• 해양환경안전학회지
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• 제15권3호
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• pp.269-274
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• 2009

LNGC(Liquefied Natural Gas Carrier)의 역사는 1959년 $5,000m^3$ 급 LNG선 "Methane Pioneer"호를 시작으로 1969년에는 $71,500m^3$ 급, 1973년에는 Moss Type의 최초 LNG운반선 "Norman Lady($87,600m^3$)호, 1980년대 $125,000m^3$ 급을 시작으로 1990년대를 거처 $135,000m^3$ 급, 2007년 $210,000m^3$급 그리고 2008년에는 $266,000m^3$ 급의 초대형 액화천연가스 운반선이 출현하였다. 또한 2006년 11월에는 기존 내 외연 기관이 아닌 발전기 기동으로 Propeller를 움직이는 DFDE(Duel Fuel Diesel Electric)엔진, 육상의 Storage Tank를 생략한 기화설비를 갖춘 LNG-RV(Re-gasification Vessel)와 주 기관은 Slow Diesel을 택하고, 운항 중 발생하는 BOG(Boil Off Gas)를 재액화시키는 설비를 갖춘 DRL(Diesel Re-Liquefaction)선박 및 해상 LNG 생산 저장시설인 LNG-FPSO(Floating Production and Storage Offshore), 그리 고 해상 LNG 인수기지 역할을 하는 LNG-FSRU(Floating Store and Re-gasification Unit) 등이 개발되었다. 이 논문에서는 LNG Project, 전 세계 에너지 시장과 LNGC의 발전 추세에 대하여 다루었다.

• 대한기계학회논문집 C: 기술과 교육
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• 제1권1호
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• pp.99-105
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• 2013

LNG 극저온기계기술 시험인증센터에 구축되는 LNG 선박용 펌프 및 압축기 성능시험에서 발생하는 증발가스는 안전을 위하여 전량 회수가 요구된다. 본 논문에서는 36 MTD 용량의 천연가스 재액화 시스템에 대한 기본 설계 연구를 수행하였다. 대기압, $-60^{\circ}C$, 일반적인 도시가스 조성비, 1,500 kg/hr 유량의 공급 가스를 기본 설계 조건으로 하여 공정 설계가 이루어졌고, 입구 온도 조건 및 가스 조성비에 따른 LNG 생산량 또한 계산하여 다양한 입구 설계 조건에 따른 시스템의 성능 변화를 비교, 분석하였다. 공정 설계 외에도 재액화 시스템의 핵심 기기인 송풍기, 압축기, 극저온 열교환기, 컴팬더의 제작 사양이 도출되었으며, 전력 및 냉각수의 유틸리티 요구조건 또한 기본 설계를 통해 도출되었다.

• 한국항해항만학회지
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• 제33권10호
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• pp.659-664
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• 2009

LNG선의 건조 동향을 보면 2003년을 기점으로 하여 기하급수적으로 증가하기 시작 하였으며, 2008년을 기점으로 하여 그 건조량은 감소하는 추세이나 건조 선박 중 많은 부분이 재액화 시스템이 장착된 대형 LNG선박으로 대형 LNG선은 216K급의 Q-Flex급, 260K급의 Q-Max급이 주를 이루고 있다. 이러한 LNG선박의 대형화는 LNG선의 화물창 보온 설계 기준인 BOR(Boil Off Rate) 0.15%를 기준해서 상대적으로 많은 양의 BOG가 발생하게 되었으며 선박의 주 추진기관의 연료로 사용 하더라도 잉여 가스가 남게 되어 화물탱크의 압력상승을 막기 위해서는 BOG를 재 액화하여 화물탱크로 반송하거나 소각하는 방법 등으로 처리하지 않으면 안 되게 되었다. 이러한 이유로 인하여 206K(206,000m3)급 이상의 대형 LNG 선박에서는 필수적으로 LNG 재액화 시스템을 탑재하도록 설계를 하게 된다. 본 연구에서는 현재 개발 되어 운항선에 적용되고 있는 여러 가지 LNG 재액화 시스템의 사이클 성능을 동일한 기기 조건하에서 해석함으로써 각각의 장단점을 비교하여 LNG선박의 설계 및 운항 시 재 액화 시스템의 최적화 방안을 제시하고자 한다.

• 설비공학논문집
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• 제20권12호
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• pp.775-780
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• 2008

A dynamic model to simulate LNG reliquefaction process has been developed. The model was applied to two candidate cycles for LNG reliquefaction process, which are Reverse Brayton and Claude cycles. The simulation was intended to simulate the pilot plant under construction for operation of the two cycles and evaluate their feasibility. According to the simulation results, both satisfy control requirements for safe operation of brazed aluminum plate-fin type heat exchangers. In view of energy consumption, the Reverse Brayton cycle is more efficient than the Claude cycle. The latter has an expansion valve in addition to the common facilities sharing with the Reverse Brayton cycle. The expansion valve is a main cause to the efficiency loss. It generates a significant amount of entropy associated with its throttling and increases circulation flow rates of the refrigerant and power consumption caused by its leaking resulting in lowered pressure ratio. It is concluded that the Reverse Brayton cycle is more efficient and simpler in control and construction than the Claude cycle.

