Search Results (333)

The modern metallurgical industry produces approximately 90% of the volume of all produced steel; for this, integrated technology based on fossil materials such as coal, fluxes, and especially iron ore is used. This industry generates large amounts of waste and by-products at almost all stages of production. Alternative iron and steel production technologies based on iron ore, methane, or pure hydrogen are also not waste-free. To ensure sustainable waste management, efforts are made to seal processes as well as capture and recycle dusty waste. This work presents the results of research on the processing of sludge resulting from the dedusting of the basic oxygen furnace (BOF) process and landfilling in a lagoon. The work discusses the treatment of fine dusty sludge hydrated to 26–60% H₂O, to which various amounts of caking agents were added; also discussed are the rheological characteristics of the tested suspension systems, the possibility of forming these systems into larger fractions, and rapid drying using 100–600 W microwaves with a drying time of 1–9 min. The aim was to identify, describe, and characterize the parameters of the agglomeration process and obtain a product that was durable enough to transport and dose into slag baths in order to reduce iron oxides in liquid phases. During the research, completely dried briquettes with an appropriate strength were obtained. The study demonstrates that microwave drying at 300 W for 6 min achieved complete drying with a weight loss of 35%, whereas a higher-power treatment at 750 W for 2 min enhanced compressive strength by up to 95% and reached 15 N/psc, which was comparable with green iron ore pellets. This approach offers a sustainable alternative to traditional methods, but with a reduced drying time. Full article

The marine gas hydrates within seabed sediments and their subsequent extraction may cause landslides. Predicting landslides in hydrate-bearing sediments is particularly challenging due to the intricate nature of the marine environment. To address this issue, we have developed a Lagrangian gradient smoothing method (L-GSM) based on gradient smoothing techniques. This approach effectively eliminates the tensile instability inherent in the original Smoothed Particle Hydrodynamics (SPH) method used for modeling solid flow. Then, we applied the L-GSM to investigate the mechanics of hydrate-bearing sediments by integrating a constitutive equation specific to these sediments, which were modeled based on the artificial methane-hydrate-bearing sediment. The robustness and precision of the L-GSM were verified through various numerical examples. Furthermore, we modeled the landslides associated with hydrate-bearing sediments under varying hydrate saturation levels. The numerical findings revealed that hydrate saturation significantly affects the dynamics of landslide movement. These satisfactory results suggest that the L-GSM has the potential to be applied to geotechnical problems associated with hydrate-bearing sediment. Full article

Laboratory acoustic measurements of hydrate-bearing sediments serve as an important reference for the geological interpretation of seismic exploration data. Tetrahydrofuran (THF) hydrates are relatively easy to form with precise control of hydrate saturation, and they overcome the long time it takes for methane in sediments to form hydrate. However, when THF hydrates are used as a substitute for methane hydrate, their acoustic properties yield different results. This study reports the results of a series of laboratory experiments on the formation of methane and THF hydrate in quartz sand and the evaluation of their acoustic properties. It compares the experimental results with the results of calculations from micro-distribution models of the four hydrates using effective medium theory (EMT). Methane hydrate formed by the excess gas method has higher acoustic velocities than THF hydrate at 0–80% saturation, but at 80–100% saturation, the situation reverses, with THF hydrate having a higher wave velocity. The methane hydrate synthesis process follows a mixed micro-distribution, with grain coating predominating at low saturations, the pore-filling mixing mode dominating at medium saturations, and grain coating dominating at high saturations. In addition, THF hydrate has a slow-velocity growth at low saturation and is dominated by a pore-filling model and a load-bearing model at high saturation. We compared our experimental data with a compilation of similar published results to confirm their reliability and support our conclusions. Both hydrate types exhibit distinct micro-distributions across different saturations. Therefore, when testing the elastic characteristics of hydrate sediments, the distinct hydrate synthesis methods and micro-distribution should be considered, especially when using THF hydrate as an alternative to methane hydrate. Full article

