Floating Liquefied Natural Gas Research Articles

Assessment of a Full-Electric Floating Liquefied Natural Gas Concept for Harsh Sea State Conditions at Remote Ultra-Deepwater Locations

_ This work describes an offshore gas monetization solution for harsh environmental conditions at ultra-deepwater and remote locations, as an alternative to conventional onshore plants associated with long subsea pipelines for Greenfield projects. Although gas-to-liquids and marine compressed natural gas are initially evaluated, associated gas is supposed to be exported from deepwater floating production storage and offloading units to a central floating liquefied natural gas (FLNG) facility for additional treatment, fractionation, and liquefaction, producing liquefied natural gas (LNG) and liquefied petroleum gas (LPG) for further tandem offloading. To demonstrate the technical feasibility of the proposed FLNG, its key technologies are reviewed, including liquefaction process selection, cargo containment system, station-keeping, offloading, and power generation. A full-electric FLNG is proposed, replacing conventional feed gas power generation systems with inner hull nuclear power modules, envisaging neutral CO2 emissions and earlier first LNG drop milestone achievement. The FLNG general arrangement is developed, along with its internal cargo tanks layout, for preliminary LNG and LPG production rundown and feed gas throughput. Numerical analyses are carried out to show that static and dynamic tilt criteria can be met, even for harsh sea states. Gas import riser configurations for the challenging ultra-deepwater location are outlined, after appropriate FLNG station-keeping analyses, in addition to a feasibility assessment of seawater intake risers, aiming for an overall gas plant efficiency increase. Keywords FLNG; FPSO; LNG/LPG; associated gas; design (general)

Study on equivalent mechanical properties of U-shaped bellows based on novel implementation of asymptotic homogenization method

As typical metal thin-walled structure, bellows are used widely in various engineering fields, especially in storage and transportation of floating liquefied natural gas (FLNG) system on the sea. While the shapes of the bellows are relatively complex with the characteristics of geometric nonlinearity in the structure, it is quite challenging to calculate basic mechanical properties of the bellows accurately through theoretical analysis. Concurrently, both numerical simulation and experiments also require high computational and economic cost. Given the typical one-dimensional periodicity of the structure of U-shaped bellows, novel implementation of asymptotic homogenization (NIAH) method was secondary developed in finite element software and unit-cell model of the whole structure with periodic boundary conditions was established, realizing equivalent analysis of the overall mechanical properties of the bellows accurately and efficiently. By comparing the NIAH equivalent results with the fine finite element model results, it was found that the relative error was within 3.00 % and the calculation cost was reduced by 40 times. Compared with the experimental results, the error of NIAH equivalent results was also less than 6.00 %, which verified the accuracy and high efficiency of the NIAH equivalent method. Furthermore, the influence of unit-cell model with different structural sizes on the prediction accuracy of the NIAH equivalent stiffness results of the bellows was also discussed. This study provides a new effective method for the design and analysis of the structure of bellows.

Technological innovations in the LNG sector: A review: Assessing recent advancements and their impact on LNG production, transportation and usage

This paper thoroughly explores the recent technological innovations in the Liquefied Natural Gas (LNG) sector, examining their impact on production, transportation, storage, and usage. The study delves into the evolution of the global LNG market, emphasizing the critical role of technological advancements in shaping the industry's future. The aim is to analyze these innovations, assess their environmental and economic impacts, and explore the influence of geopolitical and market dynamics. By employing a comprehensive literature review, the paper utilizes a multi-criteria decision support framework to select relevant technological innovations and assess their impacts. This methodology integrates environmental, social, policy, and economic dimensions, offering a holistic view of the LNG sector's technological landscape. The findings reveal significant advancements in LNG production technologies, such as green ammonia and biogas, enhancing sustainability and efficiency. Innovations in LNG transportation, including optimized carrier fleets and storage systems, have revolutionized the industry, improving economic viability and safety. The emergence of Floating LNG (FLNG) technologies marks a pivotal development, unlocking new gas monetization possibilities. The study also highlights the environmental benefits of these innovations, including reduced greenhouse gas emissions and their synergy with renewable energy systems. The paper concludes that while technological advancements offer substantial benefits, they also present challenges, including high investment costs and regulatory complexities. It recommends continued innovation, strategic collaborations, and supportive regulatory frameworks to fully exploit the potential of LNG technologies. As the global energy landscape evolves, the LNG sector is poised to play a crucial role in the transition to a more sustainable and efficient energy future.