• 대한조선학회논문집
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• 제46권4호
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• pp.444-451
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• 2009

The price increase of natural resources and the worldwide growth of LNG demand led to save the waste of Boil-Off Gas evaporating from cargo tanks of LNG carriers during navigation. As one of the efforts, a BOG reliquefaction system with BOG-to-BOG heat exchanging method was newly devised. This study was also discussed on the process details such as some features and advantages including comparisons with conventional BOG reliquefaction system, non BOG-BOG heat exchange type. The thermodynamic analysis for the system were also performed. Through the cycle simulation, the process efficiency of the BOG reliquefaction system BOG-BOG heat exchange was estimated to be increased up to 21%.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.148-153
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• 2008

As the oil price is dramatically jumping up, the consumption of LNG is rapidly expanding and the size of LNG carriers becomes bigger. For LNG ships, the application of DF (Dual-Fuel) engines gradually increases because of high efficiency, which alternatively use diesel or BOG (Boil-Off Gas) from cargo tank as a fuel. The surplus BOG from LNG cargo tank should be exhausted by GCU or liquefied through the BOG reliquefaction system and returned back. This study focused into its operational characteristics through the process simulation using HYSYS and discussed details on the influence of the variations of some operational parameters such as a distribution ratio by the change of fuel mass flow into the DF engine.

• 한국해양공학회지
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• 제32권5호
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• pp.372-379
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• 2018

High-pressure gas injection engines (HPGI) took center stage in LNG carrier propulsion systems after their advent. The HPGI engine system can be easily modified to include a re-liquefaction system by adding several devices, which can significantly increase the economic feasibility of the total system. This paper suggests the optimal operating conditions and capacity for a re-liquefaction system for an LNG carrier, which can minimize increases in the total annualized cost. The installation of a re-liquefaction system can save 0.23 million USD per year when the cost of LNG is 5 USD/Mscf. A sensitivity analysis with different LNG costs showed that the re-liquefaction system is profitable when the LNG cost is higher than 3.5 USD/Mscf.

• Journal of Advanced Marine Engineering and Technology
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• 제26권2호
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• pp.256-263
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• 2002

The Boil-Off-Gases(BOG) in the LNG production terminal are continuously generated during the unloading, storage and supply processes by the heat penetration. In order to use these gases as useful fuel, the reliquefaction process should be installed to put the reliquefied BOG in the main LNG supply line before the secondary pump in terminal. The current reliquefaction method of BOG in LNG terminal is the direct contact one between LNG and BOG in the absorption column. But the system has severe disadvantage, which is the 10 times of LNG circulation needed for unit mass of BOG reliquefaction. It causes, therefore, high power consumption of LNG circulation pump and excessive city-gas supply, even if short demand of NG is needed in the summer time. In this paper, the new reliquefaction system of BOG by using LNG cold energy with indirect contact in precooler was suggested and analysed. The result showed new indirect contact method of BOG reliquefaction system between LNG cold energy and BOG is much more effective than the current direct contact one because of only about 1.3 times of LNG circulation needed and higher energy saving by pump power reduction.

• 설비공학논문집
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• 제19권7호
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• pp.485-490
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• 2007

The LNG BOG re-liquefaction system for LNG carriers was designed based on the Claude refrigeration cycle and the thermodynamic analysis was carried out in order to find the design point of the three heat exchangers constituting the system. The thermodynamic analysis revealed that the system state could be defined by the three cold endpoint temperatures of the three-pass heat exchanger. Hence the iso-lines of the specific liquefaction work, taken as the performance indicator, were presented in terms of those three temperatures and discussed. The system was found most economical when those three temperatures approached a single temperature of $-140^{\circ}C$ and thus this system state could be taken as the design point for the heat exchangers.

• 한국수소및신에너지학회논문집
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• 제31권5호
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• pp.429-435
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• 2020

This paper describes the experimental study of reverse-Brayton refrigeration system for application to high temperature superconductivity electric devices and LNG re-liquefaction. The reverse-Brayton refrigeration cycle is designed with operating pressure of 0.5 and 1.0 MPa, cooling capacity of 2 kW at 77 K, and neon as a working fluid. The refrigeration system is developed with multi scroll compressor, turbo expander and plate heat exchanger. From experiments, the performance characteristics of used components is measured and discussed for 77-120 K of operating temperature. The developed refrigeration system shows the cooling capacity of 1.23 kW at 77 K and 1.64 kW at 110 K.