Gas Accumulation Research Articles

Transition from smouldering to flaming combustion of pine needle fuel beds under natural convection

Smouldering transition to flaming combustion (StF) of forest fuels can rekindle wildfires, possibly causing the suppression effort to be useless or the firefighters to be stuck in danger. However, the StF mechanism of forest fuels remains to be elucidated. In this work, the StF of pine needle fuel beds with different bulk densities was investigated experimentally. Two modes of transition are identified: Middle- and Trailing-StF, which occur at the middle and trailing edges of the char region in the fuel bed, respectively. The conditions for the occurrence of both modes include (1) the length of the char region exceeding a critical value and (2) a hot glowing area (strong secondary char oxidation area) appearing before StF. An overhang structure is also necessary to induce Trailing-StF. These conditions are interpreted in terms of the permeability of fuel beds, which affects the diffusion and convection supply of oxygen for smouldering. Middle-StF occurs due to sufficient oxygen diffusion and convection supply in the middle of the char region with large pores. In Trailing-StF, the overhang structure forms a region with high permeability, which significantly enhances the convection mass flow rate of oxygen and provides a favorable space for the accumulation of mixed combustible gases. The oxygen mass flow rate leading to both StF modes is in the order of 10−2 g/s.

Overexpression of PbrGA2ox1 enhances pear drought tolerance through the regulation of GA3-inhibited reactive oxygen species detoxification and abscisic acid signaling

Drought stress is a devastating natural disaster driven by the continuing intensification of global warming, which seriously threatens the productivity and quality of several horticultural crops, including pear. Gibberellins (GAs) play crucial roles in plant growth, development, and responses to drought stress. Previous studies have shown significant reductions of GA levels in plants under drought stress; however, our understanding of the intrinsic regulation mechanisms of GA-mediated drought stress in pear remains very limited. Here, we show that drought stress can impair the accumulation of bioactive GAs (BGAs), and subsequently identified PbrGA2ox1 as a chloroplast-localized GA deactivation gene. This gene was significantly induced by drought stress and abscisic acid (ABA) treatment, but was suppressed by GA3 treatment. PbrGA2ox1-overexpressing transgenic tobacco plants (Nicotiana benthamiana) exhibited enhanced tolerance to dehydration and drought stresses, whereas knock-down of PbrGA2ox1 in pear (Pyrus betulaefolia) by virus-induced gene silencing led to elevated drought sensitivity. Transgenic plants were hypersensitive to ABA, and had a lower BGAs content, enhanced reactive oxygen species (ROS) scavenging ability, and augmented ABA accumulation and signaling under drought stress compared to wild-type plants. However, the opposite effects were observed with PbrGA2ox1 silencing in pear. Moreover, exogenous GA3 treatment aggravated the ROS toxic effect and restrained ABA synthesis and signaling, resulting in the compromised drought tolerance of pear. In summary, our results shed light on the mechanism by which BGAs are eliminated in pear leaves under drought stress, providing further insights into the mechanism regulating the effects of GA on the drought tolerance of plants.

Organized natural air exchange in the room for the maintenance of animals

The organization of effective ventilation is a key task in the construction and reconstruction of animal housing. Insufficient air exchange in the room leads to the accumulation of harmful gases released by cows: water vapor, methane, nitrogen compounds and carbon dioxide, which causes not only deterioration of animal health, but also increases the heat hazard of premises. The article aims to substantiate the use of natural air exchange in the warm season in agricultural buildings for milk production. The required opening angle of the swing-out flaps of the window openings was determined to achieve a normalized air flow in the animal housing. The option of organizing an additional air flow through the opening of the entrance gate and its effect during the summer period of the year is considered. Studies have shown that the inflow of air through the external gate significantly increases the overall air exchange in the premises for cattle. As a result of the study of the issue, the article presents a method for determining the necessary air exchange for the assimilation of excess heat, moisture and carbon dioxide emissions by animals.

P-Type β-Ga2O3 film room-temperature NH3 gas sensors with fast gas sensing and a low limit of detection

p-Type β-Ga2O3 films room-temperature NH3 sensors possess fast gas sensing and low limit of detection due to the fast exothermic reactions between NH3 gas and surface hole accumulation layer.

