Gas Supply Research Articles

Optimal Design of BOG Reliquefaction Systems for LNG Carriers: A Focus on GMS Performance During Loaded Voyages

AbstractThis study proposes a strategy for evaluating efficient design of the Gas Management System (GMS) on LNG carriers by decomposing its performance to subsystems: the reliquefaction system (RS) and the fuel gas supply system (FS). With increasingly stringent maritime regulations on greenhouse gas emissions, the need for efficient LNG carrier operations has become critical. A major factor in reducing fuel consumptions and carbon emissions is optimizing the design of the RS, given its significant power demand for processing NBOG. However, effective GMS design must account for variations in RS operation performance, as well as the contributions of the FS in treating NBOG with changes in ship speed. This study compares GSM configurations with reliquefaction systems based on two representative refrigeration cycles: the nitrogen reverse Brayton cycle (NRBC) and the single mixed refrigerant cycle (SMRC), both analyzing effects of cold BOG utilization. Results indicate that the RS of GMS4A-aSMRC [the aSMRC is the refrigeration cycle which utilizes cold BOG within the Single Mixed Refrigerant Cycle (SMRC)] demonstrates superior RS design performance. However, the most efficient GMS configuration varies with the Boil-off Rate (BOR): GMS2-aNRBC [the aNRBC is the refrigeration cycle which utilizes cold BOG within the Nitrogen Reverse Brayton Cycle (NRBC)] is optimal aligning with its RS performance for a 0.11%/day BOR, while GMS3-SMRC without cold BOG in RS is the most efficient for a 0.075%/day BOR, owing to increased contributions from the FS. In this study, a performance index with a consistently comparable baseline is derived to accommodate compositional deviations from flash gas recirculation at NBOG disposal streams, enabling the GMS performance to be correlated with compatible values of its decomposed subsystem.

Damage Mechanism of Deep Coalbed Methane Reservoir and Novel Anti-Waterblocking Protection Technology

Coalbed Methane (CBM) accounts for about 5% of China’s domestic gas supply, which has been regarded as one of the most promising energies for alleviating the energy supply–demand imbalance. Deep CBM reservoirs have the characteristics of low permeability, low porosity, and low water saturation, which easily experience reservoir damage during the drilling process, further affecting the gas productivity. Based on the analysis of coal mineral composition, pore structure distribution, and the surface micromorphology change in coal surface before and after hydration, a possible mechanism for CBM formation damage was revealed. It was found that the damage caused by drilling fluid intrusion can be divided into three stages: stripping, migration, and plugging. Based on the water-sensitive, acid-sensitive, and stress-sensitive evaluation tests, a novel anti-waterblocking agent with both wettability alteration and surface tension reduction was developed; then a reservoir protection drilling fluid for deep coal formation in Daning-Jixian block was constructed; then the reservoir protection performance of drilling fluid was evaluated. The results show that as the concentration of the anti-waterblocking agent FSS increases from 0% to 1%, the surface tension of the water phase is significantly reduced from 72.15 mN/m to 26.58 mN/m, while the maximum contact angle of water on the surface reaches 117°. This enhancement in wettability leads to an improvement in the permeability recovery rate from 56.6% to 80.0%, indicating a substantial reduction in waterblocking effects and better fluid mobility within the reservoir. These findings highlight the efficacy of FSS in mitigating formation damage and optimizing gas production in coalbed methane reservoirs. The drilling fluid has good wettability alteration, inhibition, and sealing performance, which is of great significance for protecting gas well productivity.

