• Title/Summary/Keyword: BOG liquefaction

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Process Design and Analysis of BOG Re-liquefaction System with Pre-liquefaction of NGL (NGL 분리식 BOG 재액화 공정 고안 및 해석)

  • Yun, Sang-Kook
    • Journal of the Korean Institute of Gas
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    • v.19 no.3
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    • pp.32-37
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    • 2015
  • The boil-off-gases(BOG) in cryogenic LNG storage tanks are generating continuously due to the heat leakage and need to be re-liquefied by the effective way. As the present method to reliquefy BOG is using LNG cold energy to be supplied after low pressure primary pump, the demand of LNG flow rate should be over 10 times of BOG produced rate to reliquefy it. This research invented new effective re-liquefaction system having only 3~4 times of LNG flow rate against unit BOG, that the pre-liquefaction process of NGL and the use of high pressure LNG cold energy after secondary pump. By the analysis, it could be high efficient reliquefying system for all amount of BOG treatment even during the summer time, and improvement of operation safety and efficiency of LNG terminal.

A Study on the BOG Re-liquefaction System based on the Reverse Brayton Refrigeration Cycle for LNG Carriers (역 브레이튼 냉동사이클을 이용한 LNG 운반선의 증발기체 재액화 시스템에 관한 연구)

  • Chin, Young-Wook
    • Journal of the Korea Safety Management & Science
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    • v.9 no.4
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    • pp.149-154
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    • 2007
  • The LNG carriers have been propelled by steam turbines and the LNG boil-off(BOG) has been used as fuel or vented. However, as the alternative propulsion systems such as diesel engines are being equipped on the LNG carriers for better fuel efficiency, a need for the LNG BOG re-liquefaction system that liquefies the BOG and sends the liquid BOG back to the LNG cargo has arisen in recent years. This study investigates the design of the BOG re-liquefaction system based on the reverse Brayton refrigeration cycle. The thermodynamic and heat exchanger analysis are carried out and the limitations to the system performance are discussed.

Process Simulation of the BOG Re-Liquefaction system for a Floating LNG Power Plant using Commercial Process Simulation Program (상용 공정시뮬레이션 프로그램을 이용한 부유식 LNG 발전설비의 BOG 회수시스템 공정모사)

  • Seo, Ju-Wan;Yoo, Seung-Yeol;Lee, Jae-Chul;Kim, Young-Hun;Lee, Soon-Sup
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.26 no.6
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    • pp.732-741
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    • 2020
  • Environmental regulations have recently been strengthened. Consequently, floating LNG(Liquefied Natural Gas) power plants are being developed, which are new power generation plants that generate electricity by utilizing LNG. A floating LNG power plant generates BOG(Boil-Off Gas) during its operation, and the system design of such a plant should be capable of removing or re-liquefying BOG. However, the design of an offshore plant differs according to the marine requirements. Hence, a process simulation model of the BOG re-liquefaction system is needed, which can be continuously modified to avoid designing the floating LNG power plant through trial and error. In this paper, to develop a model appropriate for the floating LNG power plant, a commercial process simulation program was employed. Depending on the presence of refrigerants, various BOG re-liquefaction systems were modeled for comparing and analyzing the re-liquefaction rates and liquid points of BOG. Consequently, the BOG re-liquefaction system model incorporating nitrogen refrigerants is proposed as the re-liquefaction system model for the floating LNG power plant.

Optimal Process Design of Onboard BOG Re-liquefaction System for LNG Carrier (LNG 운반선을 위한 BOG 재액화시스템 최적 설계)

  • Hwang, Chulmin;Lim, Youngsub
    • Journal of Ocean Engineering and Technology
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    • v.32 no.5
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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.

A Study on the thermal pinch problem in the counterflow heat exchanger (역대향류 열교환기의 열 핀치(thermal pinch)에 관한 연구)

  • Choi, Sung-Eun;Chin, Young-Wook
    • Proceedings of the Safety Management and Science Conference
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    • 2008.11a
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    • pp.659-667
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    • 2008
  • The LNG carriers have been propelled by steam turbines and the LNG boil-off(BOG) has been used as fuel or vented. However, as the alternative propulsion systems such as diesel engines are being equipped on the LNG carriers for better fuel efficiency, a need for the LNG BOG re-liquefaction system that liquefies the BOG and sends the liquid BOG back to the LNG cargo has arisen in recent years. This study investigates the design of the BOG re-liquefaction system based on the reverse Brayton refrigeration cycle. The thermodynamic and heat exchanger analysis are carried out and the limitations to the system performance are discussed.