Smart IoT System for Gas Monitoring and Environmental Control in Poultry Farms

This paper focuses on a gas-monitoring and environmental control system that utilizes Internet of Things technology for poultry farms. Its main objective is to tackle the issue of toxic gas formation, specifically ammonia and hydrogen sulfide. The system is based on an ESP32 microcontroller and is capable of detecting ammonia, hydrogen sulfide, as well as temperature and humidity levels. Relay modules are utilized to actively manage exhauster fans and submersible pump motors in order to prevent the accumulation of gas and regulate temperature, thereby ensuring the well-being of both the birds and employees at the poultry farm. When there is an unexpected buildup of gas, a GSM module sends immediate warnings to farmers via SMS. The system transmits the collected data to the cloud server. Consequently, the data can be remotely accessed and utilized for the purposes of monitoring, storage, and analysis. Therefore, integrating IoT in this manner for gas monitoring and environmental control at poultry farms serves to address the crucial parameter that needs to be maintained. This system enables the control of conditions in a poultry house as needed. Consequently, farms are able to achieve higher productivity while minimizing energy and time requirements.

A Case of Mechanical Intestinal Obstruction Combined with Hepatic Portal Vein Gas Accumulation

A Case of Mechanical Intestinal Obstruction Combined with Hepatic Portal Vein Gas Accumulation

Due consideration of the breakup and direct reaction mechanisms within (d, p), (d, 2p), (d, xn2p), and (d, xn) reactions

Suitable account of available excitation-function of deuterons interaction with target nuclei components of candidates materials for the ITER fusion reactor, the European DEMO fusion reactor, and the IFMIF-DONES Irradiation Facility has been proved by consistent analysis of the reaction mechanisms involved in the complex deuteron-nucleus interaction. In this work the attention has been focused on the analysis of the deuteron activation cross sections related to the gas accumulation, (d, p), (d, 2p), (d, xn2p), and to the strong neutron emission, (d, xn), interaction processes of interest for the radiation damage and shielding design studies devoted to the structural materials selection. The key role of direct interactions, i.e., breakup, stripping and pick-up processes is stressed out by the comparison of data with theoretical and evaluation predictions.

Fundamentals of forecasting explosive gas accumulation formation in working areas of coal mines

This article presents a methodological approach to solving the problem of predicting local methane accumulations in order to prevent occupational injuries resulting from explosions of methane-air mixtures. On the basis of the analysis of accidents that occurred in coal mines and industrial injuries of miners (mine workers) it is established that the leading role belongs to explosions of methane-air mixtures. The method/methodology considered in the article is based on a comprehensive analysis, first of all, of both mining and geological and other influencing factors and conditions of operating mines of the Pechersk coal basin, as well as aerogas-dynamic processes of mass transfer of air flows in mine workings. The assumption about influence of mining equipment on the process of formation of methane accumulation sites is made. The algorithm of consecutive actions of managerial engineering and technical personnel to reduce industrial injuries is proposed. The developed algorithm implies the use of applied software for modelling aerogas-dynamic processes in the mining excavation operating region. FlowVision and ANSYS Fluent application software packages were selected to determine the methane accumulation locations based on the analysis of existing application programmes.

Refining hydrocarbon reserve location using modern geodynamics

The paper considers some aspects of the theoretical prerequisites for the influence of geodynamic processes on the distribution of hydrocarbon accumulations in natural megareservoirs. The most interesting part to study is the part of Central Siberia, where quite a lot of large and unique oil and gas fields have been discovered in a relatively small area. It is shown that hydrocarbon deposits in the study area are organized into groups according to the size of reserves. This can be explained by geodynamic processes occurring during the geological history of the region. The features of the river network pattern are interpreted as local geodynamic settings of the «pushed block» type. The relationship between the parameters of local geodynamic settings and the scale of oil and gas accumulation is noted. Keywords: geodynamic processes; large and unique reserves; natural mega-reservoirs; geodynamic conditions; scale of oil and gas accumulation.

