LNG-fueled Ships Research Articles

Greenhouse gas emissions of shipping with onboard carbon capture under the FuelEU Maritime regulation: A well-to-wake evaluation of different propulsion scenarios

International shipping has extended its decarbonization strategy to reduce greenhouse gas emissions beyond onboard CO2 emissions. Onboard carbon capture and storage systems are being investigated as a potential solution for fossil-fueled ships, however there is a lack of knowledge on the reduction of well-to-wake greenhouse gas emissions that could be enabled. Considering the ambitious emission reduction targets, this may lead to inaccurate estimations of the future fuel mix in the maritime sector and the market share of marine engines. This study defines nine ship propulsion scenarios based on combinations of fossil fuels and marine engines. To better understand the greenhouse gas emission reduction of onboard carbon capture, this study calculates the well-to-wake greenhouse gas intensity of each scenario with and without onboard carbon capture and storage from the ship’s main engine(s). Deploying onboard carbon capture and storage systems notably reduces the tank-to-wake greenhouse gas intensity (54–68 % depending on the scenario). Contrary to onboard emissions, oil-fueled ships with onboard carbon capture and storage are found to be less greenhouse gas intensive and more cost-effective than LNG-fueled ships. The four-stroke oil-fueled engine achieves the lowest well-to-wake greenhouse gas intensity of 38.31 gCO2eq/MJ, while the four-stroke LNG-fueled engine has the highest intensity of 50.34 gCO2eq/MJ. The greenhouse gas emission levels enabled by onboard carbon capture from the main engine would allow fossil-fueled ships to comply with the FuelEU Maritime greenhouse gas intensity requirement until 2044. To be compliant in subsequent periods, onboard carbon capture and storage systems will need to consider carbon capture from the auxiliary boiler and generator and higher capture rate, as well as measures to reduce upstream emissions from fossil fuel production and transport.

Experiment-based feasibility study of LNG equipment-embedded fuel gas supply system for vessels

This study introduces and validates an innovative Liquefied Natural Gas (LNG) Equipment-Embedded Fuel Gas Supply System (LEEF) designed for small LNG-fueled vessels. These ships face significant challenges in implementing LNG Fuel Gas Supply Systems (FGSS) owing to limited space and stringent regulatory requirements to reduce Greenhouse Gas (GHG) emissions. The LEEF system addresses these challenges by replacing the external Pressure Build-up Unit (PBU) with an integrated in-tank Electric PBU (EPBU) and vaporizer, enhancing spatial efficiency and safety while reducing LNG leakage risks. The experimental results indicate that the Pressure Rise Rate (PRR) accelerates with higher tank levels and increases the EPBU power. The PRR doubled at higher liquid levels and improved by 30–44 % with increased EPBU power at a constant liquid level. The EPBU effectively maintained the tank pressure against flow variations, achieving pressure control with minimal power. A review of international regulations and codes confirms that the EPBU satisfies explosion-proof standards and ensures stable operation. The LEEF system demonstrated substantial potential for application in small LNG-fueled ships by combining improved spatial efficiency and enhanced safety. This study contributes to the development of the FGSS solution that is more compact and safer compared to conventional systems, encouraging sustainable marine propulsion.

Route, speed, and bunkering optimization for LNG-fueled tramp ship with alternative bunkering ports

To reduce emissions, shipping companies are deploying eco-friendly ships, like those powered by LNG or methanol. Unlike traditional fuels, LNG bunkering is available at a limited number of ports. At the same time, tramp or bulk ships have fewer ports of call on their shipping lines, which may necessitate LNG-fueled ships sailing to alternative bunkering ports for refueling. The selection of bunkering ports impacts the operating costs of shipping lines due to differences in fuel prices and geographical locations. Moreover, it must factor in ship speed limits to meet loading and unloading schedules. To optimize the shipping route, speeds, and bunkering plan for LNG-fueled tramp ships, we develop an arc-based mixed-integer linear programming model with the objective of minimizing total operation costs. Subsequently, we propose a leg-based formulation based on the predetermined port call orders. Finally, case studies are conducted to demonstrate the effectiveness and efficiency of the models. Experimental results indicate that the bunkering mode with alternative bunkering ports effectively reduces total operating costs without altering the total voyage time, particularly with substantial differences in fuel prices between ports.