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Design of BOG re-liquefaction system of 20,000 m3 liquid hydrogen carrier

  • Byeongchang Byeon;Hwalong You;Dongmin Kim;Keun Tae Lee;Mo Se Kim;Gi Dock Kim;Jung Hun Kim;Sang Yoon Lee;Deuk Yong Koh
    • Progress in Superconductivity and Cryogenics
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    • v.25 no.3
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    • pp.49-55
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    • 2023
  • This paper presents the design of a re-liquefaction system as a BOG (boil-off gas) handling process in liquid hydrogen transport vessels. The total capacity of the re-liquefaction system was assumed to be 3 ton/day, with a BOR (boil-off rate) of 0.2 %/day inside the cargo. The re-liquefaction cycle was devised using the He-Brayton Cycle, incorporating considerations of BOG capacity and operational stability. The primary components of the system, such as compressors, expanders, and heat exchangers, were selected to meet domestically available specifications. Case studies were conducted based on the specifications of the components to determine the optimal design parameters for the re-liquefaction system. This encompassed variables such as helium mass flow rate, the number of compressors, compressor inlet pressure and compression ratio, as well as the quantity and composition of expanders. Additionally, an analysis of exergy destruction and exergy efficiency was carried out for the components within the system. Remarkably, while previous design studies of BOG re-liquefaction systems for liquid hydrogen vessels were confined to theoretical and analytical realms, this research distinguishes itself by accounting for practical implementation through equipment and system design.

Effect of Re-liquefaction System on Operating Expenditure of LNGC in Terms of Fuel Oil Consumption Cost and BOG Combustion Cost (천연가스 운반선의 재액화 장치가 운항비용에 미치는 영향에 관한 연구: 연료비용 및 증발 가스 연소비용 관점에서)

  • You, Youngjun;Lee, Joon Chae
    • Journal of the Society of Naval Architects of Korea
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    • v.57 no.3
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    • pp.152-159
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    • 2020
  • Ship owners had pursued higher benefits by demanding the new design and construction of ships with higher operational efficiency. There was a necessity for shipyards to suggest a more economical design and advanced operation concept in order to meet the demands. Especially, since BOG combustion and activation of the re-liquefaction unit had to be taken into account in ship design in addition to fuel oil and gas consumption, the evaluation of the operating efficiency considering the technological trends was necessary. In this paper, it was aimed to study the design philosophy and operation strategy by considering the effect of fuel oil and gas consumption, BOG combustion, and activation of the re-liquefaction unit on the operating cost for laden voyage according to ship speed, BOR, and activation of the re-liquefaction unit. For this purpose, the costs were acquired by conducting the sailing simulation of an LNGC based on a mathematical model including the maneuvering equations of motion. The design philosophy and operation strategy was reviewed in terms of the operating cost.

New reliquefaction system of Boil-Off-Gas by LNG cold energy (LNG냉열이용 BOG 재액화긍정 해석연구)

  • 윤상국;최형식
    • Journal of Advanced Marine Engineering and Technology
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    • v.26 no.2
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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.

LNG운반선의 증발기체 재액화 장치의 사이클 해석

  • Jin, Yeong-Uk
    • Proceedings of the Safety Management and Science Conference
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    • 2012.04a
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    • pp.221-232
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    • 2012
  • Cycle analysis has been performed to find out the optimum design point of the BOG re-liquefaction plant. The cycle state, defined by three cycle variables, was mainly described by the three cold temperatures of the three-pass heat exchanger, on which the constraints by the heat exchanger are imposed. The cycle states which are confined within a domain limited by the temperature constraints were the primary issue of this study. The BOG mass within the domain was analyzed first and then the cycle performance was related to the BOG mass afterwards, which enabled us to explain the observed behavior of the cycle performance under the temperature constraints by the heat exchanger. A good cycle performance could be ensured if the two cold Nitrogen temperatures of the three temperatures were placed close together near $-140^{\circ}C$ while the BOG temperature is kept far above enough, but not too far, from $-140^{\circ}C$ such that it does not interfere in their optimum temperature range.

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The BOG Handling System for LNG Carrier (LNG운반선의 BOG 처리설비)

  • Kim, M.E.;Kim, Y.T.
    • 유체기계공업학회:학술대회논문집
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    • 2005.12a
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    • pp.557-561
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    • 2005
  • In recent years, the LNGC fleet is expanded unprecedentedly. Ship's owners and shipbuilders are focusing on the idea how they choose the BOG handling system in economical, environmental and safety angles. This paper introduces general information for that and gives technical matters briefly.

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