Examination of Air Quality of Dr. Sami Yağız Street in Niğde

Air pollution can be defined as the accumulation of gas, air, or particulate matter released as a result of fuel residues and chemical processes in the atmosphere in amounts that harm the lives of living things. Rapid urbanization, industrialization, increase in the number of motor vehicles, meteorological conditions, fuels used for heating, and the spread of industrial establishments and thermal power plants play an important role in the increase in air pollution. Air pollution is a major environmental problem affecting people in both developed and developing countries, and it is estimated that megacities in developing countries, and a quarter of the world's population are exposed to unhealthy concentrations of air pollutants. People living in cities with high outdoor air pollution are more likely to suffer from heart disease, respiratory problems, and lung cancer than those living in urban areas with clean air. In the industrialized western world, urban air pollution is in some respects in its final stages, with a dramatic decline in SO2 and soot levels. The increase in the number of private vehicles is a newly emerging problem. Rapid urbanization in most developing countries has so far led to uncontrolled growth and environmental degradation. Air pollution levels are still rising in many cities. In this study, air quality was tried to be measured along Dr. Sami Yağız Street, which is one of the most heavily used areas of Niğde. H2S, O2 and CO measurements were made at 25 points at equal intervals on both sides of the street. Measurements were made at a total of 4 different time periods per day. The obtained values were transferred to ArcGIS 10.3 software and maps were produced. Measurement of gases other than H2S is not distributed homogeneously along the street, and traffic density and the businesses on the sides of the street cause changes in the rates of the gases.

Domanic deposits as an integral part of the reservoir of the Astrakhan carbonate massif

The object of the study of this article is the high-carbon domanic deposits of the Astrakhan carbonate massif (Caspian oil and gas province), which are assigned the role of a zonal tire isolating the reservoir of the Lower Devonian-Fransk complex. The authors study the properties of these rocks that affect the insulating ability of the deposits under consideration: multilayer structure, the effect of complex stratification, the appearance of epigenetic clay material. The results of the analysis indicate that uneven concentrations of organic matter in the domanic tire predetermine the mosaic in the manifestation of the strength properties of these rocks. The peculiarity of the domanic strata is emphasized – its enrichment with solid organic matter, which is one of the rock-forming components. The opinion on the important oil and gas-mother functions of domanic deposits is supported. The ideas of the geological role of domanic rocks as (1) the oil and gas mother strata, (2) a reservoir for autochthonous hydrocarbons, (3) a regional tire for underlying sediments are expanding, which emphasizes the importance of the formation of hydrocarbon accumulations within the considered strata by the in situ mechanism. Suggestions are made on the directions of further research detailing the possibilities of domanic deposits in oil and gas formation and oil and gas accumulation. Keywords: domanic rocks; tire; reservoir; organic matter; hydrocarbons; Caspian oil and gas basin.

Experimental study of the natural deposition of submicron aerosols on the surface of a vertical circular tube with non-condensable gases

This paper constructed an experimental platform containing a space heat exchanger tube, and performed aerosol deposition experiments under different deposition mechanisms. The objective was to study the effect of the passive containment heat removal system on the natural deposition of submicron aerosols during post-accident operation of severe accidents. By controlling the variables, we obtain the impact of gravity deposition, thermophoretic, and diffusiophoresis deposition mechanisms on submicron aerosols in the presence of a space heat exchanger tube using the experimental data stripping method. The study found that the gravitational settling rate of aerosols in two-phase mixtures at the same temperature and pressure is about 1.5 times higher than in dry air. Although submicron aerosols are subject to thermophoretic settling in the presence of temperature differences, due to the small surface area of the heat exchanger tube, the potential thermophoretic sedimentation accelerating effect on the particles can be ignored if the mixed gas temperature difference is within 2000 K/m. Unlike the steam condensation on the flat plate surface, when vapor condenses on the heat exchanger tube surface, as the steam proportion and condensation rate increase, it is easy to cause the accumulation of non-condensable gas. This phenomenon can reduce the reverse diffusion slip of the particles and enhance the influence of Stefan flow in the diffusionphoresis deposition process. The above effects make the experimental results of aerosol diffusiophoresis deposition closer to the SF model when the vapor fraction is 70 %. When the vapor fraction is 50 %, the predictions of the WM model, which considers the average mass flow of the gas mixture, are more applicable. When the condensation rate continuously increases, the convective mass transfer of vapor condensation will be enhanced, and the deposition rate of particles will be further enhanced.

