Influences of Different Acid Solutions on Pore Structures and Fractal Features of Coal

Zhang, Jingshuo; Ni, Xiaoming; Liu, Xiaolei; Su, Erlei

doi:10.3390/fractalfract8020082

Cited by 3 publications

(1 citation statement)

References 45 publications

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“…According to Eq. 1, the fractal dimension D [39][40][41][42] is derived from the slope calculation of the linear fit as shown in Figure 8 and Table 4. The adjusted correlation coefficient (Table 4) for each coal sample group is above 0.95, indicating that the impacts of different concentrations of starch-polymerized aluminum sulfate solutions on the pore surface of coal are distinctly fractal in character.…”

Section: Fractal Characteristicsmentioning

confidence: 99%

Fractal Characteristics and Microstructure of Coal with Impact of Starch-Polymerized Aluminum Sulfate Fracturing Fluids

Cai,

Zhang,

Yang

2024

Fractal Fract

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The degree of irregularity and complexity of the pore structure are comprehensively reflected in the fractal dimension. The porosity of coal was determined by its fractal dimension, where a larger dimension indicates a lower porosity. Fractal theory and the Frenkel–Halsey–Hill (FHH) model were applied to explore the variation rules of concentration on functional groups and pore structure in this study. Combined with infrared spectroscopy (FTIR) and low-temperature nitrogen adsorption, a starch-polymerized aluminum sulfate composite fracturing fluid was prepared, which plays an important role in methane adsorption and permeability of coal samples. The test results showed that, compared with the original coal, the pore volume and specific surface area of each group of coal samples were reduced, the average pore diameter was initially enlarged and then declined, and fractal dimension D1 dropped by 5.4% to 15.4%, while fractal dimension D2 gained 1.2% to 7.9%. Moreover, the nitrogen adsorption of each group of coal samples was obviously lower than the original coal, and the concentration of starch-polymerized aluminum sulfate solution existed at a critical optimal concentration for the modification of the coal samples, and the nitrogen adsorption reached a minimum value of 0.6814 cm3/g at a concentration of 10%. The novel composite solution prepared by the combination of starch and flocculant in this paper enhanced the permeability of the coal seam, which is of great significance in improving the efficiency of coalbed methane mining.

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Section: Fractal Characteristicsmentioning

confidence: 99%

Fractal Characteristics and Microstructure of Coal with Impact of Starch-Polymerized Aluminum Sulfate Fracturing Fluids

Cai,

Zhang,

Yang

2024

Fractal Fract

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Macro-Meso-Micro Evolution Characteristics of Coal Under Acid Corrosion and Its Implication to ECBM Recovery

Li,

Chen

et al. 2024

Energy Fuels

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Coalbed methane (CBM), as an associated resource of coal, has important strategic energy strategic significance. However, most reservoirs in China have low permeability, which poses challenges for CBM mining. Based on the background of acidification to increase CBM production, the macroscopic mechanics seepage, mesoscopic morphology observation, and microscopic pore measurement experiments of coal under acid treatment were carried out, and the influence of acid on macromeso-micro characteristics of coal and insights into enhancing CBM were revealed. It is found that acid corrosion can weaken the strength and energy storage capacity of coal, and obvious toughness characteristics appear under postpeak stress loading. The effect of acidification on the permeability of coal is time-dependent. In the early stage of acidification, the sensitivity index is larger, rendering the permeability more susceptible to variations over time. However, as the process advances to later stages, blindly increasing acidification time gradually weakens the effect of permeability enhancement and even decreases. Evidence of acid etching of mineral components in fracture peaks and valleys was found under the microscope, with originally blocked pores achieving unblocking and connecting to primary pores, and it was also surprising to find that acidification reaction increased the surface roughness of samples. Furthermore, following acid treatment, the samples exhibited an increase in the average pore diameter, pore volume, porosity, and Knudsen number. The pore fractal dimension and tortuosity decreased, which made it easy for gas diffusion and seepage activities. The research results have guiding significance for CBM energy development and underground disaster prevention.

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Wind Turbine Blade Fault Diagnosis: Approximate Entropy as a Tool to Detect Erosion and Mass Imbalance

Lahmiri

2024

Fractal Fract

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Wind energy is a clean, sustainable, and renewable source. It is receiving a large amount of attention from governments and energy companies worldwide as it plays a significant role as an alternative source of energy in reducing carbon emissions. However, due to long-term operation in reduced and difficult weather conditions, wind turbine blades are always seriously damaged. Hence, damage detection in blade structure is essential to evaluate its operational condition and ensure its structural integrity and safety. We aim to use fractal, entropy, and chaos concepts as descriptors for the diagnosis of wind turbine blade condition. They are, respectively, estimated by the correlation dimension, approximate entropy, and the Lyapunov exponent. Formal statistical tests are performed to check how they are different across wind turbine blade conditions. The experimental results follow. First, the correlation dimension is not able to distinguish between all conditions of wind turbine blades. Second, approximate entropy is suitable to distinguish between healthy and erosion conditions and between healthy and mass imbalance conditions. Third, chaos is not a discriminative feature to distinguish between wind turbine blade conditions. Fourth, wind turbine blades with either erosion or mass imbalance exhibit less irregularity in their respective signals than healthy wind turbine blades.

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Influences of Different Acid Solutions on Pore Structures and Fractal Features of Coal

Cited by 3 publications

References 45 publications

Fractal Characteristics and Microstructure of Coal with Impact of Starch-Polymerized Aluminum Sulfate Fracturing Fluids

Fractal Characteristics and Microstructure of Coal with Impact of Starch-Polymerized Aluminum Sulfate Fracturing Fluids

Macro-Meso-Micro Evolution Characteristics of Coal Under Acid Corrosion and Its Implication to ECBM Recovery

Wind Turbine Blade Fault Diagnosis: Approximate Entropy as a Tool to Detect Erosion and Mass Imbalance

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