Plant Design and Techno-Economy Analysis of Floating Liquefied Natural Gas (FLNG) in Masela Block

The prospects of the natural gas industry in Indonesia are very great. Considering that Indonesia has large enough natural gas reserves of 62.4 trillion cubic feet, of which 43.6 trillion cubic feet are proven. In fact, about one-third of the world's natural gas reserves are offshore. For the utilization of offshore gas production itself, it usually uses pipelines for gas distribution from offshore production facilities to the mainland commonly referred to as onshore terminals. The establishment of an offshore liquefied natural gas (LNG) plant is the solution to maximize the utilization of natural gas resources. The aim of this research is a preliminary study that obtains a decision on an effective method and economic parameters of the development plan required for an efficient process to provide maximum floating LNG plant investment and profitability. The pre-designed offshore LNG plant is planned to be commissioned in 2025 with a production capacity of 2.5 MTPA. The location for the construction of this plant is planned in the Masela Block area. It will operate continuously 24 hours a day for 330 days with raw materials of 315128 kg of natural gas/hour, producing LNG products of 230768 kg/hour, Liquefied Petroleum Gas (LPG) of 5800 kg/hour, and condensate products of 356 kg/hour. The production process of this offshore LNG plant can be divided into 4 processes, namely acid gas removal, dehydration unit, fractionation, and liquefaction, which are considered to be common processes based on low cost and high efficiency. From an economic point of view, the Internal Rate of Return (IRR) obtained at 12.3% is above the bank loan interest rate, which is 8% with a payback period (POT) of 4.81 years, which is smaller than the repayment time set by the lender, which is 10 years, and break-even point (BEP) has reached 36% that just acceptable which refers to the economic sustainability of plant development. Therefore, offshore LNG plants are feasible to be established.

A study on vibration-suppression mechanism for risers using flexible structural joints

AbstractThese new mechanisms for suppressing vibration in large diameter intake pipes and pumping systems has been developed for use in Floating Liquefied Natural Gas (FLNG) facilities. Like existing devices such as fairings and strakes, this mechanism is designed for practical use and has a flow path inside the pipe. The mechanism is designed to suppress vibration caused by both float motion and vortex-induced vibration (VIV) due to currents. Experiments were conducted using a scale model, and numerical calculations were used to evaluate the mechanism’s ability to reduce vibration. As a result, the natural frequencies of the pipes were analyzed, and it was found that the vibration damping mechanism, when installed at appropriate locations, can provide effective vibration suppression against the motion of the upper float and vibration caused by VIV due to currents over the entire length of the pipe, even at limited installation locations. On the other hand, it was found that the vibration suppression effect could not be achieved without appropriate positioning, and that the longer the pipe length, the more limited the vibration damping capability.

Enhancing Energy Efficiency and Reliability in Floating LNG Operation: A Hydrofluoroolefin-Based SMR Cycle with Thermo-Economic Assessment and Uncertainty Analysis

Natural gas liquefaction is the most energy-intensive technique in floating liquefied natural gas (FLNG) operations. Hence, a hydrofluoroolefin-based single mixed refrigerant (SMR) technology was proposed to achieve energy-efficient and eco-friendly operations. The study was perfomed to enhance the SMR process by substituting expansion valves with hydraulic turbines to improve process reversibility and enhance energy efficiency. The proposed process was optimized using a sine–cosine concept-based algorithm that tuned the design variables which yielded an overall compression energy consumption of 0.2501 (kWh/kg-LNG), resulting in a 21.43% saving as compared to the conventionally used mixed refrigerant-based process. This resulted in a reduction of about 38.81% in overall exergy destruction. The economic analysis results draw curtains that the process saves about 26.02% of total annualized cost as compared to conventional study. Owing to the appropriate mixed refrigerant component mixture ratio and process design improvement. To determine the process reliability under uncertain conditions the optimal compression power and minimum approach temperature were determined. Further, uncertainty analysis reveals that the methane and butane refrigerant flow rates along with evaporation, and condensation pressure, were among the most influential parameters that influence the process most that may affect the whole operation in uncertain process inlet conditions. In summary, our approach presents immense promise for achieving energy efficiency, environmental responsibility, and economic viability in FLNG operations, offering a robust solution for the challenges of offshore plants.