Using a model of zonal drainage of an artificial gas deposit for analytical control of gas volumes in reservoirs of UGS

One of the main tasks of the analysis of gas storage in aquifers-reservoirs is the operational control of drained volumes of gas, the value of which largely depends on the technological and technical and economic indicators of the creation and operation of UGS. An effective tool for solving this problem is the use of gas-hydrodynamic proxy models of formations. One of such models is presented, which, taking into account the implemented system of group (by assembly points) placement of vertical production wells, can be briefly described as a model of zonal drainage and seasonal interzonal gas flows in the reservoir. An example of calculations of changes in the cyclic operation of UGS of gas-saturated pore volumes and gas volumes in different drained zones, including in the peripheral poorly controlled zone of the formation, taking into account seasonal interzonal gas flows, as well as the volumes of man-made gas accumulations in the control horizons formed as a result of interplastic flows is given.

Henry's constant of helium in liquid alkali metals

The determination of the solubility of helium in liquid lithium and in lead-lithium eutectic systems is of crucial importance for the assessment of the reliability, safety and efficiency of future nuclear reactor plants based on fusion technology. In this way, an important aspect to be considered concerns the possibility of accumulations of gas inside the so called breeding blankets of the reactors, due to the low solubility of helium, leading to potentially undesired effects. In the present work we have performed molecular dynamics simulations in order to examine the characteristics of the solubility of helium in alkali metals along a temperature interval that covers near ambient conditions up to temperatures of the order of a 1000 K. Our methodology relied on the classical Kirkwood perturbative approach, which involves the gradual coupling between the infinite diluted He atom and the solvent. Such insertion proceeds along three stages that involved a previous incorporation of a softly interacting cavity that prevented singularities due to the harshly repulsive nature of the actual He-Li potential. Simulated structure factors predicted by the force fields of the different alkali metals were found to be in excellent agreement with available experimental information. Moreover, at all thermal conditions, our results of Henry's constants predict a steady volatility reduction with increasing temperatures, in good agreement with available experimental data. Furthermore, Henry's law volatility constants increase as the sizes of the atoms of the host alkali metals become more comparable to the size of the He atom (the predicted solubility increases with the size of the alkali atoms), and are coherent with the scarce experimental data available.

Comparative Study of the Characteristics of Lower Cambrian Marine Shale and Their Gas-Bearing Controlling Factors in the Middle and Lower Yangtze Areas, South China

This study comparatively analyzed the geological, geochemical, reservoir, and gas-bearing characteristics of the lower Cambrian marine shale in the Middle and Lower Yangtze regions. The main factors controlling the gas-bearing properties of the shales were identified, and the favorable and unfavorable conditions for shale gas accumulation are discussed. The results show that the organic carbon contents and thermal evolution degree of the organic matter in the lower Cambrian marine shale in the Lower Yangtze area were higher than those generally found in the Middle Yangtze area. The brittle mineral composition of the Middle Yangtze area was typically low silicon and high calcium, whereas the Lower Yangtze area was characterized by high silicon and low calcium. The development of micropores in the Lower Yangtze area was poorer than in the Middle Yangtze area, with the organic pores being particularly underdeveloped. The adsorption capacity of shale in the Lower Yangtze area was obviously higher than in the Middle Yangtze area. It was considered that the organic carbon content, thermal evolution degree, and molecular structure of kerogen were the main factors that controlled the adsorption properties of the shale. In addition, the Lower Yangtze area suffered a stronger tectonic transformation and frequent magmatic activity, and the preservation conditions were inferior to those in the Middle Yangtze area.

