Indentation of bituminous coals: Fracture, crushing and dust formation

Abstract

Bituminous coals are still the main source of energy in the world. However, these brittle porous materials are prone to crushing under action of industrial tools. Our early depthsensing nanoindentation tests of bituminous coals showed that even if the depth of indentation is within the nanoscale, these brittle coals are no longer continuous elastic media within the indentation zone but rather fine powders of crushed particles irrespectively to the coal maceral. Dust formation of the materials is a problem of great practical importance for the mining industry. Indeed, the powders of coal particles formed during crushing may cause not only explosions in mines but they also contaminate the environment around the roads of the coal transportation. In this study, the crushing of coals due to action of rigid conical indenters and formation of small coal particles is investigated. The studies are based on development of the Galanov-Grigoriev (GG) model of crushing of brittle porous materials and the model adjustment to specific features of coal fracture. Using the indentation tests, we estimate the size distribution of the dust particles formed within the region of fully crushed material. Results are presented for coals of three different stages of metamorphism.

Adhesion and wear of diamond: formation of nanocracks and adhesive craters of torn out material

“…Because fracture of many hard brittle materials may result not only in creation of a system of isolated cracks but also in crushing of materials under the indenter or its phase transition. To describe contact fracture of such materials, the so-called GG model of crushing of brittle porous materials was introduced [44], which was applied later to describe the crushing of coals [46]. According to the GG model, there arise three regions of fracture: (i) the core of crushed material under the indenter, (ii) an intermediate region having radial crack fracture and (iii) an elastic region surrounding other regions.…”

Molecular Dynamics Simulation of the Nanoindentation of Coal Vitrinite

“…So far, DSNI has already been applied for studying the mechanical properties of lots of materials, including composites, polymers, metals, and crystals (Sankaran et al, 2018;Yuemin Wang et al, 2020;Han et al, 2021;Isik et al, 2022). In recent years, this technology has received increased attention in coal research (Vranjes et al, 2018;Zhang et al, 2018;Sun et al, 2020a;Sun et al, 2020b;Kossovich et al, 2020).…”

Environmental and occupational characterisation of coals and dust from coal mining

“…Although coal is one of the most complex fossil materials, and taking into account that each coal is unique (Orem and Finkelman, 2003), a broad standard definition is a chemically heterogeneous combustible carbonaceous sedimentary black rock (Finkelman et al, 2019;Jing et al, 2020;O'Keefe et al, 2013) composed basically of organic components (macerals) and, to a much minor extent, inorganic minerals (Kossovich et al, 2020;Onifade et al, 2021;Prasanta and Patrick, 1993;Ward, 2016).…”