KR102694829B1 - Boil Off Gas Reliquefaction System And Method For Ship - Google Patents

Boil Off Gas Reliquefaction System And Method For Ship Download PDF

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KR102694829B1
KR102694829B1 KR1020220170583A KR20220170583A KR102694829B1 KR 102694829 B1 KR102694829 B1 KR 102694829B1 KR 1020220170583 A KR1020220170583 A KR 1020220170583A KR 20220170583 A KR20220170583 A KR 20220170583A KR 102694829 B1 KR102694829 B1 KR 102694829B1
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gas
heat exchanger
compressor
refrigerant
compressed
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KR1020220170583A
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KR20240085938A (en
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곽인정
최진호
이준채
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한화오션 주식회사
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B25/00—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby
    • B63B25/02—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods
    • B63B25/08—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods fluid
    • B63B25/12—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods fluid closed
    • B63B25/16—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods fluid closed heat-insulated
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63J—AUXILIARIES ON VESSELS
    • B63J2/00—Arrangements of ventilation, heating, cooling, or air-conditioning
    • B63J2/12—Heating; Cooling
    • B63J2/14—Heating; Cooling of liquid-freight-carrying tanks
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C9/00—Methods or apparatus for discharging liquefied or solidified gases from vessels not under pressure
    • F17C9/02—Methods or apparatus for discharging liquefied or solidified gases from vessels not under pressure with change of state, e.g. vaporisation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/0002—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
    • F25J1/0022—Hydrocarbons, e.g. natural gas
    • F25J1/0025—Boil-off gases "BOG" from storages
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0047—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle
    • F25J1/005—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by expansion of a gaseous refrigerant stream with extraction of work
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
    • F25J1/007—Primary atmospheric gases, mixtures thereof
    • F25J1/0072—Nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0203—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle
    • F25J1/0204—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle as a single flow SCR cycle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0257—Construction and layout of liquefaction equipments, e.g. valves, machines
    • F25J1/0262—Details of the cold heat exchange system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0257—Construction and layout of liquefaction equipments, e.g. valves, machines
    • F25J1/0275—Construction and layout of liquefaction equipments, e.g. valves, machines adapted for special use of the liquefaction unit, e.g. portable or transportable devices
    • F25J1/0277—Offshore use, e.g. during shipping
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0279—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0279—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
    • F25J1/0285—Combination of different types of drivers mechanically coupled to the same refrigerant compressor, possibly split on multiple compressor casings
    • F25J1/0288—Combination of different types of drivers mechanically coupled to the same refrigerant compressor, possibly split on multiple compressor casings using work extraction by mechanical coupling of compression and expansion of the refrigerant, so-called companders
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2221/00—Handled fluid, in particular type of fluid
    • F17C2221/03—Mixtures
    • F17C2221/032—Hydrocarbons
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2265/00—Effects achieved by gas storage or gas handling
    • F17C2265/03—Treating the boil-off
    • F17C2265/032—Treating the boil-off by recovery
    • F17C2265/033—Treating the boil-off by recovery with cooling
    • F17C2265/034—Treating the boil-off by recovery with cooling with condensing the gas phase
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2270/00—Applications
    • F17C2270/01—Applications for fluid transport or storage
    • F17C2270/0102—Applications for fluid transport or storage on or in the water
    • F17C2270/0105—Ships
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/06—Splitting of the feed stream, e.g. for treating or cooling in different ways
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/62—Liquefied natural gas [LNG]; Natural gas liquids [NGL]; Liquefied petroleum gas [LPG]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/04—Compressor cooling arrangement, e.g. inter- or after-stage cooling or condensate removal
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/30—Compression of the feed stream
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/60—Processes or apparatus involving steps for increasing the pressure of gaseous process streams the fluid being hydrocarbons or a mixture of hydrocarbons

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
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  • Ocean & Marine Engineering (AREA)
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  • Combustion & Propulsion (AREA)
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Abstract

선박의 증발가스 재액화 시스템 및 방법이 개시된다. 본 발명의 선박의 증발가스 재액화 시스템은, 선내 저장탱크에 저장된 액화가스로부터 발생하는 증발가스를 압축기로 공급하는 가스공급라인; 상기 압축기에서 압축된 압축가스가 냉각되는 열교환기; 상기 열교환기로 공급되는 냉매가 순환하는 냉매순환라인; 상기 가스공급라인으로부터 분기되어 증발가스를 가온한 후 가스공급라인으로 합류시키는 분기라인; 및 상기 분기라인에 마련되어 증발가스를 가온하는 예열기:를 포함하되, 상기 압축기에서 압축된 압축가스는 상기 예열기를 거쳐 상기 열교환기로 공급되는 것을 특징으로 한다. A system and method for re-liquefying boil-off gas for a ship are disclosed. The boil-off gas re-liquefying system for a ship of the present invention comprises: a gas supply line which supplies boil-off gas generated from liquefied gas stored in an onboard storage tank to a compressor; a heat exchanger which cools the compressed gas compressed by the compressor; a refrigerant circulation line which circulates the refrigerant supplied to the heat exchanger; a branch line which branches off from the gas supply line and heats the boil-off gas and then joins it to the gas supply line; and a preheater which is provided in the branch line and heats the boil-off gas, characterized in that the compressed gas compressed by the compressor is supplied to the heat exchanger via the preheater.

Description

선박의 증발가스 재액화 시스템 및 방법{Boil Off Gas Reliquefaction System And Method For Ship} {Boil Off Gas Reliquefaction System And Method For Ship}

본 발명은 선박의 증발가스 재액화 시스템 및 방법에 관한 것으로, 더욱 상세하게는 가스공급라인으로부터 분기되는 분기라인에 예열기를 마련하고, 압축기에서 압축된 압축가스를 예열기를 거쳐 열교환기로 공급하여, 증발가스를 가온한 후 가스공급라인으로 합류시킬 수 있도록 하는 선박의 증발가스 재액화 시스템 및 방법에 관한 것이다. The present invention relates to a system and method for re-liquefying boil-off gas for a ship, and more specifically, to a system and method for re-liquefying boil-off gas for a ship, in which a preheater is provided in a branch line branching off from a gas supply line, and compressed gas compressed in a compressor is supplied to a heat exchanger through the preheater to heat the boil-off gas and then join it to the gas supply line.

