Energy & Fuels最新文献

Poorly soluble inorganic salts forming deposits in wells and flow lines during the production of oil and gas are known as scales. If left untreated, these deposits can cause blockages, reducing the flow of hydrocarbons. Barium(II) sulfate (Barite) is probably the hardest scale to manage. Its formation can be prevented using chemical scale inhibitors, of which aminophosphonates are a well-known class. However, aminophosphonates have never been considered as scale dissolvers. Instead, salts of polyaminocarboxylic acids are used as Barite dissolvers, with salts of diethylenetriamine-N′,N′,N″,N‴,N‴-pentaacetic acid (DTPA) at high pH being the most common. We have now discovered that aminophosphonates, if the ligand is fully deprotonated and the phosphonates are doubly charged at very high pH (13–14), are capable of dissolving Barite scale. It was shown, e.g., for the decapotassium salt of diethylenetriamine-N′,N′,N″,N‴,N‴-pentakis(methylenephosphonic acid) (K₁₀DTPMP) or the hexapotassium salt of amino-tris(methylenephosphonic acid) (K₆ATMP). Dissolver efficiency was reduced for sodium salts, as it was also seen previously for DTPA. The Barite dissolution kinetics and dissolver capacity improved further using the octapotassium salt of the macrocyclic polyamino-polyphosphonic acid 3,6,14,17,23,24-hexaazatricyclo[17.3.1.1(8.12)]tetracosa-1(23),8,10,12(24),19,21-hexaene-3,6,14,17-tetrakis(methylenephosphonic acid) (K₈PYTP). The macrocycle is a ligand preorganized for complexation of large metal ions such as Ba(II), and its complex exhibits a lower charge repulsion, leading to better dissolving of Barite scale than K₁₀DTPMP does. Surprisingly, the tetrakis-monoethylester of PYTP, PYTP^OEt, was not able to dissolve Barite scale at all. An explanation of the observed facts was suggested on the basis of basicity of the chelators and on DFT calculations, which suggested that macrocyclic chelators derived from PYTA might prefer different isomers of their Ba(II) complexes, exhibiting a different strain in their structure. These results indicate that polyamino-polyphosphonic acid scale inhibitors can also function as Barite scale dissolvers at very high pH, and a rational design of the scale inhibitors is possible.

Electrochemical systems such as fuel cells, redox flow batteries (RFBs), and electrolyzers have emerged as promising green energy technologies to replace conventional fossil fuel-based sources. Among the critical components in these systems, the bipolar plate (BPP) plays a pivotal role, as its material properties and structural characteristics directly influence overall device performance. Recent years have seen considerable efforts focused on advancing BPP technology to meet the specific demands of various electrochemical applications. However, existing review articles tend to focus on either material development or fabrication techniques within a single electrochemical system, without adequately addressing the broader implications of BPP design across different systems. To bridge this gap, the present review provides a comprehensive overview of the recent progress and persistent challenges in BPP development from a cross-platform perspective, encompassing fuel cells, electrolyzers, and RFB. Particular emphasis is placed on the selection of BPP materials tailored to the specific operational environments of each system. Furthermore, the influence of BPP material characteristics on device performance is critically examined, and potential directions for future research are proposed.

To design visbreaking processes for bitumen upgrading, it is necessary to predict the product properties. This study examines the impact of visbreaking on the density and viscosity of two bitumens, a vacuum bottom and a deasphalted oil. The oils were visbroken at different combinations of temperature and space time (with conversions up to 38%) by using an in-house continuous visbreaker. In all cases, the gas yields were below 1.5 wt %, and no coke was detected. The products were separated into distillates, saturates, aromatics, resins, and asphaltenes (DSARA). The density and viscosity of the oils and each of their fractions were measured directly or indirectly from measured whole oil, maltene, and residue properties over temperatures from 20 to 150 °C, depending on the fraction. The product density was modeled with a volumetric mixing rule, and the viscosity was modeled with the Expanded Fluid model. Existing correlations for the input DSARA property parameters as a function of conversion were updated. The models with the updated correlations and a new tuning procedure were evaluated by using measured feed properties, conversion, and product compositions as inputs. The average deviations in the modeled product densities and viscosities were 2.2 kg/m³ and 28%, respectively. The models were further tested using default feed properties, and product compositions correlated to conversion. This approach eliminated the need for measured product composition and properties and had minimal impact on the accuracy of the updated models.