Estimates of optimal supplies of animal-sourced foods differ by food system goal and socioeconomic context

Reduced consumption of animal-sourced food (ASF) has been recommended for environmental and human health objectives; however, ASF can be important for food security and diet affordability. We explored country-level relationships among various metrics of food supply, socioeconomic context, food security, diet affordability, and agricultural greenhouse gas emissions (GHGe) to characterize how optimal inclusion ranges for ASF vary with socioeconomic factors and food system goals. Data from 2015 to 2022 for 153 countries were sourced to generate Bayesian Networks representing relationships among the studied food system metrics. Networks were used in simulations to characterize optimal ASF inclusion to achieve environmental, food security, or diet affordability goals based on individual country data. Results are most appropriately interpreted in aggregate rather than as representations of specific countries due in large part to data limitations. Across countries simulated, median total ASF inclusion in the food supply to support food security, GHGe, or affordability objectives was 18.2% ± 12.1%, 11.9% ± 6.8%, and 17.6% ± 8.5%, respectively. Joint optimization for these goals resulted in median ASF inclusion of 15.1% ± 7.2%, with notable regional differences. Although ASF increases were supported in most developing regions, decreases were supported in developed countries. The reported SD in optimal ASF inclusion were considerable, and represented between-country variation. Empirical relationships of food categories to goals consistently favored dairy and egg products over meats. These results support previous literature highlighting the environmental intensity of ASF, but also indicate that moderate ASF supplies contribute to multiple food system goals simultaneously.

Characteristics of cylindrical Hall ion source with floating potential magnetic pole discharge

The discharge characteristics of a cylindrical Hall ion source (CHIS) with floating potential magnetic poles and grounded magnetic poles were investigated through experiments and simulations. The results revealed that the ion density distribution and ion energy were mainly affected by the discharge voltage and magnetic pole potential. The current utilization rate is 82%–93%, which is much more efficient than that of the conventional Hall ion source with grounded magnetic poles. As the gas supply increased, the floating potential of the magnetic pole increased. Under the same discharge current condition, the discharge voltage of a Hall ion source with floating magnetic poles is 300 V larger than that of grounded magnetic poles; meanwhile, this type of ion source has a higher mean ion energy and better uniformity of ion beam distribution. Ion acceleration in the CHIS with floating magnetic poles is expected to occur predominantly in the longitudinal direction and toward the CHIS outlet. The non-uniformity of the ion beam current density within a diameter of 40 mm along the radial directions approximately ±11.7% at a discharge voltage of 800 V, which is helpful for material surface cleaning, etching, sputtering, and ion beam-assisted deposition applications.

How ADNOC Opened the UAE’s Pre-Khuff Offshore Gas Play Using Advanced Fracturing Tech

A hidden gem may lie beneath one of the world’s latest megaprojects. Next year, the Abu Dhabi National Oil Company (ADNOC) is set to launch production from its largest-ever gas development within the UAE’s shallow-water Ghasha concession. Located some 190 km northwest of Abu Dhabi, the first phase will see gas flow from the Dalma field, followed by production from the Hail and Ghasha fields, with combined output expected to boost the UAE domestic gas supply by 1.5 Bcf/D by decade’s end. Set aside for several decades due to high levels of H2S and CO2, ADNOC is now pushing to make natural gas a bigger part of its energy strategy and has thus proudly positioned this multibillion-dollar project as the world’s largest sour-gas development. As operator, ADNOC holds a 70% stake in the concession alongside partners Eni (10%), PTTEP (10%), OMV (5%), and Lukoil (5%). ADNOC has also committed to making Hail and Ghasha the first major gas fields to operate with net-zero emissions, supported by substantial investments in carbon capture technology and the use of nuclear power. Yet there may be more to Ghasha’s supply-side potential, thanks to a team of engineers and subsurface experts who weren’t ready to give up on a stubborn rock. Discovered in 1979, the Pre-Khuff formation is a gas-rich sandstone that, though free from H2S, presents other challenges that have so far kept it from reaching commercialization. “The Pre-Khuff has performed well across the region—in Saudi Arabia and Qatar—but here in the UAE, we’ve faced 4 decades of unsuccessful attempts to unlock its potential,” said Jasim Ali Alloghani, ADNOC’s subsurface manager for the Gasha concession. He explained the complexities of the Pre-Khuff formation center around its depth, temperature, and tightness. Offshore the UAE, the Pre-Khuff formation is found 16,000 ft below the mudline where temperatures are more than 350°F and reservoir pressures exceed 10,000 psi. The sandstone is also rich in clay, with estimated clay content ranging from 10 to 40%. This leaves the rock with an upper porosity of about 12%, and a permeability range of 0.01 to 1 mD. The difficulties associated with the Pre-Khuff formation intensify from there. With a Young’s modulus of around 10 million psi, the rock is more than twice as stiff as much of the prolific Wolfcamp Shale in the Permian Basin that spans Texas and New Mexico in the US. The formation is also dominated by natural fractures and varying fracture gradients. Additionally, wellbore washouts while drilling in the deep reservoir have hindered geomechanical data acquisition. ADNOC has also found that the state of stress changes both laterally and vertically, i.e., anisotropy, due to the reservoir’s structural deformation. Additionally, ADNOC has faced challenges with designing effective completion designs due to limited technology and expertise. However, ADNOC’s fortunes with the Pre-Khuff shifted in early 2023 when the company executed the first successful multistage hydraulic fracturing treatments ever performed offshore Abu Dhabi. ADNOC reported a five- to 10-fold increase in initial flow rates from Pre-Khuff wells compared with initial attempts.