천연가스(natural gas)는, 메탄(methane)을 주성분으로 하며, 연소 시 환경오염 물질의 배출이 거의 없어 친환경 연료로서 주목받고 있다. 액화천연가스(LNG; Liquefied Natural Gas)는 천연가스를 상압 하에서 약 -163℃로 냉각시켜 액화시킴으로써 얻어지는 것으로, 가스 상태일 때보다 부피가 약 1/600로 줄어들기 때문에, 해상을 통한 원거리 운반에 매우 적합하다. 따라서, 천연가스는 주로 저장 및 이송이 용이한 액화천연가스 상태로 저장 및 이송된다. Natural gas is mainly composed of methane, and is receiving attention as an eco-friendly fuel because it emits almost no pollutants when burned. Liquefied natural gas (LNG) is obtained by cooling natural gas to about -163℃ under normal pressure and liquefying it, and since its volume is reduced to about 1/600 of that in a gaseous state, it is very suitable for long-distance transport by sea. Therefore, natural gas is mainly stored and transported in a liquefied natural gas state, which is easy to store and transport.

천연가스의 액화점은 상압에서 약 -163℃의 극저온이므로, LNG 저장탱크는 LNG가 액체 상태를 유지하도록 단열처리되는 것이 일반적이다. 그러나 LNG 저장탱크는 단열처리가 되어 있기는 하지만, 외부의 열을 차단하는 데에는 한계가 있고, 외부의 열이 LNG 저장탱크에 지속적으로 전달되므로 LNG 수송과정에서 LNG가 LNG 저장탱크 내에서 지속적으로 자연 기화되어 증발가스(BOG; Boil-Off Gas)가 발생한다.Since the liquefaction point of natural gas is an extremely low temperature of approximately -163℃ at normal pressure, LNG storage tanks are usually insulated to keep LNG in a liquid state. However, although LNG storage tanks are insulated, there is a limit to blocking external heat, and since external heat is continuously transferred to the LNG storage tank, LNG is continuously naturally vaporized within the LNG storage tank during the LNG transport process, generating boil-off gas (BOG).

LNG 저장탱크에서 증발가스가 지속적으로 생성되면, LNG 저장탱크의 내압을 상승시키는 요인이 된다. 저장탱크의 내압이 설정된 안전압력 이상이 되면 탱크 파손(rupture) 등 위급상황을 초래할 수 있으므로, 안전밸브를 이용하여 증발가스를 저장탱크 외부로 배출시켜야만 한다. 그러나 증발가스는 일종의 LNG 손실로서 LNG의 수송 효율 및 연료 효율에 있어 중요한 문제이므로, 저장탱크에서 발생하는 증발가스를 처리하기 위한 다양한 방법이 사용되고 있다.If boil-off gas is continuously generated in an LNG storage tank, it becomes a factor that increases the internal pressure of the LNG storage tank. If the internal pressure of the storage tank exceeds the set safety pressure, it can cause an emergency situation such as tank rupture, so the boil-off gas must be discharged outside the storage tank using a safety valve. However, boil-off gas is a type of LNG loss and is an important issue in terms of LNG transport efficiency and fuel efficiency, so various methods are being used to handle boil-off gas generated in storage tanks.

최근에는, 증발가스를 선박의 엔진 등 연료 수요처에서 사용하는 방법, 증발가스를 재액화시켜 저장탱크로 회수하는 방법 또는 이러한 두 가지 방법을 복합적으로 사용하는 방법 등이 개발되어 적용되고 있다. Recently, methods have been developed and applied to use the evaporated gas in fuel demand sources such as ship engines, re-liquefy the evaporated gas and return it to a storage tank, or use a combination of these two methods.

증발가스를 재액화하기 위한 방법으로는, 별도의 냉매를 이용한 냉동 사이클을 구비하여 증발가스를 냉매와 열교환하여 재액화하는 방법, 별도의 냉매가 없이 증발가스 자체를 냉매로 하여 재액화하는 방법 등이 있다.Methods for re-liquefying the evaporated gas include a method of re-liquefying the evaporated gas by heat exchange with the refrigerant using a refrigeration cycle that uses a separate refrigerant, and a method of re-liquefying the evaporated gas itself as the refrigerant without a separate refrigerant.

별도의 냉매 없이 증발가스 자체를 냉매로 사용하여 증발가스를 재액화시키는 방법으로, 압축시킨 증발가스를 미압축 증발가스와 열교환으로 냉각하고 단열팽창시켜 재액화시키는 재액화시스템과, 그 개량기술도 개발되어 선박에 적용되고 있다. A method of re-liquefying evaporative gas by using the evaporative gas itself as a refrigerant without a separate refrigerant, a re-liquefaction system that cools compressed evaporative gas through heat exchange with uncompressed evaporative gas and re-liquefies it through adiabatic expansion, and its improvement technology have also been developed and are being applied to ships.

별도의 냉동 사이클을 이용하는 시스템으로는, 질소 냉매를 이용한 재액화공정을 들 수 있다. Systems that utilize a separate refrigeration cycle include a reliquefaction process using nitrogen refrigerant.

질소 냉매는 혼합 냉매를 이용한 사이클에 비해 상대적으로 효율이 낮으나, 냉매가 불활성이어서 안전성이 높고, 냉매의 상 변화가 없기 때문에 선박에 적용하기 보다 용이한 장점이 있다.Nitrogen refrigerant has relatively low efficiency compared to cycles using mixed refrigerants, but it has the advantage of being safe because the refrigerant is inert and there is no phase change in the refrigerant, making it easier to apply to ships.

이와 같이 별도의 냉매 또는 증발가스 자체의 냉열을 이용해 열교환기에서 냉각된 증발가스는 재액화되어 저장탱크로 회수된다. In this way, the evaporated gas cooled in the heat exchanger using the cold heat of a separate refrigerant or the evaporated gas itself is re-liquefied and returned to the storage tank.

그런데 열교환기를 흐르는 유체들 중 인접한 유체 흐름 간의 온도 차이가 과도하게 크면 열교환기에 상당한 열응력이 가해지고 장치 손상, 수명 감소 등으로 이어질 수 있어, 열교환기 업체에서는 인접한 유체 흐름 간의 온도 차이에 대한 제한을 두고 있다.However, if the temperature difference between adjacent fluid streams flowing through the heat exchanger is excessively large, significant thermal stress is applied to the heat exchanger, which may lead to device damage and reduced lifespan. Therefore, heat exchanger manufacturers place limits on the temperature difference between adjacent fluid streams.