Design and optimization of a steam methane reformer for ship-based hydrogen production on LNG-fueled ship

Owing to the severity of global environmental problems caused by climate change, efforts to efficiently use energy are being further strengthened. In this study, to improve energy efficiency, part of the boil-off gas generated from an LNG-fueled ship fuel tank was extracted and converted into hydrogen and then utilized as an auxiliary power source for the ship through a high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC). There are several methods for converting methane to hydrogen; however, steam methane reforming was used in this study. Integrating steam methane reforming into ship-based hydrogen production solves the problem of pure hydrogen storage and transportation as well as addresses environmental concerns by reducing pollutant emissions. Before designing the steam methane reforming reactor, a performance analysis of the reformer was performed using several parameters. The methane conversion rate decreased as the operating pressure of the reformer increased. The methane conversion rate exceeded 90 % when the reformer temperature was above 973 K, the S/C ratio was above 3, and the pressure was below 2 bar. The hydrogen yield was greater than 40 % when the S/C ratio was greater than 4 at the same temperature and pressure. Based on these results, the length of the reformer decreased as its operating temperature increased; at temperatures below 1000 K, the length of the reformer changed significantly as the pressure changed. When the S/C ratio is 3 or 4, the optimal design of the reformer is possible at a temperature range of 1023 K or more at a pressure of 2 bar and 923 K or more at a pressure of 4 bar, and it is reasonable to set the length of the reformer within 2 m considering the limited space on board.

Experiment and simulation of LNG self-pressurization considering temperature distribution under varying liquid level

For LNG-fueled ships, estimating the rate of self-pressurization is critical because the pressure limit of an LNG storage tank and the specifications of the boil-off gas processing system depend on the pressure rise rate. However, estimation using a non-equilibrium model exhibits deviated prediction on the pressure increase when thermal stratification is occurred in LNG. Therefore, in this study, a new numerical model is proposed for estimating the self-pressurization of LNG by considering the nonuniform one-dimensional fluid temperature distribution at varying LNG levels. The suggested model was verified using a pilot-scale experiment with a 150 m3 LNG tank capacity. The results show that the proposed model can explain the limited evaporation at a higher level and the vigorous evaporation at a lower level. Furthermore, the suggested model exhibits that the temperature profile in LNG can be determined by the evaporation at the liquid surface according to different levels and can successfully predict the increasing rate of pressure by excluding the assumption of a homogeneous LNG temperature.

Thermo-Economic Analysis and Multi-Objective Optimization of a Novel Power Generation System for LNG-Fueled Ships

Given the significant emissions from conventional marine diesel engines, many ship owners are increasingly turning to liquefied natural gas (LNG) as a cleaner energy alternative. In this study, a novel power generation system is proposed for LNG-fueled ships, integrating LNG cold energy and waste heat of the main engine, while considering the pressure of LNG. Firstly, this paper compares the two-stage parallel organic Rankine cycle to highlight its superiority. Secondly, the exergy loss and component cost of the system are analyzed, and the influence of these parameters on the thermal economy of the system is discussed. Finally, the multi-objective genetic algorithm is used to select the system exergy efficiency and electricity production cost (EPC), and the optimal performance point of the system is determined. Based on this, the performances of different literature studies are compared, and the system’s potential impact on the environment is evaluated. The results show that the net output power, thermal efficiency, exergy efficiency, EPC, payback period, and CO2 emission reduction of the system are 336.3 kW, 39.38%, 44.38%, 0.043 USD/kWh, 2.68 years, and 21,540 tons, respectively. Therefore, the system provides a new solution for energy saving and emission reduction of ships.

LNG 추진선박 도입 전망에 관한 연구

Purpose - This research aims to forecast the scale of LNG-fueled ships from 2020 to 2035 based on an economic performance analysis.
 Design/Methodology/Approach - This research compares the present value of costs for three alternatives (using low-sulfur fuel, installing scrubbers, and LNG-fueled ships). According to the two scenarios set in this study, the scale of LNG- fueled ship introduction was predicted from 2020 to 2035.
 Findings - The result showed that the proportion of LNG-fueled ships (based on DWT) will be 34.9% in 2035 by Scenario 1, and 20.1% in 2035 by Scenario 2. A one-year delay in global LNG bunkering infrastructure construction would reduce the introduction of LNG-fueled ships by about 2% in 2035. As a result of comparing the current situation with the results of this study, it was found to show a pattern similar to Scenario 2 assuming a pessimistic outlook.
 Research Implications - In order to activate the introduction of LNG-fueled ships, it is necessary to expand the LNG bunkering infrastructure, which is considered the most important factor hindering the introduction of LNG-fueled ships. Also, it would be a meaningful task to try forecasting considering the volume of goods transported. In addition, it would be interesting to evaluate the performance on climate change and the environment following the introduction of LNG-fueled ships.

