WO2023106660A1

WO2023106660A1 - Carbon dioxide liquefaction system

Info

Publication number: WO2023106660A1
Application number: PCT/KR2022/017720
Authority: WO
Inventors: 양영명; 김창수; 구병수; 김현준; 손성재
Original assignee: 주식회사 동화엔텍
Priority date: 2021-12-07
Filing date: 2022-11-11
Publication date: 2023-06-15
Also published as: KR102471374B9; KR102471374B1

Abstract

A carbon dioxide liquefaction system is disclosed. The carbon dioxide liquefaction system of the present invention comprises: a carbon dioxide liquefaction line for receiving flue gas generated from a combustion device using LNG as fuel and separating and liquefying carbon dioxide; a heat exchanger provided in the carbon dioxide liquefaction line and including a low-temperature heat exchange unit and a high-temperature heat exchange unit; and a fuel supply line for supplying LNG to the combustion device, wherein LNG from the fuel supply line passes through the low-temperature heat exchange unit of the heat exchanger and then passes through the high-temperature heat exchange unit again to be vaporized while being used as a refrigerant and be supplied to the combustion device, and flue gas from the carbon dioxide liquefaction line is cooled through the high-temperature heat exchange unit of the heat exchanger and then further cooled in the low-temperature heat exchange unit and is liquefied.

Description

carbon dioxide liquefaction system

The present invention relates to a carbon dioxide liquefaction system, and more particularly, to a carbon dioxide liquefaction system for separating, liquefying, and storing carbon dioxide from flue gas generated in a combustion device using LNG as fuel.

BACKGROUND ART With the intensification of global warming, efforts are being made to reduce greenhouse gas emissions worldwide.

As the 1997 Kyoto Protocol, which included the obligations of developed countries to reduce greenhouse gases, expires in 2020, the Paris Climate Change Convention, which was adopted at the 21st United Nations Framework Convention on Climate Change held in Paris, France in December 2015 and entered into force in November 2016, Change Accord), 195 parties to the agreement are making various efforts to reduce greenhouse gas emissions.

Along with this global trend, interest in renewable energy (or renewable energy) such as wind power, solar power, solar heat, bioenergy, tidal power, and geothermal heat has increased and various technologies have been developed as pollution-free energy that can replace fossil fuels and nuclear power. are losing

In addition, natural gas (natural gas), methane (methane) (methane) as a main component and as an environmentally friendly fuel that emits little environmental pollutants during combustion, attracts attention as a supplementary energy to renewable energy. Liquefied Natural Gas (LNG) is obtained by liquefying natural gas by cooling it to about -163°C under atmospheric pressure, and since its volume is reduced to about 1/600 of that in gaseous state, it is suitable for long-distance transportation through sea. very suitable

IMO (International Maritime Organization), a UN specialized organization established to internationally unify ship routes, traffic rules, port facilities, etc., also reduced greenhouse gas emissions by 50% in 2050 compared to 2008 and 100% in 2100. % reduction (GHG Zero Emission) is presented as a goal, and regulations in each country and region are expected to be strengthened accordingly.

LNG is also evaluated as an eco-friendly fuel compared to other fossil fuels, but carbon dioxide is still generated during combustion, and ships that use it as fuel emit combustion gases containing a large amount of carbon dioxide during navigation.

According to EEDI (Energy Efficiency Design Index), which is a compulsory carbon dioxide reduction regulation applied by IMO to new ships, in the case of LNGC with a capacity of 10,000 DWT or more, if the standard of Phase 5 or higher is applied in the future, LNGC using current LNG as fuel It is necessary to prepare for the strengthening of regulations, such as it can be difficult to achieve carbon dioxide emission regulations in furnaces, so various technologies are being researched, such as developing eco-friendly fuel technology that does not emit carbon dioxide, and technology that captures carbon dioxide in combustion gas and converts it to methane or methanol or liquefies it. there is.