열교환기에서 증발가스 냉열을 이용하는 경우, 저장탱크에서 발생하는 증발가스의 온도는 선박의 운전 상황이나 주위 환경 등에 따라 변화할 수 있고, 증발가스의 온도 변화로 다른 유체 흐름과의 온도 차이가 열교환기에서 요구하는 온도 차이 제한보다 커지면, 장치 손상을 방지하기 위해 열교환기를 우회시키거나 증발가스를 일부 가온하여 공급할 수 밖에 없다. When utilizing the evaporation gas cooling in a heat exchanger, the temperature of the evaporation gas generated in the storage tank may vary depending on the ship's operating conditions or the surrounding environment, and if the temperature difference with other fluid flows due to the change in the temperature of the evaporation gas becomes greater than the temperature difference limit required by the heat exchanger, the heat exchanger must be bypassed or the evaporation gas must be supplied after being partially heated to prevent damage to the device.

본 발명은 이러한 문제를 해결하여 증발가스의 온도 변화에도 가능한 한 열교환기를 우회하지 않고 증발가스의 냉열을 회수하여 재액화시스템을 가동시키고 증발가스 가온을 위한 열원을 확보할 수 있는 방안을 제안하고자 한다. The present invention aims to solve these problems by proposing a method for operating a re-liquefaction system by recovering the cold heat of the evaporation gas without bypassing the heat exchanger as much as possible, and securing a heat source for heating the evaporation gas, even when the temperature of the evaporation gas changes.

상술한 과제를 해결하기 위한 본 발명의 일 측면에 따르면, 선내 저장탱크에 저장된 액화가스로부터 발생하는 증발가스를 압축기로 공급하는 가스공급라인;According to one aspect of the present invention for solving the above-described problem, there is provided a gas supply line for supplying evaporated gas generated from liquefied gas stored in an onboard storage tank to a compressor;

상기 압축기에서 압축된 압축가스가 냉각되는 열교환기;A heat exchanger in which the compressed gas compressed in the above compressor is cooled;

상기 열교환기로 공급되는 냉매가 순환하는 냉매순환라인;A refrigerant circulation line through which the refrigerant supplied to the above heat exchanger circulates;

상기 가스공급라인으로부터 분기되어 증발가스를 가온한 후 가스공급라인으로 합류시키는 분기라인; 및A branch line branched from the above gas supply line, heated the evaporated gas, and then joined to the gas supply line; and

상기 분기라인에 마련되어 증발가스를 가온하는 예열기:를 포함하되,A preheater provided in the above branch line to heat the evaporated gas:

상기 압축기에서 압축된 압축가스는 상기 예열기를 거쳐 상기 열교환기로 공급되는 것을 특징으로 하는 선박의 증발가스 재액화 시스템이 제공된다. A ship's evaporation gas re-liquefaction system is provided, characterized in that the compressed gas compressed in the compressor is supplied to the heat exchanger through the preheater.

바람직하게는, 상기 가스공급라인은 상기 열교환기를 거쳐 상기 압축기로 연결되며, 상기 분기라인은 상기 열교환기의 상류에서 상기 가스공급라인으로부터 분기된 후 상기 열교환기의 전단에서 상기 가스공급라인으로 합류될 수 있다. Preferably, the gas supply line is connected to the compressor via the heat exchanger, and the branch line can be branched off from the gas supply line upstream of the heat exchanger and then joined to the gas supply line at the front end of the heat exchanger.

바람직하게는, 상기 가스공급라인에 마련되는 제1 밸브; 상기 분기라인에 마련되는 제2 밸브; 및 상기 가스공급라인에서 상기 분기라인의 합류지점 후단에서 상기 열교환기로 도입될 증발가스 온도를 감지하여 상기 제1 및 제2 밸브를 제어하는 온도제어부:를 더 포함할 수 있다. Preferably, the system may further include: a first valve provided in the gas supply line; a second valve provided in the branch line; and a temperature control unit that detects the temperature of the evaporated gas to be introduced into the heat exchanger at a point after the confluence of the branch lines in the gas supply line and controls the first and second valves.

상기 압축기는 복수의 컴프레서 및 중간냉각기가 교대로 마련되는 다단 압축기이고, 상기 다단 압축기의 컴프레서 최후단에서 압축된 압축가스를 상기 예열기로 공급하는 열회수라인:을 더 포함할 수 있다. The above compressor is a multi-stage compressor in which a plurality of compressors and intercoolers are alternately provided, and may further include a heat recovery line for supplying compressed gas compressed at the last stage of the compressor of the multi-stage compressor to the preheater.

바람직하게는, 상기 열회수라인은 상기 예열기를 거쳐 상기 다단 압축기의 최후단 중간냉각기 전단으로 연결되고, 상기 최후단 중간냉각기로부터 상기 열교환기를 거쳐 상기 저장탱크로 연결되는 재액화라인:을 더 포함할 수 있다. Preferably, the heat recovery line may further include a re-liquefaction line connected to the last-stage intercooler of the multi-stage compressor via the preheater, and connected from the last-stage intercooler via the heat exchanger to the storage tank.

바람직하게는 상기 냉매순환라인에는, 상기 열교환기로 공급될 냉매가 팽창냉각되는 냉매 팽창장치; 및 상기 열교환기에서 열교환 후 배출되는 냉매를 압축하는 냉매 압축부가 마련되고, 상기 냉매 압축부에서 압축된 냉매는 상기 열교환기로 도입되어 냉각된 후 상기 냉매 팽창장치로 도입될 수 있다. Preferably, the refrigerant circulation line is provided with a refrigerant expansion device for expanding and cooling the refrigerant supplied to the heat exchanger; and a refrigerant compression unit for compressing the refrigerant discharged after heat exchange in the heat exchanger. The refrigerant compressed in the refrigerant compression unit can be introduced to the heat exchanger, cooled, and then introduced to the refrigerant expansion device.

