کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
235333 465634 2015 8 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
The onset of particle agglomeration during the dry ultrafine grinding of limestone in a planetary ball mill
ترجمه فارسی عنوان
شروع ذوب شدن ذرات در خردایش سنگ خرد کردن سنگ آهک خشک در یک آسیاب توپ سیاره ای
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی مهندسی شیمی (عمومی)
چکیده انگلیسی


• Size distribution and microscopy analysis showed agglomeration of limestone particles.
• Agglomeration begun when the specific surface area of ground product reached 4000 cm2/g.
• XRD line broadening analysis only showed mild lattice distortion in calcite grains.
• EPR spectroscopy probed structural and surface defect centers induced by grinding.
• The number of electron deficient centers increased with specific surface area increasing.

This study investigates structural and morphological changes in limestone particles ground in a planetary ball mill. The grinding tests were carried out as a function of the revolution speed (100–300 rpm) and time (7–120 min). The feed size, the grinding media and the filling rate were kept constant. The size and shape of the particles were characterized by laser scattering and scanning electron microscopy (SEM), respectively. The uniformity index given by the Rosin–Rammler particle size distribution combined with SEM micrographs was useful to show the decrease of the grinding rate caused by the agglomeration of fines lying on partially broken particles. The effect of the mechanical action of grinding on the crystalline structure of calcite grains was investigated by X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) spectroscopy. EPR spectroscopy was performed before and after the samples being irradiated with a dose of 5 kGy of gamma rays. XRD analysis only showed a net reduction in the intensity of the (101¯4) peak and a slight increase in the line broadening of this peak. On the other hand, the energy input provided by the grinding action modified the population of paramagnetic defects existing in calcite lattice. In addition to the creation of electron traps responsible for a signal with a g-factor equal to 1.9999, the EPR measurements showed that the intensity of the hyperfine lines of Mn2 + substituting Ca2 + was affected by the grinding action. The morphological and particle size analysis together with the relationship found between the intensity of paramagnetic defects and specific surface area of limestone particles provided a picture of the onset of the agglomeration process. These results were discussed in order to explain the apparent grinding limit observed in ultrafine milling of limestone.

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ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Powder Technology - Volume 284, November 2015, Pages 122–129
نویسندگان
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