Synchronized tracking control for dynamic positioning vessel

AbstractThis article addresses the time‐synchronized control problem for a floating liquefied natural gas (FLNG) vessel and a liquefied natural gas carrier (LNGC) in side‐by‐side offloading operation. For such a problem, the existing finite‐time control approaches available are essentially only designed to ensure that the system state‐variables converge within a certain time. Specifically how each state‐variable converges is typically not considered in the design process. Along this line, the approach of time‐synchronized design in this paper attains the more comprehensive and desirable outcome of having the marine vessels' state‐variables arrive at the sliding mode surface in a fixed time. Also additionally, the state‐variables converge at the same moment. This approach thus can attain synchronous tracking of the LNGC to the FLNG vessel. All these desirable properties and outcomes of control system convergence are rigorously proved in the work here via the methods of Lyapunov‐type theorems and associated stability analysis. Furthermore, in order to ensure that the approaches developed here are suitably applicable in real‐world engineering conditions (with system uncertainties and external disturbances), robustness extensions are also incorporated. In the presented work, the analytical issues and the methodologies in the designed control system solution under the conditions of the disturbed systems are discussed in detail. The numerical simulations conducted verify the merits of the proposed algorithm. Comparative numerical simulations on the developed scheme, and on traditional control, are carried out to demonstrate the important and improved outcomes attained with the time‐synchronized features.

Study on competition mechanism of deformation modes of U-shaped bellows under internal pressure

Bellows are widely used in various modern engineering fields, especially in storage and transportation of floating liquefied natural gas (FLNG) system on the sea. They are prominent pressure vessels with internal pressure load as a common working condition. Concerning common U-shaped bellows in this study, the cross-section of the bellows is divided into three segments, wave peak semicircle, straight ring plate, and wave trough semicircle, to establish mechanical models. Bellows with different design parameters have different mechanical properties, producing different deformation modes of the cross-section of the bellows under the action of internal pressure load. The competition mechanism of deformation modes of different parts in the cross-section under internal pressure is discussed. Furthermore, the sensitivity analysis of design parameters is performed and the bellows with competition balance between different parts were determined, which can keep the cross-section maintaining the “U” shape without global deformation under internal pressure. In addition, the radial displacement of bellows under internal pressure is theoretically derived to improve the deep discussion on competition mechanism of deformation modes. Accordingly, the relevant theoretical results are compared with finite element simulations, illustrating the reliability of the theoretical analysis. This study may serve as a reference for the design and analysis of the structure of bellows.

A Methodology to Assess the Sloshing Effect of Fluid Storage Tanks on the Global Response of FLNG Vessels

The sloshing effect of fluid storage tanks of a Floating Liquefied Natural Gas (FLNG) vessel causes variations in its global motion response. These acceleration and motion alterations can affect the safe performance of the FLNG vessels. The classification societies’ rules are employed to standardize the storage tanks’ configuration of FLNG vessels. Herein, we report a methodology to assess the sloshing effect on the global motion response of an FLNG vessel considering four geometrical arrangements of tanks and different fluid filling fractions. This methodology includes the hydrodynamic effect in operating and storm conditions from the Gulf of Mexico using a return period of 100 years. In addition, our methodology considers the influence of the internal fluid of each tank to estimate the accelerations and motions of the vessel. This methodology can be implemented to estimate the stability of an FLNG vessel under different environmental conditions. Thereby, the naval engineers could choose the best geometrical configuration of the storage tanks for safe behavior of a vessel under different operating and extreme environmental conditions.