바람직하게는 상기 냉매순환라인을 따라 순환하는 냉매는 질소이며, 상기 열교환기는 상기 압축기로 도입될 미압축 증발가스, 재액화될 상기 압축가스, 상기 냉매 압축부에서 압축된 냉매 및 상기 냉매 팽창장치에서 팽창냉각된 냉매가 열교환되는 극저온 열교환기(Cryogenic Heat Exchanger)일 수 있다. Preferably, the refrigerant circulating along the refrigerant circulation line is nitrogen, and the heat exchanger may be a cryogenic heat exchanger in which heat is exchanged between the uncompressed evaporated gas introduced into the compressor, the compressed gas to be re-liquefied, the refrigerant compressed in the refrigerant compression unit, and the refrigerant expanded and cooled in the refrigerant expansion device.

본 발명의 다른 측면에 따르면, 선내 저장탱크에 저장된 액화가스로부터 발생하는 증발가스를 가스공급라인을 따라 압축기로 공급하여 압축하고, 상기 압축기에서 압축된 압축가스를 냉매가 순환하는 열교환기에서 냉각하되, According to another aspect of the present invention, the evaporated gas generated from the liquefied gas stored in the onboard storage tank is supplied to a compressor along a gas supply line and compressed, and the compressed gas compressed in the compressor is cooled in a heat exchanger through which the refrigerant circulates.

상기 가스공급라인으로부터 분기되어 증발가스를 가온한 후 가스공급라인으로 합류시키는 분기라인에 예열기를 마련하고, 상기 압축기에서 압축된 압축가스를 예열기를 거쳐 열교환기로 공급하는 것을 특징으로 하는 선박의 증발가스 재액화 방법이 제공된다.A method for re-liquefying boil-off gas for a ship is provided, characterized in that a preheater is provided in a branch line branched from the above gas supply line, the boil-off gas is heated, and then joined to the gas supply line, and the compressed gas compressed in the above compressor is supplied to a heat exchanger through the preheater.

바람직하게는, 상기 가스공급라인은 상기 열교환기를 거쳐 상기 압축기로 연결되며, 상기 분기라인은 상기 열교환기의 상류에서 상기 가스공급라인으로부터 분기된 후 상기 열교환기의 전단에서 상기 가스공급라인으로 합류되고, 상기 압축기는 복수의 컴프레서 및 중간냉각기가 교대로 마련되는 다단 압축기이며, 상기 다단 압축기의 컴프레서 최후단에서 압축된 압축가스는 상기 예열기를 거쳐 상기 다단 압축기의 최후단 중간냉각기 전단으로 공급될 수 있다. Preferably, the gas supply line is connected to the compressor via the heat exchanger, the branch line branches off from the gas supply line upstream of the heat exchanger and then joins the gas supply line at a front end of the heat exchanger, the compressor is a multi-stage compressor in which a plurality of compressors and intercoolers are alternately provided, and the compressed gas compressed at the last stage of the compressor of the multi-stage compressor can be supplied to the front end of the last intercooler of the multi-stage compressor via the preheater.

본 발명에서는 저장탱크로부터 발생한 미압축 증발가스를 열교환기를 거쳐 압축기로 도입시켜 미압축 증발가스의 냉열을 이용하면서, 가스공급라인으로부터 분기되는 분기라인에 예열기를 마련하여, 증발가스의 온도가 과도하게 떨어지면 압축가스를 열원으로 예열기에서 가열함으로써 열교환기의 열응력 발생 및 장치 손상을 방지할 수 있다. In the present invention, uncompressed evaporation gas generated from a storage tank is introduced into a compressor through a heat exchanger, and the cold heat of the uncompressed evaporation gas is utilized. In addition, a preheater is provided in a branch line branching off from a gas supply line, so that if the temperature of the evaporation gas drops excessively, the compressed gas is heated in the preheater as a heat source, thereby preventing thermal stress in the heat exchanger and damage to the device.

특히 압축기에서 압축된 압축가스를 예열기를 거쳐 열교환기로 공급함으로써, 압축가스의 열에너지로 예열기의 열원을 확보하는 동시에 고온 압축가스의 냉각을 위해 필요한 냉열을 확보할 수 있어, 시스템의 열효율을 높일 수 있다. In particular, by supplying the compressed gas compressed in the compressor to the heat exchanger through the preheater, the heat source of the preheater can be secured with the thermal energy of the compressed gas, while at the same time, the cold heat required for cooling the high-temperature compressed gas can be secured, thereby increasing the thermal efficiency of the system.

도 1는 별도 냉매 및 증발가스 냉열을 이용하는 본 발명의 기본 실시예에 따른 증발가스 재액화 시스템을 개략적으로 도시한다.
도 2는 본 발명의 일 실시예에 따른 선박의 증발가스 재액화 시스템을 개략적으로 도시한다. Figure 1 schematically illustrates an evaporative gas re-liquefaction system according to a basic embodiment of the present invention utilizing separate refrigerant and evaporative gas cooling.
FIG. 2 schematically illustrates a vessel's evaporation gas re-liquefaction system according to one embodiment of the present invention.

본 발명의 동작상 이점 및 본 발명의 실시에 의하여 달성되는 목적을 충분히 이해하기 위해서는 본 발명의 바람직한 실시예를 예시하는 첨부도면 및 첨부도면에 기재된 내용을 참조하여야 한다.In order to fully understand the operational advantages of the present invention and the objects achieved by practicing 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.

이하 첨부한 도면을 참조하여 본 발명의 바람직한 실시예에 대해 구성 및 작용을 상세히 설명하면 다음과 같다. 여기서 각 도면의 구성요소들에 대해 참조 부호를 부가함에 있어 동일한 구성요소들에 한해서는 비록 다른 도면상에 표시되더라도 가능한 한 동일한 부호로 표기되었음에 유의하여야 한다.Hereinafter, the configuration and operation of a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. Here, when adding reference symbols to components in each drawing, it should be noted that, even if shown in different drawings, identical components are indicated with the same symbols as much as possible.

후술하는 본 발명의 일 실시예에서 선박은, 액화가스를 저장하는 저장탱크가 마련되는 모든 종류의 선박일 수 있다. 대표적으로 LNG 운반선(LNG Carrier), 액체수소 운반선, LNG RV(Regasification Vessel)와 같은 자체 추진 능력을 갖춘 선박을 비롯하여, LNG FPSO(Floating Production Storage Offloading), LNG FSRU(Floating Storage Regasification Unit)와 같이 추진 능력을 갖추지는 않지만 해상에 부유하고 있는 해상 구조물도 포함될 수 있다.In one embodiment of the present invention described below, the ship may be any type of ship provided with a storage tank for storing liquefied gas. Representative examples thereof include ships with self-propulsion capabilities, such as LNG carriers, liquid hydrogen carriers, and LNG RVs (Regasification Vessels), as well as offshore structures that do not have propulsion capabilities but float on the sea, such as LNG FPSOs (Floating Production Storage Offloading) and LNG FSRUs (Floating Storage Regasification Units).