The price elasticity of natural gas demand of small consumers in Germany during the energy crisis 2022

Understanding how consumers respond to turbulent market conditions is crucial for planning security of natural gas supply. This paper estimates the price elasticity of demand of small consumers in Germany in the period with both high price fluctuations and a fear of natural gas shortage in the aftermath of the Russian invasion of Ukraine. Using granular data between 2018 and 2023, we estimate an Auto Regressive Distributed Lag (ARDL) time series cointegrating model. We find a price elasticity of demand for natural gas of -0.01 for wholesale prices and -0.04 for retail prices. Additionally, we quantify the effects of weather conditions and public awareness on the energy crisis. The results suggest i) that extreme price changes would be required to trigger short-term demand adjustments, and ii) demonstrate the importance of public attention on the crisis situation.

Energy Management Strategies for Hybrid Propulsion Ferry with Different Battery System Capacities

The International Maritime Organization (IMO) has been continuously strengthening environmental regulations to reduce greenhouse gas emissions from ships, which has led to increased attention on hybrid ship propulsion systems combining hydrogen fuel cells and batteries. This study analyzes the energy management strategy of a hybrid ship propulsion system in relation to changes in the battery system’s energy capacity. The target vessel was set as a 500 kW-class ferry operating for 24 h, and the maximum current rate (C-rate) and effects of the equivalence factor, which are key elements of the energy management problem, in relation to changes in energy capacity were investigated. The results show that while changes in the battery system’s energy capacity do not significantly affect the optimal operating point of the hybrid ship propulsion system, they are highly influenced by the response speed of the hydrogen fuel gas supply system and fuel cells, as well as the maximum C-rate required by the battery system. Furthermore, the equivalence factor, one of the key parameters in the optimization problem, tends to vary depending on the degree of charging and discharging, as it affects the equivalent fuel consumption of the battery system.

Analysis of Incentive Compatibility Mechanism for Content Services of Gas Companies under the Background of Universal Service

In recent years, the issue of gas billing has attracted widespread attention from the public, leading to a crisis of trust in gas public goods and services. From the perspective of universal service, based on the characteristics of the gas supply industry under monopoly conditions, this paper analyzes the reasons for the lack of motivation of gas companies to provide perfect content services, and uses incentive theory to explore the incentive compatibility mechanism of gas companies' content services, in order to promote gas companies to use the Internet, big data, cloud computing technology to provide consumers with perfect content services, so as to enhance social harmony and stability.

Suppression strategy for metal droplet overlapping fusion defects caused by droplet impact dynamics under coaxial shielding gas

High-precision droplet overlapping under coaxial shielding gas is a prerequisite for automated and lightweight metal micro-droplet deposition manufacturing. Unfortunately, the opening shielding environment exposes metal droplets directly to the atmosphere. Droplet overlapping fusion quality would be affected due to the coupling effects of impact dynamics, thermodynamics, and oxidation. In this study, based on experiments and theoretical modeling of molten droplet impact dynamics, a strategy to suppress droplet overlapping fusion defects under coaxial shielding gas was proposed for the first time. Results show that at lower shielding gas rates, molten droplet retraction, recoil, and oscillation would weaken or vanish due to the oxide film's self-limiting effect. This limits the improved model's accuracy in predicting the droplet spreading factor in lower shielding gas supply rates. The weakened droplet dynamic behaviors at low shielding gas supply rates would magnify the length and height defects of droplet overlapping, which is particularly evident at a small printing step distance. Finally, a quality mapping for different printing parameters is established, effectively suppressing overlapping defects and ensuring fusion quality through metallurgical bonding. This work could provide a solid evidence base and theoretical guidance for high-quality metal micro-droplet deposition manufacturing under an opening shielding environment.