Ejector design for compressorless BOG utilization system for a LNG fueled ship

In general LNG fueled ships, boil-off gas (BOG) produced by heat leakage into the storage tank is directly utilized as fuel for engines and generators by transport using compressors, which have many moving parts making the maintenance difficult, and require much power consumption for pressurizing the BOG. This paper proposes a new BOG utilization system with a compressorless configuration adopting an ejector and a static mixer. In this system, the BOG is transported and liquefied by the ejector and the static mixer, respectively, and then temporally stored before fueling. This paper also introduces an innovative optimization for ejector, which is a key component and should sufficiently entrain the BOG with less motive fuel gas. A preliminary thermodynamic analysis was performed to identify the effect of the ejector entrainment ratio on the effectiveness of BOG liquefaction. Considering system configurations, two ejectors depending on the motive pressure were initially designed by applying a theoretical method. A new optimization method with a modification procedure including maximizing the entrainment ratio in relation to key parameters and resizing to satisfy the requirements was applied to the initial ejector designs with validated CFD methodology. After the modification procedure, the entrainment ratios were enhanced up to 101% compared to before. The results showed that the designed ejectors achieved the liquefaction effectiveness of 10.3, which is close to that of a commercial one. Additionally, the performance characteristics for various off-design BOG conditions based on the designed ejector were also investigated.

Energy, Exergy, and Economic (3E) Analysis of Boil-Off Gas Re-Liquefaction Systems Using LNG Cold Energy for LNG-Fueled Ships

Liquefied natural gas (LNG)-fueled ships have the effect of reducing most pollutants, which is advantageous for responding to strict regulations. Because boil-off gas (BOG) is generated in the LNG storage tank of an LNG-fueled ship, a BOG re-liquefaction system is required. The representative systems for LNG-fueled ships were proposed by Kwak and Shen, but their exergy efficiencies were only 19.6% and 24.9%, respectively. To improve the system, this paper proposes novel BOG re-liquefaction systems combined with the fuel gas supply system. The systems utilize LNG cold energy in the BOG stream and N2 reverse Brayton cycle, respectively. The proposed systems were simulated using a commercial program and were optimized using a genetic algorithm. The results of energy, exergy, and economic (3E) analyses performed for comprehensive evaluation of the proposed system show that the system in which LNG cold energy is applied to the BOG stream has the best performance. Specific energy consumption, exergy efficiency, and total annual costs of this system were improved by up to 78.6%, 69.2%, and 68.2%, respectively, compared to those of the existing systems. The overwhelmingly superior system is expected to greatly contribute to the improvement of the BOG re-liquefaction system for LNG-fueled ships.

Tracking Liquefied Natural Gas Fuelled Ship’s Emissions via Formaldehyde Deposition in Marine Boundary Layer

One of the reasons that anthropogenic greenhouse gas emissions estimation is imprecise is the uncertainty of aerosol impacts on cloud properties. Maritime transportation is slowly changing fuel preferences. With the policy framework changing regulations, the shipping business is going in a direction that emits less sulfur dioxide and black carbon, which are the compounds that cause linear cloud formations known as ship tracks. Aside from their effects on the total radiative forcing of a transportation mean, this phenomenon enables the detection of ships via satellite imagery sensors. The rapidly increasing trend of shifting propulsion of maritime transportation from conventional heavy fuel oil and distillate marine fuels to liquefied natural gas causes enormous hikes in methane emissions. Therefore, oxidation of the volatile organic compound in the marine boundary layer by the hydroxyl radical in the troposphere makes significant deposition of formaldehyde which causes human effects, ecosystem damage, and climate impact. The primary triggering substance among the compounds in the ship plume is methane. This paper discusses methods to assess near real time tracking of anomalies and the deposition of the short lived substance in different seasons in one of the main occurring areas, shipping corridors. The study also employs anomaly map analysis for June and December 2010 and 2020. Several global tracking methods are available with satellites, monitoring experiments, and other satellite tracking tools. Apart from a few areas the results are not indicative since the formaldehyde formations caused by LNG fueled ships are not widespread enough alongside with overall LNG fueled fleet. On the other hand, the analysis and method are promising for the follow-up of the emissions in the future.