The present invention is to propose a method of effectively separating and liquefying carbon dioxide from combustion gas generated in a combustion device using LNG as fuel on a ship or on land.

According to one aspect of the present invention for solving the above problems, a carbon dioxide liquefaction line for receiving flue gas generated from a combustion device using LNG as fuel to separate and liquefy carbon dioxide;

a heat exchanger provided in the carbon dioxide liquefaction line and including a low-temperature heat exchange unit and a high-temperature heat exchange unit; and

Including: a fuel supply line for supplying LNG to the combustion device,

LNG in the fuel supply line passes through the low-temperature heat exchanger of the heat exchanger and then passes through the high-temperature heat exchanger again to be vaporized while being used as a refrigerant and supplied to the combustion device;

Flue gas of the carbon dioxide liquefaction line is cooled through the high-temperature heat exchanger of the heat exchanger and then further cooled and liquefied in the low-temperature heat exchanger.

Preferably, a dummy plate may be inserted into the heat exchanger to separate the low-temperature heat exchange part and the high-temperature heat exchange part.

Preferably, the dummy plate may include a plate body; and a plurality of fluid passages formed on a surface of the plate body, wherein the fluid passages are filled with air to reduce a heat transfer rate between the low-temperature heat exchange part and the high-temperature heat exchange part.

Preferably, the carbon dioxide liquefaction line includes a dewatering unit for receiving flue gas cooled through a high-temperature heat exchange unit of the heat exchanger and removing moisture; a compression unit that receives flue gas that has passed through the dehydration unit, compresses it, and transfers it to a high-temperature heat exchange unit of the heat exchanger; a membrane separator receiving flue gas that has passed through the compression unit and the high-temperature heat exchange unit, separating and removing nitrogen from the flue gas, and supplying the nitrogen to the low-temperature heat exchange unit; and a decompression unit for receiving the flue gas cooled in the low-temperature heat exchange unit and reducing the pressure.

Preferably, carbon dioxide liquefied through the pressure reducing unit is transferred to a storage tank, and carbon dioxide evaporation gas generated in the storage tank may be discharged from the storage tank through a re-liquefaction line.

Preferably, a blower provided in the re-liquefaction line to boost the carbon dioxide boil-off gas further includes, and the carbon dioxide boil-off gas pressurized by the blower passes through the low-temperature heat exchanger of the heat exchanger to the membrane of the carbon dioxide liquefaction line. It may be supplied to the rear end of the separation unit.

Preferably, in the low-temperature heat exchange unit of the heat exchanger, three flows of LNG in the fuel supply line, flue gas in the carbon dioxide liquefaction line passing through the membrane separator, and carbon dioxide evaporation gas in the re-liquefaction line are heat-exchanged, and in the high-temperature heat exchange unit Three flows of flue gas from the carbon dioxide liquefaction line transported from the combustion device, LNG from the fuel supply line passing through the low-temperature heat exchange unit, and flue gas from the carbon dioxide liquefaction line passing through the dehydration unit and compression unit may be heat exchanged.

Preferably, a refrigerant heat exchanger provided at a front end of the membrane separator in the carbon dioxide liquefaction line and additionally cooling the flue gas to be supplied to the membrane separator by a nitrogen refrigerant after cooling in the high-temperature heat exchange unit; The nitrogen refrigerant that has passed through the refrigerant heat exchanger may be reused as a refrigerant in the high-temperature heat exchanger of the heat exchanger.

Preferably, a refrigerant supply line for supplying nitrogen refrigerant to the refrigerant heat exchanger; a temperature sensor for sensing flue gas temperature in front of the membrane separator in the carbon dioxide liquefaction line; and a control valve provided in the refrigerant supply line, wherein the temperature sensor controls the control valve according to flue gas temperature to adjust the flow rate of the nitrogen refrigerant to be supplied to the refrigerant heat exchanger.

