid heating part 101 is

decreased, and the supply and consumption balance of the steam is

changed in a direction in which the pressure of the steam supply

header 46 is increased.

In this case, adjustment is performed based on the rule set

in advance so that the pressure of the steam supply header 46 is

kept at the target pressure by decreasing the opening degree of

thebleedvalve44providedontheextractionlineofthepredetermined

steam turbine 41 to decrease the extraction amount of the steam

to the steam supply header 46 side.

[0048] As a result, in the steam turbine 41, the amount of the

steam discharged to the surface condenser 43 side is increased.

Then, the power generation efficiency of each of the steam turbines

41 as a single element is improved, and the power generation amount

of the power generator 42 is increased.

When there is no change in power consumption amount in the

NG liquefaction facility in this case, it is required to decrease

the increment in power generation amount in the power generator

42.

[0049] For example, when there is a margin in actual output

with respect to a lower limit value of the output of the gas turbine

31, the increment in power generation amount in the power generator

42 can be balanced on the power generator 32 side by decreasing

the output of the gas turbine 31. In this adjustment method, the

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generation amount of the steam in the steam generation part 33 is

decreased, and hence the supply amount of the steam from the steam

boiler 52 is increased to keep balance.

[0050] Further, when there is a margin in lower limit value

of the steam discharge amount to the surface condenser 43 side,

the power generation amount of the power generator 42 can also be

returned to an original amount by decreasing the supply amount of

the cooling water to the surface condenser 43 to decrease the supply

amount of the steam from the high-pressure steam header 47 to the

steam turbine 41, to thereby reduce the output of the steam turbine

41. In this adjustment method, the decrement in consumption amount

of the steam in the steam turbine 41 is balanced by decreasing the

supply amount of the steam from the steam boiler 52.

[0051] In the above-mentioned two adjustment methods, when the

output of each of the gas turbines 31 is decreased, the fuel

consumption amount in the gas turbines 31 is decreased, and when

the output of each of the steam turbines 41 is decreased, the fuel

consumption amount in the steam boilers 52 is decreased. As long

as the constraint on the facility side is not infringed, it is only

necessary that the adjustment method in which the reduction width

of the fuel consumption amount per unit power generation amount

is large be employed.

[0052] TheNGliquefactionfacilityaccordingto theembodiment

of the present invention exhibits the following effects. Electric

power is supplied to the motor 22 configured to drive the refrigerant

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compressor 21 by the gas turbine 31 configured to drive the power

generator 32 and the steam turbine 41 configured to drive the power

generator 42 through use of the steam generated through use of the

combustion exhaust gas of the gas turbine 31, and the fluid to be

heated flowing through the processing device 100 in the NG gas

liquefaction facility is heated through use of the steam extracted

fromthe steamturbine 41. As aresult, anNGliquefaction facility,

in which the refrigerant compressor 21 can be stably operated with

the motor 22 having satisfactory operability and the energy

efficiency is high, can be achieved.

[0053] For example, simulation was performed on the NG

liquefaction facility (annual production capacity: 4,500,000 tons)

having the configuration illustrated in FIG. 1 and FIG. 2. As a

result, the totalconsumptionamount offuelgas consumedinresponse

to the drive of the gas turbine 31 and the generation of the steam

in the steam generation part 33 and the steam boiler 52 was 749

MW. Meanwhile, a total of the power generation amount of the power

generators 32 and 42 and the supply amount of the steam to the fluid

heating part 101 and the regeneration gas heating unit 142 was 463

MW. Thus, the thermal efficiency of the entire NG liquefaction

facility is 62%. This can verify the achievement of the thermal

efficiency that is extremely higher than the thermal efficiency

(from about 25% to about 35%) of a general NG liquefaction facility

in which the refrigerant compressor 21is driven by the gas turbine.

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[0054] Herein, the internal combustion engine configured to

drive the power generator 32 is not limited to the gas turbine 31.

For example, it maybe possible to employ a configuration of driving

the power generator 32 through use of a gas engine and driving the

steam turbine 41 configured to drive the power generator 42 through

use of the steam obtained by heat exchange with combustion exhaust

gasofthegasengine. InarelativelysmallNGliquefactionfacility,

electric power required in the refrigerant compressor 21 can be

supplied even with a gas engine having output that is smaller than

that of the gas turbine 31.

[0055] Further, the steam turbine 41 configured to drive the

second power generator 42 is not limited to a condensing type. For

example, a part or an entirety of the steam turbine 41 provided

in the power generation system illustrated in FIG. 1 and FIG. 2

may be a back-pressure type. A change in power generation amount

of the power generator 42 in association with an increase or decrease

in steam supply amount from the back-pressure steam turbine 41 to

the steam supply header 46 cannot be adjusted by an increase or

decrease in discharge amount of the steam to the surface condenser

43side. Therefore, thechangeinpowergenerationamountisbalanced

by decreasing or increasing the output of the gas turbine 31.

