The influence of minerals on the mechanism of microwave-induced fracturing of rocks

Published on Sep 1, 2020in Journal of Applied Geophysics1.975
· DOI :10.1016/J.JAPPGEO.2020.104123
Gaoming Lu1
Estimated H-index: 1
,
Jianjun Zhou1
Estimated H-index: 1
+ 2 AuthorsWenyuan Gao1
Estimated H-index: 1
(NU: Northeastern University)
Source
Abstract
Abstract Microwave-induced rock fracturing technology is considered as a promising method for rock fragmentation and mineral processing. However, owing to microwaves causing selective heating, different types of rocks show different heating effects. Some rocks are cracked and broken, some other rocks are molten, while some parts undergo no significant change. Based on microwave heating experiments on multiple types of rocks, three typical rocks with different heating effects were investigated. According to X-ray diffraction (XRD) patterns and microscope images, the primary mineral compositions of rocks and microstructures of minerals were determined. By employing an infrared thermal imager, the distribution of surface temperature of samples were measured. Afterwards, according to sensitivity to microwaves and thermal expansion of rock-forming minerals, the mechanism whereby different types of rocks show different heating effects was analysed. The heating capacity of rocks depends on sensitivity of minerals to microwaves while fracturing effect is determined by the thermal expansion of minerals. Chifeng basalt contains both minerals (pyroxene) sensitive to microwaves and minerals (olivine) with a high coefficient of thermal expansion, mainly manifesting itself as rock fracturing during microwave heating. As only minerals (pyroxene) sensitive to microwaves, while no minerals with high coefficients of thermal expansion were found in Anshan gabbro, the rock was mainly molten during microwave heating. Neither minerals sensitive to microwaves, nor minerals with a high coefficient of thermal expansion were contained in the Beishan granite, so these samples underwent no significant change before, or after, microwave irradiation. The uniaxial compressive strength underwent a quasi-linear reduction with duration of microwave irradiation and the strength of rocks containing minerals with high thermal expansion decreased more rapidly.
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