Liquefied Natural Gas Storage Research Articles

Research on digital twin based temperature field monitoring system for LNG storage tanks

The temperature distribution is a critical indicator of the health condition of liquefied natural gas (LNG) storage tanks. Point measurements are the main method of traditional LNG tank temperature field monitoring. To obtain more abundant temperature data and realize the digital transformation of temperature field monitoring, an LNG tank temperature field monitoring system was constructed, which consists of a model layer, a data layer, and an application layer, by combining sensing data with digital twin (DT) technology. First, the temperature distribution of the LNG storage tank under working and leaking conditions was simulated, and the sensing monitoring network was constructed by combining Fiber Bragg Grating (FBG) sensor temperature-sensing experiments. Second, a finite element calculation model of the steady-state temperature field of an LNG storage tank was developed, and the twin model was generated by fusing the sensing data to realize the inversion from local sensing data to the whole temperature field. Finally, an LNG temperature field monitoring system based on the DT was constructed. Based on physical field leakage simulations performed with the Fluent software, the functions of visual interaction, construction splitting, temperature chart analysis, leakage diagnosis, and historical data management of the twin models were realized, which provided system building samples for digital monitoring of new LNG storage tanks.

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.

Sizing-Based Flaw Acceptability in Weldments Using Phased Array Ultrasonic Testing and Neural Networks

Liquefied Natural Gas (LNG) is one of the major renewable energy sources and is stored and carried in a storage tank that is designed following international standards. Since LNG becomes highly unstable when it encounters oxygen in the air, a leakage from an LNG storage tank can cause a catastrophic industrial accident. Thus, the inspection of LNG storage tanks is one of the priorities to be completed before LNG is stored in a storage tank. Recently, the usage of Phased Array Ultrasonic Testing (PAUT) has been gradually increasing as the risks of RT emerge. PAUT has some obstacles to overcome in order to substitute RT, such as efficiency and accuracy. Specifically, the cost issue must be addressed. Therefore, many attempts to combine PAUT with Artificial Neural Networks (ANN) have been made. PAUT provides many types of 2D images of the inspected weldment. The S-scan is one of the 2D images provided by PAUT, and it displays the cross-sectional view of the specimen with a single transducer. The inspectors examine the S-scan image and other provided images of PAUT to detect, classify and size the flaw that exists in the weldment so that the decision of whether the inspected weldment with the flaw is acceptable can be made. Nowadays, most of the previous research on PAUT and ANN focuses on detecting and classifying the flaws in B-scan or S-scan images. However, the last step to determine the flaws’ acceptability is not yet covered. In this study, the flaw acceptance criteria of PAUT in various international standards are listed. EXTENDE CIVA is used to create the PAUT S-scan images. The S-scan images are labeled with the listed acceptance criteria. Then, they are used in Mask R-CNN training. After the training, some new S-scan images with flaws are used to test the performance, and this showed 96% precision and 87% recall. With the algorithm, the acceptability of a flaw in a weldment can be determined efficiently and it will reduce the burden of PAUT usage and reduce the time required for a full-length inspection.

Effect of Ultralow Temperature on Expansion, Strength, and Modulus of Cement-Stabilized Soil: Case Study for LNG Underground Storage in Singapore

Singapore has a relatively high water table. When liquefied natural gas (LNG) storage systems are built in soils below the water table in Singapore, the engineering properties of the surrounding soils could be improved through cement stabilization. Due to the extremely low temperature (T) of LNG (approximately −162°C), the effect of ultralow T on the physical and mechanical properties of cement-stabilized soil in case of accidental LNG leakage should be investigated. However, existing studies on cement-stabilized soils are limited to T above −20°C. Therefore, in this study laboratory experiments to quantify volumetric expansion, unconfined compressive strength (UCS), and Young’s modulus (E) of cement-stabilized soils at −40°C, −80°C, and −120°C were conducted. The experimental results indicated that the stabilized soils’ volumetric expansion reached ≤2.6% at −120°C. The UCS and E of the stabilized soils increased from 0.9 to 27.6 MPa and from 99.8 to 2,669 MPa, respectively, and the T decreased from 24°C to −120°C. In summary, the ultralow T induced limited volumetric expansion (<3%) for cement-stabilized soil and significantly increased its strength and E, which indicated that cement soil stabilization could be beneficial for underground LNG storage systems in Singapore when exposed to accidental LNG leakage.

