Quantitative determination of the mineral-matter content of coal by a radiofrequency -oxidation technique

Behaviour of coal mineral matter in sintering and slagging of ash during the gasification process

“…As discussed more fully in the literature [1,26], the bassanite (CaSO 4 .½H 2 O) in the LTA is thought to be the product of interaction between organicallyassociated Ca and S in the coal during the low-temperature ashing process. Similar mineralogy has been found in a number of other coals from the Witbank and Highveld coalfields [27,28].…”

Coal-Bearing Depositional Systems

“…3. Oxygen plasma ashing (also called "radio frequency oxidation" = RFO) is today the most widely used method of separating minerals from coal (Gleit 1963;Gluskoter 1965Gluskoter , 1967O'Gorman andWalker 1971: Frazer andBelcher 1973;Miller et al 1979). According to Ward (1986a), in this method the crushed coal is exposed in an evacuated chamber to a stream of oxygen which has passed through a high energy electromagnetic field produced by a radiofrequency oscillator.…”

Determination of mineral matter and elemental composition of individual macerals in coals from Highveld mines

“…A small proportion of bassanite (CaSO 4 .½H 2 O) is also present in the LTA samples; as discussed above, this was probably derived from interaction of organically-associated calcium in the coals with organic sulphur during the low-temperature ashing process (Frazer and Belcher, 1973;Matjie et al, , 2011Matjie et al, , 2012aMatjie et al, , 2012b.…”

“…The minerals in a coal sample are therefore usually isolated and identified by low-temperature oxygenplasma ashing (Gluskoter, 1965;Standards Australia, 2000), during which the coal is exposed, under vacuum, to a stream of electronically activated oxygen, which destroys the organic matter at a temperature of around 120°C, leaving a residue consisting of the essentially unaltered mineral components. The organic sulphur in the coal macerals may, however, interact with organically-associated inorganic elements to form mineral artefacts in the plasma-ashing process (Frazer and Belcher, 1973). Non-mineral calcium, for example, may react with sulphur released from the coal to form bassanite (CaSO 4 .½H 2 O) in the low-temperature ash residues of South African coal samples (Matjie et al, , 2011(Matjie et al, , 2012a(Matjie et al, , 2012bHlatshwayo et al, 2009).…”