Preferably, in the low-temperature heat exchange unit of the heat exchanger, LNG of the fuel supply line, flue gas of the carbon dioxide liquefaction line passing through the refrigerant heat exchanger and the membrane separator, and carbon dioxide boil-off gas of the re-liquefaction line are heat exchanged , In the high-temperature heat exchange unit, nitrogen refrigerant in the refrigerant supply line passing through the refrigerant heat exchanger, flue gas in the carbon dioxide liquefaction line transferred from the combustion device, LNG in the fuel supply line passing through the low-temperature heat exchange unit, and passing through the dehydration unit and compression unit The four streams of flue gas in the carbon dioxide liquefaction line can be heat exchanged.

In the present invention, carbon dioxide emissions can be reduced by separating carbon dioxide from flue gas generated from combustion devices such as engines, combustors, fuel cells, and hydrogen extractors using LNG as fuel, liquefying and storing it.

In particular, while flue gas is cooled and carbon dioxide is liquefied using LNG cold heat to be supplied as fuel for the combustion device, a dummy plate is provided inside the heat exchanger to separate the low-temperature heat exchange part and the high-temperature heat exchange part of the heat exchanger, and each area has a constant temperature Heat exchange efficiency can be increased by enabling heat exchange between fluids within the range.

1 schematically shows a carbon dioxide liquefaction system according to a first embodiment of the present invention.

2 schematically shows a carbon dioxide liquefaction system according to a second embodiment of the present invention.

FIG. 3 schematically shows a cross-sectional view of a heat exchanger in the system according to the second embodiment shown in FIG. 2 .

In order to fully understand the operational advantages of the present invention and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the configuration and operation of a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In adding reference numerals to the components of each drawing, it should be noted that the same components are marked with the same numerals as much as possible, even if they are displayed on different drawings.

1 schematically shows a carbon dioxide liquefaction system according to a first embodiment of the present invention, and FIG. 2 schematically shows a carbon dioxide liquefaction system according to a second embodiment of the present invention, and FIG. 3 shows a heat exchanger in the system according to the second embodiment. A cross-sectional view is schematically shown.

As shown in FIGS. 1 and 2, the systems of this embodiment are supplied with flue gas generated from a combustion device using LNG as fuel, and a carbon dioxide liquefaction line (CCL) for separating and liquefying carbon dioxide, and carbon dioxide It is provided in the liquefaction line and includes heat exchangers (100A, 100B) including a low-temperature heat exchange unit and a high-temperature heat exchange unit, and a fuel supply line (GL) for supplying LNG to the combustion device, but the LNG in the fuel supply line is used for low-temperature heat exchange in the heat exchanger After passing through the unit (100l), it is used as a refrigerant through the high-temperature heat exchange unit (100ha, 100hb) and is vaporized and supplied to the combustion device, and the flue gas of the carbon dioxide liquefaction line (CCL) is the high-temperature heat exchange unit (100ha, 100hb) of the heat exchanger After being cooled through 100 hb), it is further cooled in the low-temperature heat exchanger (100 l) and liquefied.

A combustion device to which the systems of this embodiment are applied may be, for example, an engine that receives LNG as fuel, a fuel cell, a hydrogen extractor, a combustor, and the like. It is a system that supplies flue gas generated by burning LNG fuel in such a combustion device to a carbon dioxide liquefaction line, separates and liquefies the carbon dioxide contained in the flue gas, and processes the flue gas.

In the systems of this embodiment, by using LNG cold heat to be supplied as fuel of the combustion device as a cold heat source for liquefying carbon dioxide in the heat exchanger, by securing cold energy for liquefying carbon dioxide and at the same time vaporizing LNG to be supplied as fuel, It can increase efficiency and reduce the use of thermal energy required for LNG vaporization.

In particular, in the systems of this embodiment, a dummy plate (DP) is inserted and installed inside the heat exchangers (100A, 100B), so that the heat exchanger is divided into a low-temperature heat exchange part (100l) and a high-temperature heat exchange part ( 100ha, 100hb) to increase heat exchange efficiency.