Besides, in order to deal with the case in which steam in a

required amount cannot be extracted from the steam turbine 41 due

to the facility constraint, such as the stop of one of the steam

turbines 41, an extraction line 48 including a depressuring valve

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481andadesuperheater 482maybe providedbetween the high-pressure

steam header 47 and the steam supply header 46 as illustrated in

FIG. 1. The depressuring valve 481 is in a closed state at normal

time (indicated by "S" in FIG. 1) and is configured to decrease

the pressure of the steam at a time ofextraction. The desuperheater

482is configured todecrease the temperature ofthe extracted steam.

[0056] Further, the NGliquefaction facility towhichthe power

generation system of this embodiment is applied may not include

all the pretreatment devices illustrated in FIG. 1. For example,

when an antifreeze liquid is not added to the NG received from the

pipeline, installment of the antifreeze liquid regeneration part

111 may be omitted. Further, when the amount of acid gas contained

in the NGis large, the acid gas may be removed bymembrane separation

instead of the acid gas removing unit 13 using an amine compound

or the like. In the case of membrane separation, the regeneration

column 131 is not juxtaposed to the acid gas removing unit 13.

Reference Signs List

[0057] 100 processing device

101 fluid heating part

11 gas-liquid separation unit (gas-liquid separation

part)

12 mercury removing device

13 acid gas removing unit (gas absorbing part)

14 dehydration unit (moisture removing unit)

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15 liquefaction processing device

16 storage tank

21 refrigerant compressor

22 motor

31 gas turbine

32 power generator

33 steam generation part

41 steam turbine

42 power generator

7 control unit

Claims (7)

85756-AU Claims

1.Anaturalgasliquefactionfacility, whichisconfiguredtoliquefy

natural gas, comprising:

a liquefaction processing device configured to perform

liquefaction processing of natural gas;

aninternalcombustionengine configured todriveafirstpower

generator by burning fuel gas;

a steam generation part configured to generate steam by heat

exchange with combustion exhaust gas obtained by burning the fuel

gas in the internal combustion engine;

a steam turbine configured to drive a second power generator

through use of the steam generated in the steam generation part;

a fluid heating part, which is provided in a natural gas

processing device forming the natural gas liquefaction facility,

and is configured to heat a fluid to be heated flowing through the

natural gas processing device through use of the steam extracted

from the steam turbine; and

a refrigerant compression part, which is driven by a motor

consuming electric power generated by the first power generator

and the second power generator, and is configured to compress

refrigerant gas that has cooled the natural gas in the liquefaction

processing device.

2. The natural gas liquefaction facility according to claim 1,

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wherein the natural gas processing device comprises an acid

gas removing unit including a gas absorbing part configured to bring

the naturalgas before being supplied to the liquefaction processing

device into contact with a gas absorbing liquid to remove acid gas

contained in the natural gas, and

wherein the fluid heating part comprises a reboiler of a gas

absorbent regeneration part, which is provided to the acid gas

removing unit, and is configured to heat the gas absorbing liquid

fed from the gas absorbing part to release acid gas, to thereby

regenerate the gas absorbing liquid.

3. The natural gas liquefaction facility according to claim 1,

wherein the natural gas processing device comprises a

gas-liquid separation unit including a gas-liquid separation part

configured to separate the natural gas before being supplied to

the liquefaction processing device and a liquid containing an

antifreeze liquid contained in the natural gas from each other,

and

wherein the fluid heating part comprises a reboiler of an

antifreeze liquid regeneration part, which is provided to the

gas-liquid separation unit, and is configured to heat an antifreeze

liquid fed from the gas-liquid separation part to release moisture,

to thereby regenerate the antifreeze liquid.

4. The natural gas liquefaction facility according to claim 1,

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wherein the natural gas processing device comprises a

fractionation unit configured to fractionate a heavy liquid

component separated from the natural gas cooled in the liquefaction

processing device into a condensate that is a liquid at normal

temperature and ethane, propane, and butane that are components

lighter than the condensate, and

wherein the fluid heating part comprises a reboiler of the

fractionation unit.

5.Thenaturalgasliquefactionfacilityaccordingtoclaiml, further

comprising a dehydration unit including a moisture removing unit

configured to bring the natural gas before being supplied to the

liquefaction processing device and an adsorbent into contact with

each other to cause the adsorbent to adsorb moisture contained in

the natural gas, to thereby remove the moisture, and a regeneration

gas heating unit configured to heat dry natural gas extracted from

the natural gas from which the moisture has been removed and supply

the heated dry natural gas to the moisture removing unit as

regeneration gas for regenerating the adsorbent after adsorbing

the moisture,

the regeneration gas heating unit being configured to heat

the dry natural gas through use of the steam generated in the steam

generation part before being supplied to the steam turbine or the

combustion exhaust gas of the internal combustion engine.

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6. The natural gas liquefaction facility according to claim 1,

whereinthesteamturbinecomprisesamulti-stagesteamturbine

having a surface condenser provided on an exhaust side of a

low-pressure stage, and

whereinthe fluidheatingpartis suppliedwithsteamextracted

froma stage on a high-pressure side withrespect to the low-pressure

stage.

7.Thenaturalgasliquefactionfacilityaccordingtoclaiml, wherein

the internal combustion engine comprises a gas turbine.