A Study on the Enhanced Process of Elaborate Heat Source Model Parameters for Flux Core Arc Welding of 9% Nickel Steel for Cryogenic Storage Tank

Various regulations are being devised and implemented to prevent the environmental pollution that is threatening mankind. The International Maritime Organization has strengthened regulations on sulfur, a notorious pollutant, to prevent sea pollution. In addition, the production of LNG fueled ships is increasing. Among various metals, 9% nickel steel is widely used in the shipbuilding industry because it is advantageous in terms of material strength and cryogenic impact toughness. Various studies are being carried out to predict and prevent its distortion, caused by welding, in the design. To predict welding distortion during flux core arc welding, this study found a way to refine the parameters constituting the Goldak welding heat source. The optimal heat source parameters were derived by using BOP experiments, cross-sectional analysis, finite element analysis and global optimization algorithm. When re-analyzed and verified based on the values, an error of up to 6.3% was found between simulation results and experimental values. The process was improved by clarifying the objective function and reducing the range of candidate welding efficiencies during global optimization and the process efficiency was also improved by reducing analysis time with a simplified model. Therefore, it is thought that this study can contribute to the productivity improvement of LNG storage containers, helping engineers apply it immediately in the industrial field.

Mechanical and Microstructural Behaviors of Gas Tungsten Arc Dissimilar Metal Welds of High-Mn Steel and Stainless Steel 316L Using Various Fillers for Cryogenic Fuel Tanks

The gas tungsten arc (GTA) weldability of high-Mn (HMn) steel and austenitic stainless steel (STS) 316L using dissimilar metal welds (DMWs) was investigated, to fabricate a fuel tank for an LNG-fueled ship. Three types of welding fillers, HMn steel, STS 309LMo and Inconel 625, were applied to the DMWs. The weldability of the DMWs was examined by investigating mechanical properties at 25 and -196 o C, followed by microstructural evolution and weld deformation. The GTA welding process was performed with a heat input range of 0.72–1.89 kJ/mm. All of the fillers employed in the study produced reasonable mechanical properties and low levels of precipitation, such as M<sub>7</sub>C<sub>3</sub> and Fe<sub>3</sub>C. However, the DN specimen using the Inconel 625 filler exhibited reduced ductility in the bending test. This was attributed to Nb-carbide precipitations at dendrite boundaries at the root weld. The DM specimen using HMn filler experienced severe thermal deformation because it had a relatively higher coefficient of thermal expansion than the other fillers during heating by arc and solidification. Therefore, STS 309LMo and HMn wires were determined to be the appropriate fillers for the DMW of HMn steel and STS 316L for cryogenic applications, and the HMn wire requires attention to weld deformation.

Development of Fire Consequence Prediction Model in Fuel Gas Supply System Room with Changes in Operating Conditions during Liquefied Natural Gas Bunkering

Recently, various dynamic risk analysis methods have been suggested for estimating the risk index by predicting the possibility of accidents and damage in real time. It is necessary to quickly estimate the risk of an accident by predicting the probability and consequences of accidents, which are quantitative criteria for ship risk assessment. This study aimed to develop an algorithm for predicting the consequences of accidents in real time to perform a dynamic risk assessment and, using this algorithm, formulate a ship accident–response procedure that can be used in fire accidents during LNG bunkering. The risk of fire was estimated by predicting the hole size due to changes in the liquefied natural gas (LNG) transport conditions and the consequence based on the fire accidents scenario in LNG-fueled ships. The prediction model was trained with the hole prediction data using Ansys CFX and with the consequence data using DNV Phast, and the consequences of fire were compared and evaluated by applying the trained results. A method for estimating the size of the fire based on the predicted consequence is proposed, which supports fast decision making in fire accidents during LNG bunkering by identifying the potential size of the fire at the beginning of an accident.