Пожарная опасность взрывных режимов испарения сжиженного природного газа

Introduction. The fire hazard of explosive regimes of liquefied natural gas (LNG) evaporation was analyzed on the basis of the published research findings. These regimes include the rollover and the rapid phase transition (RPT). Characteristics of explosive regimes of LNG evaporation. Rollover occurs in LNG storage tanks in case of spontaneous mixing of LNG layers having different temperatures and densities. These layers emerge when the “fresh” product is loaded into a vessel containing the residual amount of product stored there before. A rapid increase in the LNG evaporation rate accompanies a pressure rise inside the tank, which can exceed an allowable pressure of the tank. RPT occurs at a contact of LND and water in the case of a release of liquefied natural gas onto a water surface. An explosive evaporation of LNG can cause in this case a formation of a shock wave and a large-scale vapor cloud. Investigations of rollovers. It was mentioned that a stratification of LNG in a storage tank is a necessary condition of a rollover. Two layers with different temperatures and densities are formed during this stratification. A superheating of a lower layer occurs at a heat exchange between the LNG and tank walls with a decrease of a density of this layer. A preferential evaporation of light components of LNG (methane, nitrogen) takes place in the upper layer, and the density of this layer increases. When the densities of these layers are equalized a spontaneous mixing of these layers occurs with an explosive evaporation of the product in the lower superheated layer. A time delay of rollover can reach 60–70 hours after the supply of the “fresh” product into the tank with “old” product. Investigations of a rapid phase transition. An energy released at the explosive evaporation and a pressure in a shock wave depend on many factors such as a LNG release rate, a position of a source of the LNG release — over or under a water level, a product composition, water temperature etc. It was found that a pressure hazardous for buildings and structures can take place at distances 250–500 m from the point of the release. The empirical correlation was proposed connecting a water temperature at the RPT occurrence and the superheating tempe­rature of LNG at which a boiling takes place in the regime of a homogeneous nucleation. Conclusions. It was shown that a realization of the explosive regimes of the LNG evaporation increases a fire hazard of objects for a storage and a transportation of liquefied natural gas. Recommendations for a prevention of such regimes are formulated.

The Problem of Utilization of Liquefied Natural Gas Vapor at Large-scale LNG Plants

The liquefied natural gas (LNG) is stored under low overpressure in a saturated state in large-capacity tanks with multilayer thermal insulation. Owing to the input of heat from the environment through thermal insulation, LNG is continuously evaporated. Since natural gas is a multicomponent mixture, LNG vapors are enriched with its low-boiling components, then the supply of heat from the environment reduces the amount of liquid in the reservoir and changes its chemical composition. Similar phenomena occur during LNG transportation. The present paper deals with the problem of LNG vapor utilization during its storage and transportation. Information is presented on the causes of the LNG vapor formation (boil-off gas) and methods for its disposal during storage and transportation to consumers. A numerical experiment was performed based on the data of LNG storage in large-capacity storage facilities at the Yamal LNG plant. The technique consists of the estimation of material flows toward the system of accumulation and extradition of LNG. The results show that the vapor flow generated from the inflow of new LNG portions into the storage significantly exceeds that generated from the heat supply from the environment.

Investigation of cryogenic friction and wear properties of Invar 36 alloy against Si3N4 ceramic balls

The existing materials for liquefied natural gas (LNG) cryogenic submersible pump bearings are very susceptible to wear and failure in LNG environments where oil lubricants and greases are ineffective, posing a major hazard to the safety of LNG storage and transportation. Therefore, searching for a type of material with excellent cryogenic tribological properties for improving the life of LNG bearings has become a huge challenge for researchers. Invar 36 alloy, as a low expansion nickel-titanium alloy, is used in control instruments, moulds, laser control equipment, and materials of LNG transport hull at temperatures below −162 °C. However, there is a lack of research data in the field of bearings. Currently, the Si3N4 ceramic balls are widely used in ceramic hybrid ball bearings and exhibit excellent tribological properties. In this work, the tribological performance of Invar 36 alloy is mainly investigated against Si3N4 ceramic ball under extremely cryogenic and dry conditions using the modified ball-on-disk tribometer with a cryogenic module, with temperatures as low as −196 °C. All experiments are performed at loads of 0.5 N, 1 N, 1.5 N, and 2 N, and at temperatures of 20 °C, 0 °C, −78 °C, and −196 °C, respectively. The experimental results show that the coefficient of friction (COF) and wear rate decrease with temperature and load, with a minimum value of −196 °C. The Invar 36 alloy exhibits excellent tribological properties, whose COF decreases gradually from 20 °C to −78 °C. However, as the temperature drops to −196 °C, the COF decreases abruptly, reaching a minimum value at −196 °C. On the contrary, the COF gradually increases with load. In addition, a commercial bearing grade material (G95Cr18 steel) is tested and compared under the same conditions, proving that Invar 36 alloy exhibits better tribological properties than G95Cr18 steel, with a wear rate 55.43% lower than G95Cr18 steel at −196 °C. Further simulation comparisons demonstrate that, due to its extremely low coefficient of thermal expansion, Invar 36 alloy exhibits higher toughness and strength than G95Cr18 steel under cryogenic conditions. This study complements the tribological data of Invar 36 alloy and G95Cr18 steel against Si3N4 ceramic balls under different temperatures and loads and provides important theoretical guidance and technical support for the bearings’ future development of LNG cryogenic submersible pump.