As can be seen in the cross-sectional view shown in FIG. 3, the dummy plate DP includes a plate body P and a plurality of fluid passages F formed on the surface of the plate body, and the fluid passages are filled with air. Plates through which other working fluids flow in the heat exchanger have a similar structure in which fluid passages are formed (LY1 to LY8). In the present embodiments, LNG and carbon dioxide mainly composed of methane and carbon dioxide are introduced into the heat exchanger, and in the system of the second embodiment described later, nitrogen (l) is additionally introduced and heat is exchanged while passing through the heat exchanger. Each working fluid in the heat exchanger flows The thermal conductivity of SUS304/316, SS400, etc. applied as the material of the plate body (P) reaches 12.7 W/m K, 52 W/m K, and the thermal conductivity of carbon dioxide, which has the lowest thermal conductivity among working fluids, is 0.014, whereas air The thermal conductivity of is very low at 0.002, so the heat transfer rate between the low-temperature heat exchange part and the high-temperature heat exchange part is reduced by the dummy plate (DP) including the air-filled fluid passage (F), and cold heat loss due to heat transfer between the plates of the heat exchanger. can prevent FIG. 3 schematically shows a cross-sectional view of a heat exchanger in which a dummy plate DP having a fluid flow path filled with air is inserted and installed and each working fluid flows along the plates LY1 to LY8.

In the carbon dioxide liquefaction line (CCL), the dehydration unit 200 receives the flue gas cooled through the high-temperature heat exchange unit of the heat exchanger and removes moisture, compresses the flue gas supplied through the dehydration unit, and transfers it to the high-temperature heat exchange unit of the heat exchanger. The compression unit 300 receives the flue gas that has passed through the compression unit and the high-temperature heat exchange unit, separates and removes nitrogen from the membrane, and supplies the membrane separator 400 to the low-temperature heat exchange unit. A pressure reducing unit 500 may be provided.

The high-temperature flue gas generated in the combustion device is supplied to the high-temperature heat exchanger (100ha, 100hb) of the heat exchanger along the carbon dioxide liquefaction line, cooled partially, and then transferred to the dehydration unit 200. In the dehydration unit 200, moisture in the flue gas is separated and removed, and transferred to the compression unit. The compression unit 300 compresses the flue gas and supplies it to the high-temperature heat exchanger 100ha and 100hb of the heat exchanger to cool the flue gas. The flue gas cooled through the heat exchanger passes through the membrane separator 400 to separate and remove nitrogen contained in the flue gas, and is cooled through the low-temperature heat exchanger 100l of the heat exchanger. After removing nitrogen by membrane separation, the flue gas, that is, carbon dioxide cooled through the low-temperature heat exchanger is reduced through the pressure reducing unit 500 and further cooled, and the liquefied carbon dioxide is sub-cooled and transferred to the storage tank (T) and stored The pressure reducing part may be, for example, a J-T valve.

For example, the flue gas generated in the combustion device is supplied to the high-temperature heat exchange part of the heat exchanger at 0.5 barg, 150 ° C, cooled by heat exchange, and then transferred to the low-temperature heat exchange part of the heat exchanger at 10 barg, 200 ° C through the dehydration part and the compression part, It is cooled to -20℃ and supplied to the membrane separator. The membrane separation unit may be a hollow fiber membrane type membrane, and it is preferable to keep the inlet temperature of the membrane low at -20 to -30°C in order to increase the selectivity of carbon dioxide in the flue gas. Carbon dioxide passing through the membrane separator is introduced into the low-temperature heat exchanger of the heat exchanger at -20 ° C and cooled, and may be stored in a storage tank in a supercooled state of -50 to -70 ° C at 7 barg through the heat exchanger and the pressure reducing unit.

Meanwhile, carbon dioxide evaporation gas generated from liquefied carbon dioxide stored in the storage tank T may be discharged from the storage tank through the re-liquefaction line RL, re-liquefied, and then returned to the storage tank.