또한, 본 실시예는 가스를 저온으로 액화시켜 수송될 수 있고, 저장된 상태에서 증발가스가 발생하는 모든 종류의 액화가스의 재액화 사이클에 적용될 수 있다. 이러한 액화가스는 예를 들어 LNG(Liquefied Natural Gas), LEG(Liquefied Ethane Gas), LPG(Liquefied Petroleum Gas), 액화에틸렌가스(Liquefied Ethylene Gas), 액화프로필렌가스(Liquefied Propylene Gas) 등과 같은 액화석유화학가스일 수 있다. 다만, 후술하는 실시예에서는 대표적인 액화가스인 LNG가 적용되는 것을 예로 들어 설명하기로 한다. In addition, the present embodiment can be applied to the re-liquefaction cycle of all kinds of liquefied gases that can be transported by liquefying the gas at a low temperature and generate vaporized gas in a stored state. The liquefied gas can be, for example, a liquefied petrochemical gas such as LNG (Liquefied Natural Gas), LEG (Liquefied Ethane Gas), LPG (Liquefied Petroleum Gas), liquefied ethylene gas, or liquefied propylene gas. However, in the embodiments described below, an example in which LNG, which is a representative liquefied gas, is applied will be described.

도 1에는 별도 냉매사이클과 증발가스 냉열을 이용하는 기본 실시예의 증발가스 재액화 시스템을 개략적으로 도시하였다.Figure 1 schematically illustrates a basic embodiment of a evaporative gas re-liquefaction system utilizing a separate refrigerant cycle and evaporative gas cooling.

이는 선박의 저장탱크(T)에 저장된 액화가스로부터 발생하는 증발가스를 가스공급라인(GL)을 따라 압축기(100)로 보내 압축하고, 필요한 경우 선내 엔진 등의 연료로 공급하고, 연료로 공급되지 않은 압축가스는 재액화라인(RL)을 따라 열교환기(200)에서 열교환으로 냉각하여 재액화한 후 저장탱크로 복귀시키는 시스템이다. This is a system in which the evaporated gas generated from the liquefied gas stored in the storage tank (T) of the ship is sent to the compressor (100) along the gas supply line (GL) to be compressed, and if necessary, is supplied as fuel for the ship's engine, etc., and the compressed gas not supplied as fuel is cooled through heat exchange in a heat exchanger (200) along the re-liquefaction line (RL) to be re-liquefied and then returned to the storage tank.

가스공급라인(GL)은 저장탱크(T)로부터 열교환기(200)를 거쳐 압축기(100)로 연결됨으로써, 저장탱크에서 발생한 미압축 증발가스는 열교환기에 냉열을 공급하게 된다. The gas supply line (GL) is connected from the storage tank (T) to the compressor (100) via the heat exchanger (200), so that the uncompressed evaporated gas generated in the storage tank supplies cold heat to the heat exchanger.

압축기(100)는 복수의 컴프레서(110A, 110B, 110C)와 중간냉각기(120A, 120B, 120C)를 포함하되, 컴프레서와 중간냉각기가 교대로 배치되는 다단 압축기일 수 있다. 다단 압축기를 거쳐 압축된 압축가스는 추진엔진, 발전엔진 등의 연료로 공급될 수도 있다. 연료로 공급되지 않은 압축가스는 재액화라인(RL)을 따라 열교환기(200)로 공급되어 재액화된다. 열교환기를 통과하며 냉각된 압축가스는 저장탱크로 회수되기에 앞서 감압밸브(300), 세퍼레이터(미도시) 등을 추가로 거칠 수 있다. The compressor (100) may include a plurality of compressors (110A, 110B, 110C) and intercoolers (120A, 120B, 120C), and may be a multi-stage compressor in which the compressors and intercoolers are alternately arranged. The compressed gas compressed through the multi-stage compressor may be supplied as fuel for a propulsion engine, a power generation engine, etc. The compressed gas that is not supplied as fuel is supplied to a heat exchanger (200) along a re-liquefaction line (RL) and re-liquefyed. The compressed gas cooled while passing through the heat exchanger may additionally pass through a pressure reducing valve (300), a separator (not shown), etc. before being recovered to a storage tank.

열교환기(200)에는 미압축 증발가스 외에 냉매순환라인(CL)을 따라 순환하는 별도의 냉매가 추가로 공급되며, 이러한 냉매순환라인의 냉매는 질소(N2)일 수 있다. 냉매순환라인(CL)에는 질소 냉매를 압축하는 냉매 압축부(420)와 냉매 팽창장치(410)를 포함한 냉매공급부(400)가 마련된다. 냉매순환라인의 질소 냉매는 냉매 압축부에서 압축 후 열교환기를 거쳐 냉각되고 다시 냉매 팽창장치에서 팽창냉각되어 열교환기에 냉매로 공급되며 냉매순환라인을 순환한다. 냉매 압축부(420)는 냉매 팽창부(410)와 축 연결되어 컴팬더(compander)를 구성함으로써, 냉매의 팽창에너지를 냉매 압축에 이용할 수 있다. In addition to the uncompressed evaporation gas, a separate refrigerant circulating along the refrigerant circulation line (CL) is additionally supplied to the heat exchanger (200), and the refrigerant of this refrigerant circulation line may be nitrogen (N 2 ). The refrigerant circulation line (CL) is provided with a refrigerant compression unit (420) that compresses the nitrogen refrigerant and a refrigerant supply unit (400) including a refrigerant expansion device (410). The nitrogen refrigerant of the refrigerant circulation line is compressed in the refrigerant compression unit, cooled through the heat exchanger, and then expanded and cooled again in the refrigerant expansion device, and supplied as refrigerant to the heat exchanger and circulates through the refrigerant circulation line. The refrigerant compression unit (420) is axially connected to the refrigerant expansion unit (410) to form a compander, so that the expansion energy of the refrigerant can be utilized for refrigerant compression.