Tectonic movements of the Yanshan-Himalayan period in the northern Longmenshan and their impact on tight gas accumulation of the Shaximiao formation in the Qiulin structure, China

The Jurassic strata constitute a focal area for recent exploration and development of tight gas reservoirs in the western Sichuan Basin. This study investigates the Jurassic Shaximiao Formation in the northern Longmenshan in the Western Sichuan basin, focusing on tight gas reservoirs. The research integrates core and outcrop observations, seismic interpretations, and burial history analyses to understand hydrocarbon source rocks, sedimentation, reservoir characteristics, and structural characteristics. The impact of Yanshan-Himalayan tectonic movements on tight gas reservoir accumulation in the Shaximiao Formation is dissected, primarily around the Qiulin structure. The Western Sichuan Depression basin’s formation is influenced by gravitational gliding tectonics, which can be classified into the ‘Three Zones and One Belt,’ with Longmenshan in the frontal belt. Burial history analysis reveals distinct processes in the foreland belt and the depression basin. In the Qiulin area, gas reservoirs in the Shaximiao Formation are mainly charged by source rocks from the Xujiahe Formation. Tectonic movements play a significant role in creating favorable reservoirs and conditions for hydrocarbon migration and preservation. Natural gas accumulation is primarily controlled by fault connectivity to hydrocarbon sources and effective reservoir thickness. Gravitational sliding tectonics have shaped a fluvial-lacustrine environment for the Shaximiao Formation, with fluvial sand bodies acting as favorable reservoir zones. Small-scale normal faults formed by tectonic movements serve as conduits for natural gas migration. The research findings are of significant guidance for the exploration and development of tight oil and gas resources in western Sichuan basin.

Geochemical characteristics and genesis of the Ordovician sub-salt natural gas in the Ordos Basin, China

A significant amount of natural gas resources has been discovered in the Ordovician reservoirs under a thick layer of gypsum-salt strata as a result of ongoing research into deep natural gas in China’s Ordos Basin, however, the genetic type and source of the Ordovician sub-salt natural gas remain contentious. These limits understanding how the geochemical properties of the natural gas in Ordos Basin have evolved and how to best guide future exploration and development. Based on the components, carbon and hydrogen isotopic ratios of natural gas from the latest exploration wells, combined with the geological background, this study systematically analyzed the genetic types and sources of sub-salt natural gas of the central and eastern Ordos Basin. The results show that the Ordovician natural gas is mainly composed of hydrocarbon gases with low content of heavy hydrocarbons and dryness (CCH4/CCH4+) above 0.95, belonging to typical dry gas. Non-hydrocarbon gases mainly include N2 and CO2, and some natural gas samples contained H2S. The Ordovician sub-salt natural gas is primarily a self-generating and self-preserving oil-cracking gas with relatively high maturity (Ro ranging from 1.5% to 2.1%) mixed with coal-derived gas generated from upper-Paleozoic coal with relatively low maturity (Ro ranging from 1.1% to 1.5%). Due to the dual-source hydrocarbon supply, the Ordovician sub-salt reservoirs provide favorable gas accumulation conditions and development prospects. This study offers a reasonable explanation for the anomalous geochemical characteristics of the Ordovician sub-salt reservoirs in the Ordos Basin, and also may serve as a guide for future exploration of natural gas in the carbonate gypsum-salt sedimentary system in other basins.

FLUID MIGRATION IS THE MAIN CRITERION OF THE GAS-BEARING CAPACITY OF THE CLOSED AREA OF MINES OF THE COAL-BEARING FIELDS OF THE DONBAS

Fluid migration is determined, first of all, by different in shape and rank types of dislocations that control compression and rarefaction zones as the main regulators of the distribution of matter and energy in the Earth's crust, represented mainly by Phanerozoic formations, and in our studies by carbon deposits. Gas migration through the newly formed fractures in the massif, due to the impact of mine workings on the upper layers of the lithosphere, allows for the formation of gas accumulations in the near-surface and surface areas. As a result, a significant amount of gas is concentrated in relatively small areas, which will contribute to gas-dynamic phenomena on the surface and can cause significant damage to buildings and human life. Mass transfer of deep fluids is associated with the formation of mineral deposits, including the most explored ones, ore and oil and gas. At the same time, the distribution of gas in coal-bearing massifs is related to their tectonic structure, especially to faulting, which is a way for hydrocarbon-hydrogen mixtures to migrate from deeper horizons. The study of the signs of uneven distribution of fluids under the influence of tectonic and anthropogenic factors was based on observations of new formations in the post-sedimentary geological environment: textural and structural characteristics based on the study of samples, grinds and laboratory observations, which determine the sequence of changes in the material composition of consedimentary and post-sedimentary formations and their relationship in space and time. Unsaturated hydrocarbons, such as ethylene, propylene and acetylene, can be characterised as adventitious gases of hydrocarbon massifs that have taken their current position in the gas component of the hydrocarbon gas mixture by being transported by fractures from deep horizons to the surface.