A blower 600 for boosting the carbon dioxide boil-off gas is provided in the re-liquefaction line RL, and the carbon dioxide boil-off gas discharged from the storage tank T is boosted in the blower 600, and then the re-liquefaction line RL Accordingly, it is supplied to the rear end of the membrane separation unit 400 of the carbon dioxide liquefaction line (CCL) through the low-temperature heat exchange unit 100l of the heat exchanger. Carbon dioxide evaporation gas flowing through the reliquefaction line may flow into the middle portion of the low-temperature heat exchange unit of the heat exchanger, as shown in FIGS. 1 and 2 . When the temperature of the carbon dioxide evaporation gas elevated through the blower is around -40℃, the re-liquefaction line near the point where the temperature of the carbon dioxide flowing through the low-temperature heat exchanger of the heat exchanger through the membrane separator along the carbon dioxide liquefaction line is cooled to around -40℃ By introducing the CO2 boil-off gas and passing it through the heat exchanger in the opposite direction to the CO2 liquefaction line, the cooling heat of the CO2 boil-off gas can be used for carbon dioxide liquefaction.

After passing through the heat exchangers (100A, 100B) through the re-liquefaction line (RL), the carbon dioxide evaporation gas joined to the rear end of the membrane separation unit of the carbon dioxide liquefaction line is combined with the flue gas that has passed through the membrane separation unit in the low-temperature heat exchange unit (100 l ), and then re-liquefied through the pressure reducing unit 500, and then stored again in the storage tank T in a supercooled state.

Accordingly, in the system of the first embodiment, in the low-temperature heat exchanger 100l of the heat exchanger 100A, LNG of the fuel supply line GL, flue gas of the carbon dioxide liquefaction line (CCL) passing through the membrane separator 400, and re-liquefaction The three streams of carbon dioxide boil-off gas in the line RL are heat-exchanged, and the flue gas of the carbon dioxide liquefaction line (CCL) transferred from the combustion device in the high-temperature heat exchange unit (100ha), the fuel supply line (GL) passing through the low-temperature heat exchange unit (100l) ) of LNG, the three flows of flue gas of the carbon dioxide liquefaction line (CCL) passing through the dehydration unit 200 and the compression unit 300 are heat exchanged.

As such, in the system of the present embodiments, the main cold heat energy source of the low-temperature heat exchanger of the heat exchanger uses the cold heat of LNG to be supplied to the combustion device, and the main cold heat source of the high-temperature heat exchanger uses the cold heat of LNG that has passed through the low-temperature heat exchanger. do.

However, as in combustion devices such as fuel cells, natural gas reforming hydrogen extractors, and oxy-fuel combustors, when the flow rate of LNG to be supplied as fuel for the combustion device is less than the cooling heat required for flue gas cooling and carbon dioxide liquefaction/subcooling, or As in combustion devices such as ship engines, industrial engines, thermal power plants, and boilers, additional cooling heat is required when the amount of carbon dioxide generated in the combustion device to be recovered and liquefied is greater than the LNG cold heat to be supplied as fuel. In the system of the second embodiment, it is designed to secure additional cold heat of the heat exchanger by supplementing LNG cold heat.

As shown in FIG. 2, in the system of the second embodiment, the flue gas to be supplied to the membrane separator after being cooled in the high-temperature heat exchanger 100hb provided in the front end of the membrane separator 400 in the carbon dioxide liquefaction line (CCL) is nitrogen A refrigerant heat exchanger 150 for additional cooling by a refrigerant is additionally provided.