ДИФФУЗИОННОЕ ГОРЕНИЕ СЖИЖЕННОГО ПРИРОДНОГО ГАЗА. СКОРОСТЬ ВЫГОРАНИЯ И РАЗМЕРЫ ПЛАМЕНИ

Исследование направлено на изучение параметров горения сжиженного природного газа (СПГ), необходимых для оптимального выбора средств обеспечения пожарной безопасности при его производстве, хранении, транспортировке и использовании. Актуальность данной работы связана с существенным ростом масштабов производства и использования СПГ, являющегося одним из важнейших средств обеспечения энергобезопасности страны и ее конкурентоспособности на внешнем рынке. The study is devoted to investigation in the size of the flames of liquefied natural gas (LNG). A detailed analysis of accidents at LNG storage and processing facilities shows the potential dangers arising from its use, as well as the relevance of their scientific study. The data on the fires that have occurred, presented in the scientific literature, indicate that the height of the flame of flammable liquids (including liquefied gases) depends largely on the rate of burnout and the typical size of the spill area (side of the square, diameter), as a rule, limited by the dike. The empirical Thomas equation for determining the dimensionless flame height of flammable liquids is given in the scientific literature. The proposed dependence summarizes the data on the size of the flames of the following series of flammable liquids: gasoline, hexane, methanol. The application of this dependence to generalize the available literature data on the size of LNG flames undertaken by domestic authors showed that the calculated and experimental data differ by about 3 times. According to the authors of such an assessment, the difference indicates that the Thomas equation is not optimal for a reliable estimation of the size of LNG flames, which differ significantly in their physicochemical properties from known combustible liquids. Considering this, as well as the fact that the burnout rate depends to varying degrees on many factors (evaporation area, surface type, thickness of the combustible liquid layer, etc.), the most reliable data can be obtained by direct experiments which results are provided in this paper. Based on the results of the experiments, a comparative assessment of the dimensionless height of the flame, measured in experiments when burning LNG in steel baking trays and a concrete bath, was carried out with calculations according to the Thomas formula. In this formula, the density of the LNG vapor phase directly above the combustible liquid layer was used to estimate the burnout rate. A graphical representation of the experimental results and the calculated ones (according to the Thomas formula) using the vapor phase density parameter showed that the generalization of the literature and the present experimental data gives a more reliable result. According to the results of the study, we can conclude about the possibility of using the data obtained for design estimates of the size of LNG flames and the feasibility of further large-scale studies to obtain more complete information.

Transition corner structure optimization and ultimate bearing capacity evaluation of marine pressure cabin: experiment and numerical analysis

With the improvement of ship pollutant emission requirements, LNG (liquefied natural gas) market demand is growing strongly. The bearing capacity requirements of pressure vessels are getting higher and higher, and the optimal design of corner structures becomes the key to bearing capacity. However, in order to improve the volume ratio, traditional LNG prismatic pressure vessels usually adopt right-angle corners, and there is obvious stress concentration at the corners. In order to optimize the corner structure and improve the ultimate bearing capacity, based on similarity theory, the ultimate bearing tests on pressure vessels with four improved corners are carried out, and the corresponding numerical simulation and parametric analysis are further developed. According to the calculation results, it is found that the finite element calculation results are in good agreement with the test results. Through the establishment of four full-scale numerical models with different corners, the lightweight effect and ultimate bearing capacity are further obtained, which provides quantitative reference for the design of non-cylindrical LNG storage containers. The results show that the corner form of inclined plate is a relatively good corner form of pressure-resistant structure.