Geospatial Life Cycle Analysis of Greenhouse Gas Emissions from US Liquefied Natural Gas Supply Chains

Geospatial Life Cycle Analysis of Greenhouse Gas Emissions from US Liquefied Natural Gas Supply Chains

E-Defense Excitation Experiments for a High-Pressure Water Levitation Seismic Isolator Using a 600kN Superstructure

ABSTRACT This study discusses a high-pressure water levitation horizontal seismic isolator designed to prevent the shutdown of critical infrastructure, such as gas supplies, during earthquakes. The device employs a novel method wherein high-pressure water is ejected from levitation pads onto sliding surfaces, elevating the superstructure by approximately 50 μm. In experiments involving a 600 kN superstructure subjected to recorded seismic motions, horizontal acceleration was reduced by a factor of approximately 1/100. Analytical results indicate that the acceleration reduction rate shows an improvement of about 30% compared to conventional methods, such as laminated rubber bearings. Furthermore, integrating this device with a vertical isolator, currently in development, shows promising potential for ensuring the continuous operation of infrastructure during seismic events.

THE IMPACT OF ELECTRIC POWER OUTAGE ON THE PROFITABILITY OF SMALL BUSINESSES IN NIGERIA: A CASE STUDY OF GWAGWALADA TOWN

This study examined the impact of electric power outages on the profitability of small businesses in Nigeria, using 50 randomly selected small businesses in Gwagwalada town as a case study. A Logit regression model was adopted, incorporating a mix of qualitative and quantitative variables. The Maximum Likelihood (ML) estimation method was utilized in estimating the Logit model. Findings from the estimated Logit model showed that electric power outages had a negative impact on the profitability of small businesses in Gwagwalada town, while small businesses' expenses on alternative electricity power supplies had a positive impact on profitability. However, both electric power outages and small businesses’ expenses on alternative electricity power supplies in Gwagwalada town had an insignificant impact on the profitability of the small businesses. Based on the findings of the study, it was recommended, among other things, that the government should undertake a national demand study to determine the exact electricity requirements to meet demand in the short, medium, and long terms. Furthermore, an integrated least-cost system expansion plan should be developed for the efficient deployment of the Nigerian electricity industry in the medium and long terms. There is also a need for diversification of electricity generation to improve the security of supply, as well as the development of capacity to generate electricity closer to demand centers to reduce technical losses. Additionally, the government should explore and develop measures to ensure the long-term supply of gas for electricity generation.

Energy consumption analysis of building air-conditioning systems using centrifugal compressor with gas bearing under annual operating conditions

The water chiller using centrifugal compressor with gas bearing is an important development direction for building energy saving, but the additional refrigerant cycle for bearing and motor colling leads to more complex performance especially under the various operating condition. Based on the heating and cooling loads of a building in Nanjing and the local climate conditions, this paper innovatively establishes an air conditioning system model using centrifugal compressor with gas bearings (CCGB), and analyzes the performance of air-cooling and water-cooling methods. Considering the heating and cooling loads, the annual energy consumption of two systems was compared consider the climate condition. The results show that the COP of water-cooling system is larger than that of air-cooling system due to the better heat transfer condition. The larger power consumption of compressor for air-cooling system leads to the larger motor cooling load. The cooling methods have obvious influence on the vapor-injected mass flow rate, but have small impact on the mass flow rate of motor cooling and bearing gas supply. The energy efficiency of air-cooling and water-cooling system in summer are 3.77 and 5.12 respectively, and the total energy consumption in the whole year are 32.4 tons and 33.5 tons of standard coal.