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. Full article

Natural gas hydrates have great strategic potential as an energy source and have become a global energy research hotspot because of their large reserves and clean and pollution-free characteristics. Hydrate saturation affecting the electrical and acoustic properties of sediments significantly is one of the important parameters for the quantitative evaluation of natural gas hydrate reservoirs. The accurate calculation of hydrate saturation has guiding significance for hydrate exploration and development. In this paper, experiments regarding methane hydrate formation and dissociation in clay-bearing sediments were carried out based on the Ultrasound Combined with Electrical Impedance (UCEI) system, and the measurements of the joint electrical and acoustic parameters were collected. A machine learning (ML)-based model for evaluating hydrate saturation was established based on electrical–acoustic properties and a neural network ensemble. It was demonstrated that the average relative error of hydrate saturation calculated by the ML-based model is 0.48%, the average absolute error is 0.0005, and the root mean square error is 0.76%. The three errors of the ensemble network are lower than those of the Archie formula and Lee weight equation. The ML-based modeling method presented in this paper provides insights into developing new models for estimating the hydrate saturation of reservoirs. Full article

Research progress of carbon dioxide applied for methane exploitation from hydrates is summarized, with a focus on advances in molecular dynamics simulations and their application in understanding the mechanism of carbon dioxide replacement for hydrate exploitation. The potential of carbon dioxide in enhancing energy recovery efficiency and promoting carbon capture and storage is emphasized. An overview is provided of the advancements made in utilizing carbon dioxide for methane hydrate exploitation, highlighting its significance. Subsequently, the theoretical foundations and techniques of molecular dynamics simulations are delved into, encompassing key elements such as statistical ensembles, molecular force fields, and numerical solution methods. Through simulations, various characterization parameters including mean square displacement, radial distribution functions, coordination numbers, angular order parameters, and hydrogen bonds are computed and analyzed, which are crucial for understanding the dynamic changes in hydrate structures and the replacement process. Thorough research and analysis have been conducted on the two possible and widely debated mechanisms involved in the replacement of methane hydrates by carbon dioxide, with a particular emphasis on guest molecular replacement and hydrate reconfiguration. These processes encompass the intricate interactions between carbon dioxide molecules and the cage-like structure of hydrates, as well as the rearrangement and stabilization of hydrate structures. Several key issues surrounding the application of carbon dioxide for methane hydrate exploitation are identified, including the influence of thermodynamic conditions, the selection of auxiliary gases, and other potential factors such as geological conditions and fluid properties. Addressing these issues is crucial for optimizing the extraction process and enhancing economic and environmental benefits. A theoretical foundation and technical reference for the application of carbon dioxide in methane hydrate exploitation are provided, while future research directions and priorities are also outlined. Full article

This research deals with gas hydrates formation and dissociation within a marine quartz-based porous sediment and in batch conditions. Hydrates were formed with small-chain hydrocarbons included in natural gas mixtures: methane and also ethane and propane. The dissociation values were collected and provided both graphically and numerically. The results were then compared with the theoretical hydrate-liquid-vapor phase boundary equilibrium for the same species, defined according to the existing literature. The deviation of the experimental results from the ideal ones, associated with the porous sediment, was quantified and discussed. For the scope, the grain size distribution and chemical composition of the sediment were provided along with the text. The results proved that the different size of guest species and, consequently, the different hydrate structures formed, played a relevant role in determining the promoting, inhibiting or neutral behavior of the porous sediment during the process. Full article

Recent studies actively debate oxic methane (CH₄) production processes in water and terrestrial ecosystems. This previously unknown source of CH₄ on a regional and global scale has the potential to alter our understanding of climate-driving processes in vulnerable ecosystems, particularly high-latitude ecosystems. Thus, the main objective of this study is to use the incubation approach to explore possible greenhouse gas (GHG) fluxes by the most widely distributed species of epiphytic lichens (ELs; Evernia mesomorpha Nyl. and Bryoria simplicior (Vain.) Brodo et D. Hawksw.) in the permafrost zone of Central Siberia. We observed CH₄ production by hydrated (50%–400% of thallus water content) ELs during 2 h incubation under illumination. Moreover, in agreement with other studies, we found evidence that oxic CH₄ production by Els is linked to the CO₂ photoassimilation process, and the EL thallus water content regulates that relationship. Although the GHG fluxes presented here were obtained under a controlled environment and are probably not representative of actual emissions in the field, more research is needed to fully comprehend ELs’ function in the C cycle. This particular research provides a solid foundation for future studies into the role of ELs in the C cycle of permafrost forest ecosystems under ongoing climate change (as non-methanogenesis processes in oxic environments). Full article

