Sulphur in six coals

The sulphur content of coal is of considerable significance in relation to its industrial use. In combustion processes, such as power generation, sulphur compounds in the 

Because of the adverse effects of sulphur, a vast amount of effort has been directed towards reducing the sulphur content of coal. Mineral sulphur can be partially removed by cleaning processes, which are in widespread use, but organic sulphur, though it can be partially or entirely removed in laboratory or pilot scale processes, presents an intractable problem of removal on a large scale. For example, in coals otherwise suitable for carbonisation, processes which remove organic sulphur leave a coal residue, the coking properties of which have been destroyed. 

For these reasons, the determination of sulphur in coal is of considerable importance and a representative selection of a wide range of industrial coals has been made with the aim to establish them as coal reference materials (CRMs 331, 332, 333, 334, 335 and 336) [12]. 

The homogeneity (within- and between-bottles) was verified using the method ISO 351 — Coal and Coke, Determination of Sulphur / High-temperature Combustion Method. The coefficient of variation of the within and the between homogeneity tests did not show any significant difference and were always below 1% which is less than 1/3 of the uncertainty obtained in the certification exercise. All materials were hence considered to be of suitable homogeneity for use as reference materials. 

The stability of sulphur was verified at ambient temperature over the certification period (8 months). The results showed that the stability of the samples kept in sealed ampoules under argon was good. 

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