As a key quality control step in the manufacturing of lithium-ion batteries (LIBs), capacity grading aims to screen out low-performance batteries to ensure battery pack consistency. To break through the reliance of conventional capacity grading on high-energy and high-cost cycling tests, a formation capacity intelligent capacity grading technology (FormCap-ICGT) is proposed, which realizes capacity prediction and grading by using only the formation data. Firstly, based on multistep cleaning and multilevel feature extraction of the formation data, a FormCap model that integrates serialized feature selection and attention mechanisms is constructed. It dynamically selects key capacity-related features to enable highly accurate capacity prediction. Based on this, the task of capacity grading is done in the formation process. Experiments involving tens of thousands of cells from different batches show that the average absolute error in capacity prediction is 0.19 Ah, and the accuracy of capacity grading reaches 91%. FormCap-ICGT provides a technological route to simplify or even remove the conventional capacity grading test. It is of great practical significance for reducing costs and improving production efficiency in the battery manufacturing industry.

This study employs molecular dynamics (MD) simulations and Grand Canonical Monte Carlo (GCMC) methods to elucidate the microscopic storage mechanisms of shale oil in both hydrated and dry shale pores, as well as the key factors influencing these mechanisms. Molecular models were established for organic matter (kerogen), brittle minerals (quartz and feldspar), carbonate minerals (calcite), clay minerals (illite, kaolinite, and montmorillonite), and graphite to analyze density distributions, adsorption behaviors, and competitive adsorption under water-bearing conditions. The results reveal that shale oil forms up to three adsorption layers (0.4–0.5 nm) near pore walls, with adsorption capacity governed by pore size, temperature, pressure, and alkane composition. The adsorption affinity follows the order: toluene > hexanoic acid > dodecane > propylene > n-octane > n-pentane, while wall material preference ranks as kaolinite > graphite > montmorillonite > illite > feldspar > calcite > quartz. In water-bearing shale, pore water regulates shale oil occurrence in montmorillonite pores through competitive adsorption and spatial exclusion. Increasing water content promotes the formation of stable hydration layers, which occupy adsorption sites and weaken oil–mineral interactions, thereby markedly inhibiting shale oil adsorption and enrichment. These findings provide theoretical guidance for shale oil evaluation and development.

Studying the mechanical properties of hydrate-bearing clayey-silty sediments (HBCSs) is vital for safe hydrate exploitation. Currently, various methods are employed in the laboratory for preparing HBCS samples, but there is a lack of evaluation on hydrate formation efficiency under different effective confining pressures. Therefore, to enhance the accuracy and comparability of the HBCS laboratory test, this study investigates the formation efficiency of hydrates under different effective confining pressures by analyzing methane gas consumption. Meanwhile, to simulate the growth environment of real submarine hydrates, the “simultaneous formation and consolidation (SFC)” method was adopted. The test results indicate that the effective confining pressure has a significant influence on the hydrate formation efficiency. Taking effective confining pressures of 0.2, 0.5, 1, 3, and 5 MPa as examples, the hydrate formation efficiency is relatively higher at 0.5 MPa. The consolidation method of HBCS has an important influence on its mechanical properties. Through triaxial shear tests, it is found that SFC enhances the strain-hardening tendency of HBCS; improves its failure strength, secant modulus, and internal friction angle; and reduces cohesion. The influence of confining pressure and hydrate saturation on the stress–strain curves and mechanical parameters of HBCS does not change with a change in the consolidation method.

