Abstract
In order to study the liberation characteristics of different macerals in coal, one must improve the liberation degree of macerals in coal and promote the utilization of macerals based on their properties. Based on the idea of quick cooling to change the brittleness and toughness of different macerals, the characteristics of macerals in coal are studied here by liquid nitrogen quenching pretreatment. In particular, coarse-grained samples (with a particle size of 1–3 mm) were. For this study, coal samples were sourced from the Yan’an Formation (J2y), a middle Jurassic coal formation in the Huangling no. 1 coal mine, located in northern Shaanxi Province, China. Firstly, we analyzed the coal properties and coal petrographic characteristics by the Chinese national standard method. Secondly, the distribution characteristics of macerals in different particle sizes (>0.9, 0.5–0.9, 0.1–0.5, and <0.1) were studied. Then, the samples with different particle sizes were quenched with or without liquid nitrogen to obtain the experimental group and blank group products. Finally, the differences in the liberation characteristics between the experimental group and the blank group products were studied via analyzing the micromorphology, specific surface area, pore volume, pore size and liberation degree. Our results for the particles size and liberation degree analysis indicate that inertinite and vitrinite were enriched in the coarse particles (>0.5 mm) and fine particles (<0.1 mm) here, respectively. Moreover, quenching pretreatment could contribute to the liberation of different macerals from coal, mainly because of the different effects of stress on the different components when they suddenly encounter cold, and this kind of liberation is mainly arc-shaped liberation between different macerals. In addition, along with the above results, this paper presents an optimized model for the liberation of macerals based on a combination of screening, liquid nitrogen quenching pretreatment and re-crushing.
Highlights
Coal has always been the main fuel type in China, where it has historically accounted for nearly70% of China’s total energy production [1]
Products obtained from coal samples with a particle size greater than 0.9 mm were quenched by liquid nitrogen, and the liberation degree of vitrinite was 39.26%, an increase of
The results show that particle size plays a major factor in this phenomenon, where fine (−0.1 mm) particles are more prone to movement than stress between a major factor in this phenomenon, where fine (−0.1 mm) particles are more prone to movement than different components when they are quenched
Summary
Coal has always been the main fuel type in China, where it has historically accounted for nearly. With the continuous development of detection technology, there are many new detection methods for the mineral liberation degree These methods are mainly based on microscopic image measurement methods, paired energy spectrum detection, X-ray computed tomography and deep learning processing, so as to realize mineral liberation state recognition, three-dimensional imaging, automatic detection, and other functions [37,38,39]. Most studies in the field of maceral liberation in coal have mainly focused on typical mechanical impact breakage These methods obtain a better liberation degree by using a finer particle size, but the finer the particle size, the lower the liberation efficiency. The current research work is expected to provide technical and theoretical support for fine processing and the utilization of coal
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