Shell-side heat transfer characteristics of floating liquefied natural gas spiral wound heat exchanger under sloshing conditions

To study the influence of offshore sloshing motion on the performance of a spiral wound heat exchanger (SWHE) installed on a floating liquefied natural gas (FLNG) platform and to explore potential methods to improve heat transfer efficiency, a sloshing experimental platform was established. This platform facilitated the experimental study of the boiling heat transfer process of a subcooled falling film on the outer surface of the heat exchanger tube. A quantitative analysis of the change in the heat transfer coefficient with respect to the amplitude and period of the rolling and swaying motion was performed. The experimental results indicated that both rolling and swaying changed the liquid film morphology, leading to a decrease in the heat transfer coefficient of the heat exchanger tube. The fluctuation in the heat transfer coefficient became more drastic with an increase in amplitude, but the effect of the swaying motion was less than that of the rolling motion. When the rolling angle was 12° and the Re number was 569, the average heat transfer coefficient of the round tube decreased by 55% compared with that at the static condition. Furthermore, the research encompassed the design, processing, and rigorous testing of elliptical and egg-shaped tubes to improve their heat transfer performance, and the results were compared with those of round tubes. Under the same rolling or swaying conditions, the heat transfer coefficients of the egg-shaped and elliptical tubes were 5.1–21.5% higher than that of the round tubes. The results of this study can be used as a reference for the operational and structural design of SWHEs under sloshing conditions.

Armored steel wire stress monitoring strategy of a flexible hose in LNG tandem offloading operation

Cryogenic flexible hose is the key equipment for tandem offloading operation of Floating Liquefied Natural Gas (FLNG). The harsh marine environment leads hulls motion responses and complex hose motion characteristics during the tandem offloading, thus causing various failure behaviors of the entire hose. In this paper, a combined global-local monitoring strategy for armored steel wire stress distributions in cryogenic flexible hose is proposed. High-precision flexible hose governing equations are established by using the function to fit the relationship between the vertical force and the hose length. A reasonable monitoring strategy is given based on the pipeline configuration variations and sensor accuracy. Real-time monitoring of the flexible hose from the global (hose) to the local (armored steel wire) during the tandem offloading is carried out by installing sensors in specified locations on hulls and hose segments. The tandem offloading operation under different (static, calm and harsh) sea states is modelled by Orcaflex software. An armored steel wire model is developed using ABAQUS software. Comparisons of the pipeline configurations, curvatures, axial forces and maximum wire stresses are made with the simulation results to verify the feasibility of the monitoring strategy. The results show that the proposed monitoring strategy in this paper can accurately and effectively obtain the hose motion characteristics and maximum stress states of armored steel wires under different sea states, and can evaluate the hose structural safety in real time during the tandem offloading operation.

Design of a Device and System to Study the Liquid–Solid-Phase Equilibrium Experiment of CO2 in PLNG

Pressurized liquefied natural gas (PLNG) is a new natural gas liquefaction solution proposed in recent years for reducing the construction and operating costs of floating liquefied natural gas (FLNG). For natural gas, the liquefaction temperature is strongly influenced by the pressure; when the pressure increases, the liquefaction temperature of natural gas increases accordingly. The increase in the liquefaction temperature of natural gas leads to a higher solubility of impurities such as carbon dioxide, which means that the pretreatment standards for liquefied natural gas can be reduced. Therefore, the use of PLNG technology can simplify pretreatment plants and significantly reduce construction and operating costs. In order to better apply PLNG technology to FLNG, it is necessary to understand the solubility of carbon dioxide in pressurized LNG and the phase change during liquefaction. To achieve this, experimental setups are needed to simulate the temperature and pressure environment of the LNG to obtain the relevant data and observe the relevant phenomena. After a literature research and analysis of the advantages and disadvantages of previous experimental setups, several improvements are proposed in this paper, and based on this, a visualization device is designed for studying the liquid–solid-phase equilibrium experiment of CO2 in PLNG. The device has a pressure resistance of 20 MPa, a minimum operating temperature of 77 K, and a variable volume function. It is also equipped with a sapphire window to be able to observe the inside of the device. In order to verify the superiority of the device, experiments were conducted using the device to verify the pressure resistance, variable volume, and visualization functions of the device. The experimental results show that the experimental device designed in this paper does have a certain superiority.