A refrigerant supply line NL for supplying nitrogen refrigerant to the refrigerant heat exchanger 150 is provided, and a control valve TCV is provided in the refrigerant supply line. In addition, in the carbon dioxide liquefaction line (CCL), a temperature sensing unit (TC) is provided to detect the temperature of the flue gas in front of the membrane separation unit 400, and the temperature sensing unit controls the control valve according to the flue gas temperature and supplies it to the refrigerant heat exchanger The flow rate of the nitrogen refrigerant to be used can be adjusted. Nitrogen refrigerant and liquid nitrogen from the refrigerant supply line (NL) are supplied to the refrigerant heat exchanger at 8 barg and -175 ° C. After being cooled in the high-temperature heat exchange section, the flue gas to be supplied to the membrane separator is additionally cooled and returned to the membrane separator at around -20 ° C. By introducing it, it is possible to increase the selectivity of carbon dioxide in the membrane separation unit. The nitrogen refrigerant passing through the refrigerant heat exchanger 150 along the refrigerant supply line NL is supplied to the high-temperature heat exchange unit 100hb of the heat exchanger and may be reused as a refrigerant in the high-temperature heat exchange unit.

Accordingly, in the system of the second embodiment, as shown in FIGS. 2 and 3, the high-temperature heat exchanger 100hb of the heat exchanger has nitrogen refrigerant (FIG. 3 LY1), flue gas (LY2) of the carbon dioxide liquefaction line (CCL) transferred from the combustion device, LNG (LY3) of the fuel supply line (GL) passing through the low-temperature heat exchange unit (100l), dehydration unit 200 and compression unit Four flows of flue gas (LY4) of the carbon dioxide liquefaction line (CCL) passing through (300) are heat exchanged, and in the low-temperature heat exchange unit (100l), LNG (LY6) of the fuel supply line (GL), refrigerant heat exchanger 150 and Three streams of flue gas (LY7) of the carbon dioxide liquefaction line (CCL) and carbon dioxide boil-off gas (LY8) of the re-liquefaction line (RL) passing through the membrane separator 400 undergo heat exchange. A dummy plate DP is installed between the high-temperature heat exchange unit and the low-temperature heat exchange unit (LY5).

A small amount of nitrogen when the flow of LNG to be supplied as fuel for combustion devices such as fuel cells, natural gas reforming hydrogen extractors, oxy-fuel combustors, etc. is low and the cooling heat required for flue gas cooling and carbon dioxide liquefaction/subcooling is insufficient Refrigerant is supplied intermittently to make up for insufficient LNG cooling heat.

In addition, when the amount of carbon dioxide to be recovered and liquefied from the combustion device is greater than the cold heat of LNG to be supplied as fuel, as in combustion devices such as ship engines, industrial engines, thermal power plants, and boilers, 50 to 60% of the cold heat required to liquefy carbon dioxide is It is secured from LNG to be supplied as fuel, and 40 to 50% of the insufficient cold heat can be additionally supplied through nitrogen refrigerant.

As described above, in the present embodiments, the carbon dioxide is separated from the flue gas generated in the combustion device and then liquefied to effectively treat the carbon dioxide, and a dummy plate is provided inside the heat exchanger to convert the heat exchanger into a low-temperature heat exchange unit and a high-temperature heat exchange unit. Heat exchange efficiency can be increased by separating and allowing heat exchange between fluids within a certain temperature range for each region.

It is obvious to those skilled in the art that the present invention is not limited to the above embodiments and can be variously modified or modified without departing from the technical gist of the present invention. it did

Claims

A carbon dioxide liquefaction line for receiving flue gas generated from a combustion device using LNG as fuel, separating and liquefying carbon dioxide;

a heat exchanger provided in the carbon dioxide liquefaction line and including a low-temperature heat exchange unit and a high-temperature heat exchange unit; and

Including: a fuel supply line for supplying LNG to the combustion device,

LNG in the fuel supply line passes through the low-temperature heat exchanger of the heat exchanger and then passes through the high-temperature heat exchanger again to be vaporized while being used as a refrigerant and supplied to the combustion device;

The carbon dioxide liquefaction system, characterized in that the flue gas of the carbon dioxide liquefaction line is cooled through the high-temperature heat exchanger of the heat exchanger and further cooled in the low-temperature heat exchanger to be liquefied.
According to claim 1,

Carbon dioxide liquefaction system, characterized in that a dummy plate is inserted into the heat exchanger to separate the low-temperature heat exchange part and the high-temperature heat exchange part.
The method of claim 2, wherein the dummy plate,

plate body; and

A plurality of fluid passages formed on the surface of the plate body;

