Assessment of Graphitized Coal Ash Char Concentrates as a Potential Synthetic Graphite Source

Abstract

Coal ash char concentrates from four countries (Portugal, Poland, Romania, and South Africa) were prepared, characterised, and graphitized under the scope of the Charphite project (Third ERA-MIN Joint Call (2015) on the Sustainable Supply of Raw Materials in Europe). Coal ash chars may be a secondary raw material to produce synthetic graphite and could be an alternative to natural graphite, which is a commodity with a high supply risk. The char concentrates and the graphitized material derived from the char concentrates were characterised using proximate analysis, X-ray fluorescence, X-ray diffraction (structural), Raman microspectroscopy, solid-state nuclear magnetic resonance, scanning electron microscopy, and petrographic analyses to determine if the graphitization of the char was successful, and which char properties enhanced or hindered graphitization. Char concentrates with a lower proportion of anisotropic particles and a higher proportion of mixed porous particles showed greater degrees of graphitization. It is curious to see that embedded Al2O3 minerals, such as glass and clay, influenced graphitization, as they most likely acted as catalysts for crystal growth in the basal direction. However, the graphitized samples, as a whole, do not compare well against a reference natural graphite sample despite some particles in select char concentrates appearing to be graphitized following graphitization.

Recent Advances in Methods for the Recovery of Carbon Nanominerals and Polyaromatic Hydrocarbons from Coal Fly Ash and Their Emerging Applications

“…The recovered unburnt carbons are widely used for manufacturing a large number of premium carbon products, i.e., natural or synthesized nanostructured carbon materials and could fulfill the raw material demand of several carbon-based industries [165]. Until now, such recovered carbon particles from CFA were successfully used as an activated carbon, graphite substitutes [166], absorbents as well as adsorbents [167], lithium-ion batteries, supercapacitors [168,169], environmental remediation and protection [170], and solar cells. Moreover, there are a plenty of areas where carbon particles can be applied, but the major areas are shown above in Figure 5.…”

Fluctuations in Graphitization of Coal Seam-Derived Natural Graphite upon Approaching the Qitianling Granite Intrusion, Hunan, China

“…Previous studies have found that the ore-forming temperature of coal-to-graphite in nature is about 600-900 • C, whereas the experimental temperature of coal graphitization in the laboratory exceeds 2000 • C [19,89]. In order to decrease the activation temperature for synthetic graphite, previous researchers have tried to increase the pressure and add appropriate catalysts.…”

The Discrepancy between Coal Ash from Muffle, Circulating Fluidized Bed (CFB), and Pulverized Coal (PC) Furnaces, with a Focus on the Recovery of Iron and Rare Earth Elements

“…The treatment or utilization of coal ash was subject to coal ash properties, resulting primarily from the coal source and combustion process. Generally, the feed materials of the coal power plant have complex compositions, which are the mixture of coal collected from different areas based on the calorific value [ 4 ]. Furthermore, the behavior of inorganic constituents in combustion furnaces or other procedures has a strong effect on the apparent properties of ash particles, such as size, roughness, and combination, which concerns the possibility and ability of physiochemical separation [ 5 ].…”