Reviewing the development of floating LNG facilities and their global impact

This Review encapsulates a comprehensive review of the development and global impact of Floating Liquefied Natural Gas (FLNG) facilities. These innovative structures have revolutionized the liquefied natural gas industry by enabling offshore gas extraction, liquefaction, and storage. The study explores the evolution, challenges, and transformative influence of FLNG facilities on the global energy sector. The review begins with an examination of the historical development of FLNG technology, tracing its roots to the early 21st century. It showcases how these floating facilities have evolved from conceptual designs to operational structures, emphasizing key technological advancements that have propelled their growth. The global impact of FLNG facilities is analyzed through multiple lenses. Economic considerations, such as cost-effectiveness and accessibility to remote gas reserves, emerge as significant drivers for their adoption. The study also delves into the environmental implications, assessing the potential benefits and challenges associated with offshore liquefaction. Challenges inherent in FLNG development, including engineering complexities and regulatory considerations, are addressed. The study sheds light on how these challenges have been navigated, leading to successful deployment and operation of FLNG facilities in various regions. The transformative influence of FLNG facilities on global energy dynamics is highlighted, with a focus on their role in unlocking stranded gas reserves and facilitating timely responses to shifting market demands. The review emphasizes their adaptability to different geographic and economic contexts, showcasing their versatility as a pivotal component of the liquefied natural gas supply chain. In conclusion, this review offers a panoramic perspective on the development of FLNG facilities and their profound impact on the global energy landscape. By bridging technological innovation, economic viability, and environmental considerations, these floating facilities emerge as key contributors to the evolving dynamics of the liquefied natural gas industry, shaping a resilient and adaptive future for the energy sector.

Building Options for the Brazilian Pre-salt: A technical-economic and infrastructure analysis of offshore integration between energy generation and natural gas exploration

The objective of this work is to evaluate the technical-economic and infrastructure aspects for the Brazilian Pre-salt natural gas use. Factors like technology maturity level, fuel and facilities costs, and electricity market are analyzed; the levelized cost of energy (LCOE) of two possibilities are calculated: (i) offshore Gas-to-Wire (GtW) and (ii) molecular natural gas outflow through the pipeline with onshore thermoelectric generation. This work also discusses the possibility of natural gas (NG) transport via liquefaction, considering the Floating Liquefied NG (FLNG) technology for national and international market. The LCOE of GtW technology is higher (67–87 US$/MWh) than onshore plants (43–69 US$/MWh) for Pre-salt area, higher than the historical energy price of Brazilian NG thermoelectric generation (44 US$/MWh), but, in general, lower than Brazilian NG energy auction price cap (84.5 US$/MWh) and lower than some values found in the literature for onshore plants (42–124 US$/MWh) abroad Brazil. FLNG technology is still new, there is no scale, few players use it, and it does not seem to be a feasible option for Pre-salt NG now. It is concluded that elements such as political uncertainties of the international natural gas market, the high CO2 rate in the Pre-salt's natural gas mixture, and the difficulties in implement deep-sea infrastructure are challenging elements for the three possibilities analyzed. The Brazilian market discussion is relevant since it is a greenfield natural gas area in need of development. Thus, it is of upmost importance to implement a comprehensive energy policy to address offshore-onshore energy integration regulation and technological developments for the offshore transmission systems, and CO2 content separation process.

Downhole Sand Control Applied for High-Rate Gas Completions in Deepwater Malaysia