Dynamic evolution of gas hydrate systems affected by magmatism and Quaternary mass-transport deposits in the Qiongdongnan Basin, South China Sea, and implications for the global carbon cycle

Methane release from hydrate systems has long been considered as one of the important mechanisms for global carbon cycle perturbations and ocean acidification. Here, a Quaternary active gas hydrate system in Qiongdongnan Basin, South China Sea (SCS), has been analyzed by using seismic, logging while drilling (LWD), and core data. The results show that post-rift magmatism led to the reactivation of a magma diapir, and the faults and fractures related to its emplacement created efficient pathways for deep gas migration. The increase in overburden temperature and circulation of deep thermal fluids, especially in the center of the diapir area, thinned the gas hydrate stability zone (GHSZ). The accumulation of natural gas at the base of GHSZ and the thinning of GHSZ decreased the ability of hydrate bearing sediments to seal free gas and lead to hydraulic fracturing. The free gas entering the GHSZ was buried by mass transport deposits (MTDs) and then formed hydrates due to the overlying compaction and so further sealed the free gas under the GHSZ. This study indicates that two contrasting mechanisms are acting: (1) tectonic activity and magmatism favor the release of deep natural gas which may reach the ocean, (2) MTDs and the overlying compacted sections act as seals, inhibiting the release of such gas to the ocean. This study shows how the seal capacity of MTDs may reduce methane release from deep-seated reservoirs into the ocean. Given their widespread distribution along continental margins, we suggest that the impact of MTDs on vertical fluid flow, and potential consequences for ocean chemistry and the global carbon cycle, might be underestimated.

Operando Identification of Temperature-Dependent Pore-Scale Gas Saturations in PEM Water Electrolyzers

Polymer electrolyte membrane (PEM) water electrolysis is a promising solution for the chemical storage of intermittent renewable energy in the form of clean hydrogen (1). For the widespread adoption of this technology, the efficiency of PEM electrolyzers must be improved through informed material design and tailored operating conditions to compete with incumbent carbon-emitting technologies (2). A main source of inefficiency is related to mass transport losses, where oxygen gas, a by-product of the anode reaction, accumulates in the anode porous transport layer (PTL) and hinders reactant liquid water delivery to reaction sites (3). Although extensive studies have explored this two-phase flow phenomenon, the consideration of operating temperature on gas accumulation in the PTL adds further complexity. A duality in temperature effects has been reported in the literature where increasing the operating temperature may encourage gas coverage which obstructs liquid water transport, but it may also enhance liquid water delivery due to favorable fluid property changes in viscosity and surface tension (4). Efforts have been made previously to reconcile these competing observations using 2D visualization methods (5), however a closer investigation using 3D visualization techniques will provide valuable pore-scale insights in the comprehensive understanding of the impact of operating temperature on gas transport in the PTL, and subsequently mass transport losses in the PEM electrolyzer.In this work, we employed operando X-ray computed tomography (CT) to visualize three-dimensional (3D) pore-scale gas saturations in the PTL at various industrially relevant operating conditions. Specifically, a custom in-house electrolyzer was imaged with synchrotron CT at five different temperatures (40°C, 50°C, 60°C, 70°C, 80°C) and current densities ranging from 0.5 A/cm² to 4.0 A/cm² with 0.5 A/cm² incremental steps. Electrochemical impedance spectroscopy and Tafel measurements were also acquired to characterize the relationship between gas distributions and corresponding mass transport overpotentials. Considering X-ray transparency, a model PTL made of carbon fibers was used to achieve sufficient contrast to quantify water and gas in the obtained images. Using precise volume registration and subtraction methods, pore-scale gas distributions in the PTL were quantified to reveal changes in bubble accumulation and coverage area at different operating temperatures and over operation time. The novel insights from this work will aid in our understanding of the complex relationship between operating temperature and multiphase flow phenomena in the PTL, which is vital for tailoring operating conditions of PEM electrolyzers to curtail the costs of green hydrogen production.