The paper investigates the effect of ultrasonic cavitation, in combination with catalysts, on the fractional composition of high-viscosity oil. Ultrasonic treatment was carried out at a frequency of 22 kHz and a power of 50 W for 10 min in the presence of HY-zeolite, NiFe/Y-zeolite and NiFe/microsphere (1 wt%) catalysts. Results showed that ultrasonic treatment without a catalyst leads to a reduction in the yield of the target distillate fractions. The HY-zeolite demonstrates the greatest efficiency, increasing the yield of the light fraction with a boiling point of up to 200 °C by 7.9% compared with the initial oil. The NiFe/zeolite and NiFe/microsphere catalysts contributed to the formation of naphthenic and aromatic structures in the light and middle fractions of high-viscosity oil; however, the yields of light fractions with a boiling point of up to 200 °C and at 200–300°C decreased.
To address limited permeability enhancement caused by insufficient free faces during static fracturing in low-permeability coal seams, this study investigated the No. 2 coal seam of the 32203 working face in Hanzui Coal Mine. A coupled stress–damage–seepage fluid–solid model was developed, and COMSOL Multiphysics 6.0 was used to compare stress, plastic zone, and gas pressure evolution under single-borehole and grid-pattern multi-borehole fracturing. Simulations showed that single-borehole fracturing was constrained by the free face, with limited lateral plastic-zone expansion (0.45 m) and non-uniform distribution due to in situ stress and coal anisotropy. In grid-pattern fracturing, drainage boreholes provided multiple free faces; superimposed expansion stresses connected plastic failure zones around fracturing boreholes, enlarging pressure relief. Field tests with six fracturing and six observation boreholes, using stable flow after secondary sealing as baseline and excluding sealing improvement, showed mixed drainage flow increased by 2.5–3.1 times and pure-gas flow by 2.1–2.5 times; pure flow at 0.6 m from a fracturing borehole rose from 0.0046 to 0.018 m3/min. Permeability enhancement was significant at spacing ≤1.6 m, consistent with simulations. Grid-pattern static fracturing expanded the fracture network via stress–damage–seepage coupling, providing a theoretical basis and parameter reference for efficient permeability enhancement in low-permeability coal seams.
The article treats the pelletization process as a waste biomass processing process, which allows for minimizing waste and processing it into biofuel. One of the products of the anaerobic fermentation process in agricultural biogas plants is post-fermentation mass. Large amounts of post-fermentation mass generated in the biogas production process in the countries studied require appropriate management. Pellet production can be carried out from post-fermentation mass, forest or agricultural waste. The authors took up the subject of waste analysis and its use for the production of pellets as biofuel and indicated the most beneficial solutions based on the examples of Poland and Germany. The work is a review of solutions and possibilities of using the solid post-fermentation fraction for the production of pellets. The authors assess the conditions of waste biomass and other fractions and indicate that they can be a valuable element for the production of solid biofuels in the countries studied towards the sustainable development of renewable energy policy. The use of waste for the production of pellets will contribute to the minimization of waste.
Oil transmission pipeline failures may cause severe ecological pollution, casualties, and economic losses, making pipeline corrosion safety management crucial. Existing corrosion evaluation models rely on generalized theories and rarely adopt field-measured data to analyze circumferential weld corrosion and degradation mechanisms under multi-physics coupling, resulting in inaccurate prediction of actual pipeline damage evolution. Taking the Karamay Refinery–Fengcheng oil pipeline as the research object, this study focuses on external corrosion induced by the soil environment, stray current, and overburden stress, since no detectable internal corrosion defects were found via inline inspection. The pipeline, originally designed for diesel transmission, actually transports heavy crude oil containing free water, sulfides, and inorganic salts, with an operating temperature range of 25–45 °C. This study establishes a practical coupled corrosion model via a second-order multi-field coupling framework based on field monitoring and global failure statistical data. Corrosion distribution, risk classification, and remaining service life are systematically analyzed, and targeted prevention countermeasures are proposed for pipeline segments with different risk levels. The results show that corrosion failure is the dominant pipeline failure type, with a maximum metal loss rate of 56.1% in electromagnetically interfered sections. Circumferential weld defects mainly accumulate on the right pipe crown due to laying gradients. The minimum remaining service life of high-risk segments under multi-field coupling is only 6.4 years. This study provides reliable technical support for the safe operation and maintenance of similar oil pipelines.
Bulk density (BD) is a key quality parameter of wood pellets, influencing handling, storage and volumetric energy density. The standard procedure (ISO 17828) is accurate but time-consuming and subject to operator variability. This preliminary study introduces the mass flow rate (MFR) as a new variable, not included in the standard, and presents a prototype built for its controlled measurement. Thirty commercial wood-pellet samples were characterized for MFR, pellet length distribution metrics and BD. After multivariate analysis, the relationships between MFR, dimensional descriptors and BD were explored through correlation analysis. As a first exploratory test, Support Vector Regression, Extreme Gradient Boosting and a weighted ensemble were evaluated by nested repeated cross-validation, with Gaussian noise-based augmentation applied to training data only. The mean out-of-fold MAE was 17.5 kg/m3 for the ensemble, 17.8 kg/m3 for SVR and 18.3 kg/m3 for XGB, with overlapping confidence intervals and considerable variability across data partitions. Nevertheless, the errors are contained and comparable to those attributable to operator variability and lower than the features standard deviation (24.3 kg/m3). The results suggest that MFR, combined with dimensional descriptors, can support BD estimation, although larger datasets are needed to establish a robust relationship.