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 31413, “Applying Downhole Sand Control for High-Rate Gas Completions in Deepwater Malaysia,” by Elvy Jose Samuel, SPE, Mohd Faizal Yusoff, and Phil Bee, PTTEP, et al. The paper has not been peer reviewed. Copyright 2022 Offshore Technology Conference. Reproduced by permission. _ Designing and delivering a successful completion in a subsea high-rate gas deepwater environment is a great challenge in upstream field development. The complete paper covers the sand-control design and execution techniques applied to four high-rate gas wells in the operator’s Block H development in the deepwater region of Sabah offshore Malaysia in 2020 and 2021. Field Background PTTEP’s Block H gas development is a multifield phased subsea development designed to deliver gas to Petronas’ floating liquefied natural gas (FLNG) project known as PFLNG2. The Block H field is in the South China Sea in water depths between 1150 and 1400 m. The first phase (Phase 1A) of the project was executed in four wells between the Rotan (three wells) and Buluh (one well) fields in the midsection of the Block H development. The reservoirs completed in Phase 1A were deepwater slope turbidite sands deposited during the Late Miocene and contain high net-to-gross reservoirs. Based on evidence from sonic logs and rock-mechanics testing performed on rotary side-wall cores and fullbore cores, all targeted reservoirs required robust sand control. Openhole gravel packing (OHGP) was chosen as the recommended sand-control technique for the high-rate gas application, and the four wells were drilled nearly vertically, with high water standoff height as a mitigation against early water coning. The drilling and completion operations were completed in a batch completion strategy in which all top holes were drilled to the top of the targeted reservoir, followed by the batch completion of all wells’ lower completion phase, then the batch upper completion and well cleanups. The wells were placed on production in Q1 2021 to PFLNG2, achieving the targeted rates per well of 80 MMscf/D solids-free.

Mechanism of Mechanical Analysis on Torsional Buckling of U-Shaped Bellows in FLNG Cryogenic Hoses

Floating liquefied natural gas (FLNG) cryogenic hoses can be employed for the transmission of liquefied natural gas (LNG). Usually, U-shaped metal bellows can be applied as the inner lining of FLNG cryogenic hoses. In installation, positioning and other working conditions, torsion is one of the main loads, and torsional buckling instability is a major failure mode of U-shaped metal bellows of FLNG cryogenic hoses. In the current research, the buckling instability of bellows under torsional loads has been investigated in detail, the mechanical mechanism of deformation in torsional buckling mode of bellows has been analyzed and the influence of the structural design parameters on the stability performance has been summarized. It was seen that the axis of the bellows was presented as a spiral line shape during the torsional buckling stage. At the same time, the torsional buckling properties of toroid and spiral bellows were analyzed. The obtained results showed that the torsional buckling stability of the spiral bellows was weaker than that of the toroid bellows and increase of the spiral angle of the spiral bellows intensified this trend. In addition, the post-buckling analysis of U-shaped bellows under torsional loads was carried out by means of experiments and finite element simulation. It was shown that the results obtained from finite element (FE) analysis in this research presented a relatively accurate critical torque value and a consistent buckling instability mode, compared with the experimental results. On this basis, the effects of common defects such as thickness thinning on the torsional stability of bellows were investigated. Considering the geometric defect of thickness thinning, the error of FE analysis was reduced further, and it was found that the defect could significantly decrease the stability of the bellows. The above analysis results could provide a reference for structural design and post-buckling analysis of bellows.

Numerical investigation on thermal–hydraulic performance of supercritical LNG in a Zigzag mini-channel of printed circuit heat exchanger

• Flow mechanism of supercritical hydrocarbon fluids was investigated. • Comparison on thermal performances for two hydrocarbon fluids was compared. • Correlations for supercritical hydrocarbon fluids in a mini-channel were proposed. Printed circuit heat exchanger (PCHE) is receiving wide attention as a new kind of compact heat exchanger. It is considered as a promising vaporizer in floating liquefied natural gas (FLNG) vessels due to its compactness and high efficiency. In this paper, the numerical model with two Zigzag mini-channels was built. The cross section was a semicircle with the diameter of 1.5 mm and the overall length was 200 mm. In the simulation, SST k - ω turbulent model was employed and validated against experimental data of supercritical CO 2 flow. The mechanism of flow and heat transfer was investigated, and the influence of operating parameters including mass flux, outlet pressure and inlet temperature was analyzed from the perspective of high-speed components of turbulent core area, degree of flow separation, energy transport and dissipation rate. The results indicated that the worse flow performance and better heat transfer performance exhibited at higher mass flux and inlet temperature conditions, whereas the higher outlet pressure conditions exhibited the better flow and heat transfer performances. Correlations for the Fanning friction factor and Nusselt number were developed within a deviation of ±5%, aiming to apply to the prediction of thermal–hydraulic performance of supercritical LNG.