그에 따라 도 1에 도시된 바와 같이 열교환기에서는 압축기에서 압축된 재액화라인(RL)의 증발가스, 압축기로 도입될 가스공급라인(GL)의 미압축 증발가스, 냉매 팽창장치(410)에서 팽창 냉각된 냉매순환라인(CL)의 냉매 및 냉매 압축부(420)에서 압축된 냉매의 4가지 흐름이 도입되어 열교환된다.Accordingly, as illustrated in FIG. 1, four flows are introduced and heat exchanged in the heat exchanger: the evaporation gas of the re-liquefaction line (RL) compressed in the compressor, the uncompressed evaporation gas of the gas supply line (GL) to be introduced to the compressor, the refrigerant of the refrigerant circulation line (CL) expanded and cooled in the refrigerant expansion device (410), and the refrigerant compressed in the refrigerant compression unit (420).

이러한 열교환기(200)는 극저온인 LNG로부터 발생하는 증발가스 및 질소 냉동 사이클에 맞추어 극저온 열교환기(Cryogenic Heat Exchanger)로 설치될 수 있으며, 예를 들어 Brazed Aluminium Heat Exchanger(BAHE)일 수 있다. This heat exchanger (200) can be installed as a cryogenic heat exchanger to match the evaporation gas and nitrogen refrigeration cycle generated from cryogenic LNG, and can be, for example, a Brazed Aluminum Heat Exchanger (BAHE).

열교환기(200) 전단의 가스공급라인(GL)에는 열교환기에 열응력을 최소화할 수 있도록 열교환기로 도입되는 증발가스의 온도를 조절할 수 있는 분기라인(BL)이 마련된다.A branch line (BL) is provided in the gas supply line (GL) in front of the heat exchanger (200) to control the temperature of the evaporation gas introduced into the heat exchanger so as to minimize thermal stress on the heat exchanger.

저장탱크에서 발생하는 증발가스의 경우 대개 열교환기로 유입되는 온도가 -100 내지 -130 ℃ 내외이지만, 선박의 운전 상태나 주위 환경에 따라서 이보다 올라가거나 내려갈 수 있고, 저장탱크 컨디션에 따라 -130℃ 이하의 증발가스가 저장탱크에서 발생할 수 있다. 그런데 인접한 열교환 유체 흐름 간에 과도한 온도 차이가 있으면 열교환기에 열응력(thermal stress)이 발생하고, 아이싱(icing), 피로 파괴 등 장치 손상과 수명 감소로 이어질 수 있으므로 일정한 제한을 두고 있다. 그에 따라 미압축 증발가스 온도가 일정 온도보다 낮으면 이를 가열해주어야 한다. In the case of the boil-off gas generated in the storage tank, the temperature flowing into the heat exchanger is usually between -100 and -130℃, but it can go up or down depending on the operating conditions of the ship or the surrounding environment, and boil-off gas below -130℃ can be generated in the storage tank depending on the condition of the storage tank. However, if there is an excessive temperature difference between adjacent heat exchange fluid flows, thermal stress occurs in the heat exchanger, which can lead to device damage such as icing and fatigue failure and reduced service life, so certain restrictions are placed on it. Accordingly, if the temperature of the uncompressed boil-off gas is lower than a certain temperature, it must be heated.

가스공급라인(GL)의 열교환기(200) 상류에서 증발가스의 전부 또는 일부를 가열하여 가스공급라인의 열교환기 전단으로 공급하는 분기라인(BL)이 분기되고, 분기라인에는 증발가스를 가열하는 예열기(250)가 마련된다. 예열기의 열원으로는 예를 들어 글리콜워터, 스팀, 해수 또는 청수 등이 공급될 수 있다.A branch line (BL) is branched off from the upstream side of the heat exchanger (200) of the gas supply line (GL) to heat all or part of the evaporation gas and supply it to the front end of the heat exchanger of the gas supply line, and a preheater (250) for heating the evaporation gas is provided in the branch line. For example, glycol water, steam, seawater, or fresh water can be supplied as a heat source for the preheater.

이와 같이 분기라인(BL)을 통과한 증발가스는, 분기라인으로 분기되지 않고 가스공급라인(GL)을 통과한 증발가스와 합류되어 열교환기(200)로 도입될 수 있다. 가스공급라인의 분기라인 분기지점 하류에는 제1 밸브(V1)가 마련되고, 분기라인의 예열기 전단에는 제2 밸브(V2)가 마련된다. 온도제어부(TT)에서는 가스공급라인의 분기라인 합류지점 하류, 즉 열교환기 전단에서 미압축 증발가스 온도를 감지하여 제1 밸브 및 제2 밸브의 개폐 및 개도를 조절하여 열교환기로 도입되는 미압축 증발가스 온도를 조절할 수 있다.In this way, the evaporation gas passing through the branch line (BL) can be introduced into the heat exchanger (200) by joining with the evaporation gas passing through the gas supply line (GL) without being branched into the branch line. A first valve (V1) is provided downstream of the branch point of the gas supply line branch line, and a second valve (V2) is provided upstream of the preheater of the branch line. The temperature control unit (TT) detects the temperature of the uncompressed evaporation gas downstream of the junction point of the gas supply line branch line, that is, upstream of the heat exchanger, and controls the opening and closing and degree of the first valve and the second valve to control the temperature of the uncompressed evaporation gas introduced into the heat exchanger.

이와 같이 열교환기로 도입되는 미압축 증발가스 온도를 조절함으로써 선박의 운전 상황과 주위 환경 변화에 따라 증발가스의 온도가 변하더라도 열교환기에 과도한 온도 차이로 인해 열응력이 발생하는 것을 막고 장치 손상을 방지할 수 있다. 다만, 이 경우 예열기에 열에너지를 공급하기 위해 글리콜워터, 스팀, 해수 등 별도의 열원이 필요한데, 후술하는 실시예의 시스템은 별도의 열원을 요하지 않고 재액화 시스템 내의 열에너지를 활용할 수 있도록 고안된 것이다. By controlling the temperature of the uncompressed evaporation gas introduced into the heat exchanger in this way, even if the temperature of the evaporation gas changes depending on the operating conditions of the ship and changes in the surrounding environment, thermal stress caused by excessive temperature difference in the heat exchanger can be prevented and damage to the device can be prevented. However, in this case, a separate heat source such as glycol water, steam, or seawater is required to supply thermal energy to the preheater, but the system of the embodiment described below is designed to utilize the thermal energy within the reliquefaction system without requiring a separate heat source.