In this study, we aim to develop advanced machine learning regression models for the prediction of hydrate temperature based on the chemical composition of sweet gas mixtures. Data were collected in accordance with the BOTAS Gas Network Code specifications, approved by the Turkish Energy Market Regulatory Authority (EMRA), and generated using DNV GasVLe v3.10 software, which predicts the phase behavior and properties of hydrocarbon-based mixtures under various pressure and temperature conditions. We employed linear regression, decision tree regression, random forest regression, generalized additive models, and artificial neural networks to create prediction models for hydrate formation temperature (HFT). The performance of these models was evaluated using the hold-out cross-validation technique to ensure unbiased results. This study demonstrates the efficacy of ensemble learning methods, particularly random forest with an R² and Adj. R² of 0.998, for predicting hydrate formation conditions, thereby enhancing the safety and efficiency of gas transport and processing. This research illustrates the potential of machine learning techniques in advancing the predictive accuracy for hydrate formations in natural gas pipelines and suggests avenues for future optimizations through hybrid modeling approaches. Full article

CO₂ fracturing is known as the best solution to improve the efficiency of the CO₂ replacement of natural gas hydrates, but the effect of CO₂ thickeners on CH₄-CO₂ replacement are barely noticed. In this work, the effect of four kinds of CO₂ thickener—including DL-Lactic acid, polyvinyl acetate, ethyl trifluoroacetate and octamethyl trisiloxane—on the CH₄-CO₂ replacement in quartz sand was measured thermodynamically and kinetically. The results show that the majority of the CO₂ thickeners had no effect on the equilibria of the CH₄ and CO₂ hydrates, except for DL-Lactic acid, where the temperature depression caused by the addition of 5.5 wt% DL-Lactic acid was about 0.52 and 0.48 K for the CH₄ and CO₂ hydrates, respectively. In the kinetic measurements, the CH₄-CO₂ replacement was promoted via the addition of the CO₂ thickeners, except DL-Lactic acid. The CO₂ thickeners were suggested to strengthen the CH₄-CO₂ replacement by enhancing the gas exchange in the pore space. Octamethyl trisiloxane, which could promote CH₄ recovery and CO₂ capture at a low concentration, was suggested to be an ideal CO₂ thickener for CH₄-CO₂ replacement. Full article

Hydrate-based gas separation (HBGS) has good potential in the separation of helium from helium-rich natural gas. HBGS should be carried out under a pressure higher than the thermodynamic equilibrium hydrate formation pressure (P_eq) to ensure the formation of hydrate so that the accurate prediction of P_eq is the basis of the determination of HBGS pressure. In this work, the P_eq of the helium-rich natural gases with different helium contents (1 mol%, 10 mol%, and 50 mol%) in gas and different tetrahydrofuran (THF) contents (5 wt%, 10 wt%, and 19 wt%) in liquid at different temperatures were experimentally investigated through the isothermal pressure search method. A new thermodynamic model was proposed to predict the P_eq of helium-rich natural gas. This model can quantitatively describe the effects of THF and helium on P_eq, and it predicts the P_eq of the helium-rich natural gases in this work accurately. The average relative deviation of the model is less than 3%. This model can guide the determination of the operating condition of the HBGS of helium-rich natural gas. Full article

The behavior of low concentrations of methanol (0.5 and 1.0 wt% of water) as a promoter for hydrate formation in seawater or pure water metastable solutions of methane was investigated using the classical molecular dynamics method at moderate temperature and pressure. The influence of methanol on the dynamics of the re-arrangement of the hydrogen bond network in seawater and pure water solutions of methane was studied by calculating order parameters of the tetrahedral environment and intermolecular torsion angles for water molecules, as well as by calculating the number of hydrogen bonds, hydrate, and hydrate-like cavities. It was found that hydrate nucleation can be considered a collective process in which the rate of hydrate growth is faster in systems with low concentrations of methanol, and confident hydrate growth begins earlier in a metastable solution without sea salt with a small amount of methanol than in systems without methanol. Full article