Hazard Identification of Liquefied Natural Gas (LNG) Transportation and Storage in DKI Jakarta Province

LNG is an alternative fuel to replace diesel and gasoline. The use of LNG as a fuel has many advantages from various aspects. Besides having advantages, LNG also has disadvantages because it contains dangers in it. LNG is a volatile material that is easily flammable, which causes fires and explosions. Environmental Risk Assessment (ERA) is a systematic method used to measure the magnitude of the risk of a process and product that is a hazard to human health and ecology. By conducting an ERA, the risks and hazards of LNG are known. In carrying out the research, describing the LNG delivery system, identifying hazards in the event of LNG released from the carrier, making accident scenarios along with the outcome events that will occur, collecting data, calculating the frequency of accidents and their consequences, determining existing risks, and providing preventive actions, and mitigation. Hazard evaluation was determined using fault tree analysis (FTA) and event tree analysis (ETA). Based on identifying hazards to the storage and transportation of LNG, it is classified into category four and server (severe). Scenarios of releasing LNG into the environment in the process of transporting and storing LNG can be caused by several things, including external factors, failure in filling, and failure due to excess pressure so that it can cause fire pools/BLEVE events, cloud vapor explosions, flash fires, and cloud vapors. Based on the level of risk entered into, not tolerable action at the next opportunity.

Mechanical properties and degradation mechanism of LNG containment concrete material under cryogenic conditions

• Compressive strength and tensile strength of the concretes at cryogenic temperature were studied. • The damage degree of the concretes after cryogenic freezing-thawing cycles was investigated. • The mechanism of mechanical properties of the concretes at cryogenic temperatures was analyzed. • The degradation mechanism of damaged concrete under freezing-thawing cycles was discussed. • Application of the HCC for on all-concrete LNG storage tanks is appropriate. The mechanical properties and deterioration of concrete under cryogenic conditions are unclear. Here, high-strength and cryogenic temperature-resistant concrete (HCC) was developed for Liquefied natural gas (LNG) inner tank applications. Influences including compressive and tensile concrete strength under different temperatures (25 °C ∼ -165 °C) and freezing-thawing cycles were investigated. The results showed that lower temperatures result in higher compressive strengths, the tensile strength increases and then decreases, and the greatest increase in strength occurs at −45 °C. The tensile strength of HCC and C60 concrete decreases below −105 °C and −45 °C, respectively; more freezing-thawing cycles result in greater mechanical property degradation. Furthermore, compared to C60 concrete, HCC has a significantly lower rate of strength loss. The mechanical property mechanisms at different cryogenic temperatures and deterioration due to the freezing-thawing cycles were investigated by differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). HCC is an ideal material for LNG inner tanks.

A Comprehensive Review of Stratification and Rollover Behavior of Liquefied Natural Gas in Storage Tanks

Liquefied natural gas (LNG), as cleaner transitional energy than coal, is becoming increasingly prominent in the energy structure of various countries based on their low-carbon background, and its demand has grown rapidly worldwide. Storage tanks are the most commonly used LNG storage facilities. Owing to a variety of internal composition and external environmental factors, the instability phenomenon of LNG in the tanks may occur during storage, leading to potential safety risks. An in-depth understanding of the stratification and rollover behavior of LNG is therefore required to ensure and promote efficient utilization and stable storage of LNG. This paper provides a comprehensive review of the current state of LNG stratification and rollover behavior. The factors for causing LNG stratification and rollover behavior in the storage tanks are summarized, methods for characterizing stratification and rollover behavior are discussed, and measures for inhibiting the instability phenomenon of LNG in the tanks are highlighted. Future researchers should conduct further work in enriching the factors affecting the stratification and rollover behavior, improving characterization methods, and developing inhibition measures to ensure the safe and stable storage of LNG.

Enhancing sustainability of natural gas value chain via waste cold recovery

Liquefied natural gas (LNG) has been a rapidly growing energy source due to its low carbon emissions, high energy density and ease of long-distance transportation. However, heat leakage into an LNG storage facility is unavoidable due to the lack of complete insulation. Owing to this heat ingress a portion of LNG vaporizes, thus forming what is referred to as Boil-off gas (BOG). Due to safety and economic considerations, BOG recondensation at an LNG regasification terminal is of utmost importance. This consumes a substantial amount of energy. Additionally, at the regasification terminal, the imported LNG is regasified using sea water as a heat source. This results in the wastage of the entire cold energy associated with LNG. The available LNG cold energy can be recovered for power generation using an Organic Rankine Cycle (ORC). In this study, we demonstrate the integration of BOG recondensation process with an ORC-based power generation configuration that utilizes LNG cold energy. The technical feasibility of the proposed integrated process is investigated using process simulation and optimization.