Ідентифікація одиночного турбулентного газового факелу засобами й методами комп’ютерного зору в імітаційній установці топки котлоагрегата

The issue of optimizing the combustion process is quite relevant for modern thermal power engineering and arises even more in the context of the restoration and reconstruction of the energy infrastructure of Ukraine. The use of computer vision tools will allow directly determining the qualitative characteristics of the gas combustion process in real time without relying on measurements of secondary parameters, the change in values ​​of which is quite inertial. The process of turbulent torch combustion itself, which occurs in industrial boiler units, is poorly studied and does not allow for its modeling in advance. Therefore, an important stage in the construction of any control and management system is the identification of the object by conducting experimental measurements, on the basis of which the parameters and forms of dependencies will be determined to obtain a mathematical model of the process. In the course of the current work, the process of identifying the methane torch combustion process inside the simulated installation of the boiler unit furnace (combustion chamber) is considered. According to the results of a series of experiments, it was possible to obtain the dependences of the characteristics of the visual manifestation of the combustion process, recorded by a video camera, on its current combustion mode, which was determined by the satisfaction of the stoichiometric ratio of gas and air supply to the burner with preliminary mixing of the gas-air mixture. In general, the dependences of the spectral composition of the radiation, the area of ​​the torch and its luminosity on the combustion mode were obtained. The dependences are characterized by significant nonlinearity when the torch transitions to the mode of significant chemical underburning, but are easily linearized in the area of ​​interest, which is located near the point of satisfaction of the stoichiometric ratio. The results of this article demonstrate the suitability of the parameters obtained by computer vision for their use in traditional control systems. Taking into account the speed of obtaining such data, we can conclude that it is appropriate to create a control system based on combustion parameters completely obtained by computer vision methods and means.

PREDICTIVE ANALYTICS OF THE OBJECTS OF THE GAS DISTRIBUTION SYSTEM OF THE REPUBLIC OF BELARUS: CURRENT STATUS AND PROSPECTS

The article highlights the experience of creating, applying and developing a digital twin of the gas distribution system of the Republic of Belarus. The effect of using IT technologies in the field of gas supply as an integral part of the overall engineering infrastructure of the country is shown. The principles of the construction and functioning of the existing set of software tools that ensure the production activities of gas supply organizations and the management apparatus of GPO "Beltopgaz" are described. Scientific and methodological approaches to the creation of predictive analytics tools for objects of the gas distribution system of the Republic of Belarus are formulated.

PEMFC Gas-Feeding Control: Critical Insights and Review

Proton exchange membrane fuel cells (PEMFCs) are currently a relatively mature type of hydrogen energy device due to their high efficiency and low noise compared to traditional power devices. However, there are still challenges that hinder the large-scale application of PEMFCs. One key challenge lies in the gas supply system, which is a complex, coupled nonlinear system. Therefore, an effective control strategy is essential for the efficient and stable operation of the gas control system. This paper aims to provide a comprehensive and systematic overview of the control strategies for PEMFC anode and cathode supply systems based on an analysis of 182 papers. The review covers modern control theories and optimization algorithms, including their design, objectives, performance, applications, and so on. Additionally, the advantages and disadvantages of these control methods are thoroughly evaluated and summarized.

CHARACTERISTICS OF THE DEVELOPMENT OF THE GAS SUPPLY SYSTEM IN THE REPUBLIC OF ARMENIA

Gas distribution and transportation networks make up the gas supply system. Providing natural gas to the public and the economy is the primary objective of the gas delivery system. Every nation's gas supply network is strategically vital since the cost of natural gas directly impacts the goods and services that are produced and rendered there. It is true that developed nations are looking for innovative technology for natural gas extraction because it is a non-renewable resource. Founded during the Soviet era and throughout multiple phases of development, the Republic of Armenia's gas supply system is a component of the worldwide network. The Public Services Regulatory Commission and the Armenian government, through the Ministry of Territorial Administration and Infrastructure, oversee the country's gas supply industry. The article discusses the Republic of Armenia's domestic natural gas market's supply and sales, its background and present state, investment initiatives, and features that increase the system's operational efficiency.