The carbon dioxide liquefaction system, characterized in that the fluid passage is filled with air to reduce the heat transfer rate between the low-temperature heat exchange part and the high-temperature heat exchange part.
The method of claim 1, wherein the carbon dioxide liquefaction line

a dehydration unit receiving the cooled flue gas through the high-temperature heat exchange unit of the heat exchanger and removing moisture therefrom;

a compression unit that receives flue gas that has passed through the dehydration unit, compresses it, and transfers it to a high-temperature heat exchange unit of the heat exchanger;

a membrane separator receiving flue gas that has passed through the compression unit and the high-temperature heat exchange unit, separating and removing nitrogen from the flue gas, and supplying the nitrogen to the low-temperature heat exchange unit; and

A carbon dioxide liquefaction system, characterized in that a decompression unit for receiving the flue gas cooled in the low-temperature heat exchange unit and reducing the pressure.
According to claim 4,

The carbon dioxide liquefied through the pressure reducing unit is transferred to a storage tank,

Carbon dioxide liquefaction system, characterized in that the carbon dioxide evaporation gas generated in the storage tank is discharged from the storage tank through a re-liquefaction line.
According to claim 5,

Further comprising a blower provided in the re-liquefaction line and boosting the carbon dioxide boil-off gas,

Carbon dioxide liquefaction system, characterized in that the carbon dioxide evaporation gas increased in pressure in the blower is supplied to the rear end of the membrane separation part of the carbon dioxide liquefaction line through the low-temperature heat exchanger of the heat exchanger.
According to claim 6,

In the low-temperature heat exchange unit of the heat exchanger, three flows of LNG in the fuel supply line, flue gas in the carbon dioxide liquefaction line passing through the membrane separator, and carbon dioxide boil-off gas in the re-liquefaction line are heat exchanged,

In the high-temperature heat exchange unit, three flows of flue gas from the carbon dioxide liquefaction line transferred from the combustion device, LNG from the fuel supply line passing through the low-temperature heat exchange unit, and flue gas from the carbon dioxide liquefaction line passing through the dehydration unit and compression unit are heat exchanged. carbon dioxide liquefaction system.
According to claim 6,

A refrigerant heat exchanger provided in the front end of the membrane separator in the carbon dioxide liquefaction line and additionally cooling the flue gas to be supplied to the membrane separator by a nitrogen refrigerant after cooling in the high-temperature heat exchange unit;

The carbon dioxide liquefaction system, characterized in that the nitrogen refrigerant passing through the refrigerant heat exchanger is reused as a refrigerant in the high-temperature heat exchange part of the heat exchanger.
According to claim 8,

a refrigerant supply line supplying nitrogen refrigerant to the refrigerant heat exchanger;

a temperature sensor for sensing flue gas temperature in front of the membrane separator in the carbon dioxide liquefaction line; and

Further comprising a control valve provided in the refrigerant supply line,

The carbon dioxide liquefaction system, characterized in that the temperature sensor controls the control valve according to the flue gas temperature to adjust the flow rate of the nitrogen refrigerant to be supplied to the refrigerant heat exchanger.
According to claim 9,

In the low-temperature heat exchange unit of the heat exchanger, three streams of LNG in the fuel supply line, flue gas in the carbon dioxide liquefaction line through the refrigerant heat exchanger and the membrane separator, and carbon dioxide evaporation gas in the re-liquefaction line are heat exchanged,

In the high-temperature heat exchange unit, nitrogen refrigerant in the refrigerant supply line passing through the refrigerant heat exchanger, flue gas in the carbon dioxide liquefaction line transferred from the combustion device, LNG in the fuel supply line passing through the low-temperature heat exchange unit, carbon dioxide passing through the dehydration unit and compression unit A carbon dioxide liquefaction system, characterized in that the four flows of flue gas in the liquefaction line are heat exchanged.