Risk Assessment of an LNG Storage Tank Release

Liquefied natural gas (LNG) terminals ensure the production, storage, and transportation of LNG. Therefore, it assembles critical equipment that can cause hazards to personnel, assets, and the environment. This paper presents a risk assessment for an LNG storage tank release in an LNG terminal. Risk assessment was conducted by applying a HAZOP study, Bowtie analysis, fault tree analysis, and ALOHA (Areal Locations of Hazardous Atmospheres) simulation. The results were to identify causes, consequences, and safeguards of hazards related to over and under pressure in an LNG storage tank. Moreover, a bowtie analysis was established for LNG loss of containment (LOC) from flammable liquids storage tanks. In addition, a fault tree analysis was presented to identify the causes of tank failure considering pressure hazards. Finally, the consequences of LNG released from the storage tank are simulated using the ALOHA software

Collision-accidental limit states-based safety studies for a LNG-fuelled containership

Liquefied natural gas (LNG) is an increasingly popular fuel alternative of ships for reducing greenhouse gas emissions. The interest in LNG fuel propulsion systems is rapidly growing, yet certain important safety design and engineering issues remain poorly constrained. The safety of LNG-fuelled ships must be assessed in terms of the potential structural damage owing to collision accidents and resulting LNG spills, especially for ship types that store the LNG storage tank within the cargo hold. In this paper, accidental limit state (ALS) based safety assessment for LNG-fuelled containership structures using nonlinear finite element methods is studied at the most unfavourable scenario of collisions between a striking ship's bow and a struck ship's LNG fuel tank, where the struck ship is in full load condition at a standstill, while the striking ship of the same size as the struck ship has different loading conditions in the ballast load condition, 50% partial load condition and full load condition, with varying collision speed at 0.5, 3, 6 and 9 knots. A hypothetical 9,000 TEU (Twenty-foot Equivalent Unit) LNG-fuelled containership was designed in accordance with the requirements for the international gas fuel transport standards, accommodating a membrane-type LNG fuel tank located amidship. It is found from the present study that inner side hull structures of the struck ship can be damaged in ship-ship collisions, and the current industrial guidelines for LNG fuel tank designs are required to amend to apply for LNG-fuelled ships.

Model based analysis of the boil-off gas management and control for LNG fuelled vessels

The immense pressure to decarbonise the maritime industry has led to the Liquefied Natural Gas (LNG) uptake as a marine fuel and the LNG fuelled ships design. As LNG is stored in cryogenic conditions, the heat ingress from the ambient causes the boil-off gas (BOG) production, which, if not controlled, results in the tank overpressure with implications on the fuel storage system safe operation. This study aims at investigating an LNG storage tank behaviour for realistic operating conditions of an LNG fuelled ocean-going ship, targeting to identify the recommended control actions for avoiding tank overpressure. A dynamic model is developed by considering the mass and energy conservation in the liquid and vapour subsystems, the energy conservation in the tank walls, the vapour to liquid equilibrium (VLE), and real gas properties. Following the model validation for a holding test, simulation runs were performed for various operating conditions corresponding to typical long and short voyages of the investigated ship. The simulation results demonstrate that a boil-off gas (BOG) compressor capacity of 450 kg/h along with its on/off control setting the upper and lower limits of the tank absolute pressure at 5.5 and 4 bar leads to tank overpressure avoidance and the minimum number of BOG compressor activations.

