Stratification, Rollover and Handling of LNG, LPG and Other Cryogenic Liquid Mixtures

Scurlock, R.G.

doi:10.1007/978-3-319-20696-7

Cited by 18 publications

(20 citation statements)

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“…Comprehensive understanding of the processes and sequence timing associated with the LNG rollover phenomenon remain elusive. Disparate conclusions have been drawn from experimental and modeling studies conducted historically . Observations of the various stages of many actual rollover events reveal a significant range of time scales over which those real events unfolded, which cannot be easily reconciled to theoretical and simulation models .…”

Section: Optimum Handling Of Rollover Events On Fsrumentioning

confidence: 99%

“…Disparate conclusions have been drawn from experimental and modeling studies conducted historically. [32][33][34][35] Observations of the various stages of many actual rollover events reveal a significant range of time scales over which those real events unfolded, which cannot be easily reconciled to theoretical and simulation models. 25,[36][37][38] Some studies do provide insight to the stratification and pressure variation trends of LNG and its associated vapor stored in tanks.…”

Section: Rollover Challenges For Lng Storage Tanksmentioning

confidence: 99%

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A review: Optimizing performance of Floating Storage and Regasification Units (FSRU) by applying advanced LNG tank pressure management strategies

Wood

Kulitsa²

2017

Int J Energy Res

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Summary The demand for Floating Storage and Regasification Units (FSRU) has grown rapidly worldwide since the first unit was commissioned in 2005 and opened many new markets to LNG trade. Technology has evolved leading to a fleet of FSRU ranging from relatively cheap conversions from LNG carriers (LNGC) to larger‐capacity, new‐build vessels with higher‐tank‐pressure ratings. The different types of FSRU ideally require operating procedures tailored to their specific designs, capacities, and tank‐pressure ratings. Currently, many of the operating practices developed for the lower‐tank pressure ratings of LNGC are applied as a matter of routine across the FSRU fleet, leading to operating inefficiencies. There are therefore significant opportunities to improve operating efficiencies on many FSRU and thereby reduce onboard gas consumption and atmospheric emissions, particularly regarding ship‐to‐ship (STS)‐transfer procedures and LNG cargo rollover‐protection strategies. Additional non‐standard use of recondensing equipment, recirculating condensed boil‐off gas as warm LNG back to the cargo tanks, can also reduce unnecessary shipboard consumption of gas. These savings can be achieved without any capital investments or modifications. STS transfers for LNG were first performed in 2007 and are a relatively new, but now routine necessity for FSRU operations. The operating efficiency associated with STS transfers can be significantly improved by adopting 12 straightforward measures. Some of the STS transfer improvement measures recommended involve an increase (beyond current practices) of cooperation, planning, and coordination of tank pressures between discharging and receiving vessels. The adoption of proactive prevention and mitigation measures to limit the potential tank pressure increases associated with LNG cargo rollover events can also appreciably reduce shipboard gas consumption and improve FSRU operating efficiency at no additional cost. Other operating efficiency gains focused on tank‐vapor‐handling equipment are also attainable for the higher‐pressure rated FSRU.

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Section: Optimum Handling Of Rollover Events On Fsrumentioning

confidence: 99%

Section: Rollover Challenges For Lng Storage Tanksmentioning

confidence: 99%

A review: Optimizing performance of Floating Storage and Regasification Units (FSRU) by applying advanced LNG tank pressure management strategies

Wood

Kulitsa²

2017

Int J Energy Res

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“…The liquid LNG mass immediately adjacent to heating surfaces (e.g., tanks walls) is heated by heat ingress and becomes slightly less dense. This causes it to rise in the tank until it reaches the liquid surface (Kanazawa et al, 2004;Roh and Son, 2012;Scurlock, 2016). At that surface the excessive heat is released as a BOG "flash" into the tank vapor space (Kulitsa and Wood, 2018a).…”

Section: Introductionmentioning

confidence: 99%

“…3. Morphology of LNG surface film above the LNG bulk liquid (modified after Scurlock, 2016). Kulitsa, M. and Wood, D.A.…”

Section: Introductionmentioning

confidence: 99%

Duality in LNG tank-pressure behaviour and its relevance for ship-to-ship transfers to floating storage and regasification units

Kulitsa¹,

Wood

2020

Adv. Geo-Energ. Res.

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Floating storage and regasification units (FSRU) are in high demand globally forming a specialized and growing fleet of ships to service a steadily expanding liquified natural gas (LNG) industry. Ship-to-Ship (STS) LNG cargo transfers are an inevitable part of the FSRU day-today operating patterns. It is little more than a decade since FSRU operations began and a lack of knowledge persists concerning their relatively complex tank pressure behaviour during STS transfers. In this work, based on details from more than thirty STS operations, FSRU tank pressure trends and influencing factors are explained. The interactions between the vapor space and liquid LNG are strongly influenced by the thin surface film between those phases in an LNG tank. The saturated vapor pressure (SVP) of the LNG and the volumetric balance of gas and liquid movements in and out of the tank are also influential. These factors control the rate and extent of evaporation and condensation occurring at the surface film, thereby impacting tank pressure changes. This paper presents observations that reveal a duality in FSRU tank pressure behaviour that in over-pressured conditions allows tank pressure to rise significantly and rapidly. On the other hand, in under-pressured conditions tank pressure stabilizes at certain levels and inhibits significant reduction below those levels. Here, we explain the processes involved in determining FSRU tank pressure trends during STS transfers, and, based on observations of actual STS transfers, provide rules of thumb and empirical equations that can be used to estimate tank pressure behaviour in a range of operating conditions. These are supported by several generic cases of tank pressure, temperature and SVP trends reflecting the various tank scenarios commonly associated with routine operating patterns of FSRU during STS transfers. The principles described in this paper apply to LNG Carriers but tend to be disrupted by sloshing and wave movements also in the tanks during transit.

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“…The most common tank design consists of a perlite insulation at vacuum pressures. More recent designs, incorporate multilayer insulation (MLI) technology for insulation [3].…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic aspects of an LNG tank in fire and experimental validation

et al. 2017

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Abstract. Mechanical behaviour of a Liquefied Natural Gas (LNG) tank and the thermodynamic behaviour of its containment under extreme heat load -for instance when subjected to external fire source as might occur during an accident -are extremely important when addressing safety concerns. In a scenario where external fire is present and consequent release of LNG from pressure relief valves (PRV) has occurred, escalation of the fire might occur causing difficulty for the fire response teams to approach the tank or to secure the perimeter. If the duration of the tank exposure to fire is known, the PRV opening time can be estimated based on the thermodynamic calculations. In this paper, such an accidental scenario is considered, relevant thermodynamic equations are derived and presented. Moreover, an experiment is performed with liquid nitrogen and the results are compared to the analytical ones. The analytical results match very well with the experimental observations. The resulting analytical models are suitable to be applied to other cryogenic liquids.

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Stratification, Rollover and Handling of LNG, LPG and Other Cryogenic Liquid Mixtures

Cited by 18 publications

References 0 publications

A review: Optimizing performance of Floating Storage and Regasification Units (FSRU) by applying advanced LNG tank pressure management strategies

A review: Optimizing performance of Floating Storage and Regasification Units (FSRU) by applying advanced LNG tank pressure management strategies

Duality in LNG tank-pressure behaviour and its relevance for ship-to-ship transfers to floating storage and regasification units

Thermodynamic aspects of an LNG tank in fire and experimental validation

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