Gas displacement in natural gas hydrates (NGHs) represents a viable strategy for methane recovery and CO₂ sequestration. However, its practical implementation is limited by low displacement efficiency and slow reaction kinetics. This study investigated the enhancement of flue-gas-driven methane displacement through the combined application of temperature and pressure oscillation. Key operational parameters─including the amplitude, interval, frequency, oscillation sequence, and synchronous mode─were systematically evaluated. The results demonstrate that optimizing these parameters can significantly enhance the displacement efficiency. Specifically, a higher amplitude, increased frequency, and extended intervals contribute to improved methane recovery. Following three oscillation cycles, the displacement rate reached 64.05%, doubling that under nonoscillatory conditions, although CO₂ retention decreased simultaneously. Temperature oscillation also exerts a notable effect on the process. When the amplitude exceeded 4 K, the interval was extended to 2 h, or high-frequency oscillation was applied, and methane recovery increased to 96.23%─nearly complete─after three cycles. Different oscillation sequences were found to enhance methane recovery to varying extents and exhibited distinct impacts on CO₂ retention. Under the pressure-then-temperature sequence, the retention of CO₂ initially increased and subsequently decreased, whereas under the temperature-then-pressure sequence, it continuously declined. In synchronous oscillation mode, methane recovery displayed a steady upward trend, reaching 88.94% after three cycles. CO₂ retention initially increased and then gradually declined; however, the CO₂/N₂ molar ratio in the hydrate phase remained consistently high, indicating effective CO₂ sequestration. These findings provide important insights for the optimization of methane extraction and long-term storage of CO₂ in submarine NGH reservoirs.

Studying the resistivity response of hydrate-bearing silty-clayey sediments under an undrained state is vital for exploring and monitoring natural gas hydrates. To this end, samples with varying hydrate saturations and effective confining pressures were synthesized by using a triaxial apparatus with an integrated resistivity measurement system. The resistivity response characteristics were systematically investigated throughout the entire experimental process. The experimental results demonstrate the following: (1) Temperature and initial water saturation significantly affect sediment resistivity, and cooling can increase sediment resistivity by up to 50%. (2) Hydrate formation causes a sharp rise in sediment resistivity, while preformation conditions (including stress history, initial water saturation, and hydrate saturation) exhibit a notable influence on postformation resistivity. (3) Water saturation leads to substantial resistivity reduction, whereas consolidation shows relatively minor effects. (4) Shearing behavior gradually decreases resistivity, with drainage conditions critically impacting pore structure evolution. Under 1 MPa effective confining pressure, undrained conditions yield over 200% greater resistivity reduction than drained conditions. The research conclusions are expected to provide theoretical support for the exploration and exploitation monitoring of natural gas hydrates in silty-clayey reservoirs in the South China Sea.

The characterization of oil shales is essential for evaluating their quality and industrial potential. Existing techniques, such as X-ray tomography (XCT), scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM–EDS), infrared (IR) and Raman spectroscopies, and nuclear magnetic resonance (NMR), provide valuable information. However, none of these methods offer millimetric/sub-millimetric-scale resolution with direct sensitivity to simultaneous changes in both water and organic matter within a bulk sample. To address this limitation, terahertz (THz) imaging has previously been applied to oil shales; however, no studies have explored its use under varying temperature conditions of the sample. This is particularly relevant, as heating the samples at low temperatures (<200 °C) can provide new insights into their structural and compositional evolution. Thus, in this work, we acquired THz images after sequential heating an oil shale sample at 40, 150, and 200 °C for 15 h each, in order to monitor its change during thermal evolution. The results revealed, for the first time, changes in the THz images arising from the evaporation of free water, the release of bound water from clays, and transformation of organic matter. These findings were validated and explained by complementary analyses, including X-ray diffraction (XRD), XCT, and Rock-Eval pyrolysis. Furthermore, a first effective absorption and refractive index model was proposed, which enabled the estimation of free and bound water evaporation.