Research on the falling film flow and heat transfer characteristics of FLNG spiral wound heat exchanger under sea conditions

As the key equipment of floating liquefied natural gas (FLNG) process, the performance of spiral wound heat exchanger (SWHE) influences operation costs and reliability of the whole system. The sea conditions destroy the falling film flow state of the refrigeration and then affect the heat transfer performance of FLNG SWHE. In order to design and optimize the SWHE, a cryogenic experimental device of FLNG process and a numerical model of falling film flow have been constructed to study the effects of sea conditions on the falling film flow and heat transfer characteristics of SWHE. The cryogenic experimental results show that the pitching conditions have larger effects on the heat transfer performance than yawing. Under the pitching angle of 7°, the natural gas temperature and gaseous refrigerant temperature increase by 3.22 °C and 7.42 °C, respectively. The flow rates of refrigerant and feed natural gas have a great impact on the heat transfer performance of SWHE under pitching and compound sloshing conditions. When the tilt angle increases to 9°, the tube structure with outer diameter D = 8 mm and pipe spacing S = 4 mm is recommended to reduce the drying area of the pipe wall surface.

Numerical Study on Thermal-Hydraulic Performance of Printed Circuit Heat Exchangers during Natural Gas Trans-Critical Liquefaction

Printed Circuit Heat Exchangers (PCHEs) are considered an excellent alternative for the main cryogenic heat exchanger of Floating Liquefied Natural Gas (FLNG) facilities due to their compact structure and strong heat transfer performance. However, it is unclear how to configure the geometry of the PCHE channels to achieve its optimal performance in the trans-critical liquefaction process of natural gas (NG), which is critical for the main heat exchanger. In this paper, we numerically studied the thermal-hydraulic characteristics of PCHEs with different channel types under the specified condition. The results elucidate that all channels have an enhancement of heat transfer near the pseudo-critical point of NG. All the wavy channels could improve the heat transfer performance of PCHEs, where the trapezoidal channel achieves the largest promotion. Compared with the straight channel, the local heat transfer coefficient could be increased by up to 53% in the trapezoidal channel. Additionally, vortex appeared at the bends of the wavy channels, which greatly increase the local friction loss. Among several channels, the total pressure drop of zigzag, fillet and the sinusoidal channel was almost the same, while that of the trapezoidal channel was the largest. Furthermore, we compared the comprehensive performance of different types of channels and found that the benefit of heat transfer enhancement could not offset the penalty of flow deterioration. Our work provides important guidance for the design of PCHEs employed in FLNG.

Barge LNG Offers Benefits in Deepwater and Onshore Developments

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 30871, “Could Barge LNG Replace FLNG?” by Edward A. Hernandez, Timothy D. Highfield, and Thomas G. Forbes, io consulting, et al. The paper has not been peer reviewed. Copyright 2020 Offshore Technology Conference. Reproduced by permission. Most currently operating floating liquefied natural gas (FLNG) vessels are ship-shaped and designed for offshore, over-field locations. This approach, however, does not necessarily offer an optimized solution for gas monetization. An alternative solution is barge-based LNG (BLNG), focused on near-shore positioning with liquefaction facilities mounted on a simple floating or grounded substructure with the remainder of the systems decoupled from the liquefaction technology in a separate location. The complete paper addresses the benefits of BLNG and why it is an increasingly viable gas-monetization concept. Introduction BLNG is focused on near-shore or at-shore positioning. The LNG liquefaction facilities are mounted on a simple floating substructure and either moored near shore, connected to shore by a jetty, or set down in a prepared dry dock. The remainder of the system (preprocessing, liquids handling, and storage) is decoupled from the liquefaction technology and can be in separate locations. Examples include an FPSO in deep water over the field; adjacent to onshore gas wells; or, as technology develops in subsea processing and compression, feeding the BLNG facility. BLNG concepts typically consist of multiple LNG trains that meet the required throughput. BLNG minimizes project risk by better aligning the phasing of the development with the proving-up of the reservoirs. The approach also could help deliver greater certainty through better control over the scope of supply and fabrication away from remote, low-infrastructure locations. The authors do not advocate BLNG as a replacement for FLNG in all cases, nor are they critical of current and future FLNG developments. They write that FLNG and BLNG each have their place and that it is important for owners, consultants, and contractors to appreciate the strengths and weaknesses of each so that quality decisions can be reached.