Implementation Status and Suggestions of “Coal-to-gas” Policy in Beijing-Tianjin-Hebei Region of China

With the acceleration of industrialization for the past few years, the level of air pollution has also increased significantly. The Beijing-Tianjin-Hebei region is one of the regions that need to be improved urgently. The air pollutants produced by coal burning are the main source of pollution in this region, so it is of great practical necessity for the Beijing-Tianjin-Hebei region to replace coal burning with clean energy. At present, the status of the "coal-to-gas" policy of the Beijing-Tianjin-Hebei region has achieved remarkable results. With the strong support of the government, air pollution has been effectively improved. However, there are still many problems such as "one-size-fits-all" policy, imperfect financial subsidy mechanism, tight gas source, differentiated scope of policy implementation, and hidden dangers of rural equipment safety. For these reasons, the government should formulate differentiated policies according to local conditions, implement "coal-to-gas" and "coal-to-electricity" synchronously, improve the subsidy mechanism, strengthen technical and equipment support, enhance gas supply security, stabilize gas price and strengthen publicity and training.

A Thermal Model for a Hybrid Gas Bearing System in Oil-Free Turbochargers

Abstract With little drag friction, gas bearings operate at high rotor speed and high temperature and thus enable long operating life along with material damping for mechanical energy dissipation. However, most computational tools for modeling gas bearings are not accessible to bearing manufacturers or potential end-users, and the models are restricted to specific geometries and operating conditions or are missing important features, thus limiting their utility. This paper presents the thermal energy transport in a hybrid gas bearing (HGB) for oil-free turbochargers (TCs) with integrated heat and fluid flow models to produce a comprehensive thermohydrodynamic analysis predictive tool and to design and evaluate air-lubricated gas bearings by predictions and experiments. An efficient algorithm couples the solution of the Reynolds equations and the thermal energy transport equations in the film between the rotor and a pad of the hybrid gas bearing and updates the temperature-dependent viscosity and film thicknesses during the iterative process. The balance of the bulk-flow thermal energy transport is that the summation of drag power losses plus heat convection into the film equals to the thermal energy advected by the film. The predictions show that the film temperature varies along circumferential and axial directions by following the balance of the energy flows and shows high film temperatures corresponding to the small film thicknesses and thus large film pressures. The predicted result also shows that the peak temperature of the film occurs at the exit side of the film near the trailing edge of each pad. Thermocouples installed axially at the leading and trailing edges of each pad measure temperature of the film to validate the thermal module. The test repeats and averaged for each rotor speed from 2 krpm to 22 krpm at intervals of 2 krpm, for supply pressure varying along 25 psi to 100 psi, and predicted film temperature matches well with the measured one. The parameters of interest in this analysis include the gas supply condition, bearing configuration, and the gas properties at high altitudes and high rotation speeds. The parametric study results show that the density and kinematic viscosity are the most dominant properties of the gas lubrication for the film temperature.

Comparative analysis of CO2 emission linkages of construction between China and the United States using structural path analysis

Structural Path Analysis (SPA) and the Hypothetical Extraction Method (HEM) are both established methods for studying CO2 emissions. However, their combined application to investigate emission linkages in specific sectors, such as construction, is relatively novel. This research integrates SPA and HEM to explore the CO2 emissions linkages within the construction sectors of China and the United States, providing a comprehensive understanding of how these emissions are interlinked. The findings show that construction sector of Untied States and China is the largest production-based CO2 emissions of construction sector in the world, but the consumption-based emissions of construction sector in China contributes 29.81% of total CO2 emissions, compared to 5.63% in the U.S. This suggests that the carbon footprint of the construction sector is a significant consideration, irrespective of whether it is assessed from the standpoint of production or consumption dynamics. Meanwhile, the development of construction sector has driven the electricity, gas, steam, and air conditioning supply sectors to emit a large amount of CO2 emission in both countries. By analyzing the differences in the main emission linkages and pathways of the construction sectors between China and the U.S., this study provides insights for reducing CO2 emissions in the construction sector and assists policymakers in developing future strategies.