Characteristics of Welding Residual Stress Distribution in Dissimilar Weld Joints

For the construction of ecofriendly ships, fuels such as liquefied natural gas (LNG), ammonia, and hydrogen are being discussed as alternatives. LNG fuel has recently been applied to shipbuilding. The most important aspect of an LNG propulsion ship is the LNG storage tank, because LNG is stored at a high pressure and low temperature. Cryogenic steels are needed to evaluate safety in weld joints, especially the LNG storage tank which has a dissimilar weld joint with a STS pipe. The dissimilar weld joint has a complex welding residual stress distribution. It is necessary to evaluate the effects of temperature changes that occur during the loading–unloading process of LNG. In this study, the residual stress distribution characteristics of heterogeneous welding parts welded to STS pipes using 9% Ni steel, STS, and high-manganese austenitic steel in an LNG storage tank were investigated through experimental and analytical methods. The thermal stress due to the difference in thermal expansion coefficient between cryogenic steel and the STS pipe occurred with a small amount in loading–unloading of LNG. When high-manganese austenitic steels and the STS pipe were joined, tensile stress was generated at the dissimilar weld joint owing to the temperature difference generated during the LNG loading–unloading process. STS has a homogenous weld joint and identical thermal expansion coefficients; therefore, the shrinkage and expansion were not affected by the temperature change. The welding residual stress at the dissimilar weld joints was measured via an experimental cutting method, and the results indicated that the tensile residual stress had distribution similar to the yield stress of the material. The stress generated by the temperature change and the welding residual stress overlapped and occurred during the loading–unloading process of the LNG tank; however, the final tensile stress below the tensile stress was distributed in the storage tank.

Improvement of the Liquefied Natural Gas Vapor Utilization System Using a Gas Ejector

The production, transportation, and storage of liquefied natural gas (LNG) is a promising area in the gas industry due to a number of the fuel’s advantages, such as its high energy intensity indicators, its reduced storage volume compared to natural gas in the gas-air state, and it ecological efficiency. However, LNG storage systems feature a number of disadvantages, among which is the boil-off gas (BOG) recovery from an LNG tank by flaring it or discharging it to the atmosphere. Previous attempts to boil-off gas recovery using compressors, in turn, feature such disadvantages as large capital investments and operating costs, as well as low reliability rates. The authors of this article suggest a technical solution to this problem that consists in using a gas ejector for boil-off gas recovery. Natural gas from a high-pressure gas pipeline is proposed as a working fluid entraining the boil-off gas. The implementation of this method was carried out according to the developed algorithm. The proposed technical solution reduced capital costs (by approximately 170 times), metal consumption (by approximately 100 times), and power consumption (by approximately 55 kW), and improved the reliability of the system compared to a compressor unit. The sample calculation of a gas ejector for the boil-off gas recovery from an LNG tank with a capacity of 300 m3 shows that the ejector makes it possible to increase the boil-off gas pressure in the system by up to 1.13 MPa, which makes it possible to not use the first-stage compressor unit for the compression of excess vapours.

Пути улучшения экологических показателей мегаполисов за счет использования СПГ в качестве резервного топлива

Large thermal power plants (TPP) located within the boundaries of urban areas usually use diesel or black oil as a reserve fuel (RF). In some cases, coal is also used. That has a negative impact on the natural environment of the city. In accordance with this, the new procedure for the creation and use of fuel reserves by thermal power plants provides as an option the use of liquefied natural gas (LNG) as a reserve and emergency fuel. Replacing RF (reserve fuel) with natural gas will, to some extent, reduce the load on the environment and reduce the area occupied by reserve fuel facilities (RFF). Since the construction and maintenance of RFFs at boiler plants and thermal power plants (TPP) requires significant capital investments and operating costs, the transition to LNG, which has its own specifics, requires additional analysis, given in this article, which evaluates the requirements for LNG volumes, places of production, storage and delivery of LNG to the TPP. The potential benefits of RF's transition to LNG have been assessed and challenges requiring further research have been formulated.

Stakeholder analysis for safe LNG handling at ports

This paper presents the initial results from a project entitled “TRiTON”, funded by the Greek Ministry of Education, which addresses safety issues of Liquefied Natural Gas (LNG) at ports. Whithin this framework, a stakeholder analysis is performed for investigating the safety management operation during storage, transport, and supply of LNG at port areas. The national (Greek), the European and the international regulatory framework for LNG safety have been analysed, so as to identify relevant stakeholders and establish relationships between them. Relationships have been weighted by a group of experts to highlight the importance of some critical interactions in safety management. The social network analysis approach has been employed for creating three stakeholder networks for the most widely used methods for LNG storage and bunkering, namely: a) fixed-tank storage and tank to ship bunkering, b) truck to ship bunkering, and c) ship to ship bunkering. Statistics and metrics of the networks have been calculated, with the help of the open-source software called Gephi, such as density, centralities (degree, closeness and betweenness), clustering coefficient and modularity. Finally, the most important stakeholders for handling LNG safety at ports have been identified.