The aim of this study was to determine the influence of four inorganic salts, KCl, NaCl, KBr and NaBr, on the thermodynamic conditions of methane hydrate formation. In order to achieve this, the vapor–liquid water-hydrate (VL_WH) equilibrium conditions of methane (CH₄) hydrate were measured in the temperature range of 274.15 K–282.15 K by the isothermal pressure search method. The results demonstrated that, in comparison with deionized water, the four inorganic salts exhibited a significant thermodynamic inhibition on CH₄ hydrate. Furthermore, the inhibitory effect of Na⁺ on methane hydrate is more pronounced than that of K⁺, where there is no discernible difference between Cl⁻ and Br⁻. The dissociation enthalpy ($∆H_{diss}$) of CH₄ hydrate in the four inorganic salt solutions is comparable to that of deionized water, indicating that the inorganic salt does not participate in the formation of hydrate crystals. The Chen–Guo hydrate model and N–NRTL–NRF activity model were employed to forecast the equilibrium conditions of CH₄ hydrate in electrolyte solution. The absolute relative deviation (AARD) between the predicted and experimental values were 1.24%, 1.08%, 1.18% and 1.21%, respectively. The model demonstrated satisfactory universality and accuracy. This study presents a novel approach to elucidating the mechanism and model prediction of inorganic salt inhibition of hydrate. Full article

The flow characteristics of methane and water in sedimentary layers are important factors that affect the beneficial exploitation of marine hydrates. To study the influencing factors of methane drive-off water processes in porous media, we constructed nonhomogeneous geometric models using MATLAB 2020a random distribution functions. We developed a mathematical model of gas–water two-phase flow based on the Navier–Stokes equation. The gas-driven water processes in porous media were described using the level-set method and solved through the finite element method. We investigated the effects of the nonhomogeneous structure of pore media, wettability, and repulsion rate on gas-driven water channeling. The nonhomogeneity of the pore medium is the most critical factor influencing the flow. The size of the throat within the hydrophilic environment determines the level of difficulty of gas-driven water flow. In regions with a high concentration of narrow passages, the formation of extensive air-locked areas is more likely, leading to a decrease in the efficiency of the flow channel. In the gas–water drive process, water saturation changes over time according to a negative exponential function relationship. The more hydrophilic the pore medium, the more difficult the gas-phase drive becomes, and this correlation is particularly noticeable at higher drive rates. The significant pressure differentials caused by the high drive-off velocities lead to quicker methane breakthroughs. Instantaneous flow rates at narrow throats can be up to two orders of magnitude higher than average. Additionally, there is a susceptibility to vortex flow in the area where the throat connects to the orifice. The results of this study can enhance our understanding of gas–water two-phase flow in porous media and help commercialize the exploitation of clean energy in the deep ocean. Full article

From December 2021 to January 2022, MH21-S conducted an exploratory drilling campaign using logging-while-drilling tools to confirm the methane hydrate concentrated zone (MHCZ) for future offshore production tests. In a preliminary screening study using seismic survey data, methane hydrate (MH) prospects have been extracted in The Hyuganada Sea, offshore Kyushu. In the exploration drilling site, a previous study had reported that MH prospects were inferred from four indices. We have selected two MH prospects: one with an anticlinal structure and another with a planus structure. As a result of drilling, a resistivity value higher than 3 Ω·m, which was a criterion for interpreting MHCZs from log data, was confirmed at a depth of 336–376 mBSF in the prospect with an anticlinal structure. The MH saturation calculated using Archie’s formula was 12–95% (average saturation of 70%). The average density porosity at the same depth was 52%. P-wave velocities were faster than the upper layers. Compared with those of the MHCZ at Daini Atsumi Knoll, the MH saturation is expected to be higher, the spread of some strong-amplitude reflectors has been interpreted from seismic survey data, and the potential MH resources in this area can be sufficiently expected. Full article