A Study on the Development of an Optimization Algorithm and Determination Procedure for Toughness Deterioration Characteristics through Flux Core Arc Heat Input Control of ASTM A553-1 (9% Nickel Steel)

The International Maritime Organization has adopted the reduction of carbon dioxide emissions from ships as an important priority, and is continuously strengthening its regulations on marine air pollution. By 2035, it is expected that LNG-powered ships will account for more than 50% of the available ships. Accordingly, the demand for equipment related to LNG-fueled ships is expected to grow as well, requiring the development of a lot of equipment. However, the characteristics of LNG-powered ships mean that they require a high level of reliability and long history of operating reliably. Even when a product is developed, numerous demonstrations and quality assurance measures are needed to reach the technological level ship owners and customers require. Therefore, an optimization procedure to determine the welding quality for 9% Ni steel is necessary. In this study, the heat input criteria that induce brittle fracture characteristics were analyzed to optimize the flux core arc welding process for 9% Ni steel used in the manufacture of LNG storage tanks. We developed an optimization algorithm (Welding Current, Arc Voltage, Welding Speed) that can select a group of fracture conditions by examining the tendency of the tissue to brittle fracture due to excessive heat input among potential quality issues of cryogenic steel. Capable of selecting the range in which quality deterioration occurs, determining quality of a weld and avoiding the range in which toughness degradation occurs, through which a process to derive high quality 9% Ni welds is proposed.

A Study on Heat Input Control and a Quality Evaluation Algorithm to Prevent Toughness Deterioration of the Heat-Affected Zone in the Fiber Laser Welding Process of ASTM A553-1 (9% Nickel Steel) Material

Various international organizations and governments of many countries are making efforts to prevent environmental pollution, with the IMO (International Maritime Organization) reinforcing related regulations. With these regulations, equipment related to LNG-fueled ships, which have the greatest carbon dioxide reduction effect among eco-friendly ships, are expected to increase. Although the IGC code designates the materials that can be used for LNG containers, such as 304L stainless steel and 9% nickel steel, these materials have a tendency to deteriorate the tissue around the heat-affected zone due to excessive heat input. In this study, we analyzed the effect of brittle fracture in the weld zone and heat-affected zone after fiber laser welding and found that welding quality improved with control of the heat input. SVM discriminant analysis was applied to classify the groups in which brittle fracture and ductile fracture occurred. The shape of the penetration section, hardness in the welding zone and heat-affected zone, and fracture surface were selected as factors for discrimination; these values were determined under various welding conditions. With these data, we derived a regression model and multi-objective optimization algorithm to predict mechanical properties after welding, as well as the conditions necessary to prevent brittle fracture. Finally, the prediction models were verified, as the results of welding under the derived conditions were classified as ductile fracture group.

Unexpected Methane Emissions From Old Small Fishing Vessels in China

Diesel-fueled ships have long been considered to contribute a marginal fraction of the global methane (CH4) emission budget compared to liquified natural gas (LNG)-fueled ships. Here, based on real-world measurements, we find that a specific yet-overlooked group of diesel-fueled ships–the old small fishing vessels (OSFVs)–is associated with high levels of CH4 emissions. The emission factors of CH4 from OSFVs is on average 5.2 ± 6.4 g CH4 per 1 kg fuel consumed, approaching EFCH4 of LNG-fueled ships (5.3–30.1 g/kg) and being at least six times EFCH4 of other types of diesel-fueled ships (0.0–0.9 g/kg). We estimate that CH4 emissions from OSFVs in China amount to 570–2,240 t per year, which is comparable to the total CH4 emission from all LNG-fueled ships worldwide. Our results thus call for revision of the global CH4 emission inventory for shipping.

Formation of Dataset for Fuzzy Quantitative Risk Assessment of LNG Bunkering SIMOPs

New international regulations aimed at decarbonizing maritime transportation are positively contributing to attention being paid to the use of liquefied natural gas (LNG) as a ship fuel. Scaling up LNG-fueled ships is highly dependent on safe bunkering operations, particularly during simultaneous operations (SIMOPs); therefore, performing a quantitative risk assessment (QRA) is either mandated or highly recommended, and a dynamic quantitative risk assessment (DQRA) has been developed to make up for the deficiencies of the traditional QRA. The QRA and DQRA are both data-driven processes, and so far, the data of occurrence rates (ORs) of basic events (BEs) in LNG bunkering SIMOPs are unavailable. To fill this gap, this study identified a total of 41 BEs and employed the online questionnaire method, the fuzzy set theory, and the Onisawa function to the investigation of the fuzzy ORs for the identified BEs. Purposive sampling was applied when selecting experts in the process of online data collection. The closed-ended structured questionnaire garnered responses from 137 experts from the industry and academia. The questionnaire, the raw data and obtained ORs, and the process of data analysis are presented in this data descriptor. The obtained data can be used directly in QRAs and DQRAs. This dataset is first of its kind and could be expanded further for research in the field of risk assessment of LNG bunkering.