도 2에는 본 발명의 일 실시예에 따른 선박의 증발가스 재액화 시스템을 개략적으로 도시하였다. 전술한 기본 실시예와 중복된 설명은 생략한다. Fig. 2 schematically illustrates a ship's evaporation gas re-liquefaction system according to one embodiment of the present invention. Any description that overlaps with the above-described basic embodiment is omitted.

본 실시예에서는 예열기의 열원으로 다단 압축기(100)에서 압축 후 재액화될 압축가스를 활용한다. 압축되면서 기체의 온도가 올라가므로, 다단 압축기에서는 컴프레서와 중간냉각기가 교대로 마련되어 압축 및 중간냉각을 거듭 거치면서 증발가스를 압축한다. 본 실시예에서는 고온 압축가스의 열에너지를 예열기의 열원으로 활용할 수 있도록, 다단 압축기의 컴프레서 최후단(110C)에서 압축된 압축가스를 예열기(250)로 공급하는 열회수라인(HRL)을 마련하였다. In this embodiment, the compressed gas to be compressed and re-liquefied in a multi-stage compressor (100) is utilized as the heat source of the preheater. Since the temperature of the gas increases as it is compressed, the compressor and the intercooler are alternately provided in the multi-stage compressor to compress the evaporated gas while repeatedly going through compression and intercooling. In this embodiment, in order to utilize the heat energy of the high-temperature compressed gas as the heat source of the preheater, a heat recovery line (HRL) is provided to supply the compressed gas compressed in the last stage (110C) of the compressor of the multi-stage compressor to the preheater (250).

열회수라인(HRL)은 예열기(250)를 거쳐 다단 압축기의 최후단 중간냉각기(120C) 전단으로 연결되고, 최후단 중간냉각기(120C)로부터 재액화라인(RL)을 통해 열교환기(200)로 공급되어 냉각되고 재액화된 후 저장탱크(T)로 회수될 수 있다. The heat recovery line (HRL) is connected to the front end of the last-stage intercooler (120C) of the multi-stage compressor via a preheater (250), and is supplied from the last-stage intercooler (120C) to the heat exchanger (200) through the re-liquefaction line (RL), where it is cooled, re-liquefied, and then recovered to the storage tank (T).

열회수라인(HRL)을 통해 예열기(250)에서 미압축 증발가스를 가열시키면서 압축가스는 냉각되므로, 중간냉각기(120C)에서 필요한 냉열에너지량을 줄일 수 있고, 예열기를 거친 압축가스가 충분히 냉각된 경우 최후단 중간냉각기에서의 냉각을 거치지 않고 바로 재액화라인을 통해 열교환기로 공급하여 냉각할 수도 있다. Since the compressed gas is cooled while heating the uncompressed evaporated gas in the preheater (250) through the heat recovery line (HRL), the amount of cooling energy required in the intercooler (120C) can be reduced, and if the compressed gas that has passed through the preheater is sufficiently cooled, it can be cooled by supplying it directly to the heat exchanger through the re-liquefaction line without going through cooling in the final intercooler.

이와 같이 본 실시예 시스템은 미압축 증발가스 온도가 과도하게 낮은 경우 예열기에서 가열함으로써 열교환기의 열응력 발생 및 장치 손상을 방지하면서, 압축가스의 열에너지를 예열기의 열원으로 활용함으로써 별도의 시스템 외부 열원을 요하지 않아 배관 등 구성이 간단하며, 재액화될 고온 압축가스를 효과적으로 냉각하고 시스템의 열효율을 높일 수 있다. In this way, the system of this embodiment prevents thermal stress in the heat exchanger and damage to the device by heating the uncompressed evaporated gas in a preheater when the temperature is excessively low, and by utilizing the thermal energy of the compressed gas as a heat source for the preheater, a separate external heat source is not required for the system, so the configuration, such as piping, is simple, and the high-temperature compressed gas to be re-liquefied can be effectively cooled and the thermal efficiency of the system can be increased.

본 발명은 상기 실시예에 한정되지 않고, 본 발명의 기술적 요지를 벗어나지 아니하는 범위 내에서 다양하게 수정 또는 변형되어 실시될 수 있음은 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자에게 있어서 자명한 것이다. It will be apparent to those skilled in the art that the present invention is not limited to the above-described embodiments, and that various modifications or changes may be made and implemented without departing from the technical spirit of the present invention.

T: 저장탱크
100: 압축기
200: 열교환기
250: 예열기
300: 감압밸브
400: 냉매공급부
410: 냉매 팽창장치
420: 냉매 압축부
GL: 가스공급라인
BL: 분기라인
RL: 재액화라인
CL: 냉매순환라인
HRL: 열회수라인 T: Storage tank
100: Compressor
200: Heat exchanger
250: Preheater
300: Pressure relief valve
400: Refrigerant supply section
410: Refrigerant expansion device
420: Refrigerant Compression Unit
GL: Gas supply line
BL: Branch line
RL: Reliquefaction Line
CL: Refrigerant circulation line
HRL: Heat Recovery Line

Claims (9)