Process design of onboard membrane carbon capture and liquefaction systems for LNG-fueled ships

This study proposes an onboard membrane carbon capture and liquefaction system for LNG-fueled ships to satisfy the IMO’s 2050 greenhouse gas reduction targets. The exhaust gas from a natural gas ship has a low CO2 fraction (∼3%) and high O2 fraction (∼16%) compared to the flue gas from power plants. Herein, considering the above distinguishing features, a membrane carbon capture and liquefaction system has been proposed that is energy efficient and compact for the application of ships. To ascertain the performance of the proposed membrane-based system, it is compared to an amine-based onboard system in terms of energy consumption and major equipment size. This work evaluates four process configurations by varying the number of membrane stages and associated liquefaction processes at different CO2/N2 selectivity and CO2 permeance. The results show that energy consumption (3.98 GJe/tLCO2) is higher than the amine-based system (3.07 GJe/tLCO2) at the CO2/N2 selectivity of 50, but it can be decreased to 3.14 and 2.82 (GJe/tLCO2) with an improved selectivity of 100 and 150, respectively. The major equipment size decreases to 54%, 28%, and 20% of the amine-based system when the permeance is 1000, 2000, and 3000 GPU, respectively. The results indicate that the new onboard membrane carbon capture and liquefaction system can be a competitive solution for the IMO’s greenhouse gas reduction targets for 2050.

CFD implementation to mitigate the LNG leakage consequences: A review of explosion accident calculation on LNG-fueled ships

Liquefied Natural Gas (LNG) has a significant benefit in reducing air pollutants such as sulfur oxide, nitrogen oxide, and particulate matter emitted by Diesel Oil or Heavy Fuel Oil. The International Maritime Organization (IMO) regulates these pollutants in MARPOL Protocol Annex VI. It was implemented by establishing an Emission Control Area (ECA) in 2010 that restricts exhaust gas of ships. This regulation has resulted in new shipbuilding orders or conversions to adopt the LNG-fueled systems. Besides the benefits of LNG fuel, storing, transporting, and distributing this fuel has a different problem with conventional fuels. LNG is volatile, and it has a low flashpoint that could lead to spontaneous ignition. To assess the safety and mitigation for LNG-powered ships, Computational Fluid Dynamics (CFD), such as Kameleon Fire Ex (KFX) and Flame Acceleration Simulator (FLACS), is considered to simulate the LNG release. This technical measure is taken to observe the possible damage or loss due to the cryogenic effect, the extreme temperature of the jet fire, or Vapor Cloud Explosion (VCE). These consequences could happen sequentially that known as the “Domino Effect”. The effect of the leak and environment-related parameters could influence the severity of the damage. The applications of CFD for the LNG release cases are discussed and highlighted in this review.

Layout optimization for safety evaluation on LNG-fueled ship under an accidental fuel release using mixed-integer nonlinear programming

The Liquefied Natural Gas (LNG)-fueled ship is an alternative solution to deal with the Emission Control Area (ECA) issued by the International Maritime Organization (IMO). LNG fuel has eco-green characteristics since sulfur oxide and particulate matter are eliminated. The equipment sitting on the Fuel Gas Supply System (FGSS) layout needs a good arrangement to prevent the domino effect. This study’s scopes are to establish the feasible FGSS layout based on the equipment position and conduct an accidental LNG release that adopts the Computational Fluid Dynamics (CFD). Mixed-Integer Nonlinear Programming (MINLP) is provided as an optimization tool. The MINLP framework is written in the Python programming language. The minimum separation distance, deck size, and non-overlapping functions of equipment are included as the MINLP constraint. The separation distances are provided based on the Center of Chemical Process Safety (CCPS) recommendation. Also, several options of the separation distance are added that consist of 5.0, 6.0, and 7.0 m to observe the congestion effect. The total pipe length is considered as the MINLP objective that can be used to estimate the pipe cost. The proposed MINLP framework is designated to generate a feasible layout that has an adequate separation distance and minimum cost of the pipe. CFD results show that the increase of separation distance can reduce the gas accumulation effectively which eventually reduces the severity of other consequences. Finally, the feasible layout is proposed based on a series of several consequences under an accidental LNG release, such as gas dispersion, fire, and vapor cloud explosion.