선내 저장탱크에 저장된 액화가스로부터 발생하는 증발가스를 복수의 컴프레서 및 중간냉각기가 교대로 마련되는 다단 압축기로 된 압축기로 공급하는 가스공급라인;
상기 압축기에서 압축된 압축가스가 냉각되는 열교환기;
상기 열교환기로 공급되는 냉매가 순환하는 냉매순환라인;
상기 가스공급라인으로부터 분기되어 증발가스를 가온한 후 가스공급라인으로 합류시키는 분기라인;
상기 분기라인에 마련되어 증발가스를 가온하는 예열기;
상기 압축기의 컴프레서 최후단에서 상기 예열기를 거쳐 상기 압축기의 최후단 중간냉각기 전단으로 연결되는 열회수라인; 및
상기 최후단 중간냉각기로부터 상기 열교환기를 거쳐 상기 저장탱크로 연결되는 재액화라인:을 포함하되,
상기 압축기에서 압축된 압축가스는 상기 예열기를 거쳐 상기 열교환기로 공급되는 것을 특징으로 하는 선박의 증발가스 재액화 시스템. A gas supply line that supplies evaporated gas generated from liquefied gas stored in an onboard storage tank to a multi-stage compressor with multiple compressors and intermediate coolers arranged alternately;
A heat exchanger in which the compressed gas compressed in the above compressor is cooled;
A refrigerant circulation line through which the refrigerant supplied to the above heat exchanger circulates;
A branch line branched from the above gas supply line, heated the evaporated gas, and then joined to the gas supply line;
A preheater provided in the above branch line to heat the evaporated gas;
A heat recovery line connected from the last stage of the compressor of the above compressor through the above preheater to the last stage of the intermediate cooler of the above compressor; and
A re-liquefaction line connected from the last intermediate cooler to the storage tank through the heat exchanger:
A ship's evaporation gas re-liquefaction system, characterized in that the compressed gas compressed in the compressor is supplied to the heat exchanger through the preheater. 제 1항에 있어서,
상기 가스공급라인은 상기 열교환기를 거쳐 상기 압축기로 연결되며,
상기 분기라인은 상기 열교환기의 상류에서 상기 가스공급라인으로부터 분기된 후 상기 열교환기의 전단에서 상기 가스공급라인으로 합류되는 것을 특징으로 하는 선박의 증발가스 재액화 시스템. In paragraph 1,
The above gas supply line is connected to the compressor through the above heat exchanger,
A ship's evaporation gas re-liquefaction system, characterized in that the branch line branches off from the gas supply line upstream of the heat exchanger and then joins the gas supply line at the front end of the heat exchanger. 제 2항에 있어서,
상기 가스공급라인에 마련되는 제1 밸브;
상기 분기라인에 마련되는 제2 밸브; 및
상기 가스공급라인에서 상기 분기라인의 합류지점 후단에서 상기 열교환기로 도입될 증발가스 온도를 감지하여 상기 제1 및 제2 밸브를 제어하는 온도제어부:를
더 포함하는 선박의 증발가스 재액화 시스템. In the second paragraph,
A first valve provided in the above gas supply line;
A second valve provided in the above branch line; and
A temperature control unit that detects the temperature of the evaporated gas to be introduced into the heat exchanger at the end after the junction point of the branch line in the above gas supply line and controls the first and second valves:
A boil-off gas re-liquefaction system for a vessel including: 삭제delete 삭제delete 제 1항 내지 제 3항 중 어느 한 항에 있어서, 상기 냉매순환라인에는,
상기 열교환기로 공급될 냉매가 팽창냉각되는 냉매 팽창장치; 및
상기 열교환기에서 열교환 후 배출되는 냉매를 압축하는 냉매 압축부가 마련되고,
상기 냉매 압축부에서 압축된 냉매는 상기 열교환기로 도입되어 냉각된 후 상기 냉매 팽창장치로 도입되는 것을 특징으로 하는 선박의 증발가스 재액화 시스템. In any one of claims 1 to 3, in the refrigerant circulation line,
A refrigerant expansion device in which the refrigerant supplied to the above heat exchanger is expanded and cooled; and
A refrigerant compression unit is provided to compress the refrigerant discharged after heat exchange in the above heat exchanger,
A ship's evaporative gas re-liquefaction system, characterized in that the refrigerant compressed in the above refrigerant compression unit is introduced into the heat exchanger, cooled, and then introduced into the refrigerant expansion device. 제 6항에 있어서,
상기 냉매순환라인을 따라 순환하는 냉매는 질소이며,
상기 열교환기는 상기 압축기로 도입될 미압축 증발가스, 재액화될 상기 압축가스, 상기 냉매 압축부에서 압축된 냉매 및 상기 냉매 팽창장치에서 팽창냉각된 냉매가 열교환되는 극저온 열교환기(Cryogenic Heat Exchanger)인 것을 특징으로 하는 선박의 증발가스 재액화 시스템. In paragraph 6,
The refrigerant circulating along the above refrigerant circulation line is nitrogen.
A ship's evaporation gas re-liquefaction system characterized in that the heat exchanger is a cryogenic heat exchanger in which heat is exchanged between the uncompressed evaporation gas to be introduced into the compressor, the compressed gas to be re-liquefied, the refrigerant compressed in the refrigerant compression unit, and the refrigerant expanded and cooled in the refrigerant expansion device. 선내 저장탱크에 저장된 액화가스로부터 발생하는 증발가스를 가스공급라인을 따라 압축기로 공급하여 압축하고, 상기 압축기에서 압축된 압축가스를 냉매가 순환하는 열교환기에서 냉각하며,
상기 가스공급라인으로부터 분기되어 증발가스를 가온한 후 가스공급라인으로 합류시키는 분기라인에 예열기를 마련하여, 상기 압축기에서 압축된 압축가스를 예열기를 거쳐 열교환기로 공급하되,
상기 압축기는 복수의 컴프레서 및 중간냉각기가 교대로 마련되는 다단 압축기이며, 상기 다단 압축기의 컴프레서 최후단에서 압축된 압축가스는 상기 예열기를 거쳐 상기 다단 압축기의 최후단 중간냉각기 전단으로 공급되는 것을 특징으로 하는 선박의 증발가스 재액화 방법.The evaporated gas generated from the liquefied gas stored in the onboard storage tank is supplied to the compressor along the gas supply line and compressed, and the compressed gas compressed in the compressor is cooled in a heat exchanger through which the refrigerant circulates.
A preheater is provided in a branch line that branches off from the above gas supply line, heats the evaporated gas, and then joins it to the gas supply line, so that the compressed gas compressed in the compressor is supplied to the heat exchanger through the preheater.
A method for re-liquefying evaporative gas of a ship, characterized in that the compressor is a multi-stage compressor in which a plurality of compressors and intercoolers are alternately provided, and the compressed gas compressed at the last stage of the compressor of the multi-stage compressor is supplied to the front stage of the intercooler at the last stage of the multi-stage compressor through the preheater. 제 8항에 있어서,
상기 가스공급라인은 상기 열교환기를 거쳐 상기 압축기로 연결되며, 상기 분기라인은 상기 열교환기의 상류에서 상기 가스공급라인으로부터 분기된 후 상기 열교환기의 전단에서 상기 가스공급라인으로 합류되는 것을 특징으로 하는 선박의 증발가스 재액화 방법. In Article 8,
A method for re-liquefying evaporated gas of a ship, characterized in that the gas supply line is connected to the compressor through the heat exchanger, and the branch line branches off from the gas supply line at the upstream of the heat exchanger and then joins the gas supply